A clockwise P‐T‐t-D path of the northern Patagonia basement: Implications for the Permian evolution of the Panthalassan margin of Gondwana.

Abstract

The geologic evolution of the Gondwanide orogen recorded during the late Palaeozoic along the Panthalassan border of Gondwana is related to an active continental margin, though it is still debatable whether it was built by collision or accretion. To disentangle its orogenic processes and provide constraints on the orogen type, we characterize the physicochemical conditions of metamorphism and associated deformation of the Mina Gonzalito Metamorphic Complex from northern Patagonia (41°28’30” S-65°40’30” W). New field mapping and comprehensive petrochronologic analysis constrain the evolution of a thick-skinned fold and thrust belt in a retroarc setting, which is spatially and temporally related to the geometry and kinematics of the right-lateral reverse El Jagüelito ductile shear zone. Metamorphic evolution resulted in a clockwise P‐T‐t-D path reflecting three stages of continuously changing P-T conditions under high-pressure (8.0–9.9 kbar) amphibolite facies (540–680°C) during a single-phase progressive ductile deformation event. Monazite ages ranging from 303 ± 5 to 252 ± 6 Ma account for the single-phase regional tectono-metamorphic event spanning ~ 50 My. Our results, integrated with regional data, led to interpreting the late Palaeozoic Gondwanide orogen developed along the Panthalassan margin of Gondwana as accretionary in advancing-mode.