Stalactitic rhodochrosite from the 25 de Mayo and Nueve veins, Capillitas, Catamarca, Argentina: Physical and chemical variations

Capillitas is an epithermal vein-type deposit in Argentina known for its mineralogical diversity, with more than one hundred and twenty described minerals, including five new species, and for the presence of banded and stalactitic rhodochrosite. Stalactites occur as single or combined cylinders of different sizes, from a few cm to 1.36 m in length and diameters up to 8 cm. Their cross-sections may show diverse aspects: from simple concentric banding to more intricate textures, whereas their external surface can be smooth, with undulations or with a poker-chip-like texture. The color of the stalactites varies from white to raspberry pink, with occasional brown bands toward the edges corresponding to a variety of rhodochrosite called “capillitite”. The contents of MnO range from 27.50 to 61.71 wt. % as it may be significantly replaced by CaO, FeO, ZnO and MgO. Replacements are reflected in the various shades of pink and brown displayed by this mineral. The different substitutions in the pink specimens exert only a minor influence on the unit cell parameters, whereas, in the brown variety, their size is significantly smaller with average values for pink rhodochrosite (n = 24): a 4.776 Å, c 15.690 Å and a cell volume of 310.3 Å3, whereas, “capillitite” unit-cell parameters (n = 7) are: a = 4.739, c = 15.558 with a unit-cell volume of 302.6 Å3. Conditions of formation of the banded rhodochrosite of the 25 de Mayo vein, obtained from fluid inclusions data, indicate temperatures of 145 ° to 150 °C and salinities of up to 4 wt. % NaCl(eq). The formation of the stalactites is explained by the infiltration of epithermal aqueous liquid, oversa-turated with Mn and bicarbonate, into a transiently vapor-filled, isolated cavity.Fil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Craig, James R.. Virginia Tech University; Estados Unido

The Ag- And Au-bearing phases in the Escondida epithermal vein, Cerro Moro deposit, Santa Cruz, Argentina

The Cerro Moro deposit is located at 488505500S, 6683901.600W and 100 m.o.s.l. in Santa Cruz province, southern Argentina. It is a low sulfidation Au-Ag epithermal mineralization hosted by numerous NW-SE structurally controlled quartz veins developed in close spatial and temporal proximity to the products of Jurassic extension and magmatism. The Escondida vein is the most significant mineralized structure, as it hosts the base metal-rich and Au-Ag high grade mineralization. In this vein and the Zoe ore-shoot, ore minerals are abundant (sphalerite, galena, chalcopyrite, acanthite, and less abundant pyrite and marcasite) and frequently related to dark grey, fine-grained quartz with massive, porous, crustiform, and banded textures; variable quantities of fine-grained flakes of muscovite are locally present. The Ag- and Au-bearing mineral association is represented by acanthite, argyrodite, polybasite, pearceite, stromeyerite, mckinstryite, and jalpaite. Abundant acanthite occurs commonly associated with gold and silver; copper enrichments were detected and interpreted as nanoinclusions of Cu-bearing minerals. The occurrence of Se- and Te-enriched minerals (acanthite, argyrodite, polybasite, pearceite, stromeyerite, and mckinstryite), rather than silver selenides and/or tellurides, indicates the presence of reduced mineralizing fluids and may be ascribed to partial substitution of S by Se or Te. Polybasite and pearceite were differentiated by their chemistry. Although the presence of argyrodite in epithermal deposits with silver sulfosalts is relatively common, this first mention in Cerro Moro is highly encouraging for exploration for germanium, a critical element, which is also considered strategic by countries such as the USA and China.Fil: Mugas Lobos, Ana Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Hernández, Laura B.. Universidad de Concepción; Chil

The Don Sixto mining project: A low sulphidation Au-Ag deposit 5-08 of Permian-Triassic age, Mendoza, Argentina, mineralogy, fluid inclusions, stable isotopes and 40Ar/39Ar age results

It is described the ore mineralogy, fluid inclussion study, stable isotopes results and 40Ar/39Ar age determination of the Don Sixto, a low-sulphidation epithermal ore deposit from southern Mendoza.Fil: Mugas Lobos, Ana Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Artes y Dise?o; ArgentinaFil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

The Nb-Ta-U minerals of the María Elena pegmatite, San Luis range, Argentina

Se describe la asociación de minerales de Nb-Ta-U encontrados en la pegmatita María Elena, Sierra de San Luis, Argentina. La asociación de columbita-(Mn), kenopirocloro, plumbopirocloro con plumbomicrolita y kenomicrolite subordinados se presenta en una pegmatita de elementos raros de tipo berilo. La columbita-(Mn) considerada primaria, magmática, forma cristales grises oscuros de hasta 10 cm cubiertos por delgadas películas amarillas en la asociación de borde de núcleo de la pegmatita. Los cristales muestran #Ta variable (0.12 a 0.14), con contenidos de TiO2 entre 0.54 y 2.18% p. y de UO2 de 0.01 a 0.89% p. Los cristales de columbita-(Mn) muestran un reemplazo local menor formado por venillas milimétricas irregulares y parches de minerales del supergrupo del pirocloro. El kenopirocloro, asociado con plumbopirocloro y escaso pirocloro rico en U-Ca, contiene dominios irregulares, grietas finas y cristales tabulares principalmente de plumbomicrolita y kenomicrolita. Además, una segunda generación de minerales secundarios contiene kenopirocloro amarillo rico en uranio en finas venillas que atraviesan la columbita-(Mn). La superposición hidrotermal que modificó la fase primaria movilizando sus contenidos de Nb, Ta y U, contenía Pb posiblemente proveniente de una fuente exógena.The Nb-Ta-U mineral association of the María Elena pegmatite, San Luis range, Argentina is described. The assemblage of columbite-(Mn), kenopyrochlore, plumbopyrochlore and minor plumbomicrolite and kenomicrolite occurs in a rare-element pegmatite of beryl type. Primary, magmatic columbite-(Mn) forms up to 10 cm dark gray crystals covered by thin yellow films in the core-margin association of the pegmatite. Crystals show #Ta variable from 0.12 to 0.14, with TiO2 contents between 0.54 and 2.18 wt.% and of UO2 from 0.01 to 0.89 wt.%. The columbite-(Mn) crystals show minor local replacement by irregular millimetric veinlets and patches of pyrochlore supergroup minerals. Kenopyrochlore, associated with plumbopyrochlore and minor amounts of U-Ca-rich pyrochlore, contains irregular domains, fine cracks and tabular crystals mainly of plumbomicrolite and kenomicrolite. Besides, a second generation of secondary minerals contain yellow uranium-rich kenopyrochlore in fine veinlets that cut across columbite-(Mn). The hydrothermal overprint that reworked the primary phase mobilizing its Nb, Ta and U contents, contained a Pb input from a possibly exogenous source.Fil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Roquet, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnol.conicet - San Luis. Unidad de Direccion; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentin

Indium-bearing paragenesis from the Nueva Esperanza and Restauradora veins, Capillitas mine, Argentina

The Nueva Esperanza and Restauradora are two of the twenty-three veins described at Capillitas mine, an epithermal precious-and base-metal vein deposit located in northern Argentina. Capillitas is genetically linked to other minera-lizations of the Farallón Negro Volcanic Complex, which hosts several deposits. These include two world-class (La Alumbrera and Agua Rica) and some smaller (e.g., Bajo El Durazno) porphyry deposits, and a few epithermal deposits (Farallón Negro, Alto de la Blenda, Cerro Atajo and Capillitas). The main hypogene minerals found at these two veins include pyrite, sphalerite, galena, chalcopyrite, tennantite-(Zn) and tennantite-(Fe). Accessory minerals comprise hübnerite, gold, silver, stannite, stannoidite and mawsonite, and also diverse indium-and tellurium-bearing minerals. Quartz is the main gangue mineral. Indium participates in the structure of sphalerite, tennantite-(Zn), ishiharaite and an indium-bearing mineral, still under study, the former being the most abundant of these phases. The chemical composition of sphalerite shows very low concentrations of Fe and a wide range in indium contents from below the detection limit (0.03 wt. %) to values close to 22 wt. %. Atomic proportions of In and Cu correlate positively at a ratio In: Cu = 1: 1 atoms per formula unit. Cadmium reaches up to 0.68 wt. %. Other analyzed elements (Ge, As, Se, Ag, Sn, Te, Au, Pb and Bi) are systematically below their respective detection limits. Indium-bearing tennantite-(Zn) (up to 0.24 wt. % In) is rare and restricted to the area where ishiharaite appears. Ishiharaite and the unclassified indium-bearing mineral are extremely scarce and host up to 10 and 30 wt. % In, respectively. The zoning in sphalerite and the variable indium content of the different bands could be ascribed to significant fluctuation in the composition of the fluids (possibly pulses). They are evidenced by the presence of a high f Te2 mineral, like calaverite, and a low f Te2 phase, such as silver, within the same stage, with local periodic increments on In and Cu that could also be associated with recurring reactivation of fractures.Fil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Vymazalová, Anna. Czech Geological Survey; República ChecaFil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Watanabe, Yasushi. Mining Museum of Akita University; JapónFil: Murakami, Hiroyasu. No especifíca

Don Sixto, un depósito de Au de baja sulfuración del Pérmico-Triásico, Mendoza

Don Sixto is a 252.7±1.3 Ma, low sulfidation epithermal Au deposit located in Mendoza, Argentina. The mineralization in this area (~4 km2) reaches a gold resource of 1,258,000 ounces, occurring as Au-quartz veins and Au-dissemination in volcanic-pyroclastic units closely related to the Choiyoi magmatism. Seven stages of mineralization were recognized, where quartz is the major gangue mineral with lesser adularia and fluorite (± calcite). The most representative vein textures are massive, crustiform and comb. Bladed quartz together with adularia (± calcite) were recognized in the stages 2 and 4. Abundant pyrite and lesser arsenopyrite, chalcopyrite and sphalerite were recognized in most stages. Gold has variable fineness and occurs mainly in the stage 4, together with scarce uytenbogaardtite, acanthite and Se- and Te-bearing minerals. Microthermometry data indicate that mineralizing fluids were diluted (<5.16 wt. %ClNaequiv) with average homogenization temperatures reaching <316.0 ºC. LA-ICP-MS results indicate that the highest values of Na, K and S were reached in the stage 4 and 5, closely related to boiling conditions in the former. In general, a limited data set was obtained due to the small size of the fluid inclusions and the low signals that prevented analysis, which are common characteristics of low sulfidation deposits. The stable isotope data δ18OH2O indicate a major meteoric water source for the oxygen in the fluids. Regarding δ34S, the preliminary value does not define a unique source; instead a mixed one is feasible between magmatic source and a possible contribution from the sedimentary Agua Escondida Formation.Fil: Mugas Lobos, Ana Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Wälle, Markus. ETH Zurich; Suiz

Mineralogy of the Rincón Blanco selenide occurrence, La Rioja, Argentina

Rincón Blanco is a small selenide occurrence situated to the WNW of Jagüé, a small town of the General Sarmiento department, La Rioja province, Argentina. This occurrence, also called El Chire in recent years, is located (28°35'46.10"S, 68°44'35.78"W, 3120 m. a. s. l.) in the Precordillera environment, to the furthermost southwestern corner of the selenium ore district of Los Llantenes, defined as one of the representative metallogenic belts of the Gondwanic episodes. The selenide minerals occur as veinlets up to few centimeters or as patches or fine inclusions, widespread in calcite. We have identified eleven hypogene Se-bearing minerals (naumannite, tiemannite, chrisstanleyite, jagüéite, eucairite, clausthalite, fischesserite, umangite, athabascaite, berzelianite and bellidoite) mainly associated with gold, silver, hematite and various supergene minerals, including malachite, chalcomenite, and molybdomenite. The paragenesis should have formed from low temperature (< 133 °C), neutral to mildly alkaline pH and highly oxidizing fluids with increasing sulfur fugacity. The country-rock, rich in graptolite-fauna, could be considered, at least in part, the source for the Se and associated metals forming the minerals of this paragenesis, although this hypothesis has yet to be tested.Fil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Skácha, Pavel. National Museum; República ChecaFil: Macek, Ivo. National Museum, Prague, Czech Republic; República ChecaFil: Sejkora, Jiří. National Museum; República ChecaFil: Dolnícek, Zdeněk. National Museum; República Chec

Bismutotantalite from northwestern Argentina: Description and crystal structure

Bismutotantalite occurs in albite-rich cores of the La Elvirita granitic pegmatites, northwestern Argentina, associated mainly with bismuth, bismuthinite, ferrotapiolite, manganotantalite, microlite, uranmicrolite, bismutomicrolite, hafnian zircon and montebrasite. A fresh, cm-sized crystal, dark grey with a greasy luster and D = 8.809 g/cm3, was examined. In reflected light, it is grey with very weak bireflectance; two phases can be distinguished. Electron-microprobe analysis gives the host bismutotantalite [Bi] as [Bi,Sb], (Bi0.68Sb0.32)(Ta0.89Nb0.11)O4, is enriched in Sb. Least-squares refinement of X-ray powder-diffraction data of [Bi] gave a 4.968(1), b 11.796(3), c 5.646(1) Å, V = 330.85(9) Å3. The crystal structures of [Bi] and [Bi,Sb] were refined to R indices of 1.9 and 2.4%, based on 387 and 377 observed (4σ) reflections, respectively, measured with MoKα X-radiation. Both phases are orthorhombic, space group Pcnn. Z = 4; [Bi] has a 4.9652(4), b 11.7831(16), c 5.6462(5) Å. V 330.32(6) Å3, and [Bi,Sb] has a 4.9471(4), b 11.7878(7), c 5.6048(3) Å, V 326.83(4) Å3. These results show that the centrosymmetric structure of bismutotantalite can accommodate up to ∼40% Sb3+ substituting for Bi3+ without changing to the Pc21n structure of stibiotantalite.Fil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Direccion Nacional del Antártico. Instituto Antártico Argentino. Instituto Antártico Argentino - Sede Cricyt (Mendoza); ArgentinaFil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Direccion Nacional del Antártico. Instituto Antártico Argentino. Instituto Antártico Argentino - Sede Cricyt (Mendoza); ArgentinaFil: Cooper, Mark A.. University of Manitoba; CanadáFil: Cerný, Petr. University of Manitoba; CanadáFil: Hawthorne, Frank C.. University of Manitoba; Canad

Unraveling the petrogenesis of the Miocene La Peña alkaline intrusive complex, Mendoza, Argentina: Insights from the study of the disregarded late dykes

The La Peña Complex (LPC) is a silica-undersaturated alkaline potassic intrusive system, with a subduction-related signature, linked to the early Miocene retroarc magmatism of the Southern Central Andes, in the flat slab segment. The LPC is composed of several intrusions, predominantly plutonic (clinopyroxenite, malignite and syenite), cross cut by a voluminous swarm of radial and annular dikes with mostly volcanic-subvolcanic textures and variable compositions (foid-bearing alkali feldspar trachyte, trachyte, benmoreite, ledmorite, syenite, tephrite, tephriphonolite and alkaline lamprophyre). In the TAS classification these rocks plot in the alkaline series covering a wide spectrum of compositions following two different trends: 1) alkaline (potassic) strongly silica-undersaturated series, from tephrite, phonotephrite to tephra-phonolite, and 2) mid-alkaline, less silica-undersaturated series, ranging from basaltic trachyandesite to trachyandesite (benmoreite), and trachyte. Dikes from the alkaline series show higher K2O/Na2O ratios and Sr, La, Ce, contents compared to those from the mid-alkaline series. Rocks of the alkaline series are richer in K-feldspar, sodalite, leucite (pseudoleucite), biotite, potassic-ferro-pargasite and garnet than the less silica-undersaturated (trachytic) rocks, reflecting a stronger alkaline potassic affinity. A review of geochemical, isotopic and mineralogical data, and a new geochemical modeling performed on the LPC dikes, suggests that both trends represent separated magmatic series that evolved from two different parental magmas lodged ∼30 km deep in the crust. Our results suggest that the compositional variations observed in LPC dikes, cannot be explained by a simple magmatic evolution via fractional crystallization from a unique parental magma, and that an assimilation and fractional crystallization (AFC) process is required to explain some compositional differences. Our results suggest an upper crustal contaminant (evolved rocks) with a Grenvillian isotope signature. On the other hand, analyses of feldspar crystals from the tephriphonolitic dikes indicate local mixing effects, between an evolved tephriphonolitic melt and a less evolved and hotter mafic magma. The origin of both parental magmas could be explained by different melting degrees of the same mantle source, a phlogopite-bearing spinel lherzolite metasomatized by subduction derived fluids. We consider as a possible explanation that alkaline and coeval calc-alkaline magmatism in this part of the Andes, is due to local heterogeneities in the mantle source, and different degrees of partial melting Similar isotopic compositions of the LPC dikes, with those from other Miocene magmatic occurrences with arc-signature and similar age (e.g., Paramillos de Uspallata, Las Máquinas basalt, Abanico Fm and Farellones Fm) suggest an analogous mantle source for these rocks, from arc and retroarc in the Pampean flat slab regions. However, our results suggest that the isotopic trend contamination of LCP is different from that of Paramillos de Uspallata and other arc rocks of the Southern Volcanic Zone. The crustal contaminant of LPC possibly has another composition that those of Precordillera and Principal Cordillera Miocene rocks. The age of LPC rocks (∼19 Ma) and their arc-related signature agree with the eastward broadening of the arc magmatism between 17 and 19 Ma in this part of the flat slab. According to our interpretations, the LPC is a singular occurrence of two alkaline magmatic series on destructive plate margins, associated with calc-alkaline magmatism, occurring closely in time and space.Fil: Pagano Género, Diego Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: Enriquez, Eliel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: Morosini, Augusto Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: Galliski, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Colombo, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Martina, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Ibañes, Oscar Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: Muñoz, Brian Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: D'eramo, Fernando Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Tellurium and precious-metal ore minerals at Mina Capillitas, Northwestern Argentina

Mina Capillitas is an epithermal-type deposit located in Catamarca province of NW Argentina. Six separate stages of mineralization were identified in this complex Cu-Au-S-As-Sb-Pb-Zn association; the native elements (Au and Te) and Te minerals are concentrated in the fourth stage. Gold occurs as small grains with an average fineness of 920, hosted mainly by quartz and coexists with hübnerite and Bi minerals. Tellurium occurs locally in grains up to 10 μm in diameter, and is associated with the Te-bearing minerals of Au, Ag, Bi, Cu, and Ni. These Te minerals include krennerite, calaverite, sylvanite, petzite, hessite, stützite, goldfieldite, melonite, tetradymite, and possibly volynskite. The grains are generally arranged in larger polycrystalline aggregates. These minerals occur in quartz, generally accompanied by hübnerite, pyrite, chalcopyrite, and Bi- and Sn-bearing minerals. The mineralizing fluids cooled gradually with the typical temperatures ranges characteristic of epithermal systems. Based on the preponderance of the different gangue minerals, we suggest that the pH of the environment became progressively more basic after the third stage of mineralization. This mineral assemblage together with the fluid inclusion homogenization temperature data indicate that the log f S2 values declined as the fluids deposited the Te-bearing minerals. The absence of tellurium phases in the first three stages suggests that either the source of the tellurium had not yet been tapped or that the log f Te2 lay below -10 to -17, the minimum activity for the Te phases present in stage IV to form.Fil: Marquez Zavalia, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Craig, James R.. University Of Waterloo; Canad