STRUCTURAL CONTROLS ON GOLD MINERALIZATION IN MARIGOLD MINING SITE, HUMBOLDT COUNTY, NV

The Battle Mountain mining district, Nevada has undergone a series of compressional deformational events in Paleozoic and Mesozoic times. The Cenozoic Basin and Range extensional deformation has overprinted older N-S-striking deformational structures and formed a series of fault and fracture patterns in the region. The younger extensional deformation stage potentially reactivated some older faults and formed new fault sets in NW, NE and E-W directions through time. This study investigates sub-parallel N-S mineralized faults and their relationship with other fault generations in the Terry Complex open pit at Marigold Mine, on the north end of the Battle Mountain mining district in Humboldt County, Nevada. This study locally constrains the stress orientation of the reactivated faults and potential correlations with mineralization trends and/or regional fault/fracture orientations. Marigold’s disseminated mineralization is controlled by favorable sedimentary beds and near-vertical faults which constitute pathways for hydrothermal fluid transportation within the footwall of the Golconda Thrust. The gold is found dominantly in fault gouge and fractures within the quartzite beds of the Ordovician Valmy Formation and disseminated within the Pennsylvanian to Permian Antler group adjacent to the steeply-dipping faults. Kinematic analysis of major fault and fracture sets have been investigated to document mode, nature and magnitude of extensional deformation in the study area. Our results indicate that some of the mineralized faults have dip-slip movement overprinted by strike-slip movement. Strike-slip reactivation of extensional structures and mineralization trends along the faults creates a complex geology in the region. Structural data collected throughout the Terry Complex, with a focus on two traverses along sub-perpendicular highwalls near a N-S mineralized reactivated fault zone indicate that initial normal fault movement most likely occurred before or during the Eocene (?) based on the strong correlation between mineralized zones and normal fault orientations. In most localities within the study area, right-lateral strike-slip reactivation or faulting appears to have occurred post-mineralization likely in Miocene or younger times.