Caracterización petrográfica y geoquímica de las rocas máficas del sur de la Cordillera Real, provincias de Loja y Zamora

Abstract

This project is part of the geological survey conducted by INIGEMM in the years 2014-2015 and focuses on mafic bodies of the southern segment of the Cordillera Real. It comprises 9 topographic sheets between the provinces of Loja and Zamora. The petrographic study allowed to classify the samples in 4 lithotypes: metavolcanics, metaintrusives, schists and amphibolites. The amphibolites characterized are formed by amphibolite facies paragenesis, present basaltic protoliths of MORB affinity and are related to the Monte Olivo Unit. Quilanga mafic rocks present greenschist paragenesis and basic protoliths of MORB affinity; it represent the Peltetec Unit in the south of the Cordillera Real. The mafic schists of the northeast of Loja are formed by the paragenesis of greenschist facies. Mineralogical and geochemical evidence determine a volcanosedimentary protolith related to a mafic source. They could represent pre-Paleozoic volcanism or, in turn, a local variation of the protolith in the Paleozoic basin. The metavolcanics and metaintrusives of the Loja Norte topographic sheet present paragenesis of greenschis facies and basaltic protoliths of calco-alkaline affinity. Its origin is related to a common magmatic-volcanic event of Cenozoic age. However, could be an expression of Arc Alao magmatism.