1. P–T–t evolution of an Early Silurian medium-grade shear zone on the west side of the Famatinian magmatic arc, Argentina: Implications for the assembly of the Western Gondwana margin
- Author
-
B. Castro de Machuca, Lorena Previley, Gloria Arancibia, Mauricio Belmar, Diego Morata, and Sandra Pontoriero
- Subjects
ARGENTINA ,FAMATINIAN OROGENY ,Geology ,40AR/39AR DATING ,Ciencias de la Tierra y relacionadas con el Medio Ambiente ,P-T PATH ,Gondwana ,Paleontology ,Back-arc basin ,Margin (machine learning) ,Geología ,Shear zone ,SIERRA DE LA HUERTA ,Geomorphology ,CIENCIAS NATURALES Y EXACTAS ,METAGABBROIC MYLONITES - Abstract
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 La Huerta (30º56' - 31º29' S and 67º17' - 67º32' W), at the southwestern end of the Western Sierras Pampeanas, some mafic to ultramafic igneous bodies belonging to the Famatinian arc were affected by regional metamorphism of the medium-pressure granulite facies (7-7.5 kbar, ≈ 850 ºC). After this regional metamorphism, local mylonitization under amphibolite facies along discrete NW-SE to NNW-SSE striking ductile shear zones occurred. A 40Ar/39Ar plateau age of 432 ± 4 Ma was obtained on rather homogeneous hornblende porphyroclasts from a metagabbro mylonite. The textures and mineral chemistry of the mylonitized metagabbro allow its P-T-t evolution from magmatic crystallization to mylonitization to be constrained. Geochronological data obtained from mylonite provide evidence that orogenesis was active at least until the Early Silurian. This deformational event would have been related to uplift and decompression during the later stages of the orogenesis, probably associated with the accretion of the Precordillera terrane to the southwestern Gondwana margin. Fil: Castro, Brigida Marta Ester. Universidad Nacional de San Juan; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Arancibia, Gloria. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Geología "Dr. Emiliano Aparicio"; Argentina. Laboratorio Servicio Nacional de Geología y Minería,; Chile Fil: Morata Cespedes, Diego Antonio. Universidad Católica de Chile; Chile Fil: Belmar, Mauricio. Universidad de Chile. Facultad de Ciencias Fisicas y Matematicas; Chile Fil: Previley, Lorena Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Pontoriero, Sandra Inés. Universidad Nacional de San Juan; Argentina
- Published
- 2008
- Full Text
- View/download PDF