Geology, mineral zoning, and lithochemistry of the el Soldado manto type copper deposit, Chile.

摘要

El Soldado is the largest (>200 Mt @ 1.4 % Cu) of the known Cu-(Ag) manto-type deposits in central Chile. The submarine volcanic upper member of the early Cretaceous Lo Prado Formation, which also contains marine carbonaceous shales and volcaniclastic sandstones, hosts the deposit. Petrographic and lithochemical evidence indicates that the volcanic host rocks are a bimodal suite of arc-related, calc-alkaline basalts and rhyodacites, which have been regionally affected by very-low-grade metamorphism and extensive albitisation. The rocks have acquired the characteristic alteration of spilite and keratophyre, explaining the previous misidentification as alkaline andesites and trachytes. U/Pb dates on zircons (138-126 Ma) from a rhyodacitic host dyke confirm the Hauterivian age assigned to host rocks on the basis of paleontology.; Although stratigraphically restricted (strata-bound), the clustered orebodies are mostly vein-like and discordant, controlled by a system of NS to NNW faults formed within a dilational jog along a sinistral, strike-slip brittle shear system. (Abstract shortened by UMI.)