A 3D MODEL AND STRUCTURAL INTERPRETATION OF THE TERRY COMPLEX OPEN PIT MINERALIZATION AT MARIGOLD MINE, HUMBOLDT COUNTY, NEVADA

Mineralization in the Battle Mountain mining district is strongly influenced by multiple deformation events including the Cenozoic extensional deformation that overprints Paleozoic and Mesozoic compressional structures. Marigold Mine, owned by Silver Standard Resources Inc., is an open-pit gold mine located on the north end of the Battle Mountain mining district in Humboldt County, Nevada. Disseminated mineralization is controlled by favorable sedimentary beds and near-vertical faults which acted as feeders in the footwall of the Golconda Thrust. The gold is found dominantly in structural fractures within the quartzite beds of the Ordovician Valmy Formation and within the Pennsylvanian to Permian Antler group adjacent to the steeply dipping faults.

This study presents a 3D geological model with interpretation of structural and lithological features investigated in the Terry Complex open pit. Structural data collected from two sub-perpendicular traverses along highwalls have been analyzed and correlated with data from exploration drillholes, production blastholes, and oriented acoustic televiewer surveys in order to understand subsurface architecture of the structures in the Terry Complex. Ground-based LiDAR scans of the highwalls provided supplemental structural data from inaccessible areas of the highwall. Results indicate multiple deformation events in the study area, which from oldest to youngest include (1) deformation of the Ordovician Valmy Formation during emplacement along the low-angle Roberts Mountain Thrust (not exposed in the Battle Mountain District); (2) E-W compressional deformation of the Mississippian to Permian Havallah Formation during emplacement of the Golconda Thrust; (3) E-W extensional deformation and associated Eocene(?) mineralization represented by major N-S normal faults and possibly the NNE striking Trap Boy fault; (4) strike-slip reactivation of some N-S faults; (5) and N-S extension creating near vertical, south dipping, E-W normal faults and near-vertical tensile joints. A previously unmapped high-angle, west dipping, mineralized normal fault offsets the Golconda Thrust ~200 feet on the west so that the thrust is not continuously exposed at the surface as previously mapped.