The Permian Choiyoi in Cordillera del Viento (Principal Cordillera, Argentina): Over 25 m.y. of Magmatic Activity

SATO, A.M.; LLAMBÍAS, EDUARDO J.; BASEI, M.A.S.; LEANZA, HÉCTOR A.

San Carlos de Bariloche

Simposio; VI South American Symposium on Isotope Geology; 2008

INGEIS

The Permian Choiyoi magrnatism in Argentina characterizes the Neopaleozoic orogen developed along an N-S trending axis to the south of 28°S, covering the Frontal Cordillera and Principal Cordillera morphostructural provinces. In Principal Cordillera it forms part of the basement sequence to the Mesozoic Neuquen basin, and therefore, it crops out only in the core of eroded anticlinal structures. One such area is the Cordillera del Viento anticline (37° 10´S), where the Upper Carboniferous volcanic and sedimentary sequence is folded and thrust by the San Rafael orogenic phase in the Early Permian and is then covered and intruded by Huingancó volcano-plutonic Complex, the local equivalent of the Choiyoi magrnatism. An erosion surfáce and unconformity separate this unit from the Upper Triassic volcanic cover and subsequent sedimentary units. Conventional U-Pb zircon dating constrains the crystallization age of an early granodioritic pluton at 283 :f: 1 Ma and a late monzogranitic one at 259 :f: 9 Ma. These compositional as well as time evolution are in good agreement with the general scheme with mesesilicic Lower Choiyoi and silicic Upper Choiyoi proposed in Frontal Cordillera, as are the structural relationships with the pre-Permian rocks. The present results and pre-existing information in surrounding areas are altogether consistent with an N-S orogenic axis up to 39°S. Farther south, in the Northpatagonian Massif, the Permian magrnatism is represented by deeper levels affected by ductile deformation.