El Batolito de la Patagonia Central: Evidencias de un magmatismo Triásico-Jurásico asociado a fallas transcurrentes

RAPELA, C.W.; ALONSO, G.; DÍAS, G.; FRANZESE, J.; BENVENUTTO, A.

REVISTA GEOLóGICA DE CHILE

Sociedad Geológica de Chile

Lugar: Santiago; Año: 1991 vol. 18 p. 121 - 138

0716-0208

Lithological and structural characteristics of the Late Triassic-Middle Jurassic Central Patagonia Batholith (CPB) are here described. The CPB outcrops discontinously from Pilcaniyeu to Gastre localities along a NW-SE fracture zone. At the Gastre area, a well exposed sector of 3.000 km2 has been mapped in detail. The basement rocks of the CPB at the Gastre area are Late Paleozoic granitoid sequences. Two superunits and a single independent unit have been recognized within the CPB. A recent R-Sr geocronological study indicates that emplacement of these units began in the late Triassic and culminated during the early-middle Jurassic. The evolution of the batolith in this area started with the epizonal emplacement of the Gastre Superunit, composed by hornblende-biotite granodiorites and granites, that were intruded by leucocratic granites. The subvolcanic Lipetrén Superunit intruded the Gastre units, and is composed by leucocratic granophyric granites, quartz-monzodioritic porphyrys, hornblende-biotite granites and felsites. The biotite bearing Horqueta granodiorite shows a distinct mineralogical and modal composition. Measurements of the granitoid structures allied with micro structural observations suggest that the CPB was emplaced along a northwest-southeast-trending dextral zone of shear. Large mylonitic areas and felsites are associated with the main shear zones. Finally, a tecto-magmatic model is proposed relating the origin and evolution of the CPB with the forerunner stage of the breackup of Gondwana.