Characterization of the W ores at the Santa Comba mine, NW Spain

Abstract

The NW of the Iberian Peninsula is characterized for hosting W-Sn deposits related to peraluminous variscan granites. One of them is the Santa Comba mine, located 45 km to the northwest of Santiago de Compostela, Spain. The mine is set in a poly-intrusive epizonal complex which fits the Endogranite-Stockscheider-Exogranite model (Nesen, 1979). This deposit features two types of mineralization containing cassiterite (SnO2), wolframite (FeMnWO3), and scheelite (CaWO4): a low tonnage high-grade mineralization concentrated in the quartz vein system that crosscuts the whole complex, and high tonnage low-grade disseminated mineralization hosted in the youngest intrusion (endogranite). The disseminated mineralization is related to zones of pervasive high-temperature hydrothermal alteration and stockwork-like systems, sometimes sharing features with porphyry-like deposits. A unique feature of this deposit is that the disseminated ore is enriched in wolframite but from a certain depth becomes enriched in scheelite. In this study, we applied microprobe analysis (EPMA), Raman spectroscopy, and a textural study through the petrographic microscope to identify and examine the characteristics of each ore.