Geology And Lithogeochemistry Of The Unique Las Cruces Vms Deposit, Iberian Pyrite Belt

The Las Cruces deposit is a unique example of supergene enriched massive sulphide deposit in the Iberian Pyrite Belt (IPB). This massive sulphide, is the most easterly in the IPB hosted in shales and fine grain volcanoclastic rocks within the lower Volcano-Sedimentary (VS) Complex. Detailed lithostratigraphic study identifies four units. The footwall comprises a dacitic dome interbedded with sandstone and shale, at the bottom, where the primary mineralization is developed. The hanging wall is formed of three main units, consisting of a complex sequence of volcanoclastic breccias and sandstone, alternating with siltstone and shale, including a pumice-rich breccia. The chemostratigraphic results show a composition between rhyodacite and basalt-andesite with a calc-alkaline affinity. There is no significant geochemical difference within the entire sequence suggesting a unique magmatic pulse. Lastly, the geochemical analysis of the hosted shale suggests local anoxic conditions prevailed during massive sulphide formation.