Ordovician western Sierras Pampeanas magmatic belt: Record of Precordillera accretion in Argentina
Accretion of the Precordillera terrane, as part of a composite terrane of Laurentia derivation, is well founded, mainly based on paleontologic grounds, sedimentologic similarities, and isotopic and paleomagnetic evidence. However, the active proto-margin of Gondwana has not been analyzed to verify i...
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1999
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00721077_v336_n_p63_Quenardelle http://hdl.handle.net/20.500.12110/paper_00721077_v336_n_p63_Quenardelle |
| Aporte de: |
| Sumario: | Accretion of the Precordillera terrane, as part of a composite terrane of Laurentia derivation, is well founded, mainly based on paleontologic grounds, sedimentologic similarities, and isotopic and paleomagnetic evidence. However, the active proto-margin of Gondwana has not been analyzed to verify if the distribution, age, and composition of the early Paleozoic magmatic rocks are consistent with accretion of the Precordillera. This chapter presents an overview of the volcanic rocks and granitoids exposed in the western Sierras Pampeanas. The analysis of the composition, structure, timing, and other relevant characteristics help to define a series of pretectonic subduction-related granodiorites, tonalites, and other granitoids associated with volcanic rocks, ranging in age between 515 and 470 Ma. Scarce and volumetrically less important small bodies of syntectonic granitoids range in age from 470 to 450 Ma. Large post-tectonic batholiths, mainly in subcircular shapes of monzo- to syenogranitic composition, were emplaced from 450 to 360 Ma. A magmatic arc along the western Sierras Pampeanas is possible to reconstruct based on the available data. The time of emplacement of the subduction-related igneous rocks, as well as the collisional and postcollisional granitoids, matches the time of accretion and final amalgamation of the Precordillera terrane inferred from the sedimentary record. The time constraints of both areas, Precordillera and western Sierras Pampeanas, show a coherent pattern that reinforces the interpretation of Precordillera as a far-traveled terrane exotic to Gondwana. |
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