The role of crustal contamination in the genesis of Ni-Cu sulfide ores from the Cortegana Igneous Complex (SW Spain)

Abstract

Crustal contamination of mafic magmas with S-rich country rocks is believed to play a critical role in the formation of Ni-Cu sulfide ores in SW Spain. Whereas this process has been well recognized in the Aguablanca Ni-Cu deposit (the only economic ore of this type in SW Europe), no data existed in other less mineralized, mafic-ultramafic intrusions of the region, such as the Tejadillas prospect in the Cortegana Igneous Complex. The Tejadillas prospect is composed of igneous cumulates similar to those of Aguablanca, but their incompatible trace element abundances show more primitive patterns than those of Aguablanca. In contrast, incompatible trace element ratios of the Aguablanca rocks are much closer to the contaminant country rocks than those of Tejadillas. Therefore, we suggest that the small volume of sulfide mineralization observed at Tejadillas was the consequence of low degrees of contamination of its parental magma by S-rich country rocks. This suggest that assimilation of S-rich country rocks by mafic magmas is the key factor for the genesis of economic Ni-Cu sulfide ores in SW Spain.