That abnormally pressured compartments are fundamental to the mechanics of large transcurrent fault systems and possibly control Holocene earthquake activity on the Castle Mountain fault zone. The project requires integration of subsurface geophysical and rock data, surface mapping, and laboratory geochemical, fluid inclusion and fluid transport measurements. The results will be incorporated into a predictive model for the generation and evolution of abnormally pressured compartments in regional transcurrent and related fault systems. The Mercur gold district in north central Utah includes several sediment-hosted disseminated gold deposits in the lower member of the Mississippian Great Blue Limestone. Fe-oxides or pyrite.
Argillized limestone has identical clay mineralogy in both oxidized and unoxidized rock.
Hydrothermally altered shales occur within the Mercur district and throughout the southern Oquirrh Mountains. Additional hydrothermal features exhibited by both shales and limestones are felted and interlocking clay mineral textures, radiating clay mineral habits, crosscutting and replacement clay mineral textures, and fossil replacement by clay minerals and quartz. None of the hydrothermal illites in the deposit have Tertiary ages. The oldest ages are late Triassic and are younger than the Mississippian stratigraphic age of the host rock, which suggests they are related to burial metamorphic or fluid flow processes occurring during the existence of the Oquirrh Basin. Ar diffusion in these samples rules out emplacement of the Tertiary Eagle Hill Rhyolite as the cause of this resetting and demonstrates the minimal thermal effects of the intrusive.