Brígida Castro de Machuca- Dra. en Ciencias Geológicas
- Researcher at National Scientific and Technical Research Council
Brígida Castro de Machuca
- Dra. en Ciencias Geológicas
- Researcher at National Scientific and Technical Research Council
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Publications (55)
El hallazgo de rhönita en basaltos alcalinos triásicos de la Sierra de Valle Fértil, Sierras Pampeanas de San Juan, constituye la primera mención en Argentina de este mineral en este tipo de rocas. La rhönita se encuentra de dos formas: a) como bordes opacíticos alrededor de mega/xenocristales de kaersutita y en venillas que los atraviesan y b) en...
La Basanita El Retamo, localizada en el sector norte de la sierra de Valle Fértil, corresponde a una nueva evidencia del vulcanismo alcalino de edad triásica para esta región. Es interpretada como el remanente de una colada lávica que suprayace al basamento cristalino del Complejo Valle Fértil, topográficamente elevada por la tectónica Andina. Tien...
En Mendoza (Centro-Oeste argentino), ciudad colonial meridional, los alfareros indígenas locales manufacturaron cerámica desde el siglo dieciséis, aunque su origen étnico fue documentalmente invisibilizado. La presencia de platos tipo Viluco Colonial en los contextos urbanos evidencia que los artesanos integraron técnicas locales, ligadas a la ante...
Petrography and geochemistry of the El Retamo Basanite: new evidence of Triassic magmatism in Sierra de Valle Fértil, province of San Juan.
The El Retamo Basanite, located in the northern sector of Sierra de Valle Fértil, is a new evidence of alkaline volcanism related to the Triassic for this region. It is interpreted as the remnant of a lava flo...
Petrologic analysis of stromatitic migmatites of El Retamo creek, Sierra de Valle Fértil, province of San Juan. Along El Retamo creek, in the northern sector of Sierra de Valle Fértil, migmatic rocks with stromatitic structure derived from metasedimentary protoliths are found. They are characterized by the presence of cordierite nodules, biotite-ga...
The first geochemical and Sr-Nd isotope data of a series of Triassic basaltic rocks from Sierra de Valle Fértil, Western Sierras Pampeanas, Argentina, are herein presented. The mafic rocks are the result of continental intraplate magmatism related to an extensional tectonic setting after the climax of the Gondwanide orogeny (Upper Carboniferous-Per...
The origins of Geology at the National University of San Juan go back to the creation of the Department of Natural Sciences at the Faculty of Engineering and Exact, Physical and Natural Sciences of the National University of Cuyo. Dr. Emiliano Pedro Aparicio was the driving force behind the creation, which was completed on March 8th 1968. Since its...
In the central section of the Sierra de Valle Fértil, outcrops dome-shaped phonolite, called Jaboncillo Phonolite, surrounded by a disrupted breccia composed by basement and juvenile igneous rock fragments. The phonolite exhibits porphyritic texture with dominant alkali feldspar (main anorthoclase) and minor aegirine, both as pheno-and microphenocr...
Blue quartz and its relationship with ductile shear zones in the Western
Sierras Pampeanas of San Juan.
Blue quartz is here reported from quartz-rich mylonites and ductile deformed quartz veins
from Sierra de Pie de Palo and Cerro Guayaguás, Western Sierras Pampeanas, province of
San Juan. It is assumed that the blue color is caused by Rayleigh sc...
Blue quartz is here reported from quartz-rich mylonites and ductile deformed quartz veins
from Sierra de Pie de Palo and Cerro Guayaguás, Western Sierras Pampeanas, province of
San Juan. It is assumed that the blue color is caused by Rayleigh scattering of light by high
concentrations of sub-micrometer inclusions (<1/10 of the wavelength), although...
This work relies on the potential use of petrography to determine temper provenance and applies it to ceramics of west-central Argentina. Petrography is used to identify the raw materials, production technologies and, for the first time in this region, temper provenance of the Viluco ceramics of mixed Inca type produced by local Mendoza Valley popu...
This paper is a contribution to the knowledge of the crustal structure of the eastern flank of the Valle Fértil - La Huerta ranges (Western Sierras Pampeanas, San Juan, Argentina) at 31°S, in the Andean foreland region, where the Nazca plate is subducting horizontally at about 100 km depth. A 1D velocity model was constrained, combining petrographi...
This paper is a contribution to the knowledge of the crustal structure of the eastern flank of the Valle Fértil - La Huerta ranges (Western Sierras Pampeanas, San Juan, Argentina) at 31°S, in the Andean foreland region, where the Nazca plate is subducting horizontally at about 100 km depth. A 1D velocity model was constrained, combining petrographi...
The southern portion of the Cordillera Frontal of San Juan (western Argentina) comprises some of the best exposures of the Choiyoi Group, the eruptive counterpart of a large silicic plutono-volcanic province of Permian-Triassic age developed on the southwestern margin of Gondwana. Stratigraphic, petrologic, and geochronologic studies allowed to rec...
The southern portion of the Cordillera Frontal of San Juan (western Argentina) comprises some of the best exposures of the Choiyoi Group, the eruptive counterpart of a large silicic plutono-volcanic province of Permian-Triassic age developed on the southwestern margin of Gondwana. Stratigraphic, petrologic, and geochronologic studies allowed to rec...
La Aguadita Trachyte, in Sierra de Valle Fértil, is a new outcrop referring to the Triassic alkaline magmatism. The trachyte body was emplaced along a NNW-trending fault zone overlying the crystalline basement. The trachyte consists mainly of anorthoclase and sanidine as pheno- and microphenocrysts, with lesser amounts of arfvedsonite and ferro-eck...
Carbonate fault breccia dykes in the Cerro La Chilca area, Eastern Precordillera, west-central Argentina, provide clues on the probable mechanism of both fault movement and dyke injection.Breccia dykes intrude Upper Carboniferous sedimentary rocks and Triassic La Flecha Trachyte Formation. The timing of breccia dyke emplacement is constrained by cr...
La Aguadita Trachyte, in Sierra de Valle Fértil, is a new outcrop referring to the Triassic alkaline magmatism. The trachyte body was emplaced along a NNW-trending fault zone overlying the crystalline basement. The trachyte consists mainly of anorthoclase and sanidine as pheno-and microphenocrysts, with lesser amounts of arfvedsonite and ferro-ecke...
El terreno Cuyania situado en la zona andina de trasarco entre 29°S y 34°S se compone de un sistema de corrimientos y retrocorrimientos del cinturón plegado de Precordillera y más hacia el este por bloques de basamento cristalino de las Sierras Pampeanas Occidentales. A 31°S aproximadamente, la zona se caracteriza por una elevada actividad sísmica...
A seismic velocity analysis from teleseismic receiver functions recorded in the southwestern flank of the Sierra de Pie de Palo (Western Sierras Pampeanas, Argentina), is compared with seismic properties directly calculated from lithological composition. The seismological results show an upper layer located in the first 13 km depth. A deeper contra...
A seismic velocity analysis from teleseismic receiver functions recorded in the southwestern fank of the Sierra de Pie de Palo (Western Sierras Pampeanas, Argentina), is compared with seismic properties directly calculated from lithological composition. The seismological results show an upper layer located in the first 13 km depth. A deeper contras...
Troctolitic gabbros from Valle Fértil and La Huerta Ranges, San Juan Province, NW‐Argentina exhibit multi‐layer corona textures between cumulus olivine and plagioclase. The corona mineral sequence, which varies in the total thickness from 0.5 to 1 mm, comprises either an anhydrous corona type I with olivine|orthopyroxene|clinopyroxene+spinel symple...
La unidad ígnea Quebrada Blanca (Pérmico Superior-Triásico inferior), que intruye al basamento cristalino de la sierra de La Huerta, Sierras Pampeanas Occidentales, es el término más diferenciado de un grupo de rocas ígneas de edad y características similares. Está compuesta por un cuerpo hipabisal de pórfido riolítico, una brecha hidrotermal-intru...
The Quebrada Blanca igneous unit (Upper Permian-Lower Triassic) intruding the crystalline basement of the Sierra de La Huerta, Western Sierras Pampeanas, is the most differentiated member of a group of similar age and magmatic features distributed in the cited range. it comprises a hypabyssal rhyolite porphyry, a hydrothermal-intrusive breccia wher...
The Cuyania terrane in the Andean backarc region between 29 degrees S and 34 degrees S consists of the thin-skinned Precordillera fold and thrust belt and oldie Western Sierras Pampeanas thick-skinned basement cored uplifts. At about 31 degrees S, the region is highly seismically active at crustal levels (< 35 km depth) and intermediate depths (sim...
The stromatolites from the Pan de Azúcar Hill, Western Sierras Pampeanas, San Juan, Argentina. Correlations and stratigraphic significance. The occurrence of stromatolites (“bowl-shaped”, Conocollenia? and p lanar cryptalgal laminites),in limestone beds exposed at the Pan de Azúcar hilll(31º 25’ S - 67º 27’ W), Western Sierras Pampeanas, San Juan p...
Una faja de cizalla dúctil con foliación milonítica de dirección NEE y buzamiento al sudeste, afecta a un granitoide mesoproterozoico (Granitoide El Tigre: 31º31'30''S-68º15'12''O) que forma parte del basamento cristalino de la Sierra de Pie de Palo, Sierras Pampeanas Occidentales. El análisis cinemático de la faja indica una componente principal d...
Migmatitic paragneisses of the Valle Fértil–La Huerta Ranges at the Western margin of the Sierras Pampeanas are composed of garnet–cordierite–plagioclase–biotite–quartz-bearing units that experienced peak metamorphic conditions of ca. 800 °C at 6–7 kbar. Based on petrological studies, pseudosection modeling and petrographic observations, an anticlo...
que ocurre a niveles de corteza continental (< 35 km de profundidad) y de profundidad intermedia (~100 km). Esta última define la zona de Wadati-Benioff que ocurrieron en 2008 y 2009 con epicentros en el terreno Cuyania y sus límites. La información obtenida corresponde a estimaciones refinadas de localización sísmica, momento sísmico (M 0), magnit...
The results of petrographic analyses carried out at Viluco (Late Agroalfarero Period) and
historic pottery from Ruinas de San Francisco site are presented. The observed evidences
allow to propose a technological change between the Inca and Spanish dominations in
the north of Mendoza. Also, the presence of vitroclasts in the pottery suggests that th...
A high-strain ductile shear zone trending NEE with southeasterly dipping mylonitic foliation, has been recognized affecting a Mesoproterozoic (ca. 1105 Ma) peraluminous garnet-bearing two mica granitoid (El Tigre granitoid: 31°31'30''S-68°15'12''W) which is part of the crystalline basement of the Sierra de Pie de Palo, Western Sierras Pampeanas. Ki...
High-temperature, intermediate-pressure calc-silicate marbles occur in the granulite-facies terrain of the La Huerta Range
in the Province of San Juan, NW-Argentina, in three bulk-compositional varieties: Type (1) dolomite-absent scapolite-wollastonite-grandite-clinopyroxene-quartz—calcite
marbles; Type (2) diopside-forsterite-spinel-corundum—calci...
We document various textural occurrences of greenockite associated with several ore minerals in varying parageneses: pyrite + sphalerite + galena + chalcopyrite +/- arsenopyrite +/- pyrrhotite +/- bornite +/- tennantite +/- tetrahedrite +/- covellite +/- chalcocite +/- aikinite +/- wittichenite +/- matildite +/- berryite +/- miharaite +/- geocronit...
In the Sierra de Valle Fértil, evidence of granulite facies metamorphism have been preserved either in the constitutive associations as in deformation mechanisms in minerals from biotite-garnet and cordierite-sillimanite gneisses, cordierite and garnet-cordierite migmatites, metagabbros, metatonalites-metadiorites and mafic dikes. The main recogniz...
In the Sierra de Valle Fértil, evidence of granulite facies metamorphism have been preserved either in the constitutive associations as in deformation mechanisms in minerals from biotite-garnet and cordierite-sillimanite gneisses, cordierite and garnet-cordierite migmatites, metagabbros, metatonalites-metadiorites and mafic dikes. The main recogniz...
The geodynamic evolution of the proto-Andean margin of Gondwana during the Paleozoic was characterized by repeated subduction processes associated with the docking of several terranes, including the Cuyania-Precordillera terrane and the Chilenia terrane, and the development of the calc-alkaline Famatinian continental magmatic arc. In the Sierra de...
Dos cuerpos porfíricos subvolcánicos asignados al ciclo magmático gondwánico intruyen al basamento cristalino de la sierra de La Huerta, Sierras Pampeanas Occidentales, en el área de la quebrada El Arriero (Dacita El Arriero) y en el sector de Marayes Viejo (Andesita Marayes Viejo). Se trata de rocas andesíticas a dacíticas de medio a alto K y con...
Two subvolcanic porphyritic bodies assigned to the gondwanic magmatic cycle intrude the crystalline basement at El Arriero creek (El Arriero Dacite) and Marayes Viejo area (Marayes Viejo Andesite) in the Sierra de La Huerta, Western Sierras Pampeanas. They are medium to high-K calc-alkaline andesites to dacites. A 299.9 ± 3.6 Ma biotite Ar/ Ar age...
The ancient Sierras Pampeanas in the central west part of Argentina are a seismically active region in the back-arc of
the Andes. Their crystalline basement cored uplifts extend up to 800 km east of the oceanic trench over the flat subduction segment
of the Nazca plate. Approximately 40 felt crustal earthquakes, are reported per year for this regio...
The San Jorge porphyry copper deposit (SJPCD) is hosted by Carboniferous clastic sedimentary rocks and Permian intrusions located within the Permo-Triassic belt of Chile and Argentina. Its hypogene mineralization and alteration are products of superposed orthomagmatic and hydrothermal events that were strongly fault controlled. Copper related to or...
