Internal structure of the Late Triassic Central Patagonian Batholith at Gastre

ZAFFARANA CLAUDIA BEATRIZ; SOMOZA, RUBÉN; ORTS, DARIO; MERCADER, ROBERTO; BOLTSHAUSER, BÁRBARA; VICTOR RUIZ GONZALEZ; PUIGDOMENECH, CARLA

GEOSPHERE

GEOLOGICAL SOC AMER, INC

Lugar: Boulder; Año: 2016

1553-040X

The Central Patagonian Batholith (CPB) constitutes a suite of Late Triassic calcalkaline plutons that have been presented as the record of major dextral motion along the transcontinental Gastre Fault System (GFS) during Jurassic times. However, workers in northern Patagonia did not find evidence for such Jurassic kinematics. In contrast, workers from other regions continue including a dextral GFS crosscutting Patagonia in their tectonic models of Gondwana during the Jurassic. In order to further investigate the origin and age of deformation in the CBP, we performed a detailed study through classical structural and anisotropy of magnetic susceptibility (AMS) techniques. The internal structure of the batholith reveals a very consistent pattern of NW-SE steeply dipping magmatic foliations. Subordinately, there are localized records of low-temperature solid-state deformation which in most cases mimic the regional magmatic fabric pattern. This suggests a continuous fabric-forming process under unchanging conditions from emplacement to progressive cooling. Moreover, most of the observed low-temperature solid-state deformation would have a Late Triassic age. We consider that the batholith has been constructed by the amalgamation of NW-SE elongated, dike-like magma bodies which intruded throughout preexisting fractures. These fractures would constitute the NW-SE regional structural grain, which in turn seems to have been inherited from the pervasive Late Paleozoic deformation. Both our results and the regional geology disagree with the postulation of the Gastre Fault System (GFS) as a major Jurassic dextral fault zone.