Metallogenic evolution of the Sierras Pampeanas of Córdoba and south of Santiago del Estero: Prepampean and Pampean cycles

Abstract

This hypothesis of metallogenic evolution of the Sierras Pampeaneas of Córdoba and south of Santiago del Estero proposes the existence of five metallogenic stages, two of wich are treated in this paper: stage 1 belongs to the prepampean extensional cycle and is connected with the Neoproterozoic opening and expansion of the proto-Atlantic ocean. During this stage submarine volcanogenic deposits were developed such as Cu-Fe (Zn-Au-Ag-Co) in basalts, W (B-F-Zn) in impure limestones and dolomites, and Fe in silicoclastic sediments, as well as transition occurrences from them to MVT deposits of Cu (Au-Ag) and Pb- Zn (Ag-Cu-Au) in impure limestones and dolomites. Chromite magmatic deposits in mantle tectonites and of Fe-Ti in ultramaficmafic rocks in the transition crust-mantle zone are also related to stage 1. Distribution of the Prepampean deposits and their space relationship with the main submarine volcanogenic, SEDEX and MVT áreas in the proto-atlantic ocean are placed on a global reconstruction for Neoproterozoic age. The compressive Pampean - Famatinian cycle comprises two stages. Metallogenic stage 2 (Neoproterozoic - early Cambrian) corresponds to the pampean orogenic cycle, during which numerous deformation structures and magmatism were developed. During this stage magmatic-metamorphic occurrences of Fe-Ti in ultramafic and mafic dikes in mantle tectonites, metasomatic occurrences of Fe-Ti in rodingites and Be-Li-U-ETR rich pegmatites were generated, besides transformation events comprising metamorphism, deformation, remobilization and recrystallization occurred in deposits of Cr, Cu-Fe (Zn-Au-Ag- Co), W (B-F-Zn), Cu (Au-Ag), Pb-Zn (Ag-Cu-Au) and Fe, which affected their magnetic response.Ore deposits and occurrences included in the above metallogenic stages are distributed in this study in belts related to megastructures activated during the Prepampean and Pampean cycles and the most significant petrogenétic associations are indicated.