Petrografía, geoquímica y estratigrafía ígnea del cuerpo intrusivo Escuela Las Pircas, sierra Grande de San Luis, Argentina

CACACE, F.; FERRACUTTI, G. R.; NTAFLOS, TH.; ASIAIN, L. M.; BJERG, E. A.

Revista de la Asociación Geológica Argentina

Asociación Geológica Argentina

Lugar: Buenos Aires; Año: 2019 vol. 76 p. 229 - 253

0004-4822

Petrography, geochemistry and igneous stratigraphy of theEscuela Las Pircas intrusion, Sierra Grande de San Luis, Argentina.Escuela Las Pircas is a mafic-ultramafic intrusion locatedin the southern sector of La Jovita-Las Águilas mafic-ultramafic belt, which isa 3 to 5 km wide and 100 km long NNE trending belt located along the Easternslope of the Sierra Grande de San Luis. The mafic-ultramafic bodies of thisbelt are of great interest since they are layered intrusions which carry anassociated mineralization of Fe-Ni-Cu-Co sulfides and platinum group minerals.Modal and cryptic layering identified in Escuela Las Pircas intrusion allowsthe definition of four stratigraphic units: Plagioclase-bearing pyroxenehornblendite unit, plagioclase-bearing hornblende orthopyroxenite unit, lowerhornblende norite unit and upper hornblende norite unit. Their petrographicfeatures would suggest their belonging to the upper portion of the layeredseries. Bulk-rock and mineral chemistry results indicated that all the units ofEscuela Las Pircas intrusion correspond to the same magmatic sequence, in whichmineralogical and geochemical differences would have been mainly controlled bynucleation and crystal growth rate variations. Furthermore, petrographic andchemistry analysis indicate that the units defined in Escuela Las Pircas and inthose from Virorco Layered Series respond to the same stratigraphic igneoussequence, being Escuela Las Pircas units those that represent the higher degreeof evolution.