Vienna International Centre. International Atomic Energy Agency, Nov 1, 2020
In Argentina, Devonian-Carboniferous magmatism has played a very relevant role in uranium metallo... more In Argentina, Devonian-Carboniferous magmatism has played a very relevant role in uranium metallogenesis, driving magmatic and late-magmatic preconcentration processes, both within and in the periphery of the granitic massifs. This research has characterized different types and subtypes of uranium deposits linked to that fertile magmatism. These new studies on uranium minerals from uranium sites of interest have improved the metallogenetic knowledge of the granite-related uranium deposits, which in turn could aid the exploration for similar uranium deposits. It was determined that granites play an important role both as a uranium source and hosts of diverse types of uranium mineralization. Additionally, it is thought that, at the existing level of knowledge, there are prospects for the discovery and development of new uranium resources related to granites in Argentina.Fil: Álvarez, J.. Comisión Nacional de Energía Atómica; ArgentinaFil: Parra, F.. Comisión Nacional de Energía Atómica; ArgentinaFil: Anzil, Patricia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Bello, C.. Comisión Nacional de Energía Atómica; ArgentinaFil: Ceballos, E.. Comisión Nacional de Energía Atómica; ArgentinaFil: Salvatore, M.. Comisión Nacional de Energía Atómica; ArgentinaFil: Scarlatta, L.. Comisión Nacional de Energía Atómica; ArgentinaFil: Miyno, S.. Comisión Nacional de Energía Atómica; ArgentinaFil: Felkai, E.. Comisión Nacional de Energía Atómica; ArgentinaFil: Ferreyra, P.. Comisión Nacional de Energía Atómica; ArgentinaFil: Zelaya, A.. Comisión Nacional de Energía Atómica; ArgentinaFil: Cuney, M.. Université de Lorraine; FranciaFil: Mercadier, J.. Université de Lorraine; FranciaFil: Hanly, A.. International Atomic Energy Agency (iaea);Fil: Lira, Raul. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Museo de Mineralogía y Geología "Dr. A. Stelzner"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin
Revista de la Asociación Geológica Argentina, Mar 25, 2019
Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Aus... more Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Austral, Salta. El opalo ennodulos (~10 x 5 cm) se presenta a lo largo de lineamientos estructurales meridionales, en afloramientos intermitentes de hastaalgunos centenares de metros y <1 m de espesor, en sedimentitas-metasedimentitas ordovicicas de la Formacion Coquena. Estasmanifestaciones de opalo se restringen a vertientes actuales, cuyos canales de ascenso podrian ser los mismos que los de sistemasgeotermales erodados. Los nodulos estan compuestos mayoritariamente por opalo-CT y una delgada costra superficial de opalo-A; alo largo de algunos craquelados se formo calcedonia a partir de opalo-CT. La precipitacion inicial de opalo-A habria ocurrido a <100bares, hasta 800 m por debajo del paleonivel freatico, a partir de fluidos en ebullicion, de muy baja salinidad (<3 % en peso NaCleq.),entrampados entre ~280 y 160oC. La transformacion casi completa de opalo-A en opalo-CT se habria iniciado hace <30.000 anos.Los afloramientos actuales de opalo representarian zonas mas profundas de un paleosistema geotermal-epitermal cuyos derramesde sinter s.l., si los hubo, habrian sido erodados. Los valores calculados de d18OH2O en equilibrio con la precipitacion de opalo indicansu derivacion de aguas meteoricas mas livianas que las actuales. La calcita micritica que cementa nodulos de opalo fragmentados,se deposito a partir de fluidos meteoricos bicarbonatados, mas frios y mas recientes. El opalo de quebrada Quiron estaria geneticamentevinculado a las manifestaciones geotermales mas recientes del Complejo Volcanico El Queva, hecho que permitiria fortalecerinterpretaciones previas sobre la posible existencia de un sistema de cobre porfirico en profundidad.
The La Chinchilla granite is a ∼3.75 km2 epizonal pluton of Lower Carboniferous age located in Si... more The La Chinchilla granite is a ∼3.75 km2 epizonal pluton of Lower Carboniferous age located in Sierra de Velasco, Sierras Pampeanas, Argentina. Equigranular micropegmatitic and porphyritic main granite types host abundant millimeter- to <2 m-sized miarolitic pegmatites and pockets of simple major mineralogy (±beryl). Both granite types host micrometer-sized accessory species [i.e., monazite-(Ce), several high field strength element oxide species, ilmenite, cassiterite, fluorapatite] and fluorite. A F-Na-rich fluid phase promoted strong albitization at late-miarolitic stages, along with crystallization of extremely F-rich polylithionite and fluorite, and the formation of replacing pyrochlore group species associated with a second generation of cassiterite. The increase of the Ta# from hydroxycalciopyrochlore to hydroxycalciomicrolite and from micromiarolitic cassiterite (cassiterite 1) to hydrothermal cassiterite (cassiterite 2) supports Nb-Ta fractionation at hydrothermal tempera...
Helvine [Be3Mn2+4(SiO4)3S] occurs in less than one meter-sized spotty concentrations in some calc... more Helvine [Be3Mn2+4(SiO4)3S] occurs in less than one meter-sized spotty concentrations in some calcic skarns of Córdoba province, Argentina. The local geology, mineral chemistry, paragenetic mineral associations, and the evolution of helvine mineralizing fluids were studied from two selected localities (i.e., the Chingolo scheelite mine and Casa la Plata). Helvine from the Chingolo scheelite mine occurs in idiomorphic crystals up to 15 cm long, partially intergrown with spessartine-rich garnet, and in part or totally included in vug-filling spar calcite in the prograde garnet-vesuvianite skarn zone developed between replaced aplite-pegmatite dikes and calcic phlogopite-bearing marbles. Helvine from Casa la Plata occurs abundantly in vein-like, fluorite-rich garnet-vesuvianite skarn associations, where tetrahedrons up to 2 cm long occur preferentially included in fluorite in an illite-sericite-chlorite strongly replaced schist. The composition of helvine from both localities does not d...
Copper minerals (chrysocolla >> dioptase >> plancheite > tenorite) plus barite and quartz occur i... more Copper minerals (chrysocolla >> dioptase >> plancheite > tenorite) plus barite and quartz occur in a small lens of granulite-grade calcite-dolomite marble near Saldán, Córdoba Province (central Argentina, 31º18′50.7″S, 64º19′50.0″W). The mineralization is hosted in fractures (striking N30ºE and dipping 78ºW) that were widened by dissolution. Chrysocolla mainly fills fractures. It has variable H 2 O contents but the Cu:Si ratio is always close to 1 : 1. Plancheite forms compact fissure fillings and aggregates of interlocking spherules. Copper is partially replaced by Mg (up to 2.22 wt. % MgO), with small amounts of Na, K, Ca, Al and Fe also present. Dioptase occurs as prismatic crystals dominated by {1010} and {1121} that can reach over 2 cm in length, and also as granular fracture fillings. Unit-cell parameters are a 14.5719(6), c 7.7799(3) Å, V 1430.7(1) Å 3 ; refractive indices are ε = 1.707(3), ω = 1.656(3), with an anomalous small 2V. Magnesium (up to 0.15 wt. % MgO) is the only significant substituent. Yellow barite crystals tabular on {001} contain traces of Sr. Quartz occurs rarely, as drusy linings. A few cases of botryoidal, opal-like quartz crusts are known. Tenorite forms dark brown masses and stringers included in marble. Very scarce grains of copper sulfides (anilite altering to spionkopite and covellite along rims and cracks) are found scattered in the marble. Copper is partially replaced by Bi (≤ 0.15 wt. % Bi) and Pb (≤ 0.16 wt. % Pb). Malachite and brochantite are alteration products of sulfides. Fluid inclusion studies indicate that the minerals precipitated from a single-phase fluid initially at a temperature above 300 ºC that cooled to c. 220 ºC. Salinity was very low, 0 to 2 wt. % NaCl eq. Isotopic analyses of calcite give δ 13 C values of 0.4-0.9 ‰ PDB and δ 18 O values of 17.1-15.1 ‰ VSMOW, coincident with the isotopic signature of the regional marbles. Calculated values of δ 18 O for water in isotopic equilibrium with calcite fall into with the Metamorphic Water Box. The δ 34 S values of barite are 3.6-4.6 ‰ CDT. The mineralization possibly precipitated from fluids of meteoric origin that suffered an oxygen isotope shift due to a very low water/rock ratio. The sulfur source could have been sedimentary or igneous sulfides, or a mixture from two different sources (such as heavy seawater-derived sulfur and light sedimentary sulfides), but not exclusively seawater. Copper was probably scavenged from accessory sulfides scattered in barren marble or orthoamphibolite. The heat source remains unknown.
Copper minerals (chrysocolla>> dioptase>> plancheite> tenorite) plus barite and qu... more Copper minerals (chrysocolla>> dioptase>> plancheite> tenorite) plus barite and quartz occur in a small lens of gra-
RESUMEN Este estudio se realizó en tres pegmatitas en el borde oriental del batolito de Achala, c... more RESUMEN Este estudio se realizó en tres pegmatitas en el borde oriental del batolito de Achala, cerca de Villa Santa Cruz del Lago, provincia de Córdoba. Las rocas encajonantes son monzogranitos porfíricos y equigranulares y enclaves de monzogranito hornblendífero. ...
type affiliation (miarolitic class, miarolitic–rare earth element subclass, with features more si... more type affiliation (miarolitic class, miarolitic–rare earth element subclass, with features more similar to those reported for the gadolinite–fergusonite type). This study was performed on samples from the host granite and several zones of pegmatites, including crystals growing in miarolitic cavities and fine-grained overgrowths. Micas from the granite and massive pegmatites are rather homogeneous, but crystals coming from miarolitic cavities are usually sharply zoned with monocrystalline trioctahedral inner zones overgrown by polycrystalline dioctahedral rims. Dioctahedral micas are always paragenetically later. Micas from the granite are intermediate members of the annite–siderophyllite series. From the outer pegmatite zones inwards the substitution (SiLi)([4]AlFe) –1 in trioctahedral micas leads to compositions intermediate between siderophyl-lite and polylithionite, up to the composition KLiFe2+Al(AlSi3)O10(F,OH)2 (formerly called zinnwaldite). Dioctahedral micas also show a trend...
Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Aus... more Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Austral, Salta. El opalo ennodulos (~10 x 5 cm) se presenta a lo largo de lineamientos estructurales meridionales, en afloramientos intermitentes de hastaalgunos centenares de metros y <1 m de espesor, en sedimentitas-metasedimentitas ordovicicas de la Formacion Coquena. Estasmanifestaciones de opalo se restringen a vertientes actuales, cuyos canales de ascenso podrian ser los mismos que los de sistemasgeotermales erodados. Los nodulos estan compuestos mayoritariamente por opalo-CT y una delgada costra superficial de opalo-A; alo largo de algunos craquelados se formo calcedonia a partir de opalo-CT. La precipitacion inicial de opalo-A habria ocurrido a <100bares, hasta 800 m por debajo del paleonivel freatico, a partir de fluidos en ebullicion, de muy baja salinidad (<3 % en peso NaCleq.),entrampados entre ~280 y 160oC. La transformacion casi completa de opalo-A en opalo-CT se habr...
El hallazgo de rutilo niobifero en el Cordon Centenario, Puna Austral, permitio estudiar sus cara... more El hallazgo de rutilo niobifero en el Cordon Centenario, Puna Austral, permitio estudiar sus caracteristicas mineralogicas y discutir su origen. El rutilo se halla incluido en un unico bloque de cuarzo con escaso transporte aluvial. Los cristales (rutilo I) miden entre 0,5 y 3 cm, son negros con brillo metalico, manifiestan habito prismatico con caras estriadas, algunos maclados en “rodilla o codo”. Son caracteristicas las inclusiones de menos de 1 mm de agregados pseudomorficos de rutilo II-chamosita-cuarzo-sericita-illita-leucoxeno-hematita-dolomita que representarian el reemplazo de cristales idiomorfos mas tempranos de ilmenita I (niobifera) + biotita. El rutilo I muestra una intrincada zonacion en dominios acunados y exsoluciones micrometricas de ilmenita II en intercrecimiento tipo widmanstatten ; via microfracturas, se halla parcialmente reemplazado por una generacion tardia de ilmenita III. Los elementos Nb-Fe-V-Ta-W-Hf reemplazan diferencialmente al Ti generando zonas mas ...
Ecandrewsite (ZnTiO3) and other ilmenite-group minerals have been found in amphibolites of the Si... more Ecandrewsite (ZnTiO3) and other ilmenite-group minerals have been found in amphibolites of the Sierras de Córdoba basement, Argentina, in an area where zinc is a relatively widespread element in the associated metasedimentary and metaigneous sequences. Ilmenite group minerals occur as anhedral to subhedral, tens to a hundred micrometer-sized relic inclusions in titanite. Electron microprobe analyses reveal compositions along a discontinuous solid-solution trend ranging from manganoan ferroan ecandrewsite toward ilmenite s.s., passing through intermediate members such as ferroan manganoan ecandrewsite, zincian manganoan ilmenite, and manganoan ilmenite. Considering that thermodynamic constraints do exist for the solubility of ZnTiO3 in ilmenite under mid- to high-grade regional metamorphic conditions, we believe that ecandrewsite and Zn-rich ilmenite compositions were attained by metasomatic fluid–mineral reactions during retrograde regional metamorphism, i.e., after the centripetal ...
En Papachacra (Provincia de Catamarca, NO de Argentina) hay un plutón compuesto por varios tipos ... more En Papachacra (Provincia de Catamarca, NO de Argentina) hay un plutón compuesto por varios tipos diferentes de granitoides de tipo A con afinidad alcalina. Las rocas más tardías son riolitas peralcalinas (comenditas), que forman diques de hasta 50 cm atravesando el granito ...
La actividad minero-metalúrgica en los distritos mineros El Guaico y La Argentina, en el noroeste... more La actividad minero-metalúrgica en los distritos mineros El Guaico y La Argentina, en el noroeste de la provincia de Córdoba, comenzó a principios del siglo XIX; sin embargo, los antecedentes de la minería en la provincia se remontan a finales del siglo XVI. En la actualidad sobreviven vestigios de lo que otrora fue un foco de beneficio socio-económico para la región, como establecimientos abandonados, hornos de fundición en ruinas y voluminosas escombreras enmascaradas por la vegetación. En 2018 se halló material digno de estudio en escombreras contiguas a las ruinas del horno de fundición de mina La Argentina. Estudios por difracción de rayos X y espectroscopía de energía dispersiva de rayos X permitieron su identificación como litargirio (PbO) con inclusiones de plomo argentífero (Pb ± Ag). Si bien la muestra presentaba indicios texturales de material artificial, el estudio fue motivado debido a que ambos compuestos químicos pueden también formarse en la naturaleza conformado esp...
Vienna International Centre. International Atomic Energy Agency, Nov 1, 2020
In Argentina, Devonian-Carboniferous magmatism has played a very relevant role in uranium metallo... more In Argentina, Devonian-Carboniferous magmatism has played a very relevant role in uranium metallogenesis, driving magmatic and late-magmatic preconcentration processes, both within and in the periphery of the granitic massifs. This research has characterized different types and subtypes of uranium deposits linked to that fertile magmatism. These new studies on uranium minerals from uranium sites of interest have improved the metallogenetic knowledge of the granite-related uranium deposits, which in turn could aid the exploration for similar uranium deposits. It was determined that granites play an important role both as a uranium source and hosts of diverse types of uranium mineralization. Additionally, it is thought that, at the existing level of knowledge, there are prospects for the discovery and development of new uranium resources related to granites in Argentina.Fil: Álvarez, J.. Comisión Nacional de Energía Atómica; ArgentinaFil: Parra, F.. Comisión Nacional de Energía Atómica; ArgentinaFil: Anzil, Patricia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Bello, C.. Comisión Nacional de Energía Atómica; ArgentinaFil: Ceballos, E.. Comisión Nacional de Energía Atómica; ArgentinaFil: Salvatore, M.. Comisión Nacional de Energía Atómica; ArgentinaFil: Scarlatta, L.. Comisión Nacional de Energía Atómica; ArgentinaFil: Miyno, S.. Comisión Nacional de Energía Atómica; ArgentinaFil: Felkai, E.. Comisión Nacional de Energía Atómica; ArgentinaFil: Ferreyra, P.. Comisión Nacional de Energía Atómica; ArgentinaFil: Zelaya, A.. Comisión Nacional de Energía Atómica; ArgentinaFil: Cuney, M.. Université de Lorraine; FranciaFil: Mercadier, J.. Université de Lorraine; FranciaFil: Hanly, A.. International Atomic Energy Agency (iaea);Fil: Lira, Raul. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Museo de Mineralogía y Geología "Dr. A. Stelzner"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin
Revista de la Asociación Geológica Argentina, Mar 25, 2019
Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Aus... more Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Austral, Salta. El opalo ennodulos (~10 x 5 cm) se presenta a lo largo de lineamientos estructurales meridionales, en afloramientos intermitentes de hastaalgunos centenares de metros y <1 m de espesor, en sedimentitas-metasedimentitas ordovicicas de la Formacion Coquena. Estasmanifestaciones de opalo se restringen a vertientes actuales, cuyos canales de ascenso podrian ser los mismos que los de sistemasgeotermales erodados. Los nodulos estan compuestos mayoritariamente por opalo-CT y una delgada costra superficial de opalo-A; alo largo de algunos craquelados se formo calcedonia a partir de opalo-CT. La precipitacion inicial de opalo-A habria ocurrido a <100bares, hasta 800 m por debajo del paleonivel freatico, a partir de fluidos en ebullicion, de muy baja salinidad (<3 % en peso NaCleq.),entrampados entre ~280 y 160oC. La transformacion casi completa de opalo-A en opalo-CT se habria iniciado hace <30.000 anos.Los afloramientos actuales de opalo representarian zonas mas profundas de un paleosistema geotermal-epitermal cuyos derramesde sinter s.l., si los hubo, habrian sido erodados. Los valores calculados de d18OH2O en equilibrio con la precipitacion de opalo indicansu derivacion de aguas meteoricas mas livianas que las actuales. La calcita micritica que cementa nodulos de opalo fragmentados,se deposito a partir de fluidos meteoricos bicarbonatados, mas frios y mas recientes. El opalo de quebrada Quiron estaria geneticamentevinculado a las manifestaciones geotermales mas recientes del Complejo Volcanico El Queva, hecho que permitiria fortalecerinterpretaciones previas sobre la posible existencia de un sistema de cobre porfirico en profundidad.
The La Chinchilla granite is a ∼3.75 km2 epizonal pluton of Lower Carboniferous age located in Si... more The La Chinchilla granite is a ∼3.75 km2 epizonal pluton of Lower Carboniferous age located in Sierra de Velasco, Sierras Pampeanas, Argentina. Equigranular micropegmatitic and porphyritic main granite types host abundant millimeter- to <2 m-sized miarolitic pegmatites and pockets of simple major mineralogy (±beryl). Both granite types host micrometer-sized accessory species [i.e., monazite-(Ce), several high field strength element oxide species, ilmenite, cassiterite, fluorapatite] and fluorite. A F-Na-rich fluid phase promoted strong albitization at late-miarolitic stages, along with crystallization of extremely F-rich polylithionite and fluorite, and the formation of replacing pyrochlore group species associated with a second generation of cassiterite. The increase of the Ta# from hydroxycalciopyrochlore to hydroxycalciomicrolite and from micromiarolitic cassiterite (cassiterite 1) to hydrothermal cassiterite (cassiterite 2) supports Nb-Ta fractionation at hydrothermal tempera...
Helvine [Be3Mn2+4(SiO4)3S] occurs in less than one meter-sized spotty concentrations in some calc... more Helvine [Be3Mn2+4(SiO4)3S] occurs in less than one meter-sized spotty concentrations in some calcic skarns of Córdoba province, Argentina. The local geology, mineral chemistry, paragenetic mineral associations, and the evolution of helvine mineralizing fluids were studied from two selected localities (i.e., the Chingolo scheelite mine and Casa la Plata). Helvine from the Chingolo scheelite mine occurs in idiomorphic crystals up to 15 cm long, partially intergrown with spessartine-rich garnet, and in part or totally included in vug-filling spar calcite in the prograde garnet-vesuvianite skarn zone developed between replaced aplite-pegmatite dikes and calcic phlogopite-bearing marbles. Helvine from Casa la Plata occurs abundantly in vein-like, fluorite-rich garnet-vesuvianite skarn associations, where tetrahedrons up to 2 cm long occur preferentially included in fluorite in an illite-sericite-chlorite strongly replaced schist. The composition of helvine from both localities does not d...
Copper minerals (chrysocolla >> dioptase >> plancheite > tenorite) plus barite and quartz occur i... more Copper minerals (chrysocolla >> dioptase >> plancheite > tenorite) plus barite and quartz occur in a small lens of granulite-grade calcite-dolomite marble near Saldán, Córdoba Province (central Argentina, 31º18′50.7″S, 64º19′50.0″W). The mineralization is hosted in fractures (striking N30ºE and dipping 78ºW) that were widened by dissolution. Chrysocolla mainly fills fractures. It has variable H 2 O contents but the Cu:Si ratio is always close to 1 : 1. Plancheite forms compact fissure fillings and aggregates of interlocking spherules. Copper is partially replaced by Mg (up to 2.22 wt. % MgO), with small amounts of Na, K, Ca, Al and Fe also present. Dioptase occurs as prismatic crystals dominated by {1010} and {1121} that can reach over 2 cm in length, and also as granular fracture fillings. Unit-cell parameters are a 14.5719(6), c 7.7799(3) Å, V 1430.7(1) Å 3 ; refractive indices are ε = 1.707(3), ω = 1.656(3), with an anomalous small 2V. Magnesium (up to 0.15 wt. % MgO) is the only significant substituent. Yellow barite crystals tabular on {001} contain traces of Sr. Quartz occurs rarely, as drusy linings. A few cases of botryoidal, opal-like quartz crusts are known. Tenorite forms dark brown masses and stringers included in marble. Very scarce grains of copper sulfides (anilite altering to spionkopite and covellite along rims and cracks) are found scattered in the marble. Copper is partially replaced by Bi (≤ 0.15 wt. % Bi) and Pb (≤ 0.16 wt. % Pb). Malachite and brochantite are alteration products of sulfides. Fluid inclusion studies indicate that the minerals precipitated from a single-phase fluid initially at a temperature above 300 ºC that cooled to c. 220 ºC. Salinity was very low, 0 to 2 wt. % NaCl eq. Isotopic analyses of calcite give δ 13 C values of 0.4-0.9 ‰ PDB and δ 18 O values of 17.1-15.1 ‰ VSMOW, coincident with the isotopic signature of the regional marbles. Calculated values of δ 18 O for water in isotopic equilibrium with calcite fall into with the Metamorphic Water Box. The δ 34 S values of barite are 3.6-4.6 ‰ CDT. The mineralization possibly precipitated from fluids of meteoric origin that suffered an oxygen isotope shift due to a very low water/rock ratio. The sulfur source could have been sedimentary or igneous sulfides, or a mixture from two different sources (such as heavy seawater-derived sulfur and light sedimentary sulfides), but not exclusively seawater. Copper was probably scavenged from accessory sulfides scattered in barren marble or orthoamphibolite. The heat source remains unknown.
Copper minerals (chrysocolla>> dioptase>> plancheite> tenorite) plus barite and qu... more Copper minerals (chrysocolla>> dioptase>> plancheite> tenorite) plus barite and quartz occur in a small lens of gra-
RESUMEN Este estudio se realizó en tres pegmatitas en el borde oriental del batolito de Achala, c... more RESUMEN Este estudio se realizó en tres pegmatitas en el borde oriental del batolito de Achala, cerca de Villa Santa Cruz del Lago, provincia de Córdoba. Las rocas encajonantes son monzogranitos porfíricos y equigranulares y enclaves de monzogranito hornblendífero. ...
type affiliation (miarolitic class, miarolitic–rare earth element subclass, with features more si... more type affiliation (miarolitic class, miarolitic–rare earth element subclass, with features more similar to those reported for the gadolinite–fergusonite type). This study was performed on samples from the host granite and several zones of pegmatites, including crystals growing in miarolitic cavities and fine-grained overgrowths. Micas from the granite and massive pegmatites are rather homogeneous, but crystals coming from miarolitic cavities are usually sharply zoned with monocrystalline trioctahedral inner zones overgrown by polycrystalline dioctahedral rims. Dioctahedral micas are always paragenetically later. Micas from the granite are intermediate members of the annite–siderophyllite series. From the outer pegmatite zones inwards the substitution (SiLi)([4]AlFe) –1 in trioctahedral micas leads to compositions intermediate between siderophyl-lite and polylithionite, up to the composition KLiFe2+Al(AlSi3)O10(F,OH)2 (formerly called zinnwaldite). Dioctahedral micas also show a trend...
Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Aus... more Agregados nodulares de opalo se hallan dispersos entre Quebrada Quiron y Quebrada Honda, Puna Austral, Salta. El opalo ennodulos (~10 x 5 cm) se presenta a lo largo de lineamientos estructurales meridionales, en afloramientos intermitentes de hastaalgunos centenares de metros y <1 m de espesor, en sedimentitas-metasedimentitas ordovicicas de la Formacion Coquena. Estasmanifestaciones de opalo se restringen a vertientes actuales, cuyos canales de ascenso podrian ser los mismos que los de sistemasgeotermales erodados. Los nodulos estan compuestos mayoritariamente por opalo-CT y una delgada costra superficial de opalo-A; alo largo de algunos craquelados se formo calcedonia a partir de opalo-CT. La precipitacion inicial de opalo-A habria ocurrido a <100bares, hasta 800 m por debajo del paleonivel freatico, a partir de fluidos en ebullicion, de muy baja salinidad (<3 % en peso NaCleq.),entrampados entre ~280 y 160oC. La transformacion casi completa de opalo-A en opalo-CT se habr...
El hallazgo de rutilo niobifero en el Cordon Centenario, Puna Austral, permitio estudiar sus cara... more El hallazgo de rutilo niobifero en el Cordon Centenario, Puna Austral, permitio estudiar sus caracteristicas mineralogicas y discutir su origen. El rutilo se halla incluido en un unico bloque de cuarzo con escaso transporte aluvial. Los cristales (rutilo I) miden entre 0,5 y 3 cm, son negros con brillo metalico, manifiestan habito prismatico con caras estriadas, algunos maclados en “rodilla o codo”. Son caracteristicas las inclusiones de menos de 1 mm de agregados pseudomorficos de rutilo II-chamosita-cuarzo-sericita-illita-leucoxeno-hematita-dolomita que representarian el reemplazo de cristales idiomorfos mas tempranos de ilmenita I (niobifera) + biotita. El rutilo I muestra una intrincada zonacion en dominios acunados y exsoluciones micrometricas de ilmenita II en intercrecimiento tipo widmanstatten ; via microfracturas, se halla parcialmente reemplazado por una generacion tardia de ilmenita III. Los elementos Nb-Fe-V-Ta-W-Hf reemplazan diferencialmente al Ti generando zonas mas ...
Ecandrewsite (ZnTiO3) and other ilmenite-group minerals have been found in amphibolites of the Si... more Ecandrewsite (ZnTiO3) and other ilmenite-group minerals have been found in amphibolites of the Sierras de Córdoba basement, Argentina, in an area where zinc is a relatively widespread element in the associated metasedimentary and metaigneous sequences. Ilmenite group minerals occur as anhedral to subhedral, tens to a hundred micrometer-sized relic inclusions in titanite. Electron microprobe analyses reveal compositions along a discontinuous solid-solution trend ranging from manganoan ferroan ecandrewsite toward ilmenite s.s., passing through intermediate members such as ferroan manganoan ecandrewsite, zincian manganoan ilmenite, and manganoan ilmenite. Considering that thermodynamic constraints do exist for the solubility of ZnTiO3 in ilmenite under mid- to high-grade regional metamorphic conditions, we believe that ecandrewsite and Zn-rich ilmenite compositions were attained by metasomatic fluid–mineral reactions during retrograde regional metamorphism, i.e., after the centripetal ...
En Papachacra (Provincia de Catamarca, NO de Argentina) hay un plutón compuesto por varios tipos ... more En Papachacra (Provincia de Catamarca, NO de Argentina) hay un plutón compuesto por varios tipos diferentes de granitoides de tipo A con afinidad alcalina. Las rocas más tardías son riolitas peralcalinas (comenditas), que forman diques de hasta 50 cm atravesando el granito ...
La actividad minero-metalúrgica en los distritos mineros El Guaico y La Argentina, en el noroeste... more La actividad minero-metalúrgica en los distritos mineros El Guaico y La Argentina, en el noroeste de la provincia de Córdoba, comenzó a principios del siglo XIX; sin embargo, los antecedentes de la minería en la provincia se remontan a finales del siglo XVI. En la actualidad sobreviven vestigios de lo que otrora fue un foco de beneficio socio-económico para la región, como establecimientos abandonados, hornos de fundición en ruinas y voluminosas escombreras enmascaradas por la vegetación. En 2018 se halló material digno de estudio en escombreras contiguas a las ruinas del horno de fundición de mina La Argentina. Estudios por difracción de rayos X y espectroscopía de energía dispersiva de rayos X permitieron su identificación como litargirio (PbO) con inclusiones de plomo argentífero (Pb ± Ag). Si bien la muestra presentaba indicios texturales de material artificial, el estudio fue motivado debido a que ambos compuestos químicos pueden también formarse en la naturaleza conformado esp...
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