HAGGAN, Titus*, PARNELL, John**, CESARETTI,
Nora***
*
ED-Group, MinMet Plc,
** Dept. of Geology and Petroleum Geology,
*** Dep. de Geología, UNS, San Juan 670, 8000 Bahía Blanca, Argentina. E-mail:
ghcesar@criba..edu..ar
ABSTRACT: CERRO HUEMUL:
BITUMEN-HOSTED, SANDSTONE-TYPE U-Cu DEPOSIT,
Keywords: Cerro Huemul,
bitumen, uranium, copper, sandstone-type deposit, Neuquén Basin.
AHUMADA Selva P.
CONICET -
Universidad Nacional de Catamarca - Maximio Victoria 55 (4700) -Catamarca
ABSTRACT: Gypsum and
anhydrite are important at Bajo de la Alumbrera, as in many porphyry copper
deposits in the world. Gypsum occurs in white thin veinlets of various
orientations and it has a fibrous to platy habit. Gypsum veinlets are dissolved
in the leached capping but also in several zones at depth since 200-300 m. In
the deeper zones anhydrite is common as veinlets and disseminations. Both
sulphates are not ubiquitous: they are most common in the andesite surrounding
the main porphyry mass, apparently due to the higher original calcium content
of the andesite.
Keywords: Gypsum,
Anhydrite, Porphyry Cu-Au Deposit.
ALONSO, Ricardo N.*
*UNSa-CONICET,
Facultad de Ciencias Naturales, Buenos Aires 177, 4400-Salta, Argentina. E-mail
rnalonso@sinectis.com.ar
ABSTRACT: THE MINING
EXPEDITION OF ABRAHAM BECERRA (1887) TO THE PUNA HIGH PLATEAU (SALTA AND
JUJUY). In
the year of 1887, the government of Salta province (Argentina) sent a mining
expedition to the Puna high plateau. Abraham Alberto Becerra, a Chilean man,
resident and married in Salta, was commissioned by the governor M.G. Güemes for
a two-month trip to the “Western Cordilleras” in order to visit
metallic and borate mines. At this time, following the Pacific War of 1879
between Chile against Peru and Bolivia, the Puna region was a conflictive
territory and the mining properties were conceded at same time for different
governments. The trip of Becerra was essentially geographic and economic with
some defined geopolitical considerations. Becerra’s observations were
rich in geological, mineralogical and metallogenic aspects. He made
descriptions of gold placers, benefit metallurgical plants, silver, copper,
antimony and other metals mines, borate deposits, thermal springs and some more
points of interest. His knowledge of old mining terms, profusely used in the
report proved that Becerra was a capable and empirical without academic
geological studies. The paper, published as a booklet of 48 pages, was a
pioneer work in the history of mining in northern Argentina and one of the
scarce and values bibliographic referenced for the region in the nineteenth
century.
Keywords: Abraham
Becerra-History of Mining-Mining terms-Borate-Puna
ARGAÑARAZ Rafael A.* and INNES Angus **
*Cátedra
de Yacimientos Minerales - Universidad Nacional de Salta, Argentina. e-mail
rargana@unsa.edu.ar
** Geólogo Consultor. La Florida 770 - 4.400 Salta - e-mail ainnes@arnet.com.ar
The Cerro
Juncal area is located approximately 75 km southwest of the city of
The porphyry outcrops on the western margin of an alteration zone measuring 4.5
km². The main alteration zone consists of Ordovician marine sediments, which
display intense quartz-sericite alteration with limonite after pyrite. The
intrusive can be traced in adjoining streams over an effective strike of
approximately 900 meters. It has an exposed width of up to 200 m and it is
covered in all directions either by colluvium, by the overlying altered
Ordovician sediments or by their debris flow deposits.
The intrusive consists of a quartz-eye dacite porphyry with phyllic alteration
and a later overprint of silica flooding. It has a well-developed quartz vein
stockwork and is brecciated in places. The quartz veins are represented by both
A and B types. The intrusive is leached with the oxides being jarosite,
goethite and hematite, in order of abundance. The oxides occur both in the
quartz veins and disseminated within the intrusive. Boxworks of pyrite and
chalcopyrite can be observed. Massive limonite veins are fairly common in some
sectors.
Although the area is mainly covered, it is believed that the porphyry is near
surface. In addition, the altered Ordovician sediments have gold grades of up
to 1.8 g/t, within low sulphidation epithermal mineralization overlying the
porphyry system. There is a potential for copper mineralization and a secondary
enrichment blanket in the porphyry, as not only do the oxide minerals in the
leached intrusive indicate but also in the overlying leached sediments where
copper has values of up to 456 ppm. This is concordant with the leached caps
overlying some of the world’s most important copper porphyries, such as
El Salvador and La Escondida where copper values are up to 500 ppm and 300 ppm
respectively.
Keywords: Cerro Juncal-
gold- copper- porphyry
ESCORODITA Y NATROALUNITA EN MINA CALEDONIA, DISTRITO CERRO BLANCO,
MARAYES, PROVINCIA DE SAN JUAN, ARGENTINA.
BENGOCHEA, Leandro 1; MAS, Graciela 1 y ARRESE,
Mónica 2
1 Dto. de
Geología, Universidad Nacional delSur-CONICET. Bahía Blanca;
lbengo@criba.edu.ar; gmas@criba.edu.ar.
2 Dto. de Geología, Universidad Nacional del Sur.
ABSTRACT: SCORODITE AND
NATROALUNITE FROM CALEDONIA MINE, CERRO BLANCO DISTRICT, MARAYES, SAN JUAN
PROVINCE, ARGENTINA. The occurrence of scorodite and natroalunite in the
Caledonia mine, Cerro Blanco District, Marayes, San Juan province, Argentina,
is reported. The mineralogical characteristics of these minerals have been
studied by X ray diffraction, thermal gravimetric analysis, differential
thermal analysis, scanning electronic microscopy and EDAX analysis.
Keywords: Escorodite,
Natroalunite, Marayes
BJERG, Ernesto Alfredo* y BRODTKORB, Milka K.
de**
* CONICET
- Universidad Nacional del Sur- San Juan 670 - 8000 Bahía Blanca.
E-mail:usbjerg@criba.edu.ar
** CONICET - Universidad de Buenos Aires- Email: milkabro@gl.fcen.uba.ar
ABSTRACT: ARGENTOPENTLANDITE FROM SALAMANCA MINE: A NEW MINERAL FOR ARGENTINA. This is the first
reported occurrence of the mineral argentopentlandite [Ag(Fe, Ni)8S9] in
Argentina. It occurs as exsolutions intergrown with mackinawite in a
chalcopyrite matrix linked to sulfide mineralization located in a fault zone in
Salamanca mine, province of Mendoza. Pentlandite and cobalt pentlandite are
also present but associated to pyrrhotite. Its association to chalcopyrite and
mackinawite, the last one carrying up to 7.5 wt % Ni and 0.7 wt% Co, indicates
that the most plausible genesis for the argentopentlandite is by exsolution
from a high temperature ISS which carried Ag and Ni.
Keywords:
argentopentlandite - Argentina - mackinawite - ISS - ophiolite
BONILLA GUEVARA , Wilson*
*Gerente
Producción BIRA, Consultor-Auditor Minero. bonillawilson@hotmail.com
ABSTRACT: GEOCRONOLOGY AND
BRECCIA EPISODES IN THE VIZCAYA POLIMETALIC VEIN SYSTEM. SOUTHWEST ECUADOR. Five
magmatic-hydrotermal episodes have been characterized and identified during the
polimetalic ore deposition in the Vizcaya system. They are related to breccia
structures, hydraulic and despressuring process in a epitermal low sulfidation
environment and the gold is related to milky quartz cement and jig saw
textures.
Keywords: Zaruma Portovelo
- low sulfidation epithermal vein - Post Miocene
BRODTKORB, Milka K. de* y PAAR, Werner**
* CONICET-
Universidad de Buenos Aires. E-mail: milkabro@gl.fcen.uba.ar
**Universidad de Salzburgo. Austria .E-mail: Werner Paar@sbg.ac.at
ABSTRACT: CONTRIBUTION TO
THE MINERALOGICAL KNOWLEDGE OF LA MEJICANA MINE, LA RIOJA, ARGENTINA. Ore samples from
the epithermal La Mejicana mine, La Rioja, Argentina, probably the type
locality material of famatinite, were investigated by reflected light
microscopy and electron microprobe analyses. The ore assemblage consists of
pyrite, chalcopyrite, enargite, famatinite, different fahlores,
polybasite/pearceite, electrum, acantite, uytenbogaardtite and hübnerite, and
svanbergite as alteration product.
Keywords. La Mejicana Mine, La
Rioja- epithermal - famatinite - Stelzner
BRUNO, Natalia Edith(1,2)
1 CONICET,
2 INGEO-Departamento de Geología-FCEFN, UNSJ. E-mail: nbruno@unsj-cuim.edu.ar
ABSTRACT: NEW CONTRIBUTION
ABOUT THE GEOLOGY AND GOLD MINERALIZATION IN A SECTOR OF GUALCAMAYO MINING
DISTRICT, PROVINCE OF SAN JUAN, ARGENTINA. This paper focuses on the mineral
paragenesis and gold mineralization controls of the Quebrada del Diablo target
area, located in the Gualcamayo Mining District, Eastern Precordillera , San
Juan province. A very-fine grained disseminated mineralization is hosted by
limestones, breccias a dacite porphyry and marbles. The metallic ore includes:
native gold, cinnabar, pyrite, As-rich pyrite, marcasite, realgar, oropiment,
sphalerite, chalcopyrite and galena. Barite, calcite and quartz are the common
gangue minerals. Both structural and lithological factors control the ore
distribution. The small size and the relatively uniform distribution of the
mineral asemblage suggest that this deposit is similar to sediment-hosted gold
deposits found in Nevada (USA) and China, as described by many authors.
Keywords: Eastern
Precordillera - carbonate-hosted deposit - gold mineralization - paragenesis
CANAFOGLIA, María E.1, RAMIS, Andrea M1, BOTTO, Irma
L.1,4, CABELLO, Carmen I2,4, LANFRANCHINI, Mabel E.3, SCHALAMUK, Isidoro B3 y
MINELLI, Giuliano4
1CEQUINOR
-Facultad de Ciencias Exactas, UNLP, E-mail: botto@quimica.unlp.edu.ar
2CINDECA- Facultad de Ciencias Exactas, UNLP
3INREMI- Facultad de Ciencias Naturales y Museo-UNLP: E-mail:
inremi@infovia.com
4IMIP-CNR- Universidad La Sapienza, Roma, Italia
ABSTRACT: REDUCTION AND
THERMAL EFFECTS ON THE STABILITY OF A MINERAL OF THE HEDENBERGITE-JOHANNSENITE
SERIES. The reducibility of minerals belonging to the
hedenbergite(CaFeSi2O6)-johannsenite(CaMnSi2O6) series from a skarn called ¨El
Abuelo¨, province of Chubut (Argentina) has been studied by means of the
temperature programmed reduction (TPR) technique with the aid of the “in
situ” X-ray diffraction analysis up to 800 oC, in similar conditions to
that of the TPR measurements. The characterization of mineral samples as well
as the products of thermal treatments has been carried out by FTIR
spectroscopy, SEM and EDAX microscopy, conventional chemical analysis and XRD
analysis. The iron reduction of the structure leads to the segregation of metal
Fe and the formation of johannsenite (Mn rich end member of the isomorphous
hedenbergite-johannsenite-series) at 700 ºC. Likewise, the johannsenite
transforms to bustamite phase, structurally related to wollastonite. This
process is favoured by the small difference between Ca(II)-Mn(II) size (in
relation to that observed for Ca(II)-Fe(II)). The reduction behaviour has been
also related to that observed in the wolframite system (Mn(II), Fe(II))WO4.
Keywords:
hendenbergite-johannsenite series, reducibility, thermal behaviour
CASELLI, Alberto T.* , AGUSTO, Mariano R.*, DOS
SANTOS AFONSO, María **
* Dpto.
Cs. Geológicas, Facultad de Ciencias Exactas y Naturales. UBA, Ciudad
Universitaria, Pab.2, C.P. C1428EHA, Buenos Aires, Argentina.
acaselli@gl.fcen.uba.ar , agusto@gl.fcen.uba.ar
** INQUIMAE, Facultad de Ciencias Exactas y Naturales. UBA, Ciudad
Universitaria, Pab.2, C.P. C1428EHA, Buenos Aires, Argentina.
dosantos@qi.fcen.uba.ar
ABSTRACT: FRAMBOIDAL
SULPHIDES FROM FUMAROLES OF THE DECEPTION ISLAND, SOUTH SHETLAND, ANTARCTICA.
Pyrite framboids have been recognized from fumaroles of the Deception Island,
Antarctica. The sulphide was formed around reworked pyroclastic tephras
(lapilli). Mineralogical and geochemical studies gave microform characteristics
and environmental conditions. Although the pyrite framboid genesis was not
completely dilucidated, it might suggest that it formed as a result of the
reaction between the country rock and hydrogen sulphide.
Keywords: Pyrite,
framboids, fumarole, Deception Island, Antarctica
1CASTRO, L. N., 1 FAZIO, A. M. y 1,2 SCASSO, R. A
1Departamento
de Geología, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos
Aires, Argentina; 2CONICET
lilianacastro@fibertel.com.ar; amfazio@gl.fcen.uba.ar; rscasso@gl.fcen.uba.ar
ABSTRACT: GEOCHEMICAL
BEHAVIOUR AND RARE-EARTH ELEMENTS DISTRIBUTION IN GAIMAN FORMATION PHOSPHATIC
LEVELS, CHUBUT, ARGENTINA. Late Oligocene-Early Miocene marine Gaiman Formation
samples have been analyzed for rare earth elements content in order to sustain
paleoenvironmental interpretations from former sedimentological and
paleontological work. P2O5 content in concretions is between 15,61 to 28,97%.
Two types of phosphatic concretions are found: “Type 1” represented
by in situ concretions developed within transgressive-early highstand system
tracts which shows litlle evidence for significant transportation. and
“Type 2” related to reworking, winnowing and mechanical
concentration of resistant particles. Type 1 exhibits higher REE/ P ratios and
a significance enrichment in HREE than Type 2. The REE pattern in both shows a
slight depletion in LREE with weak Ce anomaly (-0.16 to -0.09) and an
enrichment in high rare earth elements in comparison to the "average
shale”. They show 915 ppm REE and 500 ppm in Y mean content which are the
double compared with different types of worldwide phosphorites (462 ppm and
275ppm). No significant correlation is found between REEs and P2O5 content.
Otherwise HREE enrichment (Lu/Ce) increases with the REEs bulk content. The
pattern is consistent with shallow water, inner shelf, marine environment also
suggested by sedimentological and paleontological evidence. MREE and HREE
distributions are similar to those nodules in upwelling areas like the Peruvian
shelf (Pleistocene -Holocene). Ce/La; Y/La; Th/U and V/Cr ratios also suggest
upwelling processes for Gaiman deposits. However, the paleogeographic location
of the Gaiman area, far from the edge of the shelf, is not compatible with an
upwelling zone. Instead, cold water flooding the continental shelf and mixing
with warmer surficial water could explain the high productivity and
phosphogenesis.
Keywords: Gaiman Formation,
rare earth elements, phosphatic concretions, phosphogenesis.
Castro de machuca, B.1,2,3, Conte-Grand, A.2,3,
Meissl, E.2,3, Pontoriero, S.2,
Recio, G.1,2 and SUMAY, C.2,3
1 CONICET.
bcastro@unsj-cuim.edu.ar
2 Instituto de Geología (INGEO)
3 Departamentos de Geología y Geofísica, FCEFN-UNSJ. Complejo Universitario Islas
Malvinas (CP 5407) Rivadavia, San Juan, Argentina.
ABSTRACT: The eastern flank
of La Huerta and Valle Fértil hills, Western Pampean Ranges, San Juan province,
Argentina, mainly consists of metaigneous dioritic to granodioritic rocks that
intruded the Proterozoic basement in the Early-Middle Ordovician (Famatinian
Orogeny). Small bodies of metagabbro and related ultramafic rocks, up to a few
hundred meters across, are present in minor amounts. Two-pyroxene metagabbros
display well preserved igneous textures and mineralogy comprising Mg-Ca rich
minerals:
Pl(An100-75)+Opx(En82-76Fs18-23Wo0-1)+Cpx(Wo50-46En44-47Fs6-8)±Ol(Fo83
-75)±Spl±Ilm±Mag. Abundant coronas composed of OlàOpxàCpxàAm±SplàPl were
developed at Ol-Pl boundaries. In this study, coronitic texture is interpreted
as the result of slow cooling of the mafic-ultramafic bodies under
high-amphibolite to lower-granulite metamorphic conditions. The peak of
metamorphism in the area coincided with Corona formation and was related to the
Famatinian intrusive activity. Later, the metagabbros were locally cut by
narrow ductile shear-zones associated with mylonitization.
keywords: Western Pampean
Ranges-Famatinian magmatic arc-metagabbros-mineralogy-textures
CERREDO, María Elena* and LÓPEZ DE LUCHI,
Mónica G.**
* CONICET-
Departamento. de Ciencias. Geológicas, FCEyN, UBA, Pabellón II, Ciudad
Universitaria, C1428EHA, cerredo@gl.fcen.uba.ar
** Instituto de Geocronología y Geología Isotópica, INGEIS, Pabellón INGEIS,
Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina, deluchi@ingeis.uba.ar
ABSTRACT: APPLICATION OF PROVENANCE AND TECTONIC SETTING DIAGRAMS ON METAMORPHIC
ROCKS: THE CASE OF METAMORPHIC UNITS FROM SIERRA DE SAN LUIS. Three of the
metamorphic units of Sierra de San Luis (San Luis Formation, Pringles and
Conlara Metamorphic Complexes) were analyzed from the perspective of protolith
provenance and tectonic setting. This analysis, based on major element content,
provided reliable results in the case of San Luis Formation. For the Conlara
and Pringles Metamorphic Complexes the obtained results were considered as
preliminary because the rocks display features which complicated a
straightforward application of standard diagrams.
Keywords: Provenance -
tectonic setting - metasedimentary units - Sierra de San Luis
CERREDO, María Elena*; PARICA, Claudio. A.* y
REMESAL, Marcela B.*
* CONICET
- Departamento de Ciencias Geológicas, FCEyN, UBA- cerredo@gl.fcen.uba.ar,
paricac@gl.fcen.uba.ar, remesal@gl.fcen.uba.ar
ABSTRACT: THE HIGH-GRADE
METAMORPHIC ROCKS OF CUSHAMEN FM. AT AGUADA DEL PAJARITO. NORTHPATAGONIAN MASSIF. CHUBUT PROVINCE.
The metamorphic series of Cushamen Formation at Aguada del Pajarito are composed
of biotite (± garnet) schists with interlayered amphibolites. Two ductile
deformation phases are recognized, each accompanied by foliation development
(S1 and S2). The second deformation is characterized by the development of the
main foliation (S2) which is axial plane foliation of the relic F1 folds
preserved in folded relic leucocratic veins. The observed equilibrium
assemblages in both the schists and the amphibolites suggest amphibolite facies
conditions for the climax of regional metamorphism which would have been
synchronous with the second deformation. A later decompressive path could be
inferred from reaction textures.
Keywords: Cushamen
Formation - Northpatagonian Massif - metamorphic rocks
CHACÓN, Julio César* y SUREDA, Ricardo José**
* Barrisk
Explo Argentina S.A., San Juan, Argentina. E-mail: : jchacon692000@yahoo.com.ar
** CONICET - Cátedra de Mineralogía - UNSa, Salta, Argentina. E-mail:
rjsureda@uvsa.edu.ar
ABSTRACT:
MINING EXPLORATION OF THE CERRO BLANCO PROSPECT (Au-Ag), SALTA, ARGENTINA.
NEOGENE SUBVOLCANIC METALLOGENY WITH EPITHERMAL DEPOSITS IN THE EASTERN PUNA.
The Cerro Blanco subvolcanic-hosted epithermal (Au-Ag) ore deposit is located
in the Salta-Catamarca Puna eastern border (25º16’ Lat. S - 66º46’
Long. W). The mineralization and alteration patterns on small bodies of
porphyritic rhyodacites show a predominance of sericitic massive to silicified
replacements, with minor feldspar-destructive kaolinite and alunite clusters.
The host rocks are schists, quartzites and filites of the Metamorphic Rio
Blanco Complex and the biotite granites and granitoids of the Oire Formation.
Some very important hydrothermally brecciated bodies, also in little chimneys
and dykes, occur into the metamorphic basement where the adjacent wallrock is
highly silicified and frequently bleached. These altered and mineralized structures
exhibit ductile deformation that is overprinted by later brittle faulting, both
of which appear to be gold-related. There is a positive geochemical
relationship between the precious metals (Au-Ag), As and the strong silicified
rocks, where all evidence of primary lithological textures has been obliterated
(i.e. brecciated quartz dikes, altered rhyodacites and quartzites, both with
vuggy quartz in open spaces). A scarce sulfide ore assemblage characterized by
pyrite, marcasite, chalcopyrite and minor covellite is mainly disseminated into
the vulcanites and host rocks. Pure pyrite veins in stockworks outcrop randomly
at the northeastern slope of the Cerro Blanco prospect. The epithermal gold
deposit of Cerro Blanco is typically hosted in NNE-SSW trend along a Neogen
volcanic belt. Several discrete gold-silver-bearing quartz-vein systems cut the
Late Proterozoic - Early Paleozoic basement of the eastern Puna. The
International Pacific Rim company surveyed through surface mapping and 218
trench-samples and rock-chip geochemistry. Also drilled eight boreholes, a
total 1,973 m, on Cerro Blanco prospect. The estimated reserves are 18,499,250
t with 35,000 oz tr Au and 165,000 oz tr Ag and 5,300 t Cu fine. At present,
the mining exploration shows a sub-economic target on profitable resources for
gold and silver, but the metal contents in Cerro Blanco imply concentration
factors of 28 for Au and 27 for Ag.
Keywords:
Neogene subvolcanic metallogeny - epithermal precious-metal deposits - Cerro
Blanco (Au-Ag) prospect.
COLOMBO, Fernando1, CARBONIO, Raúl E.2, PANNUNZIO MINER,
Elisa V.3 y LIRA, Raúl4
1, 4 Museo
de Mineralogía ¨Dr. A. Stelzner¨. CONICET. Facultad de Ciencias Exactas,
Físicas y Naturales. Universidad Nacional de Córdoba. ccolombo@arnet.com.ar
rlira@com.uncor.edu
2, 3 Instituto de Investigaciones en Físico Química de Córdoba (INFIQC). Departamento
de Físico Química. Facultad de Ciencias Químicas. Universidad Nacional de
Córdoba. carbonio@mail.fcq.unc.edu.ar eminer@mail.fcq.unc.edu.ar
ABSTRACT: KETTNERITE,
CLINOBISVANITE AND BISMUTITE OF THE SD-2 PEGMATITE (CÓRDOBA): MINERALOGICAL
DESCRIPTION AND QUANTIFICATION OF COMPONENTS OF A MIXTURE BY THE RIETVELD
METHOD. A mixture of bismutite Bi2(CO3)O2, clinobisvanite Bi(VO4) and
kettnerite CaBi(CO3)OF (together with quartz and goethite) was found in the
SD-2 granite pegmatite located near Tanti, Punilla Department, Córdoba province
(Argentina). Its geographical coordinates are 31º 21´ 55,3´´ S, 64º 28´ 50,3´´
W. It is a zoned body composed mainly of quartz, microcline, plagioclase,
biotite and muscovite, with Mn-rich fluorapatite, columbite-group minerals,
spessartine, bertrandite, bismutite, kettnerite, clinobisvanite, goethite,
abundant beryl, and very scarce rutile and zircon as accesory minerals. The
three species are found intimately mixed with quartz and goethite in an opaque
brownish yellow mass of 4 x 2 x 0.7 cm, with earthy luster and conchoidal to
irregular fracture. Kettnerite occurs as subhedral crystals up to 55 mm long
embedded in finely granular bismutite. Clinobisvanite looks similar to
kettnerite under the SEM but its EDS spectrum shows major Bi and V (with traces
of Al and Fe). EDS spot analyses show Bi with traces of Fe and Si (bismutite)
and Bi and Ca with traces of Al, Si and Fe (kettnerite). The Fe content is
probably due to the goethite, and the Si detected reflects quartz in the
mixture. The refined cell parameters of the bismutite, kettnerite and
clinobisvanite are (in Å): a = 3.877(2), b = 3.878(2) and c = 13.703(2) (for
bismutite), a = 3.804(6), b = 3.799(5) and c = 13.688(8) (for kettnerite) and a
= 5.238(9), b = 3.149(8), c = 11.735(8) and b = 90.408(5)º (for
clinobisvanite). A quantification of the components in the mixture was
accomplished using the Rietveld method. According to the refinement, the mass
is composed of 67(1) % of bismutite, 27.6(6) % of kettnerite, 1.6(2) % of
clinobisvanite, 1.4(9) % of goethite and 2.0(9) % of quartz. We want to stress
the usefulness of the Rietveld method for the quantification of opaque and
microcrystalline mixtures, which could not be done by other conventional
methods.
Keywords: kettnerite -
bismutite - clinobisvanite - quantification of a mixture - Rietveld method -
pegmatite - Córdoba
COLOMBO, Fernando1, GAY, Hebe D.2, SFRAGULLA,
Jorge 3 y LIRA, Raúl 4
1, 2, 4:
Museo de Mineralogía y Geología ¨Dr. A. Stelzner¨. CONICET. Facultad de
Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba.
ccolombo@arnet.com.ar hdgay@com.uncor.edu rlira@com.uncor.edu
3: Departamento de Geología Básica. Facultad de Ciencias Exactas, Físicas y
Naturales. Universidad Nacional de Córdoba.
Dirección de Minería de la Provincia de Córdoba.
costa-sfragulla@powernet.net.ar
ABSTRACT: BEUSITE IN THE
SAN JOSÉ Nº 2 PEGMATITE, CÓRDOBA, ARGENTINA. Beusite, (Mn,Fe,Ca,Mg)3(PO4)2, has
been found in the San José Nº 2 pegmatite (32º 09' 43,8´´ S, 64º 56' 17,4´´ W),
Calamuchita department, Córdoba province (Argentina). It is a zoned body some 200 m
long and between 15 and 30 m wide. Border and wall zones might be present but
have not been observed. The pegmatite has an outer intermediate zone
(plagioclase + quartz + muscovite) and an inner intermediate zone (quartz +
plagioclase + muscovite or quartz + K-feldspar + muscovite). Accesory species
include garnet, columbite-group minerals, gahnite and beryl. The core is
composed of massive quartz. A single piece of beusite was found in the dump. It
is massive, dark to medium brown and has a black rind of alteration products.
Luster ranges from glassy on cleavage surfaces to greasy on fractures. Dcalc =
3.70 gr.cm-3. Microprobe analyses (wavelenght dispersive mode) are as follows
(weight %, average of 3 points): P2O5 39.42, MnO 29.39, FeO 22.57, CaO 5.73,
MgO 0.30, SiO2 0.01, F 0.00, Cl 0.00, total 97.42 wt. %. Indices of refraction
are: a = 1.704(3), b = 1.708(3), g = 1.722 (3); 2Vcalc = 28.3º. Dispersion r
> v, strong; no pleochroism, X = Y = Z = very light brown. Cell parameters
are a = 8.757(2) Å, b = 11.830(2) Å, c = 6.1603(5) Å, b = 99.81(1)º. Cell
volume is 628.8(4) Å3. The diffraction lines match those of card 36-0401 of the
JCPDS (1997).
Keywords: beusite -
graftonite - granitic pegmatite - Comechingones - Córdoba.
CORREA, María José* y CÁBANA, María Cecilia**
* CONICET.
Instituto de Recursos Minerales. majocorrea@yahoo.com
** CICBA. Instituto de Recursos Minerales. cecicabana@yahoo.com
Abstract: STRUCTURAL
ANALYSIS OF LA CLEMIRA VEIN, SIERRA DE AMBARGASTA, SANTIAGO DEL ESTERO,
ARGENTINA. A kinematic analysis from a manganese mineralized vein is given. This
vein is part of a N-S fault system placed in the Ambargasta range. In this case
the particular orientation (N 28° W) and dextral displacement allowed to
consider this fault as a subsidiary shear fracture in Riedel’s shear
scheme. This model is associated to the main dextral shear meridian submeridian
system, originated in the Pampeanas ranges during Cretaceous times which could
be related to the whole continent extension.
Keywords: Pampeanas Ranges-
mineralized system - dextral shear - Riedel’s shear
de BARRIO, Raúl E.1 y RIBOT, Alejandro M.2
1 Inst. de
Recursos Minerales (INREMI), (UNLP), calle 47 N° 522 (1900) La Plata, E-mail:
debarrio@sinectis.com.ar
2 LEMIT-CICBA, (UNLP), calle 52 entre 121 y 122 (1900) La Plata. E-mail:
aribot@museo.fcnym.unlp.edu.ar
ABSTRACT: BASALTIC ROCKS
WITH TITANOMAGNETITES, LAS LAJAS HILL, MALARGÜE DEPARTMENT, MENDOZA PROVINCE.
Las Lajas hill is situated in the southern area of Mendoza province, near of
Neuquén province boundary. It represents a subvolcanic body made up of alkaline
basic rocks (trachybasalts and basaltic trachyandesites), Eocen-Oligocen in
age. These rocks have a high Fe-Ti oxide mineral contents (titanomagnetites and
ilmenites) whose mineralogical and texture characteristics have been studied.
These characteristics have allowed to identify initial oxidation stages of high
temperature phase.
Keywords: trachybasaltic rocks
- titanomagnetites - ilmenites - Mendoza
DELPINO, S.*, BJERG, E.**, FERRACUTTI, G.**, DIMIERI,
L.**, MOGESSIE, A.***, KOSTADINOFF, J.**
*
Departamento de Geología-UNS. San Juan 670- B8000ICN Bahía Blanca-Argentina.
E-mail: sdelpino@criba.edu.ar
** CONICET - Departamento de Geología-UNS. San Juan 670- B8000ICN Bahía
Blanca-Argentina.
*** Institute of Mineralogy and Petrology, Karl-Franzens University Graz,
Graz-Austria.
ABSTRACT: UPPER-AMPHIBOLITE FACIES MYLONITIZATION OF
MAFIC-ULTRAMAFIC ROCKS AND GNEISSIC-MIGMATITIC COUNTRY ROCKS, SIERRAS DE SAN
LUIS, ARGENTINA: IMPLICATIONS IN THE REMOBILIZATION OF ORE SULFIDES. Around
mafic-ultramafic bodies of the Sierras de San Luis Central Block, a shear zone
several kilometers wide was developed. Several authors have partially studied
the mylonitic rocks as part of petrologic and/or structural works, but a great
controversy exists among them linked to the timing and metamorphic grade at
which this event occurred. On the other hand, a post-magmatic remobilization of
sulfides±PGM of mafic-ultramafic rocks has been proposed in previous works. In
the present contribution the attention is focused on the mylonitic deformation
affecting mafic-ultramafic intrusives and their gneissic-migmatitic adjacent
country rocks, both previously metamorphosed within the granulite facies.
Physical conditions of deformation are evaluated through minerals deformation
mechanisms, the construction of a suitable petrogenetic grid and internally
consistent geothermobarometry. Considered together, deformation mechanisms in
mafic-ultramafic (ol, opx, hbl and pl) and gneissic-migmatitic (pl, kfs and
qtz) country-rocks, indicate a ductile behavior characteristic of very
high-temperature deformation. The stability field for the country-rock mineral
association in equilibrium during the mylonitization (Pl+Qtz+Kfs+Grt+Bt+Sil),
indicate thermal conditions of deformation within the upper-amphibolite facies.
Internally consistent geothermobarometry applied to this association in
equilibrium with an H2O+CO2 fluid phase, constraints the conditions of
deformation within the range 668-762 °C and 6.3-6.9 Kb at 0.29<XCO2<0.72.
Textural relationships in mylonites (distribution along foliation planes and
crystallization within porphyroclast extension sites) clearly indicate that
primary magmatic sulfide of mafic-ultramafic rocks, were remobilized during the
mylonitic event. On the base of the obtained results and previous works in the
area, a general discussion about the mylonitic event and related processes is
raised.
Keywords: Sierras
Pampeanas-mylonitization -P/T conditions-sulfides-remobilization
DOMÍNGUEZ, Eduardo* y SILLETTA, Ariel**
*
Departamento de Geología, Universidad Nacional del Sur; CONICET. E-mail:
edomin@criba.edu.ar
** Departamento de Geología, Universidad Nacional del Sur. E-mail:
arielsille@hotmail.com
ABSTRACT: TRACE, RARE EARTH ELEMENTS AND ISOTOPES IN THE
KAOLINITE GENESIS DETERMINATION: THE LOMA DEL PIOJO DEPOSIT, PROV. DE BUENOS
AIRES, ARGENTINA. In a vertical profile at the Loma del Piojo Kaolin deposit,
the distribution of some trace and rare earth elements has been studied to
verify their usefulness in understanding the origin of the clays. Chemical
analysis were made on six samples that represent the alteration from the
surface to a depth of 29 m. High contents in REE are found in the superficial
samples whereras the intermediate and deepest samples have lower REE contents.
The relationship La/Yb does not show any meaningful variation. An enrichment of
REE with Ce and Nd highs is observed in the superficial and the more altered
samples. The Winchester and Floyd (1977) graph is found useful for defining the
argilized rock, while on the Dill et al., (2000) graphs only two samples fall
within the supergenic kaolin field. The rest of the samples fall outside the
classification limits. The d 18 O‰ 18,8 to 20,0 and d D‰ -62 to -
78 isotopes indicate a weathering or supergenic origin for the kaolinite. The
oxygen and hydrogen isotopes are conclusive with respect to kaolinite genesis
whereas conclusions basic on the trace and REE elements should be weighted
carefully.
Keywords: Loma del Piojo
kaolin genesis.
FERRACUTTI, Gabriela* y BJERG, Ernesto*
*
CONICET-Departamento de Geología, Universidad Nacional del Sur, Bahía Blanca,
Argentina.
E-mail: ferracut@criba.edu.ar
ABSTRACT: PGM IN LAS
AGUILAS DEPOSIT, SAN LUIS, ARGENTINA. Several authors have studied the Las
Águilas deposit in San Luis Province, and established that the sulfide
mineralization (pyrrhotite, pentlandite and chalcopyrite) and Platinum Group
Minerals (PGM) are associated with the mafic-ultramafic rocks. But until the
present paper, PGM in the metamorphic basement have not been identified. This
contribution describes the presence of three kinds of PGM in samples from drill
5/4: platinum arsenides, platinum-palladium bismuthotellurides and palladium
bismuthotellurides, present in mafic-ultramafic and in metamorphic rocks from
the Las Aguilas East deposit.
Keywords: PGM, metamorphic,
mafic-ultramafic rocks, Las Aguilas, Argentina.
FOGLIATA, Ana Silvia1,2 y AVILA, Julio César1,2
1Facultad
de Ciencias Naturales e Instituto M. Lillo, Universidad Nacional de Tucumán
2Consejo Nacional de Investigaciones Científicas y Técnicas
E-mail: fogliat@csnat.unt.edu.ar , jcavila@csnat.unt.edu.ar
ABSTRACT: HYDROTHERMAL
ALTERATION OF VIL ACHAY TIN DEPOSIT, CATAMARCA, ARGENTINA. Hydrothermal
alteration played a very important role in the Sn mineralization at Vil Achay
deposit (Sierra de Fiambalá, province of Catamarca). The oldest rocks in the
area are amphibolites belonging to the Fiambalá Gabbro (Ordovician). They are
intruded by El Salto Granite of carboniferous (?) age. The mineralized granitic
dike is hosted by amphibolites. Hydrothermal alteration in the granitic dike
corresponds to albitization and greisenization. The greisen contains varying
amounts of disseminated cassiterite. The following mineral sequence has been
identified: cassiterite, magnetite, wolframite (scarce), chalcopyrite, pyrite,
covellite, chalcosine, hematite, limonite, malachite and azurite. The genetic
sequence can be divided into four stages: granitic dike setting, locally
pervasive albitization, locally pervasive greisenization and mineral
deposition. It is proposed that the deposit is part of a F-rich open greisen
system during the late magmatic hydrothermal stage genetically linked to El
Salto Granite.
Key
words: Sn deposit, hydrothermal alteration, Catamarca.
FRANCHINI, M.B.*, LIRA, R.**, MEINERT, L.***,
POKLEPOVIC, M.F.**, IMPICCINI, A.*, MILLONE, H.A.****
* CONICET,
CIMAR, Facultad de Ingeniería, Universidad Nacional del Comahue, Av. Buenos
Aires 1400 (8300) Neuquén, Argentina. franchini@infovia.com.ar ; aimpicc@uncoma.edu.ar
** CONICET. Museo de Mineralogía y Geología “Dr. A. Stelzner”,
F.C.E.F. y N. Universidad Nacional de Córdoba. Av. V. Sársfield 299, (5000)
Córdoba, Argentina. rlira@com.uncor.edu; fpoklepovic@com.uncor.edu
*** Washington State University, Pullman, Washington; meinert@wsu.edu
**** Gerencia de Minería de Córdoba. Celso Barrios 1665, 5016, Córdoba.
gema@arnet.com.ar
ABSTRACT: ALKALI-
METASOMATISM AND REE MINERALIZATION IN SIERRA DE SUMAMPA, SANTIAGO DEL ESTERO,
ARGENTINA. Albite+aegirine+arfvedsonite+monazite alteration in granite and
marble associated with epizonal, peralkaline and siliceous igneous dikes
(comendites), provide an important example of Na- metasomatism and rare earth
element (REE) mineralization in the Llamapampa area of the Sierra de Sumampa,
SE Santiago del Estero. Early K-metasomatism (microclinization of magmatic
feldspar) occurs in a few granite and comendite outcrops. Two generations of
albite (Ab97.5-99) +aegirine (Ae88.5-96.6) ± Mg-arfvedsonite ± hematite ±
fluor-rich apatite overprint the K-metasomatism and cross cut granite and
commendite in outcrops within an 8 km2 area. Late calcite veins and patches are
ubiquitous. Locally, the Na-rich assemblage becomes pervasive and results in
total destruction of host lithologies. Monolithologic and hetherolithologic
breccias with hydrothermal aegirine and chalcedony matrix are exposed at
granite-marble-comendite contacts. Na- metasomatism in marbles produced banded
and mottled aegirine (Ae96-97.7) ± Mg- arfvedsonite and multiple stages of
secondary carbonates (calcite- Mn and Fe calcite-ankerite-Mn ankerite)
associated with interstitial monazite (Ce>La) mineralization. Minor
hematite, barite, celestine, sulfides (sphalerite, galene, pyrite,
chalcopyrite) and quartz accompany the above alteration. The geotectonic
environment and alteration style of Llamapampa are similar to the REE deposit
at Rodeo de Los Molles, in San Luis province, except that REE mineralization in
the later occurs in britholite-(Ce)+allanite-(Ce) (partially replaced by bastnaesite)
assemblages located within a fenitizied monzogranite.
Keywords:
alkali-metasomatism, fenitization, albitization, comendite porphyries,
REE-mineralization, monacite, Sierra de Sumampa
GALLISKI, Miguel Angel * y ?ERNÝ, Petr**
*IANIGLA,
CRICYT (CONICET), C.C.330 (5.500) Mendoza, ARGENTINA. E-mail:
galliski@lab.cricyt.edu.ar
** Department of Geological Sciences, University of Manitoba, Winnipeg,
Manitoba R3T 2N2, CANADA p_cerny@Umanitoba.CA
ABSTRACT: HAFNIAN ZIRCON
FROM LA ELVIRITA PEGMATITE, NEVADOS DE PALERMO, SALTA. Hafnian zircon from a
rare-element, montebrasite-bismuthinite-microlite bearing pegmatite is studied.
The mineral occur as paralell aggregates of simple {101} bypiramidal crystals
with curved faces (EV2), that include platy albite and manganocolumbite, or
with the same crystal form (EV8) associated with uranmicrolite in the core of
an cm-sized bismuthinite crystal. The zircon crystals are unzoned and crystalline;
its chemical composition show values close to 20 and 15 of HfO2 wt%
respectively corresponding to low temperature magmatic hafnian zircon.
Keywords: Hafnian zircon,
rare-element pegmatite, El Quemado pegmatitic field.
GALLISKI Miguel Angel(1), ?ERNÝ Petr(2),
OYARZÁBAL Julio(3), CHAPMAN Ron(2) and MÁRQUEZ-ZAVALÍA M. Florencia(1)
IANIGLA,
CRICYT (CONICET), Avda A. Ruiz Leal s/n Parque Gral. San Martín, CC330, 5500
Mendoza, ARGENTINA, galliski@lab.cricyt.edu.ar; mzavalia@lab.cricyt.edu.ar
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba
R3T 2N2,
CANADA p_cerny@Umanitoba.CA; chapman@cc.umanitoba.ca
Depto. Geología, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700,
San Luis, joyar@unsl.edu.ar
ABSTRACT: Qingheiite, the
Mg end-member of the wyllieite family of primary pegmatitic phosphates, with a
formula Na2 Na Mn2 Mg2 (Al,Fe)2 (PO4)6 and known so far from only the type
locality, was discovered in a new occurrence and association. It occurs in
Santa Ana mine (32° 53' 32" S y 65° 55' 43" W) in a beryl type,
beryl-columbite-phosphate subtype of rare-element pegmatite. Qingheiite occurs
as ?0.5-cm thick irregular granular veinlets or patches of deep jade-green
color, in a nodule of beusite interlaminated with lithiophilite. The average of
four chemical analysis gives PO4 45.19, Al2O3 5.17, MnO 24.27, FeO 10.05, MgO
6.13, ZnO 0.18, CaO 0.51, SrO 0.02, BaO 0.02, Na2O 9.22, K2O 0.02, F 0.05, Cl
0.01, total 100.84. Assuming the same Fe3+/Fe2+ ratio and partition of cations
as in the type specimen, the formula obtained gives (Na1.767 ~0.226 K0.004
Sr0.002 Ba0.001)å2.000 Na (Mn0.901Ca 0.085 Na0.014) å1.000 (Mg1.423
Fe0.277Mn0.300) å2.000 (Al0.949 Fe3+0.474 Zn0.021 Fe2+0.556) å2.000 (PO4)5.957.
Least-squares refinement of X-ray powder-diffraction data of qingheiite gives a
10.900(2), b 12.420(3), c 6.433(1) Å, ? 97.97 (2)°, V = 862.52(2) Å 3. The host
beusite has the formula (Mn1.733 Fe0.660 Ca0.412 Mg0.123) å2.928 (PO4)2.012 and
a 8.790(3), b 11.475(2), c 6.156(2) Å, ? 99.11 (2)°, V = 613.11(2) Å 3.
Lithiophilite composition is Li (Mn0.511Fe2+0.299Mg0.171) å0.981 (PO4)1.005 and
a 6.063(2), b 10.324(6), c 4.712(2) Å, V = 294.94 Å 3. The Santa Ana
paragenesis is unusual and hybrid among the primary phosphate associations
recognized by Moore and Molin Case (1974) in pegmatites where P and transition
metals are available. In general, triphylite-lithiophilite series tend to
predominate in Li-rich pegmatites, wyllieite and dickinsonite-arrojadite series
are dominant in Na-rich pegmatites, and graftonite-beusite and sarcopside
prevail in Ca-rich pegmatites.
GÓMEZ, Cristina, GARRIDO, Mirta y ALIOTTA,
Guida*
*Departamento
de Geología. UNS. San Juan 670. e-mail: mcgomez@criba.edu.ar
ABSTRACT: PRESSURE AND
TEMPERATURE OF THE HYDROTHERMAL SYSTEM AT THE MOLYBDENUM BEARING QUARTZ VEIN
ELSIREN, AGUA ESCONDIDA, MENDOZA, ARGENTINA. Petrographic and microthermometric
analysis of fluid inclusions at the molybdenum bearing quartz vein El Siren
(Agua Escondida District) were done. Elsiren is located at the SE of the San
Rafael Block (Mendoza). Two types of the microstructures in the quartz vein
were found. In both shattering and recrystallization appeared but in one of
them fluid inclusions could be used for thermometric measurements. In this type
of quartz five kinds of fluid inclusions were recognized. The most abundant
types were: a three-phase ( H2O liquid- CO2 liquid and vapor), two phase (H2O
liquid and vapor) and a subordinate multiphase ( with a solid phase). Fluid
inclusions data indicated that there was neither evidence of fluid
inmiscibility nor of necking down. Minimum temperature of 340 to 380°C and 200
to 400 bars pressure were estimated during quartz formation. The main fluid is
a CO2 - H2O fluid weakly enriched in Mo and the low amount of molybdenite
precipitate was attributed to the lack of fluid inmiscibility.
Keywords: Fluid inclusions
- molybdenite - microstructure of quartz vein
GOMEZ, Silvia E.1, AVILA, Julio.C.1,2 y RUIZ,
Dora L1.
1 Facultad
de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán
2 Consejo Nacional de Investigaciones Científicas y Técnicas
e-mail: segomez@csnat.unt.edu.ar, jcavila@csnat.unt.edu.ar
ABSTRACT: PHYTOGEOCHEMICAL
PROSPECTION IN SIERRA DE NARVÁEZ, TUCUMÁN. A phytogeochemical and
lithogeochemical prospection for Zn, Rb, Cs y Li was perfomed in metamorphic
and granitic rocks in Sierra de Narváez, southwestern Tucumán. Two kinds of
plant species were sampled, one belonging to the Betulaceae family and the
other one to the Poaceae family. A good correlation for Zn and Li between
phytogeochemical and lithogeochemical profiles was found. The results suggest
that the plants selected could be useful for mineral prospection.
Keywords:
Phytogeochemistry, lithogeochemistry, Narváez hill, Tucumán
GONZÁLEZ CHIOZZA, Sebastián*, Wiechowski,
Annemarie** y BRODTKORB Milka K.de
*
Departamento de Ciencias Geológicas, FCEN, Universidad de Buenos Aires.
sebas@gl.fcen.uba.ar
** Institut für Mineralogie und Lagerstättenlehre. RWTH Aachen, Alemania.
wiechowski@rwth-aachen.de
*** CONICET - Universidad de Buenos Aires. milkabro@gl.fcen.uba.ar
ABSTRACT: mineralogycal
determinations within the sulphide phase at distrito Minero Cerro áspero,
sierras pampeanas de Córdoba. The mineralogy of the sulphide-rich late
mineralizing phase at Distrito Minero Cerro Áspero is updated. Reflected light
microscopy combined with electron microprobe analysis have been used to
determine the presence of altaite, wittichenite, miharaite and stannoidite
within the sulphide assemblage of the district. Chemical analyses by electron
microprobe are reported.
Keywords: Cerro Áspero -
altaite - wittichenite - miharaite - stannoidite
GUIDO, Diego
CONICET -
Instituto de Recursos Minerales (INREMI) - E-mail: inremi@infovia.com.ar
ABSTRACT: SILVER
HALOGENIDES IN EPITHERMAL VEINS OF THE SOUTHEAST DESEADO MASSIF. This paper
communicates the finding of silver halogenides in the Au-Ag epithermal quartz
veins from the Cerro Moro and Buena Esperanza prospects, in the southeastern
Deseado Massif. The minerals are chlorargyrite (AgCl), iodargyrite (AgI) and
chlorargyrite-bromoargyrite solid solution (Ag(Cl0,75;Br0,25)) and they were
detected by electron microprobe studies. This mineralogy occurs in the oxidized
argentiferous veins from the southeastern Deseado Massif. It is typical of
oxidized portions of silver deposits and could be present in similar epithermal
veins of the Deseado Massif.
Keywords: Silver
halogenides - epithermal deposits- Deseado Massif.
GUIDO, Diego1 y LÓPEZ, Ramiro1
1:
Instituto de Recursos Minerales (INREMI) - Calle 47 Nº 522, La Plata. E-mail:
inremi@infovia.com.ar
Consejo Nacional de Investigaciones Científicas y Técnicas de la República
Argentina (CONICET)
ABSTRACT: STRUCTURAL AND
GEOCHEMICAL STUDY FROM DEL DIQUE VEINS, BUENA ESPERANZA AREA, SOUTHEAST DESEADO
MASSIF. The Buena Esperanza area is an epithermal low sulfidation occurrence from
the southeastern Deseado Massif. It is located in the south part of a
NW-oriented horst (Leonardo’s Horst) and contains 18 quartz veins mainly
hosted in La Golondrina Formation sandstones. Nine of these quartz veins belong
to the Del Dique vein group and they have the most important precious metal
anomalies. These veins, characterized by very poor outcrops and mainly
consisting of floats (aligned fragments) of quartz veins, were mapped in detail
and structural and geochemical studies were carried out in order to understand
its behavior and predict the economical potential. Three directions (NNW, N5º
and ENE) of fracturing and mineralization and its kinematic has been inferred
from the detailed mapping. They are coincident with Buena Esperanza regional structure,
in agreement with the extension produced during the opening of the South
Atlantic Ocean by the end of Jurassic. Detailed geochemical studies allow to
argue that fluid flow moved mainly from the edges (1 and 3 veins) to the Main
Structure (2 and 9 veins), with three main concentrations zones (ore-shoots):
the north, south and center of the Main Structure.The center and the edges of
the Main Structure, specially in the fracture intersections, are highly
prospective by concentration of low temperature (Au-Ag) metal precipitation.
Also, potential to find Au-Ag bonanza mineralization in the Del Dique veins is
inferred by the proximity with the La Golondrina and Bahía Laura volcanics
unconformity and by the ore-shoot morphologies. The methodology proposed here
could be applied to this type of “float veins”, very common in
Deseado Massif auroargentiferous province, where other type of studies
(mineralogical and quartz textures) do not show important variations.
Keywords: epithermal veins
- geochemistry - structure - Deseado Massif.
IDOYAGA, Marcelo G.*, PUCCIARELLI, Diego M.**,
JUAREZ, Pablo D.** y GALVAN ALBERTI Leonardo**
* UBA,
Dpto Cs. Geológicas. marcelogi@sinectis.com.ar
** INTEMIN, CIGA. dmpucciarelli@yahoo.com.ar
ABSTRACT: HYDROTERMAL
ALTERATION IN ESTANCIA SAN ANTONIO (Santa Cruz Province, Argentina). A
petrografic study of the geologic unities and the characterization of the
alteration minerals in Estancia San Antonio are here presented. Tuff, andesites
and traquiandesites of the Bajo Pobre Formation, and ignimbrites of the Chon
Aike Formation show intense alteration and quartz-hematite-adularia-calcite
epithermal mineralization in veins, stockworks and hidrothermal eruption
breccias of the low sulfidation style. A broad argillic alteration area is
zoned outward to illite/sericite, illite/smectite, and smectite, with
increasing distance from the breccias. Silicified ignimbrites horizon is
believed to be generated in or inmediatly below the paleo-water table.
Acid-stable minerals as kaolinite, intimately associated with cristobalite,
dickite and natrojarosite, are formed as a late stage steam-heated alteration
overprinted to the shallow low-sulfidation environment.
Keywords: hydrotermal
alteration - epithermal - low sulfidation
IDOYAGA, Marcelo G. *, SCASSO, Roberto A. *,
LOPETRONE, Ernesto J. **
*
Universidad de Buenos Aires. marcelogi@sinectis.com.ar - rscasso@fcen.uba.ar
** YPF - REPSOL
ABSTRACT: MINERALISED
STRUCTURES IN THE CERRO CONTINUACION, AND HYDROTHERMAL ALTERATION ZONES IN
BYERS PENINSULA, LIVINGSTON ISLAND, SOUTH SHETLAND, ANTARTIDA. Sulfide
mineralization and hydrothermal alteration are analyzed in relation to the
tectonic - geological environment. Tectonic breccias hosted by Jurassic-Cretaceous
marine sedimentary rocks shown pyrite, sphalerite and iron oxides in quartz and
carbonate gangue, and zinc values up to 5053 ppm. Layers of anoxic black
mudstones are shown remplacements by diagenetic pyrite. Alteration assemblages
are also present in several areas. The genesis occurs during the evolution of a
backarc basin with subduction zone variable in the time, with volcanic activity
related to intermediate magmas, between tholeiitic islandic arc and
calcoalcalic magmas, since upper Jurassic to upper Tertiary.
Keywords: Livingston,
Byers, mineralization, zinc, anomalies, hydrothermal, alteration
IMPICCINI, Agnes*, Franchini, Marta*,
Schalamuk, Isidoro B.A. ** y Meinert, Lawrence***
*CONICET,
CIMAR, Facultad de Ingeniería, Universidad Nacional del Comahue, Av. Buenos
Aires 1400 (8300) Neuquén, Argentina. aimpicc@uncoma.edu.ar;
franchini@infovia.com.ar
** CONICET, INREMI, Facultad de Ciencias Naturales, UNLP. Argentina.
ischala@infovia.com.ar
*** Department of Geology, Washington State University, Pullman, WS.
meinert@wsu.edu
ABSTRACT: MINERALOGY AND
CHEMICAL COMPOSITION OF PHYLLOSILICATES IN THE CAMPANA MAHUIDA PORPHYRY CU
DEPOSIT, NEUQUÉN, ARGENTINA. Phyllosilicates from different zones in the
Campana Mahuida porphyry copper deposit have been analysed by electron
microprobe analysis in order to understand spatial variations in mineral
composition within the porphyry Cu alteration zones. The Campana Mahuida
deposit is characterized by a central chlorite zone superimposed on the
potassic core, and peripheral illite and smectite zones within the phyllic
halo. In the chlorite zone, the chlorite octahedral cations vary between 11.2
and 12.19 per O20 (OH)16 formula unit and the tetrahedral cation composition is
between (Si7Al1) and (Si4.6Al3.4) with an overall composition of (Al1.9-2.5 Mg
6.3-7.2 Fe2+ 2.3-3.2 ) (Si5.3-5.8 Al2.2-2.7) O20(OH)16. Thus, all are typical
trioctahedral chlorites. Based on the Fe/Fe+Mg+Mn and Si contents, they are
classified as Fe-Al clinochlore and Fe-clinochlore. The chlorite zone formed by
destruction of hydrothermal biotite due to a K activity decrease, although
chlorites have more Mg and less Fe than biotite. Surrounding the central
potassic > chlorite zone is a phyllic zone dominated by illite
(K1.2-1.9Na0.1 (Al3.3-3.9Fe0.1Mg0.02)Si5.9-7.3Al0.7-2.1) O20(OH)4. Illite from
vein centers and vein selvages has a composition close to muscovite, whereas
disseminated illite in altered protholiths contains more Mg and Fe cations in
the octahedral sites. A smectite-rich zone [(Al2.8-3.5 Mg0.3-0.9 Mn0-0.7Fe0-0.6
Ti0-0.1)](Si7.3-7.9 Al0.1-0.7) O20(OH)4 (Ca,Na,K)0.2-1.4] occurs in the phyllic
halo to the N and NW of the chlorite zone. Based on the structural formula,
this smectite is of the aluminum montmorillonite-beidellite dioctahedral
series. For these smectites, more than half of the charge originates in octahedral
sites, with divalent cations, thus they are properly classified as
montmorillonite. Surficial samples of this clay are Al-rich and interlayer
cation depleted compared to montmorillonite from deeper zones. This likely
resulted from intense leaching at low temperatures as is typical of a supergene
environment.
Keywords: porphyry copper,
hydrothermal alteration, illite, montmorillonite, chlorite
KOSTADINOFF, José*, BJERG, Ernesto*, RANIOLO,
Ariel** y SANTIAGO, Emiliano***
*Consejo
Nacional de Investigaciones Científicas y Técnicas - Universidad Nacional del
Sur - Departamento de Geología, San Juan 670, 8000 - Bahía Blanca - E-mail:
gfkostad@criba.edu.ar
**Consejo Nacional de Investigaciones Científicas y Técnicas - Universidad
Nacional del Sur - Departamento de Ingeniería, Alem 1253, 8000 - Bahía Blanca
***Universidad Nacional del Sur - Departamento de Geología, San Juan 670, 8000
- Bahía Blanca
ABSTRACT: GEOPHYSICAL
ANOMALIES IN THE EASTERN SECTOR OF CANTANTAL AND GUAYAGUAS RANGES, SAN LUIS AND
SAN JUAN PROVINCES. There are no outcrops of the ultrabasic rocks of the
Sierras de Valle Fértil and La Huerta to the south of this mountain range. In the
Sierras de Cantantal and Guayaguas most of the outcropping units are
sedimentary rocks of Mesozoic age with scarce or absent ultrabasic rocks. Two
equipotential methods, gravimetry and magnetometry allowed us to recognize the
continuity of these rocks in the plains but displaced 20 km to the East of the
Sierras de Cantantal and Guayaguas. The size of these ultrabasic bodies which
do not crop out is consistent with the recognized units in the Sierras de Valle
Fértil and La Huerta. Their identification means that these rocks are extend
from 31º 28’ S (Marayes locality, San Juan) 32º 15’ S (in San Luis
province).
Keywords: Geophysical
exploration-ultramafic rocks-structure-Guayaguas and Cantantal ranges
LAGORIO, Silvia Leonor*
*
Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, 1428, Buenos
Aires, lag@gl.fcen.uba.ar
ABSTRACT: CLINOPYROXENES
FROM THE ALKALINE CRETACEOUS VOLCANIC ROCKS OF THE SIERRA CHICA OF CÓRDOBA:
THEIR IMPORTANCE IN THE MAGMATIC EVOLUTION INTERPRETATION An optical and
chemical study of the clinpyroxenes from the alkaline rocks of the Sierra Chica
of Córdoba has been carried out. Clinopyroxenes classify as diopside and
augite, with more than 40% Wo, according to the alkaline nature of these rocks.
Nevertheless, the majority of them are not titaniferous, with Ti/Al < 0,5.
Mg contents of clinopyroxenes are high, even in those which belong to the more
evolved rocks, so that a clear fractionation trend parallel to the
diopside-hedenbergite join, typical of alkaline series, is not shown. Textures
involving resorption and reaction with the liquid by some phenocrysts, together
with chemical anomalies indicate frequent mixing between batches of magma.
Specially, the increase of Mg from the rim of the phenocrysts to the groundmass
microlites suggests recharge with more primitive magmas. Also, liquid
immiscibility is attested by the presence of little ocelli in some samples,
mainly formed by aegirinic clinopyroxene and alkaline felsic phases.
Differentiation processes would have taken part under relative low pressures
(<10 kb), in accordance with the AlVI contents (? 0,1). Si, Al and Ti contents
and ratios fall in the compositional fields of clinopyroxens of other potassic
alkaline provinces as Paraguay oriental and the Roman Region (Italy).
Keywords: Córdoba - Sierra
Chica - Cretaceous - alkaline basalts - clinopyroxenes
LAZARTE, José E. (1)
(1):
Facultad de Ciencias Naturales e Instituto Lillo, CONICET,.Miguel Lillo 205,
(4000) Tucumán.
ABSTRACT: MINERALIZED BASIC
DIKES AT ALTO DE LA MINA, CATAMARCA, ARGENTINE. Basic dikes mineralized with
Pb-Zn-Cu sulfides (galena, sphalerite, chalcopyrite, pyrite) -DBM- and quartz
veins occur at the Alto de la Mina, Catamarca. The geology is constituted by
pretectonic granitoids (Chango Real Formation, Cambrian?), intruded by specialized
granites (Papachacra Granite, Carboniferous?). There are also barren dikes
(DBE) and veins with wolframite and minerals of Bi near the granite -
ortogneiss contact. Generally the deposits and polimetallic mineralizations of
the Alto de la Mina are considered the product of hydrothermal activity related
to the Stock El Portezuelo (Papachacra Granite), on the basis of petrographic
and geochemical information. This paper deals with new geochemical evidence
that indicates the presence of two types of mineralization, therefore a basic
magmatic source for mineralizer solutions is considered for DBM dikes.
Keywords: geochemistry,
polimetallic mineralization, Pampean Ranges.
LIRA, Raúl *, ORLANDI, Paolo **, DORAIS,
Michael J. *** y MILLONE, Hugo A. ****
* Museo de
Mineralogía y Geología “Dr. A. Stelzner”, U.N.C.- CONICET.
rlira@com.uncor.edu
** Dipartimento di Scienze della Terra, Università Degli Studi di Pisa, Italia.
orlandi@dst.unipi.it
*** Department of Geology, Brigham Young University, Provo, Utah, USA.
mjd@geology.byu.edu
**** Gerencia de Minería de Córdoba. gema@arnet.com.ar
ABSTRACT : REDDISH BROWN
EPIDOTE FROM CERRO DE LOS BURROS PORPHYRY, SIERRA NORTE RANGES, CÓRDOBA PROVINCE,
ARGENTINA. Moderate reddish brown epidote, easily mistaken in the field for
grossular, was identified in mylonitized porphyries from Sierra
Norte-Ambargasta ranges, near Puesto de los Caminos (29º 45´ 41,3´´ S; 64º 07´
13,9´´ W). Vein and nodular styles of epidotization are frequently found
affecting a dacite-rhyolite porphyry. Epidote-quartz nodules (@ 2 to 6 cm long)
are elliptically shaped and compositionally zoned. Four main zones are
distinguished from outer unaltered porphyry towards nodule center; zonation is
characterized by an increasing degree of replacement of porphyry phases by
fine-grained assemblages of greenish and yellowish members of the epidote -
clinozoisite series, quartz, sericite, clay and opaque minerals. Drussy
crystals of reddish brown epidote, scarce fibrous Ca-amphibole and minor
titanite occur at the nodule core, included in anhedral quartz and minor
vug-filling calcite. Reddish epidote occurs in crystals up to 3 mm long, in
parallel and irregular associations. Identified forms are: { 0 0 1 }, { 1 0 0
}, { 2 0`1 }, { 1 0`1 }, { 0 1 1}, and {1 1 0}. Some crystals show patchy color
zoning along the b-axis, from yellowish green to reddish brown. Moderate
pleochroism varies from light pink to yellowish green. Backscattered electron
scanning and microprobe analyses show no compositional zoning. Average of five
analyses yielded (in wt. %): SiO2: 37.19, TiO2: 0.076, Al2O3: 23.66, CaO:
23.43, MnO: 0.39, Fe2O3 (T): 13.00, absence of MgO and negligible percentages
of La2O3 (0.03) and Ce2O3 (0.01), which are within known ranges for epidote
s.s. Cell parameters computed from x-ray powder patterns are (in Å): a= 8.893
(s= 0.003), b= 5.635 (s= 0.002), c= 10.161 (s= 0.004), b= 115.39º (s= 0.03),
cell volume= 460.1 Å3 (s= 0.2). These unit cell dimensions are highly similar
to those of typical epidote; b is slightly lower and c is higher than
equivalent parameters of piemontite. The low MnO contents of reddish epidote
(0.31 to 0.52 wt. %) do not substantially influence the unit cell dimensions.
The infrared spectrum is identical to that of epidote s.s. confirming the
identity of the mineral species. Average of total Fe from microprobe data (as
Fe+3= 0.78 a.p.u.f.) is in good agreement with Fe+3 computed from the infrared
spectra (Fe+3= 0.73 a.p.u.f.). The origin of the red color remains unrevealed.
Keywords: red epidote-
epidote replacement- mylonitic dacite-rhyolite porphyries- Sierra Norte-
Córdoba.
LOGAN, M. Amelia V. de*, BRODTKORB, Milka K.
de** y SUREDA, Ricardo J.***
*
Smithsonian Institution, Washington, USA. E-mail: logan.amelia@nmnh.si.edu
** CONICET - Área de Geología Económica - FCEN - UBA, Argentina. E-mail:
milkabro@gl.fcen.uba.ar
*** CONICET, Cátedra de Mineralogía - Universidad Nacional de Salta, Argentina.
E-mail:rjsureda@unsa.edu.ar
ABSTRACT: BOURNONITE FROM
LA CONCORDIA MINE, LOS ANDES, SALTA. The composition of bournonite from the La
Concordia vein, Los Andes department, Salta province (24º12’ S -
66º24’W) was determined by EMPA. This mineral commonly shows a zonal
distribution of Sb, As, Ag and Pb within the bournonite-seligmannite series of
the crystal structure. The isostructural group shows two diadochic mechanisms
that give rise to substitutional and interstitial solid solutions between Sb-As
and Ag-Pb. Tabular, short prismatic and twinned on {110} idiomorphic crystals,
up to 7 mm, have been found in quartz-druses at 5th, 6th and 7th mining levels
of the La Concordia mine.
Keywords: Bournonite, La
Concordia mine, Salta.
LÓPEZ, Katthy*, BOTTO, I. Lía** y ETCHEVERRY,
Ricardo***
*DAAD,
Deutscher Akademischer Austausch Dienst German e INREMI-UNLP.
inremi@infovia.com.ar
**CEQUINOR, Centro de Química Inorgánica, Facultad de Ciencias Exactas - UNLP.
botto@quimica.unlp.edu.ar
***INREMI Instituto de Recursos Minerales, FCNyM-UNLP. retcheve@museo.fcnym.unlp.edu.ar
ABSTRACT: GEOLOGY
MINERALOGY OF CLAY MINERALS, BUENOS AIRES PROVINCE ARGENTINA. Clay minerals
production in Sierras Septentrionales of Buenos Aires Province is very
significant (2.300.000 to 3.000.000 tn/year). These minerals are used in the
manufacture of ceramic, refractary materials, etc. Clay deposits are seated
within the sedimentary coverage of Tandilia System over the igneous-metamorphic
basement called Complejo Buenos Aires. The studied area, located at the south
of Tandil city, involves La Rosalía, San Eduardo and Sierra de Los Barrientos
ranchs. The lithology survey description and sampling of pelitic beds were done
in order to analyze the clays physicochemical and mineralogical
characterization. Samples were studied by means of X-Ray diffraction, scanning
electron microscopy (SEM-EDAX), FTIR spectroscopy and thermal analysis.
Kaolinite, illite, quartz, feldspar, goethite and hematite minerals have been
identified in pelitic beds of the studied area. The lithology and the
mineralogical characteristics allow a preliminary comparison with precambric
pelitic units of Sierras Bayas Group and Ordovician Balcarce Formation,
suggesting a possible homologation.
Keywords: Clay Deposits,
Mineralogical characterization, Tandilia, Buenos Aires Province, Argentina.
MARCHIONNI, Daniela; TESSONE, Mario; DEL
BLANCO, Miguel; CURCI, Marcela y ETCHEVERRY, Ricardo.
*
Instituto de Recursos Minerales, Calle 47 Nº522, La Plata (1900). E-mail:
inremi@infovia.com.ar
ABSTRACT: FLUID INCLUSIONS
STUDY OF SAN PEDRO-LA EVELINA EPITHERMAL MINERALIZATION, MACIZO DEL DESEADO,
SANTA CRUZ, ARGENTINA..In this contribution we present the principal
characteristics of an area with epithermal mineralizations located near to
Estancias San Pedro and La Evelina, in the central part of the Macizo del
Deseado. These mineral veins and veinlets, with high amounts of Mn, Fe, Sb, Tl,
Hg and As, represent an ore type with only a few precedents in this geological
province. The microthermometric analysis of quartz samples indicated salinities
of 0,88 to 2,0 wt % NaCl eq. and temperatures between 135 and 180ºC. The
geochemical, mineralogical and microthermometric study reveal a structurally
high position inside the epithermal system for these deposits.
Keywords: Macizo del
Deseado-Fluid Inclusions-Epithermal Mineralization
MARFIL, Silvina Andrea 1,2, MAIZA, Pedro
José1,3 y PIERONI, Daniel 1
Dpto. de
Geología. Universidad Nacional del Sur. San Juan 670. 8000 Bahía Blanca.
Argentina. TE: 54-291-4595184. email: smarfil@criba.edu.ar.
Investigador adjunto s/d CIC
Investigador principal CONICET
ABSTRACT: MOTTRAMITE -
DESCLOIZITE OCURRENCE IN THE SE OF LOS MENUCOS KAOLIN DEPOSIT (Prov. of Río
Negro). A mineral of the mottramite-descloizite series from the Blanquita
deposit (Los Menucos, Province of Río Negro), was studied by means of X-ray
diffraction, petrographic microscope and SEM-EDX analysis. The mineral occurs
as well developed transparent crystals with bright yellow colours and yellowish
surficial films. The kaolinic mineralization in Blanquita quarry occurred
within the Sierra Colorada Formation (riolitic tuff).
Keywords: Mottramite -
descloizite - kaolin
Mas, Graciela1; Bengochea, Leandro1 y Lastra
Fabián 2
1
Dpto.Geología. UNS - CONICET. San Juan 670. 8000 Bahía Blanca;
gmas@criba.edu.ar; lbengo@criba.edu.ar
2 M.Moreno 674, 8340 Zapala; Prov. del Neuquen; adryfa@zapala.com.ar
ABSTRACT: Fibroferrite from
La MEJICANA MINE, ARGENTINA. The occurrence of fibroferrite in the San Pedro
vein, la Mejicana mine, Argentina is reported. The mineralogical
characteristics of this hydrated basic ferric sulphate has been studied by
means of optical microscopy, X ray diffraction, thermal gravimetric analysis,
scanning electronic microscopy and EDS analysis.
Keywords: fibroferrite, La
Mejicana.
Mas, Graciela 1, Peral, Hebe2 y Bengochea,
Leandro1
1 Dep. de
Geología; UNS. CONICET. San Juan 670; 8000 Bahía Blanca. gmas@criba.edu.ar;
lbengo@criba.edu.ar
2 Dep. de Geología; Universidad Nacional del Sur. San Juan 670; 8000 B. Blanca.
hperal@criba.edu.ar
Abstract: Triplite from
Cerro Blanco, Córdoba, Argentina: triplite or zwieselite? A mineralogical
research into the isomorphic series triplite-zwieselite of the Cerro Blanco
pegmatite, using the classical methods of identification by X-ray diffraction,
optical microscopy and wet chemical analysis, was performed with the aim of
revealing the identity of this phosphate, which seems to be an intermediate
member of the series. Triplite is a common accessory mineral in the Sierras
Pampeanas pegmatites of Córdoba, San Luis, La Rioja and Catamarca provinces,
and is very conspicuous in the El Gaucho and El Criollo quarries of the Cerro
Blanco, Córdoba.
Keywords: Triplite, zwieselite, Cerro Blanco
MONTENEGRO, Teresita* y BRODTKORB, Milka K.de *
*CONICET-Universidad
de Buenos Aires, mon@gl.fcen.uba.ar; milkabro@gl.fcen.uba.ar
ABSTRACT: FLUID INCLUSIONS
IN SPHALERITE FROM EL RECUERDO, PROVINCE OF SALTA. Fluid inclusions studies
were carried out in sphalerite from El Recuerdo vein, Concordia District. All
cavities have two-phase (L+V) fluid with H2O+NaCl composition. V/L ratios are
constant between 20 and 30%. The salinity is low to moderate, between 1,5 and 9
equiv. wt% NaCl. Homogenization temperatures in sphalerite fall within the
range of 156-223°C and are consistent with those in gangue quartz. These
temperatures are minimun precipitation temperature of the sphalerite but the
real temperature is not higher. Salinity and temperature are characteristics of
fluids in epithermal deposits.
Keywords: fluid inclusions - sphalerite - epithermal deposits
MOREIRA, Pilar*; FERNÁNDEZ, Raúl**; MONDELO,
Roberto***; SCHALAMUK, Isidoro**** y ETCHEVERRY, Ricardo*****
*Instituto
de Recursos Minerales-CONICET. Calle 47 Nro 522 (LP). pilimoreira@yahoo.es
**Instituto de Recursos Minerales-CICBA. Calle 47 Nro 522 (LP).
rfernand@infovia.com.ar
***FOMICRUZ (Fomento Minero Provincia de Santa Cruz). Alberdi 643 (Rio
Gallegos).
****Instituto de Recursos Minerales-CONICET. Calle 47 Nro 522 (LP).
***** Instituto de Recursos Minerales-CONICET. Calle 47 Nro 522 (LP).
ABSTRACT: MINERALOGICAL
CHARACTERISTICS FROM “VETA NORTE” AREA. LA JOSEFINA DISTRICT. SANTA
CRUZ PROVINCE. La Josefina District is defined as a low sulfidation type
epithermal mineralization. The hipogenic assemblage is composed of
arsenopyrite, pyrite, chalcopyrite, sphalerite and galena with freibergite
inclusions within quartz, chalcedony and adularia gangue minerals. Overprinting
the hipogenic assemblage, oxidation processes have taken place that removed the
gold from the sulfides and have redeposited it as relatively coarse secondary
high purity gold. Subtile variations of chemical composition of sulfides has
been detected.
Keywords: mineralogy,
epithermal mineralization, Au, Santa Cruz
MUTTI1, D.I., GÓMEZ1, A., RIVEROS2, C. y
SCAVUZZO2, V.
1
Universidad de Buenos Aires, Departamento de Cs. Geológicas,
muttix@gl.fcen.uba.ar
2 Cerro Vanguardia S.A., criveros@cvanguardia.com.ar
ABSTRACT: ACTUAL HOT
SPRINGS IN SOUTH WEST CERRO VANGUARDIA MINING DISTRICT, SANTA CRUZ PROVINCE,
ARGENTINA. The purpose of the present contribution is to communicate the
discovery of an active hydrothernal spring related to travertine accumulation
located in south west square of Mine Concession of Cerro Vanguardia.
Hydrochemistry study reveals that these are alkaline waters rich in Na-Cl-HCO3;
with a pH of 8,12 and an average contents of Ca, Mg, K and SO4, with minorities
concentrations of Li, Br, Rb, Sr, Y, Zr, Mo, Cs, Ba, As, Mn, Fe, Cu, Zn, Ti,
Sc. These active hot springs can spill around 1liter/minute of alkaline brines
(Cl + HCO3 > SO4) solid residues of 8152 mg/Kg. Main characteristic above
mentioned would allow us to homologate this hot spring to the mentioned in
Bilran (Filipinas) and Broadlands (New Zealand). All of given information would
support the first hypothesis about the presence of an active convective
hydrothermal cells in the Deseado Massif, in Santa Cruz Province.
Keywords: Macizo del
Deseado- hot springs- Quaternary
MUTTI, Diana Irene*, IGLESIAS, Sheyla Elian* y
GONZÁLEZ CHIOZZA, Sebastián*
*
Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales.
Universidad de Buenos Aires. muttix@gl.fcen.uba.ar
ABSTRACT: Hydrothermal
Solution Dispersion at Cerro áspero MINING DISTRICT, Province of Córdoba,
ARGENTINE Hydrothermal solution circulation, responsible for ore mineral
deposition and transformations such as changes in porosity and permeability, is
analized at Cerro Áspero Mining District. Alteration patterns, petrological and
structural elements together with geochemical prospective information are used
to model the geochemical in dispersion the district. We propose that mechanisms
of ore deposition are related to later episodes to the Cerro Áspero Batolith
emplacement and have been controlled by high fluid pressure conditions,
multiepisodic extensional stresses and preexisting basement structural
discontinuities.
Keywords: Cerro Áspero ore
deposits - structural controls - geochemistry - hydrothermal solutions
MYKIETIUK, Karina*; GOBBO, Esteban J*. y
FERNÁNDEZ Raúl R**.
*
Instituto de Recursos Minerales, UNLP. CONICET E-mail: mykietiuk@yahoo.com
* Instituto de Recursos Minerales, UNLP. CONICET E-mail: egobbo@sinectis.com.ar
** Instituto de Recursos Minerales, UNLP. CICBA E-mail: rfernand@infovia.com.ar
ABSTRACT: STRUCTURAL
ANALYSES RELATED TO HYDROTHERMAL ALTERATION, ESTANCIA LA ESPERANZA, DESEADO
MASSIF, SANTA CRUZ, ARGENTINA. At Estancia La Esperanza, central part of the
Deseado Massif, the brittle deformation has been studied at different scales in
order to reconstruct the palaeo-stress fields and their relationships with the
epithermal mineralization. The lineaments have been surveyed using a mosaic of
low altitude photographs at scale 1:18000. Additionally, field data from faults
and joints have been obtained from five differents areas: Cerro Tornillo, Cerro
Guanaco, SSW vein structures and two other localities with no hydrothermal alteration.
These results supported a principal stress from the NW. The Au and Ag
mineralization was mainly located at structures oriented N-S.
Keywords: Deseado Massif -
structural analysis - lineaments - epithermal systems.
NILLNI, Adriana Mónica
Universidad
Nacional de la Patagonia San Juan Bosco. Km 4. Comodoro Rivadavia.
adriananillni@yahoo.com.ar
Abstract: Infrared
spectroscopy of epithermal quartz. Cerro Vanguardia, Santa Cruz province,
Argentina. Infrared spectroscopy studies of natural clear quartz and amethyst
from the Cerro Vanguardia District were carried out to analyze the
crystallization of these minerals within epithermal veins. Different zones in
an individual crystal were identified by cathodoluminescence (CL). Blue and
yellow colors (CL), which are not permanent after a few minutes of radiation,
are typical of these zones. Brown colors are typical of microquartz and clear
quartz with zoning and defects. In blue-yellow (CL) types, water is present
principally as a proton joined to an oxygen atom, and related to a cation
(Li+). In brown (CL) varieties, water is present in fluid microinclusions. The
content of H/106Si varies from 750 in the yellow quartz zone (CL) to 4000 in
the blue quartz zone (CL). The limit between the zones has 2000 H/106Si.
Amethyst normally has less than 100 H/106Si. The blue zones have different
contents of aluminum that are attributable to differences in crystallization
velocities and pH, during mixing in the epithermal system. Brown varieties of
quartz represent pulses of boiling.
Keywords: Argentinian Patagonia - epithermal quartz - infrared
spectroscopy
ORMEÑO, Pablo1; WEIDMANN, Nestor2; LANZILOTTA,
Isabel3 y ROSSA, Norma3
1 CONICET.
IIM, Facultad de Ingeniería, UNSJ - ormeno@unsj.edu.ar
2 Departamento de Geología, FCEFyN, UNSJ
3 Departamento de Geología, INGEO, FCEFyN, UNSJ
ABSTRACT: CONTACT MARBLES
IN THE CERRO ALTO LARGO, ULLUM COMPLEX, CENTRAL PRECORDILLERA OF SAN JUAN,
ARGENTINA. The studied area is located in the eastern side of Central
Precordillera, 30 km westward of San Juan. The geology of the area is
characterized by a calcareous and detrital Paleozoic sequence overlied by
Cenozoic rocks and intruded by subvolcanic mesosilicic bodies. Marbles produced
by contact metamorphism, outcrop in the area of cerro Alto-Largo and they are
formed by calcite, wollastonite, garnet, brucite, periclase, chlorites and
pyrite.
Keywords: Contact
metamorphism. Marbles. San Juan Precordillera
OYARZABAL, Julio* and GALLISKI, Miguel Angel***
Cátedra de Mineralogía, Depto. de Geología, UNSL, San Luis, Argentina.
joyar@unsl.edu.ar
** IANIGLA, CRICYY (CONICET), Mendoza, Argentina.
galliski@lab.cricyt.edu.arABSTRACT: COMPOSITIONAL AND STRUCTURAL
CHARACTERISTICS OF K-FELDSPAR AND MUSCOVITE FROM THE LA VISTOSA PEGMATITE, SAN
LUIS, ARGENTINA. La Vistosa is a zoned, almost barren pegmatite located at 32º
56´ 12´´ S and 65º 56´ 56´´ W, 5 km east of Paso del Rey, province of San Luis.
It is placed in a discrete lens of leucogranite in the Totoral LCT pegmatite
field, the southernmost of the Pampean Ranges. The geochemistry of trace elements,
structural state, and cell parameters of the K-feldspar and muscovite studied
from this pegmatite show variations related to (1) the type of pegmatite, (2)
the internal unit of sampling, and (3) the history of crystallization. K/Rb
ratios of K-feldspar vary from ~ 1000 in the parental host-rock to ~ 100 in the
intermediate zone of the pegmatite and, at the same time, Cs varies from 6 to
160 ppm; triclinicity index increases from 0,73 to 0,95 in the same way.
Muscovite shows similar fractionation of trace elements with K/Rb from 129-88
and Cs from 6-2200 ppm and increasing c dimensions in the 2M1 politypes. Both
minerals properly record the different evolution degree of each internal unit
of the pegmatite.Keywords: K-feldspar- muscovite- structural characteristics-
composition- pegmatite- internal evolution
OYARZABAL, Julio*, CADILE, Sebastián* y Jorge
GONZALEZ**
* Cátedra
de Mineralogía, Depto. de Geología, Proy. 349001 CyT, UNSL, San Luis,
Argentina. joyar@unsl.edu.ar
** Instituto de Investigaciones en Tecnología Química (INTEQUI-CONICET-UNSL).
jgonza@unsl.edu.ar
ABSTRACT: MINERALOGIC AND
CHEMICAL CHARACTERIZATION OF THE GYPSUM OF AGÜERO AND LUCIA DEPOSITS,
DEPARTAMENTO GENERAL ROCA, RIO NEGRO, ARGENTINA. The Agüero and Lucía deposits
represent a sequence of different evaporite levels accumulated during the
Maastrichtian-early Paleocene (Allen Formation) located in the Neuquén basin,
southwestern Argentina. The mineralization has been studied and characterized
by several mineralogical and chemical techniques. Due to the high quality and
volumetric concentration of its resources, both mines could be considered like
two of the most important gypsum-bearing deposits of Argentina.
Keywords: gypsum-
characterization- Fm Allen- Agüero and Lucía mines.
PAAR, Werner H.*, TOPA, Dan* y SUREDA, Ricardo
J.**
* Institut
für Mineralogie, Universität Salzburg, 5020 Salzburg, Austria. E-mail:
Werner.Paar@sbg.ac.at
** CONICET, Cátedra de Mineralogía - Universidad Nacional de Salta, 4400 Salta,
Argentina. rjsureda@unsa.edu.ar
ABSTRACT: WATANABEITE,
Cu4(As,Bi,Sb)2S5, AND UNNAMED “Cu3AsS3” FROM CERRO ATAJO, CATAMARCA
PROVINCE, ARGENTINA. Polymetallic ores from Triunfo, one of several
hydrothermal veins at Cerro Atajo, contain abundant sulfosalts. Cerro Atajo is
a subvolcanic deposit and is located in the Farallón Negro mining district,
Andalgalá department, Catamarca province, Argentina (27º18’S -
66º28’W). Watanabeite is a rare constituent in these ores and commonly
associated with aikinite, luzonite, annivite (the Bi-variety of tetrahedrite)
and a compound optically resembling fahlore and chemically representing almost
stoichiometric “Cu3AsS3”. Watanabeite from Triunfo vein is
optically close and chemically similar to the Japanese occurrence, but with an
appreciable amount of bismuth. The ideal chemical formula can be given as
Cu4(As,Bi,Sb)2S5, where As>Bi?Sb, thus representing a Bi-rich variety of
watanabeite. This mineral from the Cerro Atajo epithermal system is the first
mention for Argentina and represents the second world-wide reference of this
very rare sulfosalt.
Keywords: Watanabeite,
epithermal veins, Farallón Negro mining group, Catamarca
PAGE, Stella*,**, LITVAK, Vanesa D.*,** y
LIMARINO, Carlos O.*,**
*Departamento
de Ciencias Geológicas, Facultad de Ciencias. Exactas y Naturales, Pabellón II
Ciudad Universitaria, (1428) Nuñez. Universidad de Buenos Aires.
**Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).
stella@gl.fcen.uba.ar
ABSTRACT: EVIDENCE OF
TERTIARY MAGMATISM IN DIVISADEROS NEGROS WEST OF SIERRA DE VILGO, PROVINCE OF
LA RIOJA. The ultramafic alkaline volcanic rocks from Sierra de Vilgo, province
of La Rioja, are characterized in this contribution. They crop out as small
cones and diques in the south-western margin of the sierra and are mainly
composed of basalts with feldespatoids. This rocks are nefeline-normative, they
belong to the basanite field of the TAS diagram and according to its (Na2O-2) ³
K2O= ratio, they can be classify as sodic. The age of this rocks is considered
tertiary as a result of previous K/Ar studies.
Keywords: Alkaline basalts
- Ocelli - Sierras Pampeanas - Tertiary
PINCHEIRA, M*; DAGNINO, A**; KELM, U*; HELLE,
S*; RODRIGUEZ, M* y HERNÁDEZ, L*
*Instituto
GEA, UNIVERSIDAD DE CONCEPCIÓN. mpinchei@udec.cl
**CODELCO-NORTE, División Chuquicamata. adagnino@chuq.codelco.cl
ABSTRACT: MINERAL
COMPOSITION OF COPPER WAD IN OCCLUDED PATTERNS OF METALLURGICAL SAMPLES FROM
THE EXOTIC DEPOSIT OF EXTENSIÓN NORTE MINA SUR. Samples of metallurgical tests
from the exotic copper deposit of Extensión Norte Mina Sur in Chuquicamata,
including drilling cores, head and waste materials are characterized
geometallurgically by optic microscopy, X ray diffraction, TEM, EMPA-EDAX.
Exotic mineralization which includes crisocolla, atacamite, pseudomalachite,
brochantite and copper wad, was deposited from acidic solution derived from
lateral migration from the leached and supergene enrichment zone of the
Chuquicamata deposits. The microscopic studies show that copper wad is easily
remobilized forming occluded textural patterns in head and waste samples,
filling fractures, cleavages and replacing formerly altered gangue minerals.
Transmission electron microscopy analyses of copper wad show that copper wad
has an amorphous structure intergrown with fibrous phyllosilicates. Electron
probe microanalyses of copper wad revealed also a complex composition with Si,
Cu, Mn, and Fe as mayor and Ca, Na, K, Cl, P, Pb, Zn and Ni as minor elements.
The presence of copper wad occluded in waste samples does not appear to be
negligible since it reaches up to 3% in volume.
Keywords: Exotic copper
deposits, copper wad, geometallurgy
PONS, María J.*, FRANCHINI, Marta B. **,
ETCHEVERRY, Ricardo O.*
*
CONICET-INREMI (FCNyM-UNLP) inremi@infovia.com.ar
** CONICET-CIMAR, Facultad de Ingeniería, Universidad Nacional de Comahue,
Neuquén, franchini@infovia.com.ar
ABSTRACT: SKARN ZONATION
AND FE-MINERALIZATION AT VEGAS PELADAS SKARN, SOUTHWEST MENDOZA, ARGENTINA The
Vegas Peladas Fe skarn is located in the Cordillera Principal of SW Mendoza, in
the Malargüe Thrust Belt. Mineralized skarn exposures show similarities with
typical oxidized Fe skarn deposits worldwide. Skarn formation has particularly
affected silstone intercalated with mudstone and calcareous sandstone of Cerro
Puchenque Formation (lower Jurassic) in the contact with diorite and
gabbro-diorite stock (Los Molles Group; Eocene- upper Miocene). Diorite and
gabbro-diorite stock margins exhibit different grades and types of alterations:
magmatic amphibole, and feldspar patchy and vein replacement by amphibole ±
chlorite ± calcite ± titanite ± magnetita and ortoclase ± epidote ± calcite ±
clay. Along the contacts, replacement of diorite by quartz ± orthoclase ±
epidote pervasive endoskarn overprints the above alteration and may result in
complete destruction of the original igneous texture. The earliest alteration
preserved in the sedimentary protholiths involve recrystallization of the
siltstone, mudstone and calcareous sandstone to fine-grained pyroxene-rutile
hornfels, and subordinate biotite-rutile hornfels; both are pyrrhotite rich.
Hornfels are overprinted and veined by zoned exoskarn of irregular
distribution. An inner garnet-rich zone is exposed at the porphyry contact,
followed by an intermediate pyroxene - garnet rich zone; these prograde skarn
zones are magnetite and sulfide barren. The early retrograde assemblage epidote
± amphibole envelopes magnetite-rich veins and pods that cross cut early
hornfels and skarn zones. Later epidote ± quartz ± ortoclase± pyrite are also
present in minor amounts as late cross cutting veinlets and alteration products
of hornfels and skarn.
Keywords: Cordillera
Principal of Mendoza- Hornfels- Skarn zonation- iron mineralization
PUGLIESE Luis Eduardo (*)VILLAR Luisa María
(**)
(*)
Geólogo Consultor, Avenida Felix Paz 120, 5010, Córdoba, Argentina. E-mail:
imartige@fcq.unc.edu.ar
(**) CONICET SEGEMAR Dirección de Recursos Geológico-Mineros, Argentina, Email:
lvillar@arnet.com.ar
ABSTRACT: PETROLOGICAL AND
GEOCHEMICAL DATA OF THE MAFIC-ULTRAMAFIC LAYERED COMPLEX CERRO LA COCHA,
PROVINCE OF CORDOBA, ARGENTINA. The layered mafic-ultramafic Cerro La Cocha
complex crops out in Sierra Chica, Punilla Department, Cordoba. It is located
in a metamophic complex formed by schists, amphibolites and marbles intruded by
aplopegmatite dykes. The igneous complex is concordant with the regional
structure. It is constituted by an intrincate group of mafic and ultramafic
cumulates with vertical zonation. Ultramafic cumulates with orthopyroxene can
be seen at the bottom of the body; whereas those with ortho and clinopyroxene
are placed at the top; gabbro cumulates crop out in the middle of the lens
placed in the higher topographic levels. The tholeitiic character of this
series is accompanied by conspicuous magnetitite layers, chromite nodules and
lenses. Presence of the all the PGE elements is restricted to the ultramafic
cumulates and is strongly related to the petrographic and mineralogical
composition; mafic cumulates only contains Pt and Pd. The layering is cyclic
and rhyithmic. This body would not belong to the ophiolite sequence of the
Sierra Chica de Córdoba whose parental basaltic magma seems to fluctuate
between ocean floor basalt or island arc sources. It may ,instead, belong to
the called “rift gabbros “.
Keywords: Sierras
Pampeanas, layered ignous complex, PGE
PUTZ, Hubert*, PAAR, Werner H.* y SUREDA,
Ricardo J.**
* Institut
für Mineralogie, Universität Salzburg, 5020 Salzburg, Austria. E-mail:
Hubert.Putz@sbg.ac.at
* Institut für Mineralogie, Universität Salzburg, 5020 Salzburg, Austria.
E-mail: Werner.Paar@sbg.ac.at
** CONICET, Cátedra de Mineralogía - Universidad Nacional de Salta, 4400 Salta,
Argentina. rjsureda@unsa.edu.ar
ABSTRACT: THALCUSITE,
Tl2Cu3FeS4, FROM EPITHERMAL VEINS AT CAPILLITAS MINE, CATAMARCA PROVINCE,
ARGENTINA. Thalcusite, Tl2Cu3FeS4, is reported in an epithermal subvolcanic
vein-type deposit. It was found in bornite-chalcocite-rich samples from old
dumps near the Rosario vein, at the Capillitas mine, Catamarca province,
Argentina (27º21’S - 66º23’W), where it occurs as small inclusions
in bornite and chalcocite. Others associated minerals are tennantite, wittichenite,
and two possibly new germanium phases. Generally, thalcusite forms tabular
grains up to 260 x 35 ?m with a very good parallel cleavage, weak reflection
pleochroism in shades of grey (colour change from pinkish grey to brownish
grey) and strong anisotropism between yellow, yellowish grey and bluish grey
colours. Several polished mineral sections using EMPA were analysed and
thalcusite from Capillitas is close identical with the ideal formula. It is the
first mention of the thallium-copper-iron sulfide for Argentina and the first
world-wide occurrence in an epithermal deposit.
Keywords: Thalcusite,
epithermal polymetallic veins, Neogene Andean subvolcanic ores, Capillitas
mine, Catamarca.
QUENARDELLE, Sonia*, MONTENEGRO, Teresita*,
BRODTKORB, Milka K. de* y FERNANDEZ TASENDE, Jorge**
*Depto. de
Cs. Geológicas (UBA y CONICET) sonia@gl.fcen.uba.ar, mon@gl.fcen.uba.ar,
milkabro@gl.fcen.uba.ar
**Depto. de Geología (UNSL) jrft@mailbox.unsl.edu.ar
ABSTRACT: NEW ALKALINE
BASIC ROCK OUTCROPS IN THE PROVINCE OF SAN LUIS. In the granitic environment of
the Sierra de San Luis was found out three new outcrops of alkaline basic
rocks. They are basanite and trachybasalt and their outcrops suggest that they
would correspond to a single eruption and they would have formed monogenetic
cones but they had not kept up to the present. The petrography and geochemistry
show clearly alkaline characteristics and they make it possible to classify the
rocks as transitional to a potassic serie. Their trace elements and REE
contents allow us to support a low grade of melting from an enriched
lherzolitic mantellic source. On the basis of all these features we infer that
they can correlate with the cretacic basanite and trachybasalt near Las Chacras
town, also in the same granitic environment of San Luis, and they would
represent the influence of the Atlantic ocean opening.
Keywords: alkaline basic
rocks, San Luis, Cretaceous.
QUIROGA, Alicia G.*, RUIZ, Teresita del V.* y
ALONSO, Ricardo N.**
* Cátedra
de Mineralogía - Universidad Nacional de Salta, Argentina. E-mail:
ruiz@unsa.edu.ar
** CONICET, Cátedra de Mineralogía - Universidad Nacional de Salta, Argentina.
E-mail: rnalonso@sinectis.com.ar
ABSTRACT:
HYDROBORACITE CaMgB6O11·6H2O OF APALACHEANA MINE, SIJES, SALTA. The
hydroboracite deposit of the Sijes hill (Los Andes department, Salta province)
contains the largest known reserves of this mineral in the world. Luciano
Catalano discovered hydroboracite in the region around 1925. Hydroboracite is
interlayered with gypsum, claystones, siltstones and tuffs in the lower section
of the Sijes Formation (Monte Amarillo Member). The age of the borate beds is
Late Miocene (6.8 to 6.2 Ma). Generally, hydroboracite occur as massive hard
beds, yellow to white in color, from 0.10 to 1 m thick. In this paper we
introduce a couple of new occurrences of hydroboracite, discovered in the
southern sector of Apalacheana mine. At this point, a 0.30 m bed contains two
different types of habits. One of them occurs as clear to milky crystals up to
1.5 cm long, often forming rosettes, resembling gypsum crystals. The second one
has acicular habit, forming fibrous, fibro radiated and parallels aggregates of
silky luster. The optical and physical properties, XRD, FTIR analytical data
are given. The strongest diffration lines for the prismatic crystals are:
5.771(100), 3.319(77), 6.681(58), 1.912(39) and for the acicular crystals are:
6.702(100), 5.794(99), 3.324(77), 2.438(50). Optical refractive indices: a =
1.520(1), b = 1.534(1), g = 1.569(1). Birefringence: 0.049 for wavelength 589
nm. Biaxial positive. Optic axial angle: 2Vcalc 65º51’. Optical
orientation: X ? c 31º, Y = b, Z ? c 59º. Pleochroism: none, X = Y = Z =
colourless.
Keywords: Hydroboracite,
Borate, Puna, Sijes, Continental evaporites
RAMOS Gabriel A.* y ULACCO José H.*
*Universidad
Nacional de San Luis, Chacabuco Nº 917, 5700 San Luis, Argentina, C. Eléct.:
gramos@unsl.edu.ar, ulacco@unsl.edu.ar.
ABSTRACT: GEOCHEMICAL AND
PETROLOGIC CHARACTERISTICS OF THE LOW GRADE METAMORPHICS AT PASO DEL REY
TUNGSTEN DISTRICT, SAN LUIS, ARGENTINA. The Paso del Rey tungsten district is
located at the low grade metamorphic belt in the southern portion of the
igneous-metamorphic basement (late Proterozoic - early Paleozoic) Sierra of San
Luis, Eastern Pampean Ranges, Argentina. The litology consisting of phyllites,
metapsamites, metapsephites and metavolcanic rocks of the San Luis Formation
and low to middle grade quartz-micaceous schists, situated to the west of this
formation. Rich-garnet quartzites (coticules), metavolcanic rocks and schists
are found in neighbouring scheelite mines. Based on electron microprobe
analyses, the composition of zoned garnets corresponds to almandine and
spessartine. The chemical data of several metasedimentary protolitic rocks and
geochemical analyses would support the genetic relationship between the San
Luis Formation and quartz-micaceous schists. Also an attempt to establish the
possible manganese and tungsten source in the original sedimentary basin is
made.
Keywords: geochemistry,
metamophic rocks, wolfram deposits, San Luis, Argentina
RAMOS COLLORANA, Wilfredo *, MEDRANO, René ** y
FERNÁNDEZ, Raúl R. ***
*
Instituto de Recursos Minerales, FCNyM, UNLP-DAAD, wramoscollorana@yahoo.com
** Empresa Minera San José de Berque, Bolivia
*** Instituto de Recursos Minerales, FCNyM, UNLP-CICBA, rfernand@infovia.com.ar
ABSTRACT: EXPLOTATION AND
PERSPECTIVES OF THE PUEBLO VIEJO MINE (W, Bi, Au, Ag), SOUTHWEST BOLIVIA. The
Pueblo Viejo mine is a tungsten veins deposit and it is emplaced in the Galán
Volcanic Complex (Miocene). The veins have east-west direction, and its
mineralogy is complex. The principal ore mineral is wolframite associated with
pyrite, bismuthinite, hematite, chalcopyrite, cassiterite, Au and Ag species.
Genetically this polymetallic vein type is related with a Miocene subvolcanic
stock. The explotation is in Shrinkage system and there are perspectives for
the continuity of the veins in the deepest levels, currently geologic
resources.
Keywords: Explotación, Mina
Pueblo Viejo, wolframio, suroeste Bolivia
REMESAL, Marcela B. *, CERREDO, María Elena* and TASSONE, Alejandro A. *
* Departamento de Geología,
FCEyN, UBA. Pabellón II Ciudad Universitaria. Ciudad de Buenos Aires.
(cerredo@gl.fcen.uba.ar; remesal@gl.fcen.uba.ar; atassone@gl.fcen.uba.ar)
ABSTRACT: Along the northern shoreline of
Millerand Island a widespread volcanic unit -mainly composed of rhyolithic/
rhyodacitic crystalline and lithic tuffs and andesitic lava flows- rests
unconformably over heterogeneous plutonic rocks of probably Early Jurassic age.
An homogeneous compositionally unit of monzo- and syenogranites intrudes the
volcanics. A set of rhyolite dikes predates granite emplacement. A
compositionally diverse group of mafic dykes represents the final magmatic
activity in this area
Keywords: Millerand Island - Antarctic
Peninsula - volcanic rocks - granites
RIOS, Francisco1; FUZIKAWA, Kazuo1; SCHALAMUK,
Isidoro2-3; de BARRIO, Raúl2; GODEAS, Marta4 y PEREZ, Carlos5
1.
Laboratorio de Inclusões Fluidas e Metalogênese, CDTN-CNEN. Cx. Ps. 941.
30123-970, Belo Horizonte, Brasil.
2. Instituto de Recursos Minerales (FCNyM, UNLP)-CONICET. E-mail:
inremi@infovia.com.ar
3. CONICET
4. Instituto de Geología y Recursos Minerales, SEGEMAR. Av. J.A.Roca 651,
Cap.Federal.
5. Laboratorio Nacional de Luz Sincrotron, Campinas, Brasil.
ABSTRACT: FLUID INCLUSION
STUDIES IN Cu-Au VEINS FROM BAJO DE LA LEONA, SANTA CRUZ: SUPERPOSITION OF
DIFERENT MINERALIZING FLUID SYSTEMS. Fluid inclusions in quartz from different
Bajo de La Leona vein systems which are related to granitic and granodioritic
rocks outcroping in the eastern part of Macizo del Deseado, Santa Cruz
province, were studied. Barren veinlets hosted by leucogranite are similar to
those related to porphyry-type environment. The mineralized (Au) veins in the
same unit are generated in epithermal conditions. The Cu-veins in La Leona Mine
and Schultz vein, related to granodioritic rocks (La Leona Formation), are
generated by another different epithermal system. Therefore, the veins
associated to granite and the La Leona and Schulz epithermal system are
considered as being formed at different depths.
Keywords: Fluid inclusions
- Bajo de La Leona - Santa Cruz
ROMERO, Sonia*, CURCI, Marcela**, DEL BLANCO,
Miguel** y MARCHIONNI, Daniela**
*
Universidad Nacional de Salta, Sede Regional Tartagal. Warnes y Ejército
Argentino. E-mail:sromero@rhnet.com.ar
** Instituto de Recursos Minerales, Calle 47 Nº522, La Plata. E-mail:
inremi@infovia.com.ar
ABSTRACT: MINERALOGY AND
SUPERFICIAL TEXTURES OF SALINAS CHICAS EVAPORITIC DEPOCENTER, VILLARINO, BUENOS
AIRES PROVINCE. Salinas Chicas is a modern continental evaporitic deposit
(salt-pan), located inside a structural basin at - 42 m. It is placed in the
southern region of Buenos Aires Province, 60 km far from Bahía Blanca. Clastic
facies occur in the sand-flat and mud-flat. The salt-pan is composed mainly by
halite, with minor gypsum and glauberite. The NaCl is extracted by
“harvest” method, with a production of 200.000 annual tons. In this
paper, the superficial textures and fluid inclusions of chevron, cornet and
hopper halite-shaped- fabric are described.
Keywords: Salinas Chicas -
salt-pan deposit - halite textures
ROQUET, María Belén* y OYARZABAL, Julio*
*Departamento
de Geología, Proy. 349001 CyT -UNSL-. maber@unsl.edu.ar, joyar@unsl.edu.ar
ABSTRACT: GEOLOGY AND
MINERALOGY OF THE AIDA PEGMATITE, CONLARA DISTRICT, SAN LUIS, ARGENTINA. The
Aida mine is located at 32º 14´ 08´´ S and 65º 39´ 28´´ W, 16 km to the east of
Quines, San Luis, Argentina. This mineral deposit is part of the San
Martín-Cautana group, of the Conlara pegmatite district. The pegmatite is
hosted by the micaschists of medium metamorphic grade; it has irregular shape,
with 400 m longth and 200 m width size in the central segment, N-S strike and
sub-vertical dip. The deposit displays internal zonation, from the margin
inwards is identified: border, wall, intermediate external, intermediate
internal and core zones. Some fracture-filling and replacement units have been
recognized. On the basis of its mineralization, this deposit is a beryl type
pegmatite, and probably a beryl-columbite-phosphate subtype, with LCT
geochemical signature, and a significant economic potential in ceramic
minerals. The structural state of the alkali feldspars of the Aida mine
indicates that they have a full ordered structure, the muscovite samples
analyzed belong to 2M1 polytype.
Keywords: pegmatite -
mineralogy - internal structure - feldspar ordering - muscovite polytypism
RUBINSTEIN*, Nora; CARPIO**, Francisco y
MALLIMACCI**, Hugo
*
Departamento de Geología, Universidad de Buenos Aires. nora@gl.fcen.uba.ar
** SEGEMAR, Delegación Mendoza. segemar_mza@lanet.com.ar
ABSTRACT: THE ALTERATION
ZONE OF CERRO TRES HERMANOS, MENDOZA, ARGENTINA. The alteration zone of cerro
Tres Hermanos, Bloque de San Rafael, Mendoza, is characterized by areas with
intense bleaching in carboniferous quarzites and propilitic alteration in lower
permian subvolcanic rocks. Evidences of potassic alteration related to the acid
lower permian porphyries are also recognized. Close to the alteration out three
base metal veins zone crop. Based on this preliminary data a porphyry type
mineralization model is suggested.
Keywords: Porphyry deposit;
Lower Permian; Cerro Tres Hermanos; Mendoza
† SAULNIER, María Elena y MORELLO,
Orquídea
Comisión
Nacional de Energía Atómica, morello@cnea.gov.ar
ABSTRACT: U-Ta-Nb MINERAL
OF SAN IGNACIO-CUMBRE DE LOS PINOS GRANITE, CATAMARCA-TUCUMAN. This paper
reports the second occurrence in Argentina of uranium-tantalum-niobium oxide
crystals, which are associated to the quartz-muscovite pegmatite of San Ignacio
and Cumbre de los Pinos granites, province of Catamarca and Tucumán. The
mineral was studied by petrographic, XRD and SEM-EDAX techniques. It forms
small, pale yellow to ochre crystals (£ 1 mm) or aggregates that occur among
the pegmatite columbite-tantalite grains and muscovite flakes. The idealized
formula for this species could be: A1-2B2O6(O,OH,F).nH2O. The presence of U
partially (or completly?) oxidized, U4+ to U6+, or (UO2)++, as well as small
amounts of Ca, Al, Fe and Ti, is noteworthy. This mineral is found as an
alteration product of columbite-tantalite.
Keywords: U-Ta-Nb oxide-
pegmatite- granite
TOURN, Selvia Mabel* y VATTUONE, María Elena**
*
Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires,
Argentina. E-mail: selvia@gl.fcen.uba.ar
** Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y
Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos
Aires, Argentina. Ingeis, CONICET. E-mail:elena@gl.fcen.uba.ar
ABSTRACT: NATIVE COPPER AND
CUPRITE IN ASSOCIATION WITH ZEOLITES IN AMYGDALES IN BASALTIC LAVAS, CHAPELCO,
NEUQUEN PROVINCE. Amygdules in basaltic lava flows filled with native copper,
cuprite, zeolites, fluorapophyllite and other minor silicates were identified
at the base of Chapelco Mt., 10 km south of San Martín de los Andes, Neuquen
Province. The geological setting is the western belt of the Andean-Patagonian
Volcanic Province. The volcanics of the Andean Andesitic Series ageing
Paleoceno-Eoceno are represented in the area by mafic lavas mainly composed of
sub-alkaline basalts and basaltic andesites. The metamorphism ranges from very
low grade to low grade reaching the zeolite to prehnite-pumpellyite facies with
some minor greenschist facies. Shear zones of local extension are identified in
the area. Conspicuous alteration due to regional hydrothermal metamorphism
affected the lavas. The secondary minerals fill amygdales and replace the
primary minerals of the original rock. Geochemically, these rocks are
sub-alkaline tending to alkaline tholeiitic basalts with a middle potassium
content. The abundant secondary silicate minerals associated in amygdules with
native copper and cuprite are laumontite, chabazite, fluorapophyllite,
smectites, chlorite, pumpellyite and scarce prehnite. The silicate minerals
were the first minerals to precipitate followed by native copper, which filled
available intergranular spaces mainly in the central part of the cavities. By
weathering, the native copper was replaced by cuprite. The association of
native copper with basaltic lavas is common and widespread, being the Keweenaw
Peninsula deposits the most important from an economic point of view.
Comparison is made between these last deposits and Chapelco occurrences.
Keywords: basaltic
lavas-amygdales-native copper-cuprite-zeolites-Neuquen province
TOURN, Selvia Mabel*, LYONS, Wilfredo ** y
MORELLO, Orquídea ***
*
Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, 1º P., 1428 Buenos
Aires, Argentina. E-mail: selvia@gl.fcen.uba.ar
** Arenales 3022, 6º “24”, 1425 Buenos Aires, Argentina. E-mail:
wlyons@dd.com.ar
*** Comisión Nacional de Energía Atómica, Avda. del Libertador 8250, 1429
Buenos Aires, Argentina. E-mail: morello@cnea.gov.ar
ABSTRACT: THE ORPIMENT FROM
GREAT BRITAIN MINE, AZULCOCHA MINING AREA, PERÚ. In the Great Britain mine,
Azulcocha mining area, Central Andean region of Perú, orpiment was identified.
This mine was intensively mined for Zn and As until the last decade. The
mineral occurs in association with sphalerite, marcasite, pyrite, melnikovite
and realgar, plus other minor sulfides. This paper includes a thorough
description of the orpiment from this locality. It occurs in bright
lemon-yellow foliated aggregates of up to 5 cm in size and perfect {010}
cleavage surfaces horizontally striated due to cristallographic translation
along {001}. Its composition is close to the chemical formula but with an
average content of 1.5% in weight of Cu, giving rise to the structural formula
Cu0.06As1.8S3.14. The anomalous Cu content is attributed to local conditions of
mineral formation.
Keywords: orpiment -
foliated aggregates - Great Britain mine - Azulcocha mining area - Perú.
Vattuone, María Elena1 y LATORRE, Carlos Oscar2
1 Facultad
de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad
Universitaria, CP 1428, Buenos Aires, Argentina. INGEIS, CONICET, Ciudad
Universitaria, E-mail: elena @gl.fcen uba.ar
2 Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad
Universitaria, CP 1428, Buenos Aires, Argentina. INGEIS, CONICET, Ciudad
Universitaria, E-mail: latorre @gl.fcen uba.ar.
ABSTRACT: DACHIARDITE-CA IN CRETACIC METANDESITES OF CERRO NAHUEL
PAN, CHUBUT. REPUBLICA ARGENTINA. Dachiardite-Ca in metandesitic breccias of
cretacic age, in Cerro Nahuel Pan, near Esquel, Chubut: (42° 30 y 43°LS), was
found. This is the first mention of dachiardite in Argentina. It is found in
the matrix with yugawaralite and in veins formed by quartz, cristobalite and
dachiardite, which is altered to calcite. The optical data of dachiardite are:
2Va=40-55° and strong dispersion v>r. It has [100] acicular or fibrous
habit, and two perfect cleavages {100} and {001}. The chemical formula is Ca
1.16 K 0.91 Na 0 (Al 2.95 Si 20.98 O 48 ) 13H2O. The three strongest space
lines of the X-Ray Powder Diffraction pattern are: 3.3259 (100); 3.0207 (55)
and 2.0837 (12).
Keywords: dachiardite-Ca-
yugawaralite-quarz- cretacic metandesites- Nahuel Pan - Chubut
VATTUONE, María Elena* y TOURN, Selvia Mabel**
*
Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales,
Univ. de Buenos Aires, Ciudad Universitaria, CP 1428, Buenos Aires, Argentina.
Ingeis, CONICET. E-mail:elena@gl.fcen.uba.ar.
** Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y
Naturales, Universidad de Buenos Aires, Ciudad Universitaria, CP 1428, Buenos
Aires, Argentina E-mail: selvia@gl.fcen.uba.ar.
ABSTRACT: ORTHORHOMBIC
POLYMORPH OF THE FLUORAPOPHYLLITE/HYDROXYAPOPHYLLITE SERIES IN ASSOCIATION WITH
CHABAZITE AND LAUMONTITE IN BASALTIC AMYGDALES. CHAPELCO, NEUQUEN. An
apophyllite mineral was discovered in a paragenesis with chabazite, laumontite,
cuprite and native copper in amygdales of basaltic rocks affected by VLGM in
zeolite facies, in Chapelco, Neuquen. This apophyllite is a member of the
hydroxyapophyllite-fluorapophyllite series. Its chemical formula is : (K 0.91
Ca 3.60) Si 7.81 O 20 (F, OH), 8 H2O. It is biaxic with 2Va= 5°-10° and a weak
v>r dispersion. The parameters of the unit cell are a0=8.9639; b0=9.0192;
c0=15.7713. In accordance with DRX and its optical character, it is a
fluorapophyllite orthorhombic polimorph. The chabazite has R=0,71 and its
chemical formula is (Ca 1.12 K 0.10)Al 3.53 Si 8.77 O24.12H2O. The metamorphic
assemblage of the rocks is: laumontite, wairakite, Ca-heulandite, epidote,
pectolite, pumpellyite, smectite/ chlorite and chlorite. It shows a calcic to
lightly magnesian fluid composition. The fluorapophyllite, with an alkaline
composition, and sericite veins were generated as the fluids became enriched in
alkali elements. Native copper, cuprite and Fe2O3 ocurred after the zeolite
formation at temperatures lower than 200°C. The hydrothermal fluids would be
linked to the intrusion of Tertiary granitoids in this area. The mineralization
corresponds to an epithermal environment with a ƒO2 ~ 50 with low
ƒS2, which is in accordance with the hematite, cuprite and native copper
stability field.
Keywords: fluorapophyllite/
hydroxyapophyllite -chabazite-laumontita- native copper-cuprite-basaltic
amygdales-Chapelco -Neuquen
Vattuone, María Elena1; LATORRE, Carlos Oscar2
y LEAL, Pablo Rodrigo3
1 Fac. de
Ciencias Exactas y Naturales, UBA, Argentina. INGEIS, CONICET, E-mail:
elena@gl.fcen.uba.ar.
2 Fac. de Ciencias Exactas y Naturales, UBA, Argentina. INGEIS, CONICET,
E-mail: latorre@gl.fcen.uba.ar.
3 Fac. de Ciencias Exactas y Naturales, UBA, Argentina E-mail:
leal@gl.fcen.uba.ar.
ABSTRACT: ASSEMBLAGES OF
BARRERITE-OFFRETITE-CLINOZOISITE-SMECTITE IN AMYGDALOID BASALTS. RIO ARRAYANES,
CHUBUT. The purpose of this contribution is the study of a very low grade
mineralogical association restricted to precretacic basalt in northwestern
Chubut province. This association is composed by pumpellyite, clinozoisite,
smectite, barrerite, offretite and cristobalite. Offretite and barrerite
together with smectite are found intergrowing into the amygdales and replacing
albite and adularia, which take part of a prior very low grade metamorphism
(VLGM) process in prehnite-pumpellyite facies. The zeolites are a consequence
of an albite and adularia breakdown nearest 200°C in the zeolite facies.
According with the textural characteristics, offretite was formed prior to
barrerite; this would indicate that part of the original offretite's K, could
have been replaced by increasingly sodic fluids, which also contributed to
generate barrerite at lower temperatures. Clinozoisite (Ps = 7.19/10.14) is
stable at temperatures nearest to 200°C . At such temperatures, low
pistacite-epidotes coexist with zeolites. Pumpellyite located in amigdales'
walls, would be the aluminous variety typical of VLGM. The smectite is a calcic
montmorillonite of the montmorillonite-nontronite series which would confirm
lower temperatures than 200°C.
Keywords: barrerite -
offretite - clinozoisite - smectite - amygdaloid basalts - Río Arrayanes -
Chubut.
VILLAR, Luisa M. */ **, ZAPPETTINI, Eduardo O.
** y HERNÁNDEZ, Laura***
* Consejo
Nacional de Investigaciones Científicas y Técnicas, Argentina.
lvillar@arnet.com.ar
** Servicio Geológico Minero Argentino. Av. Julio A. Roca 651, Argentina.
ezappe@secind.mecon.gov.ar
*** Laboratorio Microsonda Electrónica, Instituto GEA, Universidad de
Concepcion, Chile. lahernan@udec.cl
ABSTRACT: MINERALOGY OF PUESTO LA PEÑA ALKALINE COMPLEX, MENDOZA,
ARGENTINA. In this paper new mineralogical data of the Puesto la Peña alkaline
complex are presented. Analized rock-forming minerals include: biotites
(annite-rich for borolanite-malignite series and eastonite-rich for
piroxenite), titaniferous garnet, pyroxene (diopside-hedembergite serie with
aegirine molecule), orthoclase, nepheline, and spinels (ulvöspinel and
magnetite). These analyses confirm the original petrological classification of this
complex as an undersaturated potassic complex belonging to the
malignite-borolanite group.
Keywords: alkaline complex,
nepheline, biotite, titaniferous garnet, pyroxene, amphibol