Applied geochemistry for the discrimination between mafic and ultramafic rocks in Cu-Ni-PGE-bearing layered complexes: A case study at the la Jovita-Las Águilas belt, Sierra Grande de San Luis, Argentina

Abstract

The Virorco intrusive body is comprised in La Jovita-Las Águilas mafic-ultramafic belt, Sierra Grande de San Luis, Argentina. The ultramafic rocks of this belt carry a base metal sulphide mineralization and platinum group minerals. Macroscopic description of mafic and ultramafic rocks, done by the mining exploration companies, can not differentiate the mineral percentages. Therefore, considering the geochemical composition of the already classified mafic-ultramafic rocks of surface samples from the mentioned belt, we established compositional ranges of geochemical parameters (MgO, Al2O3, Na2O, Sr and Cr) for both mafic and ultramafic rocks. Linking the geochemical data of drill cores made by Castillian Resources Corp. company over the Virorco body, with the mentioned ranges, it was possible to discriminate between mafic and ultramafic rocks present in such drill cores. This provides a useful prospecting tool to identify the mafic and ultramafic units that carry the mineralization and to correlate mineralized units from the different drill cores. This method can be applied, not only on the bodies of the mentioned belt, but in other similar deposits elsewhere. The methodology proposed in the present contribution was validated by the Machine Learning algorithm Random Forrest with a 91% success rate.