Role of fluid mixing and fault-related sulfide in the origin of the Ray Point uranium district, south Texas

The Lamprecht and Felder deposits are roll-type deposits hosted by the Miocene Oakville Sandstone. Four distinct stages of FeS ₂ mineral formation are recognized: (1) a generation of isotopically light (delta ³⁴ S < -20 per mil) preore pyrite, (2) a generation of isotopically light (delta ³⁴ S < -20 per mil) marcasite that formed mostly before, but also during ore deposition, (3) a postore generation of isotopically heavy pyrite (delta ³⁴ S > 0 per mil), and (4) a yet later generation of marcasite with isotopically light sulfur close to the values of stages 1 and 2. Complex zone of mixing between saline brines migrating up the fault from depth and oxygenated meteoric water recharging at the outcrop. Bacterial activity.