MAGMATISMO MÁFICO DEL PALEOZOICO INFERIOR. SIERRA DE CALALASTE -PUNA AUSTRAL. MARGEN ACTIVO DEL SW DE GONDWANA

NIEVES, ALEXIS; BECCHIO, RAÚL A.; NESTOR SUZAÑO O.; DOS SANTOS, GIANA; SOLA, ALFONSO M.; AHUMADA, MARIA F.; ORTIZ, AGUSTÍN

Córdoba

Congreso; XIII CONGRESO DE MINERALOGÍA, PETROLOGÍA ÍGNEA Y METAMÓRFICA, Y METALOGÉNESIS; 2019

There are mafic/ultramafic rocks (CBUT, Tramontana Basic-Ultrabasic Complex)that intrude the sedimentary and volcanic nature country rocks (CSVCC, Cortaderas Chica Volcanic-Sedimentary Complex). These lithologies were metamorphosed into green schist facies. The intrusion of the mafic bodies (dikes and sills) produced wide thicknesses of hornfels in the country rock. In some sectors, the gabbroic bodies were differentiated by mechanical accumulation of crystals forming ultramafic cumulates rocks. In others sectors, they are differentiated by fractional crystallization generating a base layer with pyroxenites cumulates. These vary towards a middle zone of gabbros, whereas to the top of the sequence, there are leucogabbros with anorthosites cumulates. The gabbros have a tholeiitic nature, mainly with a MORB type signature, corresponding to a magmatic arc environment.Isotopic data suggest that mafic and ultramafic rocks were derived from a depleted mantle source with little or no contribution of cortical components. The TDM ages indicate that the possible source of the vulcanites were Paleo to Mesoproterozoic rocks, while the source of the mafic/ultramafic magmas were essentially Neoproterozoic.The rhyolite is ~ 495 Ma. This indicates that the mafic/ultramafic intrusives are necessarily younger than 495 Ma (Upper Cambrian). The described units have a ductile deformation, which possibly occurred during the Ocloyic Tectonic Phase.Based on the evidence, an ophiolitic complex setting of preordovic age is discarded for the mafic/ultramafic sequences and associated metasedimentary sequences; instead we suggest a magmatic arc, back-arc environment.