Anisotropy of magnetic susceptibility study in two classical localities of the Gastre Fault System, central Patagonia

The Central Patagonian Batholith is a suite of acid and meso-silicic rocks cropping out in central Patagonia. The emplacement of these rocks has been proposed to be related to the activity of a system of dextral transcurrent faults, the NW-SE Gastre Fault System. This fault system has been ascribed a transcontinental magnitude and a ∼500 km dextral displacement during Gondwana dismembering in Jurassic times. However, the timing, kinematics and amount of displacement of the Gastre Fault System are still controversial. In this work we have visited two localities which were subject of controversial observations, in order to perform petrographical, microstructural and anisotropy of the magnetic susceptibility studies to contribute to the ongoing discussion. The results mostly agree with the findings von Gosen and Loske (2004) in that rocks spatially and temporally associated to the Gastre Fault System do not show evidence supporting the existence of a major dextral fault system active during Jurassic times.

Research highlights► AMS, petrographic and rock magnetic studies were performed. ► We propose a new geologic map for the granitoids of the Gastre region. ► The main deformation affecting the Central Patagonian Batholith is pre-Jurassic in age. ► The Gastre Fault System was not a major dextral fault system during Jurassic times. ► The rotation of the Falkland Islands was not accommodated by the activity of this fault.