8 research outputs found
New Late Permian paleomagnetic data from Argentina: Refinement of the apparent polar wander path of Gondwana
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95004/1/ggge1994.pd
Petrologia do Granito Chasqueiro, região de Arroio Grande, sudeste do Escudo Sul-Rio-Grandense
The Famatinian granitoids of Southwestern Sierra de San Luis, Argentina
The Sierra de San Luis is located in the southern part of the Eastern Sierras Pampeanas. The most conspicuous orogenic events (arc magmatism, deformation and metamorphism) took place during the Lower Paleozoic Famatinian orogeny, overprinting the metamorphic and sedimentary rocks already delineated by the previous Pampean orogeny (Proterozoic? to Early Cambrian). The granitoids were c1assified into pre-, syn- and post-orogenic plutons on the basis of their structural relationship with the penetrative NNE-SSW trending Ordovician structures, attributed to the main Famatinian phase (Ortiz Suarez et al., 1992; Llambias et al., 1998). Available data constrain the low- to high-grade regional metamorphism associated with the deformation mainly within the Early to Middle Ordovician (see synthesis in Sato et al., 2002).Centro de Investigaciones GeológicasLaboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológic
Geochronology and geochemistry of Devonian magmatism in the Frontal cordillera (Argentina): geodynamic implications for the pre-Andean SW Gondwana margin
Tectonic implications of post-folding Permian magnetizations in the Carapacha Basin, La Pampa province, Argentina
The Las Matras tonalitic–trondhjemitic pluton, central Argentina: Grenvillian-age constraints, geochemical characteristics, and regional implications
Retrowedge-related Carboniferous units and coeval magmatism in the northwestern Neuquén province, Argentina
The studied Carboniferous units comprise metasedimentary (Guaraco Norte Formation), pyroclastic (Arroyo del Torreón Formation), and sedimentary (Huaraco Formation) rocks that crop out in the northwestern Neuquén province, Argentina. They form part of the basement of the Neuquén Basin and are mostly coeval with the Late Paleozoic accretionary prism complex of the Coastal Cordillera, south-central Chile. U–Pb SHRIMP dating of detrital zircon yielded a maximum depositional age of 374 Ma (Upper Devonian) for the Guaraco Norte Formation and 389 Ma for the Arroyo del Torreón Formation. Detrital magmatic zircon from the Guaraco Norte Formation are grouped into two main populations of Devonian and Ordovician (Famatinian) ages. In the Arroyo del Torreón Formation, zircon populations are also of Devonian and Ordovician (Famatinian), as well as of Late Neoproterozoic and Mesoproterozoic ages. In both units, there is a conspicuous population of Devonian magmatic zircon grains (from 406 ± 4 Ma to 369 ± 5 Ma), indicative of active magmatism at that time range. The eHf values of this population range between -2.84 and -0.7, and the TDM-(Hf) are mostly Mesoproterozoic, suggesting that the primary sources of the Devonian magmatism contained small amounts of Mesoproterozoic recycled crustal components. The chemical composition of the Guaraco Norte Formation corresponds to recycled, mature polycyclic sediment of mature continental provenance, pointing to a passive margin with minor inputs from continental margin magmatic rocks.The chemical signature of the Huaraco Formation indicates that a magmatic arc was the main provenance for sediments of this unit, which is consistent with the occurrence of tuff—mostly in the Arroyo del Torreón Formation and very scarcely in the Huaraco Formation—with a volcanic-arc signature, jointly indicating the occurrence of a Carboniferous active arc magmatism during the deposition of the two units. The Guaraco Norte Formation is interpreted to represent passive margin deposits of mostly Lower Carboniferous age (younger than 374 Ma and older than 326 Ma) that precede the onset of the accretionary prism in Chile and extend into the earliest stage of the accretion, in a retrowedge position. The Arroyo del Torreón and Huaraco formations are considered to be retrowedge basin deposits to the early frontal accretionary prism (Eastern Series) of Chile. The presence of volcanism with arc signature in the units provides evidence of a Mississippian magmatic arc that can be correlated with limited exposures of the same age in the Frontal Cordillera (Argentina). The arc would have migrated to the West (Coastal Batholith) during Pennsylvanian–Permian times (coevally with the later basal accretionary prism/Western Series). The source of a conspicuous population of Devonian detrital zircon interpreted to be of magmatic origin in the studied units is discussed in various possible geotectonic scenarios, the preferred model being a magmatic arc developed in the Chilenia block, related to a west-dipping subduction beneath Chilenia before and shortly after its collision against Cuyania/Gondwana, at around 390 Ma and not linked to the independent, Devonian–Mississippian arc, developed to the south, in Patagonia