Graciela I. Vujovich

• Dr.
• ad-honorem resarch at National Scientific and Technical Research Council

The Precordillera mafic-ultramafic belt (PMUB), located in central-western Argentina, comprises mafic and ultramafic bodies interlayered and/or in tectonic contact with marine silici-clastic units. Whole-rock, mineral geochemistry and Nd-Sr isotope analyses performed in magmatic rocks suggest a relatively different spatial and temporal evolution al...

In central-western Argentina, a mafic-ultramafic belt occurs throughout the western margin of the Precordillera. This belt is interpreted as the suture zone between the Cuyania terrane and the Chilenia terrane, both accreted onto the Gondwana margin during the Early Paleozoic. The belt comprises rocks from different setting and age and can be divid...

In central-western Argentina, a belt including marine metasedimentary rocks and mafic-ultramafic bodies occurs throughout the western margin of the Precordillera. The belt is considered as the suture zone between the poorly known Chilenia terrane and the Cuyania terrane, part of the composite West Gondwana margin. It is assigned to the Late Neoprot...

The basement of the Central Andes located in central-western Argentina (31º20′S - 69º22′W) is composed by the Cuyania and Chilenia terranes which were amalgamated to Gondwana in the Early-Mid Paleozoic. Between the Precordillera (Cuyania) and Frontal Cordillera (Chilenia) there are exposures of marine metasedimentary rocks associated with mafic roc...

The evolution of the western margin of South America comprised different tectonic regimes responsible of the present geological composition and structure of the Central Andes. Remote sensing, geological and geophysical data (aeromagnetic and seismological data) have been processed to understand the polyphase structural evolution of the Argentine So...

In central-western Argentina, an Early Paleozoic belt including mafic-ultramafic bodies, marine metasedimentary rocks and high-pressure rocks occur along the western margin of the Precordillera and in the Frontal Cordillera. First pressure-temperature estimates are presented here for low-grade rocks of the southern sector of this belt based on two...

In this paper the geology and geophysics of northern part of the Sierra de Villa Corral is presented. The study area is located in the Western Precordillera of San Juan (31°08'LS - 69°24'LW). Here are compared the structural and stratigraphic features of a NE-SW cross-section with aeromagnetic data and remote sensing. Techniques of band ratios were...

Serpentinites are a powerful tool to evaluate mantle composition and subsequent alteration processes during their tectonic emplacement. Exposures of this type of rocks can be found in the Argentine Precordillera (Cuyania terrane) and Frontal Cordillera, both located in central-western Argentina, within the Central Andes. In these regions a Neoprote...

The magnetic anomaly profile performed along the NE-SW (31º08'LS-69º24'LO) structural section at the western edge of the Argentine Precordillera, is presented. By the application of ratios between bands, Landsat 7 ETM+ satellite images were processed as well as aeromagnetic data by filtering methods (reduction to the pole and calculation of the res...

We present a subsurface structural reconstruction from a NE-SW cross section at the San Juan river headwaters, in the Western Precordillera. The stratigraphy of study area is mainly represented by marine rocks of lower-middle Paleozoic age which are uncomformably covered by Neopaleozoic continental and marine rocks. The structure is characterized b...

En el presente trabajo se realizaron cocientes de bandas y se ensayaron técnicas de clasificación supervisada y no supervisada en imágenes satelitales Landsat 7 Enhaced Thematic Mapper (ETM+), correspondientes a un sector de la Precordillera occidental argentina. Con el objetivo de arrojar luz sobre los aspectos estratigráficos y estructurales de l...

The Bajo Pequeño Shear Zone (BPSZ) is a lower-crustal shear zone that records shortening and exhumation associated with the establishment of a new plate boundary, and its placement in a regional structural context suggests that local- to regional-scale strain localization occurred with progressive deformation. A kilometer-scale field and analytical...

EDITORIAL NOTE The XXVI Scientific Meeting of the Argentine Association of Geophysicists and Geodesists was held in Tucuman, Argentine, November 5-9, 2012. It included numerous contributions from representatives from the neighboring countries. The first issue of GEOACTA Volume 2014 is a Special Edition based on papers carefully selected from the sc...

New U–Pb detrital zircon ages are presented for the Tordillo Formation. The ages indicate that the most important source region of sediment supply was the Jurassic Andean arc (peaks at c. 144, 153 and 178 Ma), although two secondary sources were defined at c. 218 and 275 Ma. Temporal variation in the provenance indicates that at the beginning of th...

[1] The Famatina margin records an orogenic cycle of convergence, metamorphism, magmatism, and extension related to the accretion of the allochthonous Precordillera terrane. New structural, petrologic, and geochronologic data from the Loma de Las Chacras region demonstrate two distinct episodes of lower crustal migmatization. The first event preser...

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a b s t r a c t The Argentine Precordillera is located in the central western region of Argentina, within the Central Andes. Throughout its westernmost sector, mafic and ultramafic bodies including serpentinites, mafic granulites, basaltic dikes/sills and pillow lavas are associated with metasedimentary rocks deposited in a deep marine and slope en...

Seismic velocities in outcropping units in the western flank of the la Invernada range, San Juan Precordillera. P-wave seismic velocity (Vp) determinations are shown in this work for a region in the western flank (Don Carmelo nature reserve) of the la Invernada range in the Ullúm Department of the San Juan Province. The velocities obtained using th...

The Argentine Precordillera is located in the central western region of Argentina, within the Central Andes. Throughout its westernmost sector, mafic and ultramafic bodies including serpentinites, mafic granulites, basaltic dikes/sills and pillow lavas are associated with metasedimentary rocks deposited in a deep marine and slope environment. These...

P-wave seismic velocity (Vp) determinations are shown in this work for a region in the western flank (Don Carmelo nature reserve) of the la Invernada range in the Ullúm Department of the San Juan Province. The velocities obtained using the seismic refraction method indicate Vp values of 550; 1.670 and 4.134 m/s and thicknesses of 1 m and 7 m approx...

En el cordón del Peñasco, ubicado en el sector norte de la provincia de Mendoza, dentro del ámbito de la Precordillera Occidental, aforan metasedimentitas en contacto tectónico con una asociación máfica-ultramáfica. Dentro de las metasedimentitas en facies esquistos verdes se han reconocido dos asociaciones: metalimolitas carbonáticas y metaarenisc...

In Cordón del Peñasco area, located in northern Mendoza province, western Precordillera, metasedimentites are in tectonic contact with a mafic-ultramafic association. The former have been under greenschist facies metamorphism and two associations have been recognized: carbonate metasiltstones and metasandstones and metapelites. The mafic-ultramafic...

Intraplate deformation has been described in several tectonic settings and recently in western central Argentina it has been proposed to explain the complex structural patterns developed between Early Jurassic and Cretaceous times along the Huincul deformation zone. We integrate new field data and detrital zircon ages of the exposed portion of the...

A petrological and geochronological study of Cordilleran granitoid intrusions in the Bariloche area (Argentina) point to a complex time-compositional evolution of magmatic processes in relation with oblique subduction of the Phoenix plate below the South America active margin during Jurassic times. The observed geochemical variations in both major...

Transitions from convergence to extension during an orogenic cycle result from the dynamic interaction between plate bounding forces, the thermal and rheologic evolution of the lithosphere, and contrasts in gravitational potential energy within an orogen. The presence of melt in the middle and lower crust, in particular, exerts a profound effect on...

The Guarguaraz Complex in West Argentina formed during collision between the microplate Chilenia and South America. It is composed of neritic clastic metasediments with intercalations of metabasic and ultrabasic rocks of oceanic origin. Prograde garnet growth in metapelite and metabasite occurred between 1.2 GPa, 470°C and 1.4 GPa, 530°C, when the...

The Caucete Group and structurally overlying Pie de Palo Complex in western Argentina are characterised by two generations of west-verging folds and thrust-related shear zones, which formed under amphibolite facies conditions. The Caucete Group is separated from the Pie de Palo Complex by the Pirquitas thrust. These structures are interpreted to ha...

The Sierra de Pie de Palo of northwest Argentina preserves middle to lower crustal metamorphic rocks that were penetratively deformed during Ordovician accretion of the Precordillera terrane to the Gondwana margin. New structural, petrologic, and geochronologic data from a 40 km structural transect reveals that the Sierra de Pie de Palo preserves a...

The Caucete Group is a low-grade metasedimentary sequence of probable late Neoproterozoic-Cambrian age. It is exposed on the western flank of the Sierra de Pie de Palo, a basement block of the Cuyania terrane from western Argentina. The geochemical composition (major, trace and rare-earth elements, and Sm–Nd isotopes) of the El Quemado, La Paz, El...

The Geological Sheet 3369-III, Cerro Tupungato, is located in the western sector of the province of Mendoza. It comprises part of the geological provinces known as Cordillera Principal, Cordillera Frontal and Precordillera. The stratigraphic column of this region has four main sequences: the Proterozoic basement, the Paleozoic and Mesozoic sequence...

A detailed U-Pb geochronological study has been carried out on granitoids of the North Patagonian batholith in the region of Bariloche (Argentina), between 40°30' S and 41°45' S. In this region, the calc-alkaline, subduction-related, granitic bodies of the North Patagonian batholith intruded an Early Jurassic volcano-sedimentary sequence contempora...

Metamorphic basement and its Neoproterozoic to Cambrian cover exposed in the Sierra de Pie de Palo, a basement block of the Sierras Pampeanas in Argentina, lie within the Cuyania terrane. Detrital zircon analysis of the cover sequence which includes, in ascending order, the El Quemado, La Paz, El Desecho, and Angacos Formations of the Caucete Group...

The recent completion of a high-resolution aeromagnetic survey over the Pie de Palo uplift of the western Sierras Pampeanas has revealed an area of large magnetic anomalies associated with the Pie de Palo Complex. The Las Pirquitas thrust, which has transported and uplifted the Pie de Palo Complex, is recognized for at least 30 km in a roughly NE d...

A lo largo del arroyo San Juan en el sector central de la sierra de Valle Fértil aflora una sección cortical caracterizada por la presencia de rocas plutónicas máficas interestratificadas con migmatitas máficas y migmatitas metasedimentarias. Esta relación de campo permite observar la transición de procesos ígneos a metamórficos asociados con la cr...

A sequence of plutonic mafic rocks inter-stratified with both mafic- and metasedimentary-derived migmatites is found along the San Juan valley in the center of the Sierra de Valle Fértil. This natural example shows the transition from igneous to metamorphic petrologic processes which occurred during the crystallization of mafic magmas and the subse...

The source regions of dioritic and tonalitic magmas have been identified in a deep crustal section of the Famatinian arc (Sierras Pampeanas of western Argentina). The source zones of intermediate igneous rocks are located at the transition between a gabbro-dominated mafic unit and a tonalite-dominated intermediate unit. In the upper levels of the m...

The ranges of the Sierras Valle Fértil-La Huerta expose natural cross sections through a paleo-arc crust that formed in the Late Cambrian - Early Ordovician Famatinian magmatic arc, northwestern Argentina. Thick mafic sequences of amphibole gabbronorites to orthopyroxene-amphibole-biotite diorites form the lower levels of the exposed paleo-arc sect...

Magmatic structures related to the mechanical interaction between mafic magmas and granitoids have been studied in the Valle Fértil calc-alkaline igneous complex, Argentina. Excepcional outcrops with vertical walls of more than 300 m high allow us the study of three-dimensional geometries of individual blobs of mafic magma as well as the geometry o...

of from the in Sierras Valle Fértil--La Huerta, San Juan, Argentina.

Details on the polyphase reactivation of the Valle Fertil fault system with special emphasis on the Las Chacras fault.

Details on the reactivation history of the Las Chacras fault system.

Migmatite terranes commonly develop at mid crustal levels as a result of decompression melting. The Loma de las Chacras of the western Sierras Pampeanas, Argentina preserves a lower crustal migmatite terrane that formed as a result of advective heating under increasing pressure conditions. Pelitic migmatites in the footwall of the Villarcán shear z...

Resumen: El presente trabajo comprende estudios sobre isótopos estables (carbono y oxígeno), Sr natural (87 Sr/ 86 Sr), 206 Pb/ 207 Pb y Sm/Nd aplicados sobre rocas esencialmente carbonáticas aflorantes en el terreno Precordillera-Cuyania del oeste argentino. Las rocas analizadas son metacarbonatos, mármoles y metamargas aflorantes en la sierra de...

The western Sierra Pampeanas of west-central Argentina preserves a tectonically imbricated middle to lower crustal suture zone that developed over tens of millions of years, from the Cambrian to Early Silurian. The suture zone juxtaposes mafic and clastic rocks in the west against an eastern arc complex thought to have formed on the Gondwana margin...

The Sierra Pie de Palo and Loma de las Chacras of the western Sierras Pampeanas are largely comprised of amphibolite facies metamorphic rocks that constitute part of the composite Cuyania terrane and separate the Precordillera terrane from the Gondwana margin. Recent studies indicate that the rocks underwent pervasive ductile deformation from the m...

The studies based on systematic isotope variations in carbonate rocks are valuable tools to understand the evolution of marine sedimentary basins, especially those developed during a key Earth history time such as the Neoproterozoic-Lower Paleozoic, interval from which fossil register is incomplete. The isotopic data allow to gather important infor...

New U-Pb age determinations confirm earlier interpretations that the strongly deformed and metamorphosed mafic and intermediate igneous rocks of the Pie de Palo Complex represent a Mesoproterozoic fragment of suprasubduction zone oceanic crust.A gabbroic pegmatite, interpreted to have formed during arc rifting or subsequent back-arc spreading, yiel...

Basement rocks comprising ortho- and paragneisses and schists whose tectono-metamorphic evolution is poorly known, are exposed in the Sierras de Umango, Maz-Espinal and Las Ramaditas, in the northwest of the La Rioja Province, Argentina. These units were included in the Maz, El Taco, El Zaino complexes, as well as the Tambillos Metamorphics that wo...

Evidence of the Pampean cycle in the basament of the north-western sector of Sierra de San Luis. A preliminary zircon U-Pb age is presented for a feldspar-biotite gneiss from the Nogoli Metamorphic Complex, Sierra de San Luis, at San Francisco del Monte de Oro. The data show a cristallization age of 554 ± 4,8 Ma, which represents one of the first e...

Los metasedimentos del Grupo Caucete aflorantes en la sierra de Pie de Palo constituyen una pieza importante para entender la evolución del margen gondwánico durante el Proterozoico tardío a Paleozoico temprano. Esta secuencia metamórfica está en contacto tectónico, a través del Corrimiento Las Pirquitas, con el Complejo Pie de Palo (Mesoproterozoi...

A preliminary zircon U-Pb age is presented for a feldspar-biotite gneiss from the Nogoli Metamorphic Complex, Sierra de San Luis, at San Francisco del Monte de Oro. The data show a cristallization age of 554 ± 4,8 Ma, which represents one of the first evidences of the Pampean Cycle in this geological setting. An episodic lead loss for Cretaceous ti...

Metasedimentary rocks of the Caucete Group outcropping at the western slope of Sierra de Pie de Palo are an important key to understand the geological evolution of the western margin of Gondwana during late Proterozoic - early Paleozoic times. This metamorphic sequence is in tectonic contact with the mesoproterozoic-age Pie de Palo Complex through...

Newly acquired U-Pb SHRIMP-zircon ages from the western Sierras Pampeanas of northwest Argentina refine existing age data on early Paleozoic deformation events and substantiate previous suggestions for the existence of a late Proterozoic basement east of the Cuyania terrane. U-Pb ages were obtained from the Sierra Pie de Palo, an area believed to c...

We describe a series of Middle Proterozoic to early Paleozoic ultramafic and mafic rocks in the basement of the Central Andes that have different geochemical attributes and paleogeographic settings. Several ophiolitic belts are identified on the basis of lithologic assemblages and geochemical characteristics, but only the most important belts are d...

The study region encompasses the eastern half of the Precordillera sanjuanina and the western foothills of the Sierras Pampeanas. The first geological province consists of a Paleozoic sedimentary sequence that begins with Cambrian carbonates, with an almost complete fossil record with faunas of Lower, Middle, and Upper Cambrian ages. The basement i...

This paper is included in the Special Publication entitled 'The proto- Andean margin of Gondwana', edited by R.J. Pankhurst and C.W. Rapela. Whole-rock trace element, field, and petrographical studies indicate that the protoliths of highly deformed metamorphic rocks of the Pie de Palo Complex, Argentina, formed in an oceanic setting like that of SW...

This paper is included in the Special Publication entitled 'The proto- Andean margin of Gondwana', edited by R.J. Pankhurst and C.W. Rapela. 40Ar/ 39Ar incremental-release ages have been determined for muscovite and hornblende concentrates prepared from basement rocks of the Sierra de Pie de Palo, in the western Sierras Pampeanas, east of the Early...

A series of medium grade metamorphic rocks of the western sector of the Sierras Pampeanas Terrane in central western Argentina are represented by amphibolites, gneisses and schists derived from sedimentary as well as from igneous rocks. The metavolcanics consist of amphibolites, quartz-K-feldspar-muscovite schists, and hornblende-biotite and biotit...

The igneous-metamorphic basement of western Sierra de La Huerta, western Sierras Pampeanas of San Juan province, is exposed in Loma de Las Chacras. The metamorphic basement, assigned to the Valle Fertil Complex, is characterized by mid grade amphibolite facies, and by low grade greenschist facies. Different formations are recognized based on the me...

Recent plate reconstructions, based largely on paleomagnetic data and fueled by the SWEAT hypothesis for the Grenville orogen, connect eastern North America and western South America (SA) during Proterozoic and Early Paleozoic time. Before accepting this modei, the following must be considered: Most western SA cratonic blocks show evidence for impo...

The recent proposal of the SWEAT hypothesis has produced a series of alternatives for the tectonic evolution and possible connection between the Laurentia and Gondwana cratons. This paper summarizes the different alternatives and presents the constraints based on a South American perspective of the tectonic evolution of the distinct cratonic blocks...

The southwestern Gondwanaland continent was the result of the accretion of different Precambrian and Paleozoic era tome terranes duríng the Brasilíano and younger orogenies. The geologic history of some of these terranes such as Amazonia, Pampia and Patagonta, undoubtly indicates that older Middle Proterozoic metamorphic and igneous events are stil...

INTRODUCCIÓN Una de las áreas clave para entender la evolución geológica del Gondwana sudoccidental durante el Proterozoico – Paleozoico inferior es el basamento metamórfico de la Cordillera Frontal, de alli la importancia de caracterizar las diferentes unidades que lo constituyen. Tratar de reconstruir la tectónica de placas imperante para esos ti...