Abstract

ORTIZ SUAREZ, Ariel; MOROSINI, Augusto; ULACCO, Humberto  and  CARUNGO DURAN, Andrés. Geology and geophysics of the Las Cañas mafic-ultramafic stock, San Luis province. Ser. correl. geol. [online]. 2012, vol.28, n.2, pp.151-166. ISSN 1666-9479.

Las Cañas is an elongated stock located to the NE of San Luis province. Its structure is concordant with that of the country rock and has a size of 800 m wide by 2 km long, located in schists belonging to the Las Aguadas Metamorphic Complex (Conlara Metamorphic Complex) with N 20º - 30º schistosity and an eastward high angle dip. The predominant facies is a gabbro that shows magmatic stratification and contains ultramafic sectors of up to 50 m in diameter; in some cases the rock is a pyroxenic hornblendite formed by poikilitic amphibole crystals with inclusions of clinopyroxene, altered olivine and opaque minerals. These rocks show alteration and mineralization of Ni, Cr, Fe, Zn and platinum group elements. The geomagnetic terrestrial survey reveals an anomaly in the mineralized zone that coincides with the ultramafic rocks, with positive and negative peaks of 1955 and -480 nT that are close to each other. Contrasts of approximately 500 in nT amplitude characterize the igneous body without mineralization, whereas the metamorphic host rocks rarely exceed 100 nT. The geochemical features indicate that the Las Cañas body is formed by two groups of rocks, one with high values of MgO and the other predominantly tholeitic, with the former case possessing between 2 and 22 ppb of Pt or Pd.

Keywords : Mafic-ultramafic complexes; Conlara Metamorphic Complex; Magnetometry; PGM.

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