VIII CONGRESO DE MINERALOGIA Y
METALOGENIA
MINERALOGÍA
HALLAZGO DE ZEOLITAS DURANTE LA
PROSPECCIÓN DE BORATOS EN JANCUYO, DEPARTAMENTO PUNO, PERÚ
ALONSO, Ricardo N.**, RUIZ, Teresita del V.* y
QUIROGA, Alicia G.*
* CONICET - Universidad Nacional de Salta. E-mail: rnalonso@uolsinectis.com.ar
* Universidad Nacional de Salta. E-mail: ruiz@unsa.edu.ar - gquiroga@unsa.edu.ar
ABSTRACT:During a borate prospection program
in southern
Palabras clave : Zeolitas, boratos, Mioceno, Grupo Maure, Perú
Key words : Zeolites, borates, Miocene, Maure Group, Peru
ESTUDIO DE INCLUSIONES FLUIDAS DEL
CUARZO AURÍFERO DE MINA LA CHIRUZA, SIERRA DE CULAMPAJÁ, PROVINCIA DE CATAMARCA
BENGOCHEA, L. 1,2 , AVILA, J. C 1,3 , FOGLIATA,
A. S 3,4 , MAS, G 1,2 y LAZARTE, J. E. 1,3
1 CONICET e-mail: lbengo@criba.edu.ar , jcavila@csnat.unt.edu.ar
2 Departamento de Geología, Universidad
Nacional del Sur
3 Facultad de Ciencias Naturales e I.M.L.,
Universidad Nacional de Tucumán
4 Fundación Miguel Lillo.
ABSTRACT: Culampajá auriferous district is
located in the north sector of the eastern edge of the homonymous hill, Belén
department, Catamarca province. La Chiruza deposit is situated in the north
flank of Lampacito gulch at an approximate height of 3.700 m a. s. l. In the
studied area out crop mainly ortogneis rocks of Chango Real Formation. The ore
mineral is native gold disseminated in quartz veins filling tension fractures
that affect the ortogneis rocks. The fluid inclusions of La Chiruza Mine were
studied. Several types of inclusions have been recognized, including biphasic
aqueous inclusions, H 2 O–CO 2 -CO 2 inclusions and polyphasic inclusions, with
H 2 O-CO 2 and one or more solid phases. It is suggested that the deposit was
formed during the late magmatic hidrothermal stage genetically liked to
granitic rocks. Until this moment there are not new data that allow define to
which magmatic event of the area is related.
Palabras clave : Culampajá - Mina La Chiruza – cuarzo aurífero
- inclusiones fluidas
Key words: Culampajá – La Chiruza Mine – auriferous quartz
- fluid inclusions
INCLUSIONES FLUIDAS EN EL CUARZO
AMATISTA DE LA PEGMATITA DE PAILEMAN, RÍO NEGRO, ARGENTINA
BENGOCHEA, L. 1,2 , LOPEZ, N. 1 , MAS, G. 1,2
1 Departamento de Geología, Universidad
Nacional del Sur. San Juan 670, Bahía Blanca
2 Consejo Nacional de Investigaciones
Científicas y Técnicas
email: lbengo@criba.edu.ar; nlopez@uns.edu.ar;
gmas@criba.edu.ar
ABSTRACT:
Fluid
inclusions of an amethyst quartz found in the Paileman pegmatite were studied. Four
different types of inclusions were found, including biphasic aqueous
inclusions, biphasic CO 2 inclusions, triphasic fluid inclusions and triphasic
inclusions with a solid phase. By means of thermometric analysis the
characteristics of fluids were determined, and the trapping conditions are
proposed.
Palabras Clave : Cuarzo amatista, inclusiones
fluidas, termometría.
Keywords : Amethyst quartz, fluid inclusions, thermometry
EVAPOFACIES SULFATADAS Y CLORURADAS
DEL SALAR DE RÍO GRANDE, PUNA AUSTRAL, SALTA. ARGENTINA
Boso, M. A.*; Brandán, E. M.* y Castillo, A. L.
*
* Universidad Nacional de Salta, Consejo de
Investigaciones de la UNSa. e-mail: mboso@unsa.edu.ar
ABSTRACT:
Mineralogical
characteristics from central sector of Salar Rio Grande, southern Puna, Salta,
Argentina, are described. Halita, mirabilita, thenardita and hidroglauberita
are the present evapofacies, which are accompanied by grains of quartz, feldspar,
litics volcanics and piroclastics and particles of clays which are analyzed
through to a depth of 20 meters. It is observe a predominance of the halítica
evapofacies on the sulfatadas (thenardite and mirabilita). The processes
observed are poikilitic, dissolution and sobrecrecimiento. Not very marked
cyclic, probably produced by changes seasonal winter-summer, are determined.
COMPOSICIÓN QUÍMICA DE
TIEMANNITA-NAUMANNITA EN EL DISTRITO LOS LLANTENES, LA RIOJA.
BRODTKORB, M.K.de * y BERNHARDT, H.J. **
* CONICET - Facultad de
Cs.Exactas y Naturales. UBA.
E-mail: milkabro@gl.fcen.uba.ar
** Ruhr-Universität Bochum. Alemania. E-mail
heinz-juergen.bernhardt@rub.de
ABSTRACT:
The
seleníferous Los Llantenes district, La Rioja, has a very complex mineralization
where chemically anomalous tiemannite and naumannite were found within droplets
in normal tiemannita grains.
Palabras clave : Distrito Los Llantenes, La Rioja,
naumannita, tiemannita
Key words : Los Llantenes district, La Rioja, naumannite,
tiemannite
Hallazgo de estellerita en rocas de
la Serie Andesítica, en las cercanías de la localidad de Aluminé, Neuquén
BUCETA, María Guadalupe 1 ; VATTUONE, María
Elena 2 ; LATORRE, Carlos Oscar 3
Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires, Ciudad Universitaria,
CP (1428), Buenos Aires, Argentina. 1 guadislupe@gmail.com, 2
elena@gl.fcen.uba.ar, 3 latorre@gl.fcen.uba.ar
Abstract:
The present
contribution describes the mineralogy of stellerite, present in veins of a
mesosilic volcanite from the Auca Pan formation, aged Paleoge, affected by very
low grade metamorphism. The stellerite presents millimetric crystals in the
form of agreggates with a botroydal habit. It's orange, with a {010} cleavage,
parallel extinction and a 2V a of aproximately 50º. The chemical analysis by
EDS show a calcic composition, with with no Na + and only one case with K +
subordinated. The Si/Al ratio ranges between 3,21 and 3,44 and the T Si ranges
between 0,762 y 0,775. The unit cell parameters calculated from an X-ray
difracction are a = 13.5999Å; b = 18.1953Å and c
= 17.8639Å. The metamorphic assemblages suggests crystallization
conditions at temperatures lower than 200ºC from hydrotermal fluids that
altered the rock's vitreous matrix.
Palabras clave : Estellerita - Mineralogía - Química - Aluminé
- Metamorfismo de muy bajo grado
Key words : Stellerite - Mineralogy - Chemistry - Aluminé -
Very low grade metamorphism
CONDICIONES DIAGENETICAS DE LA
FORMACION LAS LAJAS (JURASICO CUENCA NEUQUINA) A PARTIR DEL ESTUDIO DE
INCLUSIONES FLUIDAS EN RESTOS FOSILES.
CESARETTI, N.N.*, GOMEZ, M.C.**, GARRIDO,
M.M.*** y DOMÍNGUEZ, E.A.****
* Departamento de Geología – UNS. e-mail: ghcesar@criba.edu.ar
** Departamento de Geología – UNS. e-mail: mcgomez@criba.edu.ar
*** Departamento de Geología – UNS.
e-mail: mgarrido@criba.edu.ar
**** CONICET - Departamento de Geología –
UNS. e-mail: edomin@crib.aedu.ar
ABSTRACT:
The aim of
this study is analyze fluid inclusions in fossil record of silicified vegetable
from Lajas Formation for understanding the digenetic process which affect this
formation. Organic fluorescent rings were identified into the internal
structure of the vegetable. Trends of organic fluid inclusions attributed to a
liquid hydrocarbon were found leading the biological structure. Aqueous fluid
inclusions into a quartz overgrowth show homogenization temperature between
120-130°C. A permineralization process is interpreted as the way of
fossilization. An evolution of fluid during diagenesis is inferred and pH and
Eh conditions are estimated.
Palabras clave:
restos fósiles
– inclusiones fluidas – fluorescencia – permineralización - diagénesis
Key words : fossil record – fluid inclusions – fluorescence –
permineralization - diagenesis
INDEXADO DE CRISTALES USANDO UNA
CÁMARA FOTOGRÁFICA DIGITAL Y LUPA BINOCULAR
COLOMBO, F.
Museo de Mineralogía y Geología “Dr. A.
Stelzner” – Universidad Nacional de Córdoba
e-mail: fosfatos@yahoo.com.ar
ABSTRACT:
Crystal forms
can be indexed using digital pictures taken through a binocular microscope. When
taking the picture, the line defined by the intersection between the two faces
must coincide with the optical axis of the microscope. The angle can be
measured using a software or on the printed image. The information is later
processed to calculate the Miller indices of the form. In many cases, the
indices can be found by a trial-and-error method, comparing the measured value
with calculated angles between possible pairs of faces. This works specially
well when the Miller indices are low.
Palabras clave : indexado de cristales –
cristalografía morfológica – cámara digital
Keywords : crystal indexing – morphological crystallography –
digital camera
CYRILOVITA Y EOSFORITA EN LA
PEGMATITA GRANÍTICA “GIGANTE”, CÓRDOBA (ARGENTINA)
COLOMBO, F. y LIRA, R.
CONICET - Museo de Mineralogía y Geología “Dr.
A. Stelzner” – Universidad Nacional de Córdoba. e-mail: fosfatos@yahoo.com.ar ; rlira@com.uncor.edu
ABSTRACT:
Cyrilovite and
eosforite occur as inclusions in fluorapatite associated with triplite masses
in the El Gigante pegmatite (Punilla Department, Córdoba Province, Argentina). This pegmatite is a well-zoned body
hosted by monzogranite of the Achala Batholith and probably belongs to the
Hybrid Family, Rare Element class, Complex type, beryl-columbite-phosphate
subtype. The species were identified by microprobe analyses and confirmed by
X-ray diffraction when possible. Si and Cl were sought but rarely detected. In
the following formulae, OH and H 2 O were calculated assuming full site
occupancy. Cyrilovite is found as scarce bright yellow translucent anhedral to
subhedral grains up to 0.8 mm long. Its composition is Na 0.52 (Fe 3+ 2.61 Al
0.23 Mn 0.13 Mg 0.05 ) S 3.02 (PO 4 ) 1.98 (F 0.14 OH 3.86 )·2H 2 O. The very
low Na value (Na should be ~1.00 apfu ) is due to the high instability
of cyrilovite under the electron beam. The Mn content is remarkably high.
Eosforite forms anhedral grains that reach ~ 0.5 mm. A representative analysis
gives (Mn 0.77 Fe 0.18 Ca 0.01 ) S 0.96 Al 1.02 (PO 4 ) 1.00 (OH 1.98 F 0.02
)·H 2 O. The host Mn-bearing fluorapatite occurs as pale bluish gray masses. Its
chemical composition is (Ca 4.89 Mn 0.08 ) S 0.97 (PO 4 ) 3.00 F 1.07 and the
unit cell dimensions are a = 9.367(2), c = 6.874(2) Å. The
chemical composition of the associated triplite ranges between (Mn 2+ 1.87 Fe
2+ 0.14 Ca 0.02 ) S 2.03 (PO 4 ) 1.04 (F 0.81 OH 0.19 ) (light pinkish brown)
and (Mn 2+ 1.30 Fe 2+ 0.63 Ca 0.07 Na 0.01 ) S 2.01 (PO 4 ) 1.02 (F 0.81 OH
0.19 ) (dark brown). Al and Mg are present at or below the detection limit in
triplite. Thin veinlets crosscutting triplite are probably
carbonate-fluorapatite.
Palabras clave : fosfatos – pegmatita granítica – cyrilovita –
eosforita – Córdoba
Keywords : phosphates – granitic pegmatite – cyrilovite –
eosforite - Córdoba
ESCAPOLITAS DE AGUAS AMARILLAS, LOS
MOLLES, PROVINCIA DE MENDOZA CARACTERÍSTICAS MINERALÓGICAS Y ESPECTROSCOPÍA DE
INFRARROJO
de BARRIO, R. E. 1 , BOTTO, I. L. 2-3 ,
LANFRANCHINI, M. E. 1-3 , FRANCHINI, M. B. 3-4
CURCI, M. V. 1 y PONS, M. J. 1-3
1. Instituto de Recursos Minerales, Facultad de
Ciencias Naturales y Museo (UNLP). E-mail: debarrio@inremi.unlp.edu.ar
2. CEQUINOR, Facultas de Ciencias Exactas
(UNLP), E-mail: botto@quimica.unlp.edu.ar
3. CONICET.
4. CIMAR-Universidad del Comahue, Neuquén.
ABSTRACT:
The main mineralogical
characteristics of scapolite-bearing deposits from Aguas Amarillas creek, Los
Molles, Mendoza, are presented. The mineralizations appear in two different
kinds: like veins and veinlets filling joints into the El Potrerito diorite
pluton and Vaca Muerta Formation, and calc-silicate mineral assemblages forming
an extended skarn, close to the eastern contact. The mineral associations are
studied by means of optical properties, X-ray diffraction, X-ray energy
dispersive analyses (EDAX) and infrared spectrometry analyses. The
interpretation of FTIR spectra performed on scapolite crystals allowed to
determine that they correspond to 23-25 % Me in composition.
Palabras clave : escapolita, mineralogía,
espectroscopia de infrarrojo, Aguas Amarillas, Mendoza.
Key words : scapolite, mineralogy, infrared spectrometry,
Aguas Amarillas, Mendoza.
PRESENCIA DE UN MIEMBRO DE LA SERIE
PILSENITA (BiTe) -HEDLEYITA (~ Bi 14 Te 6 ) EN LA VETA MARÍA, DISTRITO EL ORO,
PROVINCIA DE LA RIOJA, ARGENTINA
DE LA CRUZ CARRIZO, R * , SEGAL, S. J.** y
PINTO, A***
*Servicio Geológico Minero Argentino
(SEGEMAR)-Delegación La Rioja
** Servicio Geológico Minero Argentino
(SEGEMAR) IGRM-Dirección de Recursos Geológico- Mineros . e-mail: ssegal@secind.mecon.gov.ar
*** Laboratorio de Microscopía Electrónica-
CIDEMAT-INTEMIN-SEGEMAR
ABSTRACT:The present paper shows the
mineralogical results of an investigation about El Oro district, La Rioja
province. This area is located at 3000 m above sea level on the oriental side
of Famatina range. The El Oro district consists of Au-Cu deposits. Veins with
pyrite, specularite, chalcopyrite and precious metals – gold,electrum and a Bi
telluride. In Veta Maria, a series member between pilsenita and hedleyita is
described. The mineralization was emplaced in Tertiary volcanic rocks.
Palabras clave : La Rioja- Distrito El Oro- Veta María- serie
pilsenita- hedleyita
Key words: La Rioja province- El Oro district. Maria Vein- pilsenita- hedleyita
series
APATITA AZUL CLARO DEL DISTRITO LOS
GUINDOS, CÓRDOBA, ARGENTINA
DEL BLANCO, M * y AMETRANO, S. **
* Instituto de Recursos Minerales, FCNyM, UNLP.
e-mail: mdelbanco@inremi.unlp.edu.ar
**Div. Mineralogía y Petrología, Museo de La
Plata. e-mail: ametrano@fcnym.unlp.edu.ar
ABSTRACT:
Petrographical,
chemical, XRD, IR, TR studies were carried out in order to determine the origin
of the conspicuous light blue colour of a patite from crystalline limestones of
Los Guindos District (ALG), Córdoba, Argentina. Greenish apatite data from
Cerro Blanco pegmatite, Córdoba (ACB), are also presented to be compared . Both
correspond to fluorapatites with higher CaO contents (less FeO and MnO) in ALG
compared to ACB. Light blue colour disappears over 650º C in ALG, as well as
the greenish tint in ACB. Data obtained do not allow to relate blue and green
colours in these apatites to trace elements but probably to structural defects.
Palabras clave : Mineralogía – Apatita – azul claro – gris
verdosa - Distrito Los Guindos – Cerro Blanco
Key words : mineralogy – apatite – light blue – greenish grey
- Los Guindos District – Cerro Blanco
NUEVOS DATOS MINERALOGICOS DEL
PROSPECTO DE ETRL (Nb) JASIMAMPA, SIERRA DE SUMAMPA, SANTIAGO DEL ESTERO
FRANCHINI, M.*, LIRA, R.** y CORNELIUS, S.***
* CONICET, CIMAR, Facultad de Ingeniería,
Universidad Nacional del Comahue. mfranchi@uncoma.edu.ar
**CONICET. Museo de Mineralogía y Geología “Dr.
A. Stelzner”. Universidad Nacional de Córdoba. rlira@com.uncor.edu
***Washington State University.
cornelius@wsu.edu
ABSTRACT:
In the
Jasimampa LREE (Nb) prospect of Santiago del Estero province, REE-
fluorcarbonates, cheralite and strontianite were found in samples of strong
fenitized marble, and taienolite occurs in moderate fenitized granite, close to
an aegirine vein. Their textures and some chemical compositions are presented
and compared to literature data, as well as some genetic considerations are
discussed.
Palabras clave : Jasimampa -flúorcarbonatos de tierras raras -
taeniolita -cheralita - estroncianita
Keywords : Jasimampa - REE-fluocarbonates - taeniolite -
cheralite - strontianite
PRESENCIA DE PROBERTITA EN LA
PERFORACIÓN Nº 1 DE LA PERTENENCIA SORPRESA, SIJES, SALTA
Galliski * Miguel A., Márquez Zavalía * María
Florencia y Alonso ** Ricardo N.
*IANIGLA-CRICYT-CONICET, e-mail: galliski@lab.cricyt.edu.ar , mzavalia@lab.cricyt.edu.ar
**CONICET-Cátedra de Mineralogía-Universidad
Nacional de Salta, e-mail: rnalonso@sinectis.com.ar
ABSTRACT: Probertite, the monoclinic P 2 1
/ a (NaCa[B 5 O 7 (OH) 4 ](H 2 O) 3 ) was found in between -56 and -60
m in a drill core from Sorpresa claim, in Sijes, Salta. The mineral occurs as mm-sized
crystals included in halite, or as partial centripetal replacement of small
ulexite lenses included in halite. Probertite was formed after primary
evaporitic ulexite by thermal diagenesis.
Palabras clave : Probertita – Pertenencia Sorpresa
- Sijes – Salta
Key words : Probertite – New occurrence – Sorpresa Claim –
Sijes -Salta
MINERALOGÍA MAGNÉTICA DE LA
FORMACIÓN ALCAPARROSA (ORDOVÍCICO)
Y DEL PÓRFIRO PÉRMICO QUE LA INTRUYE, CALINGASTA, PROVINCIA DE SAN JUAN
GEUNA, Silvana* y ESCOSTEGUY, Leonardo**
* CONICET- Universidad de Buenos Aires. e-mail: geuna@gl.fcen.uba.ar
** IGRM - SEGEMAR
ABSTRACT:
The
Alcaparrosa Formation near Calingasta, San Juan Province, is mainly represented
by metabasalts and dolerites as part of an Ordovician metasedimentary sequence.
It is intruded by a moderately ferromagnetic Permian rhyodacite porphyry which
generated a 3-km-long alteration halo on the Ordovician rocks. The study of
magnetic properties has shown that the intrusion of the porphyry is responsible
for a widespread remagnetization of Alcaparrosa Formation, carried either by
pyrrhotite or magnetite. The abundance of magnetic minerals is usually low,
although locally high amounts of
monoclinic pyrrhotite (and hence high values of susceptibility and remanence)
have been found. Positive, induction-dominated magnetic anomalies are expected
over the porphyry, whereas negative, remanence-dominated anomalies should be
produced by local concentrations of pyrrhotite.
Palabras clave: pirrotina - magnetita - magnetismo de rocas -
remagnetización - pórfiro
Keywords: pyrrhotite - magnetite - rock magnetism -
remagnetization - porphyry
THE TOURMALINITES FROM THE PAMPA DEL
TAMBOREO, SAN LUIS: CHEMICAL ASPECTS
HENRY, Darrell J.* and BRODTKORB, Milka K. de
**
*Department of Geology and Geophysics. Louisiana State University, USA.
E-mail: dhenry@geol.lsu.edu
** CONICET- University of Buenos Aires. E-mail:
milkabro@gl.fcen.uba.ar
ABSTRACT: The tourmalinites of the Pampa del Tamboreo area,
San Luis, Argentina, are distally associated with tungsten deposits. The
tourmalinites are schistose and comprised of 70-80% tourmaline with lesser
amounts of quartz, graphite, muscovite, rutile, ilmenite, pyrite and
pyrrhotite. Tourmaline grains uncommonly contain small (20-30 µm) grains of
detrital tourmaline with a variety of absorption characteristics implying
variable compositions. Analysis of a single detrital tourmaline grain reveals
that it is a Ca-rich “oxy-dravite” (Mg/ (Mg + Fe) = 0.90) likely from a
high-grade, magnesian metasedimentary source. Proximal to the detrital cores
there are inner domains of asymmetric tourmaline overgrowths that developed at
low grades of metamorphism. The volumetrically dominant tourmaline overgrowths
in the outer domain are concentrically zoned aluminous dravite and
“oxy-dravite” with Al/(Al + Fe + Mg) = 0.71-0.74 and Mg/(Mg + Fe) = 0.64-0.71.
Keywords: Tourmalinites- chemical composition-
Pampa del Tamboreo- San Luis.
Palabras clave: turmalinitas- composición química- Pampa del
Tamboreo- San Luis.
HALOTRICHITA y BILINITA EN MINA LA
MEJICANA, LA RIOJA, ARGENTINA
LOPEZ, N. 1 , BENGOCHEA, L. 1,2 , MAS, G. 1,2
1 Departamento de .Geología. Universidad
Nacional del Sur – San Juan 670. 8000 Bahía Blanca
2 Consejo Nacional de Investigaciones
Científicas y Técnicas
e-mail: nlopez@uns.edu.ar; lbengo@criba.edu.ar;
gmas@criba.edu.ar
ABSTRACT:
The occurrence
of halotrichite and bilinite in the San Pedro vein, La Mejicana mine,
Argentina, is reported. The mineralogical characteristics of these hidrated
basic ferric sulphates, have been studied by means of optical microscopy, X ray
diffraction, scanning electronic microscopy and EDAX analysis.
Palabras clave:
halotrichita,
bilinita, sulfatos secundarios, Mina La Mejicana
Keywords : halotrichite, bilinite, secondary sulphates, La
Mejicana Mine.
ANÁLISIS MINERALÓGICO Y CONDICIONES
DE SERPENTINIZACIÓN EN LOS CUERPOS ULTRAMÁFICOS DEL COMPLEJO GUARGUARAZ,
MENDOZA, ARGENTINA
LOPEZ de AZAREVICH, V.L. * y SUREDA, R.J. **
* UNSa. e-mail: vlllopez@yahoo.com.ar
** CONICET – UNSa. e-mail:
sureda@sinectis.com.ar
ABSTRACT:
The ultramafic
bodies of the Guarguaraz Complex (Frontal Cordillera – Mendoza) are
serpentinites derived from original lherzolites with paragenesis
Ol+Opx+Cpx+Pl+Spl. Serpentine is accompanied by talc, brucite, magnesite,
whereas pyrite, pyrrhotite, calcopyrite, sphalerite and galena constitute the
major metallic assemblage. Serpentinization produced successively talc,
serpentine, brucite and a second generation of serpentine, as temperature
decreased from 800-700ºC to 500ºC, 400ºC and <300ºC, respectively.
Calcium-Na metasomatism and post-tectonic deformed zones with neoformed
chlorite are associated to the borders. Fragile deformation occurred as late-
and post-tectonic episodes.
Palabras clave : lherzolitas, serpentinización, metasomatismo,
deformación frágil, Mendoza.
Key words : lherzolites, serpentinization, metasomatism,
fragile deformation, Mendoza.
ORIGEN DE LA ALUNITA Y LA
NATROALUNITA DEL DEPÓSITO DE CAOLÍN DE MINA EQUIVOCADA (Prov. de Río Negro,
Argentina )
MAIZA, P. J. 1 ; MARFIL, S. A. 2 ; CARDELLACH 3
, E.; CORBELLA, M. 3
• CONICET – UNS. email:
pmaiza@uns.edu.ar
• Comisión de Inv. Cient. de la
Prov. de Bs. As. – UNS. email: smarfil@uns.edu.ar
• Departament de Geología.
Universidad Autónoma de Barcelona, España. email: esteve.cardellach@uab.es
ABSTRACT:
The origin of
alunite and natroalunite from a kaolin deposit (Equivocada Mine, Rio Negro
Province) has been studied. Chemical analysis showed that alunite is K 0.89 and
natroalunite Na 0.97 , in agreement with X ray diffraction data. The high
contents of minor elements in alunite, especially Ba and Sr are compatible with
a hydrothermal origin in contrast to natroalunite whose very low values suggest
a secondary origin. Alunite has a d 34 S = +15.9‰ and a d 18 O = +12.9‰, while
in natroalunite these values are -5.8‰ and +19.0‰ respectively. d 34 S values
suggest that alunite formed from a hypogenic process of hydrothermal origin
whereas natroalunite is probably related to a supergen origin. The occurrence
of alunite in veins crosscutting the other minerals, indicates that it was the
last mineral to crystallize .
Palabras clave: alunita – natroalunita – caolín – Mina
Equivocada
Key words: alunite – natroalunite – kaolin – Equivocada Mine
BURKEITA, (SO 4 ) 2 (CO 3 ) Na 6 ,
EN EL CAMPO GEOTÉRMICO COPAHUE, PROVINCIA DE NEUQUEN, ARGENTINA
MAS, G. 1 ; BENGOCHEA, L. 1 ; MAS, L. 2
1 Dpto. de Geología; Universidad Nacional del
Sur; CONICET. E-mail: gmas@criba.edu.ar;
lbengo@criba.edu.ar
2 EPEN. Gerencia de Ingeniería. Dirección de
Energías Alternativas. Prov. de Neuquen.
E-mail: lucarmas@yahoo.es
ABSTRACT:
The
mineralogical characteristics of a material found as a concretion in a vapor
output of the COP-2 well, in the Copahue Geothermal Field were studied. This
material was studied by means of XR diffractometry, electronic dispersive
energy analysis and thermogravimetric – thermo analytical differential
analysis. These studies confirmed that the material is predominantly
constituted by burkeite (SO 4 ) 2 (CO 3 ) Na 6 , with subordinated presence of
hanksite (SO 4 ) 2 (CO 3 ) Cl Na 6 K.
Palabras clave: burkeita, hanksita, Copahue
Keywords: burkeite, hanksite, Copahue
GREENOCKITE (CdS) AND CADMIUN-RICH
SULPHIDES FROM THE CALEDONIA GROUP GOLD MINES, SIERRA DE LA HUERTA, PROVINCE OF
SAN JUAN, ARGENTINA
MEISSL, E. 1 , CASTRO DE MACHUCA, B. 1,2 ,
MOGESSIE, A. 3 , GALLIEN, F. 3 , SCHNEIDER, I. 3 , BJERG, E. 2,4 , DELPINO, S.
4 , PREVILEY, L. 1,2 , PONTORIERO, S. 1 , KOSTADINOFF, J. 2,4
1 Institute of Geology, FCEFN, Universidad
Nacional de San Juan, Argentina (emeissl@unsj-cuim.edu.ar).
2 CONICET.
3 Institute of Earth Sciences, Department of
Mineralogy and Petrology, University of Graz, Austria.
4 Department of Geology, Universidad Nacional
del Sur, Bahía Blanca, Argentina.
ABSTRACT:
Greenockite
and cadmium-rich sulphides (sphalerite, galena and bornite) are identified for
the first time in the old gold mines of the Caledonia Group, located in
southern Sierra de La Huerta (S31º23'21''- W67º20'33''), province of San Juan.
Chemical and textural features of the identified ore minerals (auriferous
pyrite, sphalerite, arsenopyrite, galena, chalcopyrite, bornite,
tennatite-tetrahedrite and greenockite) are presented in this contribution.
Palabras clave: greenockita * sulfuros ricos en Cd *
características químicas y texturales * Minas del Grupo Caledonia * Sierra de
La Huerta.
Keywords: greenockite * Cd-rich sulphides * textural and
chemical features * Caledonia Group mines * Sierra de La Huerta
ORIGEN DEL ÓPALO DE LA FORMACIÓN
AUQUILCO, VEGA DE ESCALONE, PROVINCIA DEL NEUQUÉN.
MONTENEGRO, T. y CONCHEYRO, A.
CONICET y Dpto. Ciencias Geológicas, FCEN -
Universidad de Buenos Aires.
Correo electrónico: mon@gl.fcen.uba.ar ; andrea@gl.fcen.uba.ar
ABSTRACT:
The Auquilco Formation
constitutes a thick evaporit stratigraphic unit that crops out in the
northwestern area of the Neuquen province. It is mainly composed by anhydrite
and gypsum beds, and includes remarkable opal-chalcedony lents. The origin of
this opal has been discussed previously, and under new evidences of its
mineralogy and X-rays, a mechanism for th is silica genesis is herein
proposed.
Palabras clave: evaporitas – diagénesis - ópalo – calcedonia -
cuarzo autigénico.
Key words: evaporites – diagenetic processes – opal –
chalcedony - authigenic quartz
ESTUDIO DEL ESPECTRO DE ABSORCIÓN EN
EL INFRARROJO DE PREHNITA
MONTENEGRO, T. y VATTUONE, M.E.
UBA -CONICET. Correo electrónico: mon@gl.fcen.uba.ar ; elena@gl.fcen.uba.ar
ABSTRACT:
Prehnite from
Trevelin, Chubut province, has been investigated by infrared spectroscopy,
x-ray diffraction, EDS analysis, and conventional microscopy. Vibrational
absorption spectrum in infrared region was interpreted with assignments taking
into account two structures.
Palabras clave: prehnita – espectro de absorción en el
infrarrojo – filosilicato – inosilicato
Key words: prehnite - infrared spectrum - phyllosilicate –
chain silicate
MEGACRISTALES DE BRUCITA EN SIERRAS
PAMPEANAS, ARGENTINA
MUTTI, D. * y KORZENIEWSKI, L.
I **
* Universidad de Buenos Aires, Departamento Cs.
Geológicas, Ciudad de Buenos Aires, e-mail muttix@gl.fcen.uba.ar
** Servicio Geológico Minero Argentino, IGRM –
SEGEMAR. Julio A. Roca 651, 8 piso sector 8. Ciudad de Buenos Aires
ABSTRACT:
Megacrystals
of brucite in veins were found in skarnificated marbles of Cerro Azul, Córdoba
province. Their characteristics and possible genetic origin are discussed.
Palabras clave: brucita - Sierras Pampeanas - inclusiones fluidas.
Key words: brucite - Sierras Pampeanas - fluid inclusions.
BERMANITA, Mn +2 (H 2 O) 4 [(Mn +3 2
(OH) 2 (PO 4 ) 2 ], DEL YACIMIENTO SAN LUIS,
DISTRITO PEGMATÍTICO TOTORAL, SAN
LUIS, ARGENTINA
OYARZÁBAL, Julio*
* Cátedra de Mineralogía, Universidad Nacional
de San Luis, San Luis, Argentina. joyar@unsl.edu.ar
ABSTRACT:
Bermanite, the
monoclinic P 2 1 Mn +2 (OH) 4 [Mn +3 2 (OH) 2 (PO 4 ) 2 ], has been
found in San Luis II lithium-bearing pegmatite, located in the Paso del Rey
group of the Totoral pegmatitic field, San Luis range, Argentina. The mineral
occurs as idiomorphic flattened crystals hosted in dufrenite, in association
with strunzite, hureaulite and cryptomelane. Bermanite is deep red and shows
burgundy internal reflections, has a vitreous luster, a Mohs hardness of 3-3.5
and a density of 2.861 gr/cm 3 . Optically it is biaxial (-), 2Va ~ 75º, with
Z>X>Y, strong dispersion r<v, a 1.688, ß 1.729, ? 1.751, d 0.063 and X
= b , Y^ c = -34º. The unit cell parameters data are: a 5.435(3)
Å, b 19.240(4) Å, c 5.433(2) Å, ß 110.48º, V 532.217
Å 3 . The chemical composition, based on EDS X-ray and TGA analyses give O, Mg,
P, Ca, Mn and Fe, with Mn:Fe ~ 1:1.04-1.06, Mn:Mg ~ 1:0.03-0.05, Mn:Ca ~
1:0.02, and a water contents of 20.43 wt. % (eq. ~ 4H 2 O); the thermal
analyses show loss of mass by dehydratation in three different steps, at
125-367ºC (-?m= 10.37 wt. %), 367-559 (-?m= 7.09 wt. %) and 559-774ºC (-?m=
2.97 wt. %). Bermanite is the product of hydrothermal alteration of primary
lithiophilite-triphylite, under oxic conditions.
Palabras clave : bermanita - fosfato - mina San Luis -
distrito pegmatítico Totoral
Key words : bermanite - phosphate mineral - San Luis mine -
Totoral pegmatitic field
MINERALES DE Ti COMO NÚCLEOS DE
CIRCONES : CLAVES DEL ORIGEN CORTICAL DE GRANITOS?
QUENARDELLE 1 , S., POMA 1 , S. y ZIMMERMANN 2
, U.
1 Departamento de Cs. Geológicas, FCEN, UBA y
CONICET, sonia@gl.fcen.uba.ar , stella@gl.fcen.uba.ar
2 Department of Geology, University of
Johannesburg, uz@rau.ac.za
ABSTRACT:
This study was
developed as part of a major project focused on Famatinian and pre-Famatinian
granitoids. In this case the stock studied was Poman granite, placed in the
western flank of Ambato range (Sierras Pampeanas Noroccidentales). Petrographic
studies developed on the granite samples showed abundant and large zircons.
Analyses SEM-EDS-BSE and CL of those zircons revealed growth zoning taking the
boundaries of Ti-minerals as crystallization nuclei. This kind of cores is not
often cited in the bibliography and we think that is a key of the granite
origin.
Palabras clave: núcleos de circones – granitos corticales –
Sierras Pampeanas Noroccidentales
Keywords: zircon cores – crustal granitoids – Pampean Ranges
INCLUSIONES FLUIDAS EN CUARZOS DE LA
PEGMATITA LA DICHOSA, SIERRA DE AMBATO, LA RIOJA
RAMIS, A.*; CURCI, M** y BOTTO, I*
*Centro de Química Inorgánica CEQUINOR-CONICET
(Facultad de Ciencias Exactas, UNLP), La Plata. e-mail: andrearamis@yahoo.com.ar , botto@quimica.unlp.edu.ar
**Instituto de Recursos Minerales, INREMI
(Facultad de Ciencias Naturales y Museo, UNLP), La Plata.
e-mail:marcecurci@yahoo.com
ABSTRACT: Fluid inclusion analyses in quartz
samples from La Dichosa andalusite-bearing Al-rich pegmatite (Sierra de Ambato,
La Rioja) are reported in this communication. The preliminary study, carried
out by means of microthermometric analyses, clearly reveals the presence of
three types of fluid inclusions. Type I corresponds to a H 2 O-CO 2 -NaCl
fluid, with a salinity between 0-5 wt % NaCl and homogenization temperature (T
h ) between 320 and 390ºC. The second type (H 2 O-NaCl) presents a salinity
between 4.18 and 6.45 wt % NaCl whereas the T h ranges from 230 to 260ºC. The
last type corresponds to a H 2 O-NaCl low temperature fluid (T h 140-180ºC).
Palabras clave: cuarzo - inclusiones fluidas –
microtermometría - CO 2 - Pegmatita La Dichosa
Key words: quartz - fluid inclusions – microthermometric - CO
2 - La Dichosa pegmatite
DIFRACCION DE RAYOS X EN MINERALES
DEL GRUPO DEL APATITO PROVENIENTES DE PEGMATÍTAS DE LA SIERRA DE VELASCO, LA
RIOJA, ARGENTINA
SARDI, F.*, BAEZ, M.* y GROSSE, P.*
* INSUGEO-CONICET, Universidad Nacional de
Tucumán. Email : fgsardi@csnat.unt.edu.ar
ABSTRACT
: Cell dimensions
of five apatite-group minerals from the Velasco Pegmatitic District, La Rioja
Province (Argentina) , were refined from X-ray diffraction data. The results
are: a = 9.3546 – 9.371 Å and c = 6.8524 – 6.880 Å. Based on
this, it is inferred that F is an important anion (besides oxygen) and some Mn
is substituting for Ca.
Palabras claves : apatito, pegmatita, sierra de Velasco.
Key words : apatite, pegmatite, Velasco range.
HALLAZGO DE MOTTRAMITA EN LA
MANIFESTACIÓN CORTADERAS, DISTRITO SAN FRANCISCO DE LOS ANDES, SAN JUAN,
ARGENTINA
SEGAL, S.J.*, COZZI, G.A.** , PINTO,A.** y CARDÓ, R.***
* Instituto de Geología y Recursos Minerales-SEGEMAR
** Instituto de Tecnología Mineral-SEGEMAR
*** Delegación San Juan-SEGEMAR
ABSTRACT:
In the
Cortaderas Prospect, San Francisco District, San Juan, mottramite PbCuVO4 (OH)
is found. It was studied by X ray powder diffraction and electronic microprobe
analyses.
Palabras clave: Mottramita – San Juan, Distrito San
Francisco, Manifestación Cortaderas
Key words: Mottramite – San province -San Francisco
District- Cortaderas Prospect
TITANITA RICA EN ALUMINIO EN EL
PLUTON DE LA YEYA, SIERRA DEL TIGRE, CORDOBA; ARGENTINA
SFRAGULLA, J. A. 1,3 , MARTINO, R. D. 2,3 y
VLACH, S. 4
1 Secretaría de Minería de la Provincia de
Córdoba, Av. Hipólito Yrigoyen 401, 5000, Córdoba.
2 CONICET y 3 Departamento de Geología Básica,
Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de
Córdoba. Av. Vélez Sársfield 299, 5000, Córdoba. E-mail: rdmartino@com.uncor.edu
4 Laboratório de Microssonda Eletrônica,
Departamento de Mineralogia e Geotectônica, Istituto de Geociências,
Universidade de Sao Paulo. Rua do Lago 562 – Cidade Universitária. 05508-080
Sao Paulo, SP, Brasil. E-mail: srfvlach@usp.br
ABSTRACT:
Unusual
high-Al titanite (X Al = 0,35 – 0,37) from granitic rocks of the Sierras de Córdoba
is described for the first time. The richness in aluminium and its F content is
attributed to the magma composition that controls the mineral association,
mainly the plagioclase composition (oligoclase) and not to pressure effects.
Palabras claves: titanita aluminosa, granitos, Sierras de
Córdoba, Argentina.
Keywords: High-Al Titanite, granites, Sierras de Córdoba,
Argentina.
Estudio de los minerales magnéticos
de la Ofiolita Sarmiento ( Sur de Chile): contribución al conocimiento de su
historia metamórfica.
Singer, Silvia E. * y Rapalini, Augusto E. *,**
* INGEODAV, Dto. Cs. Geológicas, FCEN,
Universidad de Bs. As. E-mail: singer@gl.fcen.uba.ar
** CONICET
ABSTRACT:
The Sarmiento
Ophiolitic Complex (SOC), located in the southern Andes of Chile, represents
the mafic portion of the Late Jurassic to Early Cretaceous oceanic-type floor
of a marginal basin closed and uplifted in the Mid Cretaceous. Its igneous
pseudostratigraphy consists of mainly mafic pillow lavas, dikes, and gabbros.
These rocks underwent a non - deformative “ ocean floor metamorphism” which
developed secondary mineral assemblages in a vertical steep metamorphic
gradient passing from zeolite to actinolite facies, followed by a transition to
fresh gabbros. Syntectonic phengite, stilpnomelane, chlorite and actinolite in
mylonitic rocks bordering the thrust slices that expose the SOC, represent a
different metamorphic event, that probably occured before the latest Cretaceous
(ca. 75 Ma).This paper presents the results of a research on the magnetic
minerals of the SOC which allowed to study the incidence of the mentioned
metamophic processes on the natural remanent magnetization as well as to
distinguish them
Palabras clave: Complejo Ofiolítico Sarmiento- minerales
magnéticos- metamofismo.
Keywords: Complejo Ofiolítico
Sarmiento- magnetic minerals- metamorphism .
Mineralogía de THOMSONITA. junín de
los andes, neuquén
VATTUONE, María Elena 1 , CROSTA, Sabrina 2 ,
BERBEGLIA, Yanina 2 , MARTÍNEZ DOPICO, Carmen Irene 2 y GALLEGOS, Ernesto 2
1 Cátedra de Mineralogía , Departamento de
Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Universidad de
Buenos Aires, Argentina; INGEIS (CONICET), Ciudad Universitaria, 1428, Buenos
Aires, Argentina. e-mail: elena@gl.fcen.uba.ar
2 Departamento de Ciencias Geológicas, Facultad
de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
e-mail: sabrina.crosta@gmail.com ,
yanina@berbeglia.com , candusky@gmail.com , ernestog@gl.fcen.uba.ar
ABSTRACT:
An assemblage
of thomsonite and natrolite has been found in tertiary amygdaloid basalts of
Junín de los Andes, Neuquén. The thomsonite crystals appear in an intergrowth
with natrolite. The physical and optical properties of this thomsonite are:
radiated acicular crystals; lenght along c axis, with {100}, {010} and {h0l}
forms; straight extintion; 2V ? =45° and weak dispersion r>v ; the
orientation is: a , ? , ß = a,b,c. The XRD shows that a 0 =13,027, , b 0
=13,064 and c 0 =13,178; Tsi=0.60 and Si/Al=1,48. These parameters are in
accord with the ordered variety of thomsonite formed with natrolite in alkaline
environment at low temperatures.
Palabras claves: Thomsonita, Zeolitas alcalinas, Junín de los
Andes, Neuquén.
Keywords: Thomsonite , Alkaline Zeolites, Junín de los Andes,
Neuquén
Pumpellyita del Lago Futalaufquen,
CHUBUT, PATAGONIA ArGENTINA
VATTUONE María Elena*, LEAL Pablo Rodrigo* y
LATORRE Carlos*
* Departamento de Ciencias Geológicas,
Universidad de Buenos Aires. E-mails: elena@gl.fcen.uba.ar,
leal@gl.fcen.uba.ar, latorre@gl.fcen.uba.ar
ABSTRACT:
The aim of
this contribution is to describe the mineralogical features, genesis and
geodynamic implicances of Fe-pumpellyite in low grade metamorphic assemblages
(pumpellyite-actinolite facies). This mineral together with chlorite, epidote,
actinolite (+ albite – quartz) were found in Jurassic/Cretacic basaltic rocks
where they appear in the groundmass or filling amygdules of several millimeters
long. Optical properties allowed us to determine two varieties of pumpellyites:
1) fibrous habit, green colour, 2V =40° (+); ? :c =35°; ß =1.72 and 2)
prismatic or equant crystals of brown colour, 2V= 40°(+) to uniáx. (-) and ß
=1.69-1.72. Both optical characteristics and the chemical analyses corresponds
to Fe rich pumpellyite. Green pumpellyite could have grown of primary chlorite
meanwhile brown pumpellyite genesis seems to be related to poor Ca-pyroxene.
The pumpellyite composition suggests that lithological units were generated in
marginal basins under steep or moderate steep geothermal gradients with high ƒO
2 .
Palabras Clave: Fe-pumpellyita, facies pumpelliyta-actinolita,
Fytalaufquen, Patagonia.
Keywords: Fe-pumpellyite, pumpellyite-actinolite facies,
Futalaufquen, Patagonia.
METALOGENIA
ALUVIONES AURÍFEROS DEL RÍO PUCARÁ Y
EL PLUTÓN GRANÍTICO POTRERILLOS, SANTA VICTORIA, PROVINCIA DE SALTA
Argañaraz, Pedro *, Castillo, Alfredo ** y
Sureda, Ricardo***
* Secretaría de Minería y Recursos Energéticos,
Salta. E-mail: pedroargayaraz@hotmail.com
** Universidad Nacional de Salta. E-mail: acasti@unsa.edu.ar
*** Universidad Nacional de Salta. CONICET.
E-mail: sureda@sinectis.com.ar
ABSTRACT:
The genetic
relationships among the different gold deposit models in the Eastern Cordillera
of Santa Victoria, Salta province, Argentina, and the distribution of the
alluvial gold deposits -related to glaciofluvial accumulations of the
Vizcachani-Minas area and to current terraces and alluvium in the Santa Cruz
and Pucará rivers- are analysed. Also the gold anomalies detected in the
Condado, San José and Lipeo rivers, in the Subandean environment of Los Toldos,
international border between Argentina and Bolivia are evaluated . The
gold-iron-copper-bearing quartz veins lodged in Precambrian, Cambrian and
Ordovician sediments of the Vizcachani-Santa Victoria area are described, in
contrast with the non-gold baritine-lead-zinc-bearing veined system of the
Hornillos-Nazareno at the south border of the study area. The Potrerillos
granitic intrusive, associated gabbron dikes and auriferous hydrothermal
alterations from the Santa Cruz Mount are related to the Pucara gold placer
sources. There is first mention to the gold anomalies in the lenticular
oligomictic quartz layers of the Lizoite Formation in the zone of Los Toldos.
Palabras clave : aluvión aurífero y vetas – granitos y
alteración hidrotermal – Pucará, Santa Victoria, Salta
Key words : veins and alluvial deposits - gold and
hydrothermal alterations – Pucará, Santa Victoria, Salta
EDAD Y GEOQUÍMICA DE FLUIDOS EN
FLUORITAS DE ASTURIAS ORIENTAL (N DE ESPAÑA)
CARDELLACH, Esteve* , CORBELLA, Mercè*,
SANCHEZ, Virginia **, VINDEL, Elena**, MARTÍN-CRESPO, Tomás***, FUENLABRADA,
José Manuel****
* Departament de Geologia. Facultat de
Ciències. U. Autònoma de Barcelona, 08193 Bellaterra.
** Dpto. Cristalografía y Mineralogía, F. C. C.
Geológicas, U. Complutense, 28040 (Madrid).
*** Dpto. Matemáticas y Física Aplicadas y
Ciencias de la Naturaleza. U. Rey Juan Carlos, 28933 Móstoles (Madrid).
**** C.A.I. de Geocronología. U. Complutense,
28040 (Madrid).
ABSTRACT:
The most
important fluorite deposits of the Iberian Peninsula are located in Asturias (N
Spain). They consist of veins and manto-like mineralizations of Mississippi
Valley type. Mineralogy is composed of fluorite, barite, calcite dolomite,
quartz and minor amounts of sulphides. The microthermometric study of fluid
inclusions in fluorite, barite, calcite and dolomite points to a mixing, in a
temperature range of 75 to 170ºC, between a low salinity fluid with a Ca-rich
brine as a significative process for precipitation. Crush-leach analyses show
that the low salinity fluid originated from the evaporation of seawater whereas
the Ca-rich brine obtained the salinity from halite dissolution. Individual
analyses of inclusion fluids in fluorite by LA-ICP-MS reveal that metal
concentrations are high with respect to present day basinal brines, although
similar to some Zn-Pb mineralizations. Sm/Nd ratios in fluorites from the
Villabona subdistrict allowed to obtain an isocrone age of 185 ± 29 Ma (Early
Jurassic) a period of time related to the opening of the North Atlantic and
thinning of the crust which enhanced large-scale hydrothermal circulation.
Palabras clave : microtermometría – crush leach – ICP-MS –
isocrona Sm-Nd – fluorita – Asturias
Key words : microthermometry – crush leach – ICP-MS – Sm-Nd
isochrone – fluorite - Asturias
GEOLOGÍA DEL YACIMIENTO LA
ESMERALDA, DISTRITO PEGMATÍTICO CONLARA, SAN LUIS, ARGENTINA
CASTRO, Gladys E. y OYARZÁBAL, Julio*
* Cátedra de Mineralogía, Universidad Nacional
de San Luis, San Luis, Argentina. joyar@unsl.edu.ar
ABSTRACT
: La Esmeralda
mine, a rare element class, beryl type, beryl-columbite subtype pegmatite, is
located at 32º 50´ 25´´ S and 65º 37´ 22´´ W, in the Paso Grande-La Toma group
of the Conlara pegmatite field of the Eastern Pampean Ranges of San Luis
province, Argentina. The pegmatite is hosted in Qtz-Bt-Ms±Chl-Ap-Zrn
micaschists of low metamorphic grade, it N10-15ºE strikes and 50-70º SE dips,
and is tabular to irregular shaped, 270 m long and 25 m average wide in us
central segment. Its internal structure is complex and asymmetric, and is
possible to recognize the following units: border zone (Ab-Ms-Qtz±Ap), wall
zone (Ab-Qtz-Ms±Grt-Tur-Bt), outer intermediate zone (Mc-Qtz-Ab-Ms±Grt-Tur-Bt),
middle intermediate zone (Mc-Qtz-Ms±Tur-Grt-Brl-Ab), inner intermediate zone
(Mc-Qtz-Ms±Zrn-Grt-Ap-Bi), core (Qtz-Mc±Ms-Ab-Ap-Zrn) and several replacements
and filling units. The pegmatite emplacement shows a forced behavior, with
displacement of the host rock by tensional efforts during the cooling period.
Palabras clave : La Esmeralda - pegmatita - berilo - distrito
pegmatítico Conlara
Key words : La Esmeralda - pegmatite - beryl - Conlara
pegmatite field
RECURSOS METALIFEROS DE LA PROVINCIA
DE SALTA
CASTILLO, A. L.* y ALONSO R. N. * **.
* Universidad Nacional de Salta y Secretaría de
Minería y Recursos Energéticos de la Provincia de Salta. e mail:
acasti@unsa.edu.ar
** SMRE y CONICET.e mail:
rnalonso@uolsinectis.com.ar
ABSTRACT:
In the Salta
province the metallic resources are present in different kinds of mineral
deposits like porphyry copper-gold, IOCGD, precious metal epithermal, pegmatite
(tantalum and niobium), stratabound copper-lead, uranium-vanadium sedimentary,
gold placers, between others metallogenetically distributed in the geological
provinces of Puna, Eastern Cordillera, Northern Pampean Hills and Subandean
belts. The main metallogenic provinces of Chile and Bolivia are represented in
Salta province.
Palabras clave: Recursos - Metalíferos - Salta
Key words: Resources . Metalliferous - Salta
MAGMATISMO DEVÓNICO DE LAS SIERRAS
DE CÓRDOBA: FUENTE POSIBLE DE FLÚOR DE LAS MINERALIZACIONES MESOZOICAS. EL
EJEMPLO DEL BATOLITO CERRO ÁSPERO
Coniglio, J. * , D`Eramo, F. **, Pinotti, L. **
, DEMARTIS, M.* *, PETRELLI, H . *
* Departamento de Geología, UNRC; email: jconiglio@exa.unrc.edu.ar
** Departamento de Geología UNRC-CONICET
ABSTRACT:
The main
Mesozoic epithermal fluorite veins of southern Sierras Pampeanas occur in
porphyritic biotite monzogranites belonging to the Cerro Aspero batholith
(Upper Devonian). The fluorite veins were formed by fluid-rock interaction
processes with the fluids being dominantly composed of meteoric water. The chemical
composition of the granitic rocks and biotite of the Cerro Aspero batholith are
similar to the granites from other fluorite districts in the world, which
usually belong to the high K magmatic series.The Cerro Aspero batholith is an
anormally F-rich specialized granite. The average F content in these granitic
rocks is 1210 ppm, which is higher than in the hosting metamorphic rocks and in
some Famatinian granitoids of the Sierras de Córdoba. We suggest that the
breakdown of F-rich biotite and fluor-apatite by hydrothermal alteration in
fracture zones is the most plausible source of fluorine for the epithermal
veins formation. According to this idea it is not necessary to invocate an
hypothetical external source.
Palabras clave: Flúor en granitos - vetas de fluorita -
metalogenia
Keywords: Fluorine in granites - fluorite veins - metallogeny
APLICACIÓN DE IMÁGENES ASTER PARA LA
PROSPECCIÓN Y MAPEO DE PEGMATITAS RICAS EN CUARZO Y GRANITOIDES ASOCIADOS.
SIERRA DE COMECHINGONES, CÓRDOBA
DEMARTIS, M.* , Pinotti, L. *, D`Eramo, F. * ,
Coniglio, J. **, AGULLEIRO INSÚA, L.** , PETRELLI, H .* *
* Departamento de Geología UNRC-CONICET; email:
mdemartis@exa.unrc.edu.ar
** Departamento de Geología, UNRC
ABSTRACT:
Quartz-rich
pegmatitic bodies and associated granites of the southern Comechingones
pegmatitic district were consistently discriminated by means of satellite
multispectral remote sensing. The application of image processing techniques,
specifically designed for mineral mapping to selected spectral bands of the
Terra/ASTER multispectral sensor, resulted in a detailed map for the southern
area of the district, located between 64º 47' and 64º 59,5' W, and between 32º
19' and 32º 31' S . The mapping was carried out through the analysis of the 90
m resolution thermal infrared (TIR) radiance bands. The application of a
decorrelation stretch to the RGB 13, 12, 10 false color composite image was
usefull to discriminate quartz-rich areas. Comparison between the results
achieved through remote sensing with field data confirmed the accuracy of these
techniques. This mapping technique also demonstrates the utility of ASTER
thermal bands in quartz-rich pegmatites and granitoids exploration.
Palabras clave: pegmatitas cuarzosas, granitoides, bandas
ASTER del infrarrojo termal, mapeo litológico
Keywords: quartz-rich pegmatites, granitoids, TIR bands ASTER,
lithologic mapping
META-EXHALITAS ASOCIADAS CON
DEPÓSITOS VOLCÁNICOS SUBMARINOS DE HIERRO Y COBRE, EN LAS SIERRAS PAMPEANAS DE
CORDOBA
DI MARCO, Alejandro* y MUTTI, Diana*
* Dpto. de Ciencias Geológicas, Universidad de
Buenos Aires. E-mail: geoecono@gl.fcen.uba.ar
ABSTRACT:
The geology
and geochemistry of iron formations, ferríferous cherts, and apatite and
zincian spinel rich rocks, associated with exhalative volcanogenic Cu-Fe
submarine deposits in Córdoba, are described and analysed. A common
meta-exhalites regional origin, related with the neoproterozoic Sierras
Pampeanas evolution, is proposed.
Palbras clave : meta-exhalitas, volcanismo submarino,
Neoproterozoico, Córdoba.
Keywords : meta-exhalites, submarine volcanism,
Neoproterozoic, Córdoba.
ORO EN EL DEPÓSITO ESTRELLA GAUCHA,
SIERRAS PAMPEANAS DE CORDOBA
DI MARCO, Alejandro* y MUTTI, Diana*
* Dpto. de Ciencias Geológicas, Universidad de
Buenos Aires. E-mail: geoecono@gl.fcen.uba.ar
ABSTRACT:
Disseminated
gold (electrum) blebs in quartz and a telurium mineral, were identified in the
Estrella Gaucha cooper-iron deposit. The gold and telurium mineral are related
with neoproterozoic volcanic submarine exhalations, although its current lying
reflects the pampeano and famatiniano metamorphic effects.
Palabras claves : oro, depósitos volcanogénicos exhalativos
submarinos, Córdoba.
Keywords : gold, volcanogenic exhalative submarine deposits,
Córdoba.
PROSPECCIÓN Y EXPLORACIÓN
GEOLÓGICO-GEOFÍSICA DE ARCILLAS EN LAS SIERRAS SEPTENTRIONALES DE LA PROVINCIA
DE BUENOS AIRES
ETCHEVERRY, R.O.* ***; TESSONE, M.O.* ** ;
CABALLÉ, M.F.**, CORIALE, N.* ; RAMAYO CORTES, L.* y RAMOS COLLORANA. W.*
(*) Instituto de Recursos Minerales, FCN y
Museo, UNLP.
(**) Dirección Provincial de Minería – FCN y
Museo, UNLP.
(***) CONICET
ABSTRACT:
Thi s work
aims to discuss over the application of geolectrical surveys in clay
prospection. The made works have demonstrated that the method offers a suitable
resolution, whenever lithologies exhibit different electrical coductivity The
results of geoelectrical studies, in the localities of Barker-Villa Cacique,
allowed to discover and to extend commercial clay reserves.
Palabras claves : arcillas, geoeléctrica, prospección, Buenos
Aires
Key Words : Geolectrical Surveys, clays, prospection, Buenos
Aires
EL PROSPECTO DE Cu (Ag) LAS CHOICAS
(34°54´55¨S -70°16´40¨O), UN MODELO DE MINERALIZACION TIPO IOCG EN LA
CORDILLERA PRINCIPAL DEL SO DE MENDOZA
FRANCHINI, M. 1-2 , de BARRIO, R. 3 ,
SCHALAMUK, I. 1-3 , RÍOS, F. 4 , PONS, M. 1-2 Y MEINERT, L. 5
1 CONICET.
2 CIMAR, Facultad de Ingeniería, Universidad
Nacional del Comahue, Av. Buenos Aires 1400 (8300) Neuquén, Argentina.
mfranchi@uncoma.edu.ar
3 Instituto de Recursos Minerales (INREMI).
Universidad Nacional de La Plata, Calle 64 Nº 3, La Plata, Argentina
4 Laboratorio de Inclusiones Fluidas y
Metalogénesis, Centro de Desenvolvimento de Tecnología Nuclear (CDTN-CNEN),
Belo Horizonte, Brasil.
5 Department of Geology, Smith College,
Northampton, MA 01063, USA.
ABSTRACT:
The alteration
and mineralization at Las Choicas have many features in common with IOCG
deposits located in the Central Andes Cordillera of Perú and Chile. The most
important are the following: 1) spatial and genetic relationship to mafic
diorite intrusions, 2) early widespread chlorite + calcite ± albite ± ilmenite
or sphene ± apatite and local actinolite ± hematite ± biotite alteration of
diorite and sedimentary rocks along contacts, 3) superposed Cu mineralization
(1-10 wt % Cu) with Sb, As, Co, Ni, with Mo and Zn anomalies, associated with
calcite ± albite ± quartz alteration in fractures, vein stockworks, and crackle
breccias,and 4) late, barren calcite veins in distal zones.
Palabras clave : Mina Las Choicas –mineralización de Cu-
Depósito IOCG – Mendoza
Key words : Las Choicas mine – copper mineralization - IOCG deposit
– Mendoza
MINERALIZACIÓN EPITERMAL EN Ea. LA
MARÍA, MACIZO DEL DESEADO, PROVINCIA DE SANTA CRUZ.
GONZÁLEZ GUILLOT, M (1) , M. DEL BLANCO (2) ,K.
MYKIETIUK (2) E I. SCHALAMUK (3) .
(1) Centro Austral de Investigaciones Científicas
(CADIC) – CONICET, B. Houssay 200, Ushuaia, Tierra Del
Fuego.e-mail:g_guillot@hotmail.com
(2) INREMI, Instituto de Recursos Minerales,
FCNyM, (UNLP) calle 64 y 120, La Plata.
(3) INREMI, Instituto de Recursos Minerales,
FCNyM, (UNLP) calle 64 y 120, La Plata. CONICET.
ABSTRACT:
Epithermal
mineralization in Ea. La María, Deseado Massif, Santa Cruz, were studied. The
area are integrated by many volcanic-piroclastic units of Bahía Laura Group,
and Tertiary-Quaternary Basalts. There are many evidences of hydrothermal
activity: quartz veins, silicified breccias, silica caps and siliceous sinter.
In many cases are accompanied by anomalous precious metals and Hg, Tl and As
values. This facts would reflect a structural high position of this
mineralization in the low sulfidation ephitermal system.
Palabras clave : Macizo del Deseado, Ea. La María,
Mineralización epitermal
Keywords : Deseado Massif, Ea. La María, epithermal
mineralization.
ESTUDIO DE ISÓTOPOS ESTABLES DE
AZUFRE EN DEPÓSITOS MINERALES DEL DISTRITO MINERO VALCHETA, PROVINCIA DE RÍO
NEGRO, ARGENTINA
GOZALVEZ, M. R. (1) Y OSTERA, H. (2)
1 CONICET-SEGEMAR. e-mail:
mgozal@mineria.gov.ar
2 CONICET-INGEIS
Abstract
: The Valcheta
District is situated in the center-east of Río Negro province and it is part of
northeastern border of Nordpatagonian Massif. It has important tungsten
deposits, exploited in the middle of the past century, as well as lead–zinc
deposits. The preliminary data of sulfur isotopes in sulfide minerals of five
deposits (three of them in lead-zinc deposits and two in tungsten deposits)
make evident the magmatic origin of metallic minerals and the physical and
chemical changes of the hydrothermal fluids. In future works, new isotopic and
fluid inclusion data to will be available to relate themselves and characterize
the different mineralization events.
Palabras clave : isótopos estables, depósitos minerales,
Distrito Valcheta, Río Negro
Key words : stable isotopes, ore deposits, Valcheta District,
Río Negro
MANIFESTACIONES POLIMETÁLICAS EN LA
SIERRA DE TONTAL, AL ESTE DE CALINGASTA, SAN JUAN
HERRMANN Carlos 1,2 , LEAL Pablo R. 1,3 y
BRODTKORB Milka K. de 1,3
1 Depto de Ciencias Geológicas. Facultad de
Ciencias Exactas y Naturales, Universidad de Buenos Aires. E-mail: l e al@gl.fcen.uba.ar y milkabro@gl.fcen.uba.ar
2 SEGEMAR. E-mail: cherrm@secind.mecon.gov.ar
3 CONICET.
ABSTRACT:
In the western
margin of Tontal Range, a few kilometers to the east of Calingasta location,
there are pollymetallic veins that have been studied. The ore is composed by
pyrite, chalcopyrite, galena, sphalerite and gold; barite, calcite and quartz
are the gangue minerals. Host rocks are basic volcanic rocks of Alcaparrosa
Formation (Ordovician). The mineralization could be related to nearer intrusive
bodies, which are silicified and limonitized. Magmatic rocks into the area
belong to the Choiyoi Group and Tertiary cycle.
Palabras clave: vetas polimetálicas – Tontal – Grupo Choiyoi –
mineralización.
Keywords : Polymetallic veins - Tontal - Choiyoi Group -
mineralization.
PETROLOGÍA Y GEOQUÍMICA DEL
MAGMATISMO JURÁSICO-CRETÁCICO VINCULADO A LAS MINERALIZACIONES DE Fe-Cu DEL
CERRO PEPITA, SO DEL CHUBUT
LANFRANCHINI, M.E. 1-3 , GONZÁLEZ, P.D. 2-3 ,
de BARRIO, R.E. 1 , ETCHEVERRY, R.O. 1-3 y AMETRANO, S.J. 4
1 . Instituto de Recursos Minerales, FCN y M
(UNLP). Calle 64 N°3, (1900) La Plata.
E-mail: mlanfranchini@inremi.unlp.edu.ar
2 . Centro de Investigaciones Geológicas (UNLP-CONICET).
1 N° 644, (B 1900 TAC) La Plata.
3 . Consejo Nacional de Investigaciones
Científicas y Técnicas (CONICET).
4 . Cátedra de Mineralogía, FCN y M (UNLP).
ABSTRACT:
Fe-Cu skarn
and hydrothermal deposits, at the Pepita Hill (SW Chubut Province), are related
to Jurassic-Cretaceous magmatism. Detailed petrographic studies and whole rock
geochemical analyses performed on basalt-basaltic andesite flows (Lago La Plata
Fm) and rhyolitic-dacitic dikes and subvolcanic bodies (El Gato Fm) allowed to
characterize the meta-aluminous to weakly per-aluminous,
tholeiite-calc-alkaline signature, associated to a magmatic arc setting. The
iron source of the El Abuelo ore deposit is possibly related to the tholeiitic
affinity of rocks from Lago La Plata Formation.
Palabras clave : Petrología – magmatismo Jurásico-Cretácico –
Cerro Pepita - Chubut
Keywords : Petrology – Jurassic-Cretaceous magmatism – Pepita
Hill – Chubut
GÉNESIS DE LA ARCILITA CAOLINÍTICA
DE LA MINA “EL CEFERINO”, SIERRA DE LOS BARRIENTOS, PROVINCIA DE BUENOS AIRES.
LÓPEZ ESCOBAR, Katthy*; ETCHEVERRY, Ricardo** y
BOTTO, Irma L.***
*DAAD, Deutscher Akademischer Austausch Dienst
- INREMI-UNLP. katthylopez@inremi.unlp.edu.ar
** INREMI Instituto de Recursos Minerales,
Facultad de Ciencias Naturales y Museo -UNLP. retcheve@museo.fcnym.unlp.edu.ar
*** CEQUINOR, Centro de Química Inorgánica,
Facultad de Ciencias Exactas - UNLP. botto@quimica.unlp.edu.ar
ABSTRACT:
In El Ceferino
mine crops out a succession assigned to Balcarce Fm. (Lower Paleozoic). These
rocks are exposed in the Tandilia System, SE from La Numancia faraway place.
The sequence is constituted of kaolinite-rich claystone and quartz-arenite,
with claystone (illite>>kaolinite) interbedded. It forms a tableland
exposure NNO oriented, dipping 6°-11° SE. Towards the base of the kaolinite
claystone an Ordovicic diabasic sill is intruded. The subject of this paper is
to establish the relationship between the diabase and the claystone. The
analytical techniques used include: X-Ray diffraction, FTIR spectroscopy and
thermal analysis, scanning electron microscopy (SEM) with dispersive energy
accessory for surface chemical analysis (EDAX) and XR-Flourescence (for minor
elements). The results obtained indicate that claystone derives from a
continental margin and was formed in an oceanic environment with low energy.
Towards the Ordovician the sedimentary sequence was cut by the intrusion of the
basic rocks that caused thermal metasomatic processes in the diabase-claystone
contact. This hypothesis allows to define a sedimentary origin for claystone,
without a genetical relationship with the diabase.
Palabras claves: génesis, geoquímica, minerales de arcilla,
Formación Balcarce.
Key words: genesis, geochemistry, clay minerals, Balcarce
Formation.
ALTERACIONES Y GEOQUÍMICA DE LOS
CERROS LOS BAÑOS Y EL QUEBRADO EN EL COMPLEJO VOLCÁNICO DE ULLUM-ZONDA. SAN
JUAN.
MENDOZA Nilda*, CASTRO Ricardo* y WEIDMANN
Nestor*
* Departamento de Geología. Universidad
Nacional de San Juan. E-mail: nildamza@hotmail.com
, nweidmann@unsj-cuim.edu.ar
ABSTRACT
: This paper
comprises the study of hydrothermal alteration and geochemistry of the volcanic
body of the Cerros Los Baños and El Quebrado, in Precordillera, 20km from San
Juan city. There are three types of alteration in the area, Argillic, Potassic
and Propylitic, common in the superficial area of low sulfidation epithermal
system; there were not found anomalies of precious metals but it doesn't mean
that there isn't mineralization of interest, because superficial zones of
epithermal systems are generally barren in precious metals. However, there were
found values above background in the studied rocks.
Keywords: hydrothermal alteration – volcanic body – Los Baños
– El Quebrado
Fluorita en el sector NE del Macizo
del Deseado. Estancia La Henriette, Santa Cruz, Argentina
nillni, A.*, FRACCHIA, D.** y GUZMÁN, S.*
* U niversidad Nacional de la Patagonia San
Juan Bosco. E-mail: anillni@unpata.edu.ar
**Instituto de Geología y Minería, Universidad
Nacional de Jujuy. E mail:
fracchiadiego@yahoo.com.ar
ABSTRACT:
Several
mineralized sectors were recognized in Estancia La Henriette, Santa Cruz
province. They are dominated by quartz veins and veinlets, stockworks,
hydrothermal breccias and pervasive silicification; less common are the
fluorite-calcite veins. The geology of the area is represented by the jurassic
volcanic rocks of Bahía Laura Group (ignimbrites, tuffs, tuffites and lavas),
mainly calc-alkaline rhyolites; however subvolcanic intrusive bodies located in
the south of the area has tholeiitic affinities. Epithermal quartz textures are
common (sacaroid, pseudomorph after calcite , banded-crustiform),
and alteration is tipically of the low sulfidation epithermal type, with
silicification and argilization near the veins, and propilitization away from
them. Metal contents are low, represented by scarce pyrite, calchopyrite,
limonites and gold grains. Fluid inclusions (FI) in fluorite have been
analyzed. As in the fluorite of estancia La Beatriz and estancia Tres Hermanas,
the FI shapes are regular in the case of green fluorite and irregular in violet
fluorite. Homogenization temperatures range between 130 and 135 °C, and the
salinity is smaller to 1,5% wt. NaCl equiv. The mineralogical and textural
characteristics of this deposit correspond to the Superzone of Chalcedony. If
FI data are compared with those of quartz FI in this area, fluorite might
correspond to a late mineralization pulse. Besides, it could be related to
subvolcanic intrusives located at the south of the area which are different
from the rhyolitic domes that are related to the quartz mineralization.
Palabras clave : Macizo del Deseado – depósitos epitermales –
fluorita – inclusiones fluidas
Key words : Deseado Massif – epithermal deposits – fluorite –
fluid inclusions
GEOLOGÍA,
ESTRUCTURA INTERNA Y MINERALOGÍA DEL YACIMIENTO PEGMATÍTICO MARÍA DEL HUERTO,
DISTRITO CONLARA, SAN LUIS, ARGENTINA
ROQUET, M. B.*, OYARZÁBAL, J.** y GALLISKI, M.
A. ***
* CONICET - Dpto. Geología, Proy. CyT 349001
UNSL - maber@unsl.edu.ar
** Cát. de Mineralogía, Dpto. Geología, Proy.
CyT 349001 UNSL - joyar@unsl.edu.ar
*** CONICET - IANIGLA, Mendoza, Argentina -
galliski@lab.cricyt.edu.ar
ABSTRACT:
María del
Huerto pegmatite is located at 32º 31´ 46´´S and 65º 24´ 17´´W, 20 km west of
Concarán, San Luis, Argentina. This deposit is part of the Villa Praga-Las
Lagunas group, of Conlara pegmatitic field. The pegmatite is hosted
predominantly in a granodioritic lens; it has tabular form with NE-SW strike
and sub-vertical dip. The internal structure shows from the margin inwards:
border, wall, intermediate external, intermediate internal and core zones; Ms
units replacement and Qtz-Pl-Ms ± Brl units have been recognized. The mineral
assemblage comprises: Qtz-Pl-Ms-Mc-Spd-Brl-Grt-Ap-Tur-Dick-Ill-Mn and Fe
secondary oxides. The (Al,Si) ordering in the blocky K-feldspars correspond to
maximum microcline. The muscovite belongs to the 2M 1 polytype. Based in the
mineralogy the pegmatite is classified as a complex type, spodumene-subtype,
with LCT geochemical signature.
Palabras clave : pegmatita - mineralogía - estructura interna
- ordenamiento de feldespatos - politipismo de Ms
Key word : pegmatite - mineralogy - internal structure -
feldspar ordering - muscovite polytipism
ALTERACIÓN HIDROTERMAL EN LA ZONA DE
ESTANCIA CECCHI, MACIZO NORDPATAGÓNICO, RÍO NEGRO
SERENO, G. M. *, GARRIDO, M. M. **, BERTOTTO,
G. W. *, GÓMEZ, C. **, BONUCCELLI, R. ***
* Facultad de Ciencias Exactas y Naturales,
UNLPam. e-mail: gasseren@hotmail.com / gwbertotto@yahoo.com.ar
** Departamento de Geología, UNS. e-mail:
mgarrido@criba.edu.ar / cgomez@criba.edu.ar
*** Marifil S.A. e-mail: rebo@infovia.com.ar
ABSTRACT:
In the
Nordpatagónico Massif, province of Río Negro, a new alteration zone is
described. It is developed on Triassic volcanic rocks and is silicification,
quartz-illite, chloritic and kaolinitic type. Geochemical analyses indicate
weakly anomalies of As, Cu and Mn without significant values of gold and silver
.
Palabras clave : alteración hidrotermal – Macizo Nordpatagónico
– volcanismo Triásico
Key words : hydrothermal alteration – Nordpatagónico Massif –
Triassic volcanism
ESTUDIO GEOLÓGICO Y PETROGRÁFICO DE
LOS YACIMIENTOS VIRORCO (Cu) Y EL FIERRO (Fe), PROVINCIA DE SAN LUIS
ZAFFARANA, Claudia B. 1 , LEAL, Pablo R. 1,2 y
BRODTKORB, Milka K. de 1,2
1 Universidad de Buenos Aires, e-mail:
zaffarana@gl.fcen.uba.ar, leal@gl.fcen.uba.ar
2 CONICET, e-mail: milkabro@gl.fcen.uba.ar
ABSTRACT:
The aim of
this contribution is the study of the copper and iron deposits (Virorco and El
Fierro respectively) hosted in mafic-ultramafic rocks (Las Águilas Group) that
occur in San Luis ranges. Las Aguilas Group also present a primary
mineralization of nickel, iron, copper and platinum group elements (PGE).
Vein-filling textures and pyrite-chalcopyrite assemblages suggest that Virorco
copper mineralization is a secondary process superimposed to the above
mentioned primary ore minerals. Thus, the copper mineralization could have been
originated by remobilization from a copper-enriched lense within the layered
mafic-ultramafic igneous body. El Fierro iron deposit seems to have been
generated by a similar process, however the protolith must not have been as
rich in copper as Virorco mine.
Keywords: Virorco, El Fierro, copper deposit, Iron deposit,
San Luis.
Palabras clave: Virorco, El Fierro, cobre, hierro, San Luis
PETROLOGÍA
EQUILIBRIO DE FASES EN XENOLITOS
ULTRAMÁFICOS DE SANTA CRUZ, ARGENTINA
ALIANI, P. A. 1 ,
BJERG, E. A. 1 y NTAFLOS, Th. 2
1 CONICET – INGEOSUR, Departamento de Geología,
Universidad Nacional del Sur, San Juan 670, B8000ICN
Bahía Blanca, Argentina. E-mail: paliani@uns
.edu.ar
2 Department of Geological Sciences, University
of Vienna , Althanstrasse 14, A-1090 Wien, Austria.
ABSTRACT: Partition coefficients (K D s) in
mantle xenoliths from Ea. Poklepovic, Santa Cruz province, Argentina, were
calculated. The comparison of the obtained K D amphibole/cpx1 and K D cpx2/melt
with published data shows that (a) amphibole crystallised in equilibrium with
matrix clinopyroxene and (b) as suggested by petrographic evidence, secondary
clinopyroxene and glass from melt pockets are not in equilibrium.
Palabras clave : manto - xenolitos – metasomatismo – elementos
traza – coeficientes de partición
Key words : mantle – xenoliths – metasomatism – trace elements
– partition coefficients
Petrología de la aureola de contacto
del Batolito Cerro Aspero, Sierra de Comechingones, Córdoba, Argentina.
FAGIANO, Marcelo 1 , PINOTTI, Lucio 1,2 ,
TRAMANNONI, Pablo 1 y ESPARZA, Ana 1 .
1 Dpto. de Geología. Universidad Nacional de
Río Cuarto. e-mail: fagiano@exa.unrc.edu.ar
2 CONICET- Universidad Nacional de Río Cuarto.
e-mail: lpinotti@exa.unrc.edu.ar
ABSTRACT:
In the Sierra
de Comechingones, Córdoba, an extensive zone was transformed thermally to
metamorphic rocks by the intrusión of the Cerro Aspero batholith. Hornfels and
semihornfels are the dominant rocks in the hornblende hornfels facies of
thermal metamorphism. The most representative mineral paragénesis is
cordierite-andalucite-sillimanite-biotite, suggesting temperatures between 500º
C and 600º C and pressure about 2 kbar.
Palabras clave: aureola de contacto, facies de hornfels
hornbléndico, batolito Cerro Áspero, Sierra de Comechingones, Córdoba.
Key words : contact aureole, hornblende hornfels facies, Cerro
Aspero batholith, Sierra de Comechingones, Córdoba.
SEGREGACIÓN TEMPRANA DE SULFUROS EN
LA EXTRACCIÓN DE ELEMENTOS DEL GRUPO DEL PLATINO DE LAS ROCAS
MÁFICAS-ULTRAMÁFICAS DE LAS ÁGUILAS Y ALREDEDORES, SAN LUIS, ARGENTINA.
FERRACUTTI, G. *, BJERG, E. A. ** y MOGESSIE,
A. ***
* INGEOSUR-Dpto. de Geología, UNS. San Juan
670, Bahia Blanca. e-mail: gferrac@uns.edu.ar
** CONICET – INGEOSUR - Dpto. de Geología, UNS.
e-mail: ebjerg@uns.edu.ar
*** Institute of Earth Sciences, Department of
Mineralogy and Petrology, University of Graz, Austria. E-mail:
aberra.mogessie@uni-graz.at
ABSTRACT
: The
mafic-ultramafic rocks of the Las Águilas deposit occur 30 Km. NE of San Luis
city, Argentina. Their outcrops have a NE-SW bearing, parallel to regional
orientation of the Sierra Grande de San Luis. In this area the presence of
platinum group element (PGE) has been mentioned before by different authors. In
this contribution we explore the possibility of PGE plus Ni and Cu associated
with them, being the result of an early sulfide segregation which extracted
them from the magma and analyze the relationship between the type of magma and
the relative abundances of the recognized mafic-ultramafic rocks in the Las
Aguilas deposit.
Palabras clave : Complejo máfico-ultramáfico Las Águilas – EGP
– MGP– metales base – magma máfico.
Key words : Las Aguilas mafic-ultramafic Complex – PGE – PGM –
base metals – mafic magma
PETROGRAFÍA Y GEOQUÍMICA DE ROCAS
MÁFICAS Y ULTRAMÁFICAS DE CORDILLERA FRONTAL, MENDOZA.
GARGIULO, M. F. * y BJERG, E. A. *
* CONICET – INGEOSUR – Departamento de
Geología, San Juan 670, B8000ICN Bahía Blanca. E-mail: mfgargiulo@uns.edu.ar
ABSTRACT: We present new geochemical data of
pre-Carboniferous ultramafic and mafic rocks exposed on the eastern part of
Frontal Cordillera of Mendoza province, in the area of Salamanca Mine and
Quebrada de la Yesera. The comparison of these results with those published
elsewhere shows that in Frontal Cordillera at least two types of dikes can be
differentiated: one group with OIB and the other E-MORB signature. The E-MORB
type correlates with the Western Precordillera basic rocks. The ultramafic
samples from Salamanca Mine have primitive mantle signature while those of the
Metales Belt and Precordillera have E-MORB geochemical signature.
Palabras clave : Geoquímica – Faja Máfica-ultramáfica – Río de
las Tunas – Cordillera Frontal - Mendoza
Key words : Geochemistry – Mafic-ultramafic Belt – Las Tunas
River – Frontal Cordillera – Mendoza
LA MOVILIDAD DE ELEMENTOS
MAYORITARIOS Y TRAZAS EN EL PROCESO DE ALTERACIÓN DE ROCAS RIOLITICAS A
BENTONITA, EN EL DEPOSITO HIPO, SAN JUAN, ARGENTINA
GÓMEZ, M. C.*, LUNA, L.*; GARRIDO, M* y
DOMÍNGUEZ, E**
* Departamento de Geología. Universidad
Nacional del Sur Bahía Blanca.
e-mail: mcgomez@criba.edu.ar
, liluna @criba.edu.ar, mgarrido@criba .edu.ar,edomin@criba.edu.ar
CONICET-UNS
ABSTRACT:
In San Juan
Province, northwest Argentine, a white bentonite deposit was formed after
Pleistocene volcanic rocks (Las Trancas Formation). These rocks were
subsequently faulted and intruded by andesitic / trachyandesitic dikes. The
deposit, found in the central part of a 10 Km 2 elliptical area, results from
the alteration of both vesicular and a poorly vesicular interlayered rhyolitic
glasses. The main alteration products are smectites, opal C-T and zeolites
(clinoptilolite). The highest concentration of smectites is controled by dikes
and faults. The conversion of volcanic rocks to bentonite results in removal of
Si, alkalis (K) and Mg and H 2 O is taken up. The trace elements Th is
immobile, while Nb and Y are leached and Zr is enriched during the degree of
alteration to bentonite. There are not fractionation of REE. In conclusion, the
mobility of major and trace elements during alteration depend on the nature of
the parent rock and the composition of the fluid phase and relationship water/
rock.
Palabras clave: Alteración- bentonita- vidrios riolíticos -
Provincia de San Juan- Argentina
Key words: Alteration- bentonite- rhyolitic glasses- San Juan
province- Argentina
MINERALOGÍA Y TRAYECTORIA TEXTURAL
DE ANFIBOLITAS DE LA SIERRA DE BACHICHA, SISTEMA DE TANDILIA (BUENOS AIRES)
GONZÁLEZ, Pablo Diego 1 y CÁBANA, María Cecilia
2
1 Centro Investigaciones Geológicas
(UNLP-CONICET). E-mail: gonzapab@cig.museo.unlp.edu.ar
2 Instituto de Recursos Minerales (UNLP-CICBA).
E-mail: mccabana@inremi.unlp.edu.ar
ABSTRACT:
In the Sierra
de Bachicha (Tandilla System), at Punta Tota ( 37°49'S, 58°12'W), relics of
medium pressure mafic granulites have been described as inclusions within
amphibolites of the Buenos Aires Complex. At least four regional metamorphic
events have been recognized: (1) Relict M 1 medium pressure granulite facies
metamorphism characterized by granoblastic opx-cpx 1 -pl 1 assemblage (2) Peak
metamorphic conditions at M 2 high amphibolite facies, with nematoblastic am 1
-cpx 2 -pl 2 and coronitic reaction textures of am 1 around M 1 assemblage. (3)
Retrograde M 3 low amphibolite facies metamorphism characterized by am 2 +
brown mica. (4) M 4 prhenite-pumpellite facies metamorphism, with
pmp-prh-ab-ep-chl-cal overprinting pl 1-2 + am 1-2 . Mineral and textural
analyses suggest that the mafic metamorphic rocks follow a general
retrogressive P-T- time path from M 1 , with decompression
contemporaneous with cooling and hydration, up to M 4 .
Palabras clave : metamorfismo-facies
anfibolita-granulita-Sierra de Bachicha-Tandilia.
Keywords : metamorphism-amphibolite-granulite facies- Sierra
de Bachicha-Tandilia.
GEOQUÍMICA DE FELDESPATOS Y BIOTITAS
DEL GRANITO ORBICULAR DE LA SIERRA DE VELASCO, LA RIOJA, ARGENTINA
GROSSE, P., ROSSI, J. N. y TOSELLI, A. J.
INSUGEO-CONICET, Universidad Nacional de
Tucumán
E-mail: pablogrosse@yahoo.com
ABSTRACT: The orbicular granite of the Sierra
de Velasco is one of only two orbicular rocks described in Argentina. It forms
an irregular body of around 65 x 15 m bounded by the Huaco Granite (GH) and
consists of ovoid-shaped orbicules immersed in an aplitic to pegmatitic matrix.
The orbicules have an internal concentric structure consisting of a central
K-feldspar megacryst, partially replaced by plagioclase, surrounded by shells
of radially oriented plumose plagioclase and tangentially oriented biotite.
Microprobe chemical analyses of plagioclase and biotite from the orbicules and
the matrix were carried out. Plumose plagioclase shows inverse zoning from An
9-14 to An 18-20 . This zoning can be explained by sudden undercooling
(possibly due to pressure loss) followed by isothermal crystallization, which
provokes non-equilibrium conditions and high growth but low nucleation rates.
Biotites from different zones of the orbicules have similar compositions,
supporting rapid isothermal crystallization conditions. The Fe/(Fe+Mg) ratio of
the biotites increases from those of the GH, to those of the orbicules, to
those of the orbicular matrix, suggesting increasing differentiation. Orbicular
rocks are very rare because their formation seems to require the unlikely
combination of various processes. The orbicular granite probably formed close
to the roof of the GH.
Palabras clave : Granito orbicular – química mineral –
feldespato – biotita – sierra de Velasco
Key words : Orbicular granite – mineral chemistry – feldspar –
biotite – Sierra de Velasco
QUÍMICA MINERAL DE LOS GRANITOS
SANAGASTA, HUACO Y LA CHINCHILLA, SIERRA DE VELASCO, LA RIOJA, ARGENTINA
GROSSE, P., ROSSI, J. N., SARDI, F. G. y
TOSELLI, A. J.
INSUGEO-CONICET, Universidad Nacional de
Tucumán.
E-mail: pablogrosse@yahoo.com
ABSTRACT:
Microprobe
chemical analyses of feldspars, micas and apatites from the Sanagasta (GS),
Huaco (GH) and La Chinchilla (SLC) granites of the Sierra de Velasco, La Rioja
province, have been carried out. K-feldspar compositions are mostly Or 88-93 in
all three granites and no chemical difference is found to account for their
pink color in the GS. This coloration could be due to higher oxygen fugacity
conditions during the evolution of the GS, consistent with the presence of
magnetite. Plagioclase is oligoclase in the GS (An 18-24 ) and the GH (An 10-23
), and almost pure albite in the SLC (An 1-2 ). Biotites from the GS and the GH
are Fe-biotite and siderophyllite. They are characterized by a high Fe/(Fe+Mg)
ratio (0.76-0.82), typical of felsic granites, and in discrimination diagrams
they plot alternatively in the peraluminous and calc-alkaline fields. Biotites
from the GS are slightly poorer in Al and Na and richer in Si than biotites
from the GH. The mica of the SLC is zinnwaldite, rich in Li, and has a very high
Fe/(Fe+Mg) ratio (0.94-0.97). Apatites from the GH have higher contents in Mn,
Na, Fe and F, and lower contents in Si and LREE than those from the GS, similar
to the differences shown by apatites from S- and I-type granites, respectively,
although both have compositions comparable to those of felsic granites, either
S- or I-type. The mineral chemistry of the GS and the GH suggest that both are
evolved granites. The GH has mineral compositions comparable to those of felsic
S-type granites while the GS shows characteristics intermediate between I- and
S-type granites. The SLC is a highly fractionated granite similar to some
A-type granites and probably originated from a water- and volatile-rich melt.
Palabras clave : Química mineral – feldespato – biotita –
apatito – granitos carboníferos – sierra de Velasco
Key words : Mineral chemistry – feldspar – biotite – apatite –
Carboniferous granites – Sierra de Velasco
La alteración de las hialoclastitas
basálticas neopaleozoicas del Cordón del Jagüel, provincia de Mendoza
KOUKHARSKY, M.*, QUENARDELLE, S.* y MONTENEGRO,
T.*
* Universidad de Buenos Aires – CONICET.
e-mail: mkou@gl.fcen.uba.ar
ABSTRACT:
Two types of
alteration were detected in basaltic hyaloclastites from Cordón del Jagüel
(Mendoza province, Argentina). These rocks were deposited in submarine
environment during Upper Carboniferous times. The first alteration is composed
by reddish brown to orange and light brown colored birrefringent palagonite
replacing glass, mostly with fibrous structures as thin and irregular lenses up
to 1 mm length. This material has been slightly transformed to pale green
chlorite. The other alteration is composed by clinozoisite, identified by X ray
and chemical analyses, which replaces mostly xenomorphic former plagioclase
crystals. It has brownish gray color, high relief and very low birefringence.
These alterations are associated with fresh colorless fragments of
clinopyroxenes crystals. Palagonite represents the first alteration of these
rocks, related to hydration with sea water. The clinozoisite, in microscopic
crystalline aggregates, is in paragenetic association with albite and chlorite.
The whole association is interpreted as the result of hydrothermal alteration
related to water circulation in a marine volcanic environment, probably with
the contribution of high geothermal gradients, established in the region during
the deposition of Permian welded ignimbrites, and specially during the
development of a rift in Lower Triassic times.
Palabras clave: alteración - hialaoclastitas basálticas –
palagonita - clinozoisita
Keywords: alteration – basaltic hyaloclastites – palagonite -
clinozoisite
MICROANÁLISIS DE LAS ANFIBOLITAS DEL
COMPLEJO GUARGUARAZ, MENDOZA.
López de Azarevich, V. L.*
* UNSa, vlllopez@yahoo.com.ar
ABSTRACT:
Chemical
composition determined by EMPA in metamorphic minerals of amphibolites from
Cordillera Frontal (Mendoza) indicates that metamorphic conditions evolutioned
from amphibolite to transitional to greenschist grades. Analytical data support
the paragenetic assemblage.
Palabras clave: EMPA, anfibolitas, condiciones del
metamorfismo, Mendoza.
Keywords: EMPA, amphibolites, metamorphic conditions, Mendoza.
Preliminary geochemical
characterization of the Granito Flores, NE North Patagonian Massif: an insight
into the mineralogical controls on T h distribution
M. López de Luchi *, A. E. Rapalini **, R.
TOMEZZOLI**
* Instituto de Geocronología y Geología
Isotópica, Pabellón INGEIS. Ciudad Universitaria, C1428EHA, Buenos Aires,
Argentina
** Instituto de Geofísica Daniel Valencio
(INGEODAV), Departamento de Ciencias Geológicas, Facultad de Ciencias Exactas y
Naturales, Universidad de Buenos Aires, CONICET, Pabellón 2, Ciudad
Universitaria, C1428EHA, Buenos Aires, Argentina
ABSTRACT:
The Granito
Flores represents the epizonal plutonism of the Early Jurassic Complejo
Plutónico-Volcánico Treneta. Two magmatic facies made up the intrusions: a
medium to coarse grained pink to reddish somewhat porphyric biotite
monzogranite and a fine grained leucomonzogranite with very scarce biotite.
These high-K and ferroan granites correspond to a mildly peraluminous suite
with a trend towards per-alkaline compositions and straddle the fields of the
sub-alkaline to medium alkaline types in the TAS diagram. Alkalies show an
opposite behaviour against SiO 2 whereas K 2 O exhibit a negative correlation
Na 2 O correlates positively indicating enrichment in sodium at the most
evolved terms. Rubidium contents range from 200 to 400 ppm whereas the rocks
are depleted in Sr and Ba. The granites are relatively enriched in Y, Nb, Ta,
Cs, and Th. The coherent behaviour of Th against K, Fe, Ti, La, Ce, Nd and Hf
suggest that biotite and other mafic minerals are the sink for Th. U is
decoupled from Th and therefore it may form its own minerals or may have been
mobilized. A trend towards increasing Na with SiO 2 does not reflect increasing
depth of crystallization but may be connected with the presence of fluorine as
fluorite is an ubiquitous, albeit scarce, constituent of the alteration
assemblages of feldspar and biotite.
Palabras Clave : Geoquímica-Torio-Granito Flores-NE Macizo
Norpatagónico
Keyword s: Geochemistry-Th -Granito Flores- NE North
Patagonian Massif
PERFILES DE ALTERACIÓN EN LA
DISCORDANCIA ENTRE EL COMPLEJO BUENOS AIRES Y LA FORMACIÓN LA TINTA, AREA DE
BARKER, TANDILIA
MARTÍNEZ, J.C.** y DRISTAS, J.A.*
** CONICET- Departamento de Geología,
Universidad Nacional del Sur. e-mail jcmartin@uns.edu.ar
*CIC y Departamento de Geología. Universidad
Nacional del Sur. e-mail: jdristas@criba.edu.ar
ABSTRACT:
At the
unconformity between the Buenos Aires Complex and La Tinta Formation, Barker
area (Tandilia Ranges), seven new profiles were surveyed. The petrography and
‘x' ray difractometry studies show an asymmetric alteration pattern from the
unconformity. The mineral parageneses involved are: chloritization,
sericitization, pyrophillitization, kaolinitization, carbonatization and silicification
as result of hydrothermal processes. This study confirms a regional
hydrothermal alteration at the unconformity basement-sedimentary cover.
Palabras clave : Discordancia – área de Barker – alteración
asimétrica – procesos hidrotermales.
Key words : Unconformity– Barker area – Asymmetric alteration
– hydrothermal processes.
CARACTERIZACIÓN PETROLÓGICA DEL
COMPLEJO VOLCÁNICO AGUA DE LA PIEDRA, PROVINCIA DE RÍO NEGRO
REMESAL, Marcela B.*, SALANI, Flavia M. * y
CERREDO, María E.*
*CONICET –, Departamento de Ciencias
Geológicas, Facultad de Ciencias Exactas y Naturales. Universidad de Buenos
Aires. Pabellón II Ciudad Universitaria (1428) Buenos Aires.
fms@gl.fcen.uba.ar
, remesal@gl.fcen.uba.ar , cerredo@gl.fcen.uba.ar
ABSTRACT:
The Neogene
Agua de la Piedra Volcanic Complex is a postshield eruptive assemblage located
at the western border of the Oligocene basaltic plateau Somún Curá of
the northern extrandean Patagonia. This volcanic building is composed of basal
pyroclastic flows of trachytic composition and upper lava flows which span from
early trachyte and lesser amount of rhyolite to posthumous basaltic
compositions. The series is characterized by its alkaline nature and displays a
typical compositional gap in the mesosiliceous realm. The inferred evolution
from the basic rocks to the trachyte-rhyolite differentiates would have been
controlled by the early olivine-clinopyroxene fractionation and later by
plagioclase+feldspar crystallization. The facies association and chemical
evolutionary path relates this volcanic complex to other post- plateau assemblages
of the Somún Curá environment.
Palabras clave: Patagonia Extraandina – Vulanismo neogeno –
Agua de la Piedra - Petrología
Keywords : Extrandean Patagonia – Neogene volcanism – Agua de
la Piedra - Petrology
GRANITOS Y ENCLAVES CON CORDIERITA
EN LOS PLUTONES SEÑOR DE LA PEÑA Y MAZÁN: POSIBLE ORIGEN COMÚN
ROSSI, J. N.* y TOSELLI, A. J.*
*Facultad de Ciencias Naturales Universidad
Nacional deTucumán - juanitarossi@csnat.unt.edu.ar
ABSTRACT:The chemistry of cordierite-bearing
granites, cordierites and enclaves of the Señor de la Peña and Mazán plutons
are compared to the granites and cordierites of the Central Iberian System. In
the latter, cordierite seems to have directly cristallized from melted rocks,
while cordierites of the Señor de la Peña and Mazán display characters of being
formed peritectic, remaining in fused contact with the granites under high
water activity conditions
Palabras clave: granitos cordieríticos – enclaves
cordieríticos – relación Mg-Fe-Mn
Key words : cordierite-granites – cordierite-enclaves –
Mg-Fe-Mn ratio -
LAS ROCAS TRAQUITICAS DEL COMPLEJO
VOLCANICO BARRIL NIYEU
SALANI, Flavia M.*; REMESAL, Marcela B.* y
CERREDO, María E.*
* CONICET – Departamento de Ciencias Geológicas,
Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Pabellón
II Ciudad Universitaria (1428) Buenos Aires.
fms@gl.fcen.uba.ar
, remesal@gl.fcen.uba.ar , cerredo@gl.fcen.uba.ar
ABSTRACT:
The Neogene
Barril Niyeu Volcanic Complex is a postshield eruptive assemblage located at
the SW of the Oligocene basaltic Somún Curá plateau of the northern
Extrandean Patagonia. The complex is made up of pyroclastic and lava facies
which span from basaltic through trachyte to minor rhyolite compositions.
Petrography and geochemistry outline of the trachyte rocks is reported in this
contribution. Trachyte rocks mostly occur as thick lava flows; rocks are
porphyric, with sanidine and aegirine, aegirine/augite phenocrysts set in a
trachytic groundmass. The domes within the four cauldrons of the complex are
composed either of comendites or quartz-trachytes. All the distinguished
trachyte groups share a peralkaline character, as is common in other Neogene postshield
complexes of the Somún Curá area.
Palabras clave :Patagonia Extrandina – Vulcanismo Neogeno –
Traquitas – Barril Niyeu
Keywords : Extrandean Patagonia – Neogene volcanism –
trachytes – Barril Niyeu
PRESENCIA DE ESTAUROLITA EN LAS
ROCAS MIGMÁTICAS ESTROMATÍTICAS DEL CAMPO LAS GUINDAS – UNRC, SIERRA DE
COMECHINGONES, CÓRDOBA.
SOMMARO, C 1 , FAGIANO, M. 2 y ESPARZA, A 2 .
1 Tema 2000 S.A. cecisommaro@yahoo.com.ar
2 Universidad Nacional de Río Cuarto. Depto. de Geología . mfagiano@exa.unrc.edu.ar
ABSTRACT:
In the Campo Las Guindas-UNRC, Sierra de Comechingones, Córdoba, the
staurolite is found. The presence of this mineral in stromatic migmatites enables
us to constraint the peak metamorphic conditions ranging from upper amphibolite
and lower granulite facies.
Palabras clave: estaurolita, migmatitas estromatíticas, Sierra
de Comechingones, Córdoba, Argentina.
Key words : staurolite, stromatic migmatites, Sierra de
Comechingones, Córdoba, Argentina.
REINTERPRETACIÓN DE LAS GRANULITAS
ÁCIDAS AFLORANTES EN VIRORCO, PROVINCIA DE SAN LUIS
ZAFFARANA, Claudia B. 1 , POMA, S. M. N 1,2 ,
LEAL, Pablo R. 1,2 y BRODTKORB, Milka K. de 1,2
1 Departamento de Ciencias Geológicas,
Universidad de Buenos Aires, e-mail: zaffarana@gl.fcen.uba.ar,
2 CONICET, e-mail: stella@gl.fcen.uba.ar,
leal@gl.fcen.uba.ar, milkabro@gl.fcen.uba.ar
ABSTRACT:
The aim of
this study is to provide a modern interpretation of the origin of the rocks
formerly named acid granulites which outcrop along the eastern border of
Virorco mafic-ultramafic body. The analysis of their macroscopical properties
suggests a similarity between these outcrops and the Sin-kinematic Granitoids
that occur in the study area, therefore they could be considered part of this
unit. However, their petrographic features demonstrate that the studied rocks
can be classified as granodiorites, while the surrounding Sin-kinematic
Granitoids belong to the granite field. Geochemical analyses confirm these
differences. Moreover they also evidence their peraluminous character and a
heavy REE pattern similar to the mafic-ultramafic rocks of Virorco. With
regards to the origin of the acid granulites, they could be the product of the
metamorphism of either a granodiorite or a plagi-granite. If the protolith were
a granodiorite, they could be interpreted as the result of the partial melting
of the country rocks (Pringles Metamorphic Complex) with contribution of the
Virorco mafic-ultramafic rocks. If we consider the second option
(plagi-granite), they could represent the acid residue of the crystallisation
of the stratified mafic-ultramafic rocks.
Kewords: Virorco, granulites, metamorphism, Sin-kinematic
Granitoids
Palabras clave: Virorco, granulitas,
metamorfismo, Granitoides Sincinemáticos