Fluids associated with the caxias mesothermal gold mineralization, São Luiz Croton, Northern Brazil: a fluid inclusion study

Abstract

The Caxias deposit is situated in the Gurupi Auriferous Province of the Paleoproterozoic São Luís Craton, northern Brazil. It is a lode-type gold mineralization associated with a narrow, steeply dipping, NE-trending, shear zone crosscutting a hydrothermalized microtonalite (northern sector) and schists (southern sector). Fluid inclusion studies on vein quartz crosscutting the microtonalite (northern sector) have identified early carbonic and aqueous-carbonic inclusions and late aqueous inclusions, unrelated to the mineralizing event. The CO2/ H2O ratio and the other microthermometric properties show a wide range of values, which are interpreted as product of heterogeneous trapping of two (partially) immiscible fluids and to deformation-related post-formational processes.