Medium-high grade igneous-metamorphic basement unit in Central Patagonia, Argentina at its relation with the Terra Australis Orogen

RENDA, EMILIANO; GONZÁLEZ, PABLO DIEGO; ORIOLO, SEBASTIÁN; MARCOS, PAULO; SUÁREZ, RODRIGO

Cambridge

Congreso; Metamorphic Studies Group Research in Progress Meeting; 2021

The Mineralogical Society

During the Late Neoproterozoic to middle Paleozoic time span, the southwestern margin of Gondwana has beenexposed to protracted subduction [1,2,3,4], which has been considered as part of the widespread Gondwanan TerraAustralis Orogen (TAO) [2]. In southwestern Gondwana, the TAO comprises a series of accretionary systems which areassociated with crustal extension and back-arc basin development [2]. This tectonic setting alternates with sporadiccontractional episodes related with increased plate coupling, accretion of oceanic material, or collision ofallochthonous/para-autochthonous crustal blocks [1,2,3,4].In this context, the Patagonian continental block has been considered as a peri-Gondwanan block, accreted either inEarly or Late Paleozoic times [5,6,7]. In recent years, compelling evidence points out to an Early Paleozoic accretion ofthe northern part of Patagonia [7,8], within the tectonic framework of TAO. However, the Middle to Late Paleozoictectonic history of central and southern Patagonia, the tectonic setting of Gondwanide orogeny, and therefore theproper assessment of the culmination of TAO in this area are yet a matter of debate [9,10].In the past decades, a Middle-Late Paleozoic igneous-metamorphic belt was described in Central Patagonia[5,6], a keyarea for integrating central and southern Patagonia, and its precise location, crossing this area with a ~NNW-SSEstructural trend, was defined by geophysical means [9]. This belt comprises a series of fault-controlled basementblocks, formed by medium-high grade metamorphic complexes and coeval magmatism [5,10,11]. Recently, theLagunita Salada Igneous-Metamorphic Complex was defined in this area. The regional metamorphism of this complexattained upper amphibolite-lower granulite facies, constrained by Th-U-Pb EPMA monazite ages between ca- 379-320My [12]. Based on dated syn- and post-tectonic granitoid intrusions in the area an isotopic system re-opening couldnot be discarded for the ~320 Ma isochron monazite model age. Moreover, a magmatic lull of ~20 My coeval or slightlyposterior to the medium-high grade metamorphism [12], could present important implications for the tectonic regimefor the the TAO in this area, previous to the syn- to postectonic Upper Carboniferous – Early Permian magmatism andthe initiation of Gondwanide orogeny in southwestern Gondwana.