Abstract

SANTILLANA-VILLA, Cecilia; VALENCIA-MORENO, Martín; OCHOA-LANDIN, Lucas  and  DEL RIO-SALAS, Rafael. Ree signatures of intrusives associated with porphyry copper of Sonora. Epistemus (Sonora) [online]. 2021, vol.15, n.31, pp.31-37.  Epub May 26, 2023. ISSN 2007-8196.  https://doi.org/10.36790/epistemus.v15i31.188.

REE signatures in samples of plutonic rocks from five copper porphyry systems in Sonora, suggest that there is a petrogenetic process linked to the cooling of a major pluton that generates magma columns of porphyritic texture, which are emplaced at shallow levels in the crust. This is revealed by an apparent reversal in the polarity of the europium anomaly in the REE normalized patterns. In general, the patterns display a LREE-enriched slope, with a well-developed negative europium anomaly in the case of the main pluton. The signatures of the intrusives associated with mineralization are very similar, excepting the europium anomaly, which becomes less negative and even positive. According to existing models, this can be explained by considering that there is a significant fractionation of hornblende during the generation of the porphyritic stock, perhaps under more reducing magmatic conditions.

Keywords : Copper porphyry; REE; europium anomaly.