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El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas

2010; National Geology and Mining Service; Volume: 37; Issue: 1 Linguagem: Inglês

10.4067/s0718-71062010000100002

0718-7092

José Piquer, Juan Carlos Castelli, Reynaldo Charrier, Gonzalo Yáñez,

Geological and Tectonic Studies in Latin America

The Cenozoic of the upper Teno River, Cordillera Principal, Central Chile: stratigraphy, plutonism and their relation with deep structures. The Cenozoic geologic evolution of the central part of the Cordillera Principal at ~35°S, is intimately related to the geodynamic evolution of deep crustal structures, which during different stages con- trolled the deposition of volcanosedimentary sequences, and the ascent and emplacement of epizonal intrusions. Newly defined stratigraphy around these structures confirms the Cenozoic age of a group of pyroclastic and sedimentary rocks, which conformably underlie andesitic lavas of the Abanico Formation (assigned to the Late Eocene-Early to Middle Miocene). Intrusive rocks correspond to four main phases (from oldest to youngest: diorite, granodiorite, rhyo-dacitic and dacitic porphyry), which occurs in a North-South trending belt. The granodiorite was dated at 7.8±0.4 Ma (K-Ar in biotite). Rhyo-dacitic porphyries, considered as a marginal lithodeme of the granodiorite, yielded 7.9±0.4 Ma (K-Ar in plagioclase phenocrysts). Two main structures of regional importance were observed: the El Fierro thrust, and, towards the west, the Infiernillo-Los Cipreses Fault System. In the characterization of the latter, magnetic modeling of cross-sections were analyzed as a complement to the geologic information. The ascent of the different intrusive phases mentioned before, is interpreted as being controlled by the Infiernillo-Los Cipreses Fault System. This structure, as well as the El Fierro thrust, acted as a basin-margin normal fault during the Late Eocene-Middle Miocene, controlling the deposition of the Abanico Formation. These faults were reactivated as reverse faults during an episode of major tectonic contraction and magmatic-induced high fluid pressure in the Late Miocene, focusing the ascent of the intrusive bodies.