Summary:
Mineralization at Fire Creek occurs in steeply dipping epithermal veins within Tertiary basalt flows and intrusive rocks. The mineralized basaltic rocks are a suite of mafic, extrusive rocks associated with the regional north-northwest-trending Northern Nevada Rift ("NNR") structural zone.
The deposit is a low-sulfidation epithermal deposit vertically-zoned within high-angle northwest striking structures, hosted in a mid-Miocene basalt package. Mineralization occurs as shallow structurally-controlled fault hosted gold mineralization in variably altered Tertiary basalts and as native gold in steeply dipping quartz-calcite veins or structures. A package of middle Miocene basalt and basaltic andesite flow has been cut by high-angle normal faults related to both NNR and Basin and Range extension that form grabens and half-grabens which are the structural controls in the district.
High-grade mineralization has been delineated between approximately 4,900 feet and 5,700 feet and is open both up and down dip as well as along strike. Lower-grade mineralization occurs from the surface and mineralization is open at depth. Vein textures, gangue minerals, and alteration seen at Fire Creek are typical of low-sulfidation epithermal systems. Widespread propylitic alteration changes to argillic alteration proximal to veins and/or other structural fluid conduits. Low-grade gold mineralization is often spatially associated with the argillic alteration zone surrounding the high-grade gold. Mineralization often occurs along discrete horizons within vein structures. An opaline silica cap is discontinuously preserved at surface above the main mineralization at Fire Creek.
Fire Creek is defined by two major north-northwest striking vein arrays, each comprised of several en-echelon veins. Several new target areas outside of the known vein arrays have been defined by both gradient-array and dipole-dipole induced polarization surveys as well as versatile time domain electromagnetic system geophysical surveys.
The Hollister mine is located along the NNR, and is on trend with the north-western end of the Carlin Trend, which is approximately 5 miles wide and 40 miles long. Mineralization is related to the Miocene period of magmatic activity associated with the NNR while gold mineralization on the Carlin Trend has been dated to late Eocene/early Oligocene magmatism.
The Hollister property also includes the Hatter Graben vein system, which is located approximately 2,500 feet east of the Hollister mine's underground development and has been down dropped approximately 800 feet lower than the current mine resource. The system of mineralized veins has a known vertical extent of 1,400 feet and strike length of 2,000 feet. This East-West trending zone is open along strike to the east and west and at depth and mineralization is strengthening in the east as historic high-grade intersections occur up to 4000 feet along strike to the east. Gold and silver mineralization is dominantly in the Ordovician quartzites, siltites and argillites. Higher grades are associated with banded quartz veins from inches to feet in width and extensive zones of quartz vein stockwork and quartz matrix breccias also contain significant mineralization. The first surface holes were initiated at Hatter Graben in the third quarter of 2018 with the intent to extend the current identified mineralized material east and west. Drill holes at 300-foot intervals have intersected swarms with multiple veins and mineralized breccias at the anticipated distance. Development of a drift from the Hollister mine's underground workings to the Hatter Graben area commenced in the third quarter of 2018.
Midas is a high-grade, epithermal vein deposit, and the land package covers approximately 30,000 acres (~47 square miles), which includes fee lands, federal unpatented mining claims, seven mining leases.
Gold and silver mineralization at Midas is hosted in several northwest-striking veins. The veins are divided into four principal groups based on their location and orientation. The two principal groups that host the majority of the identified mineralized material are the Main Veins and East Veins. The Main Veins dip easterly and are gold dominant, while the East Veins dip to the west and contain higher silver content than the Main Veins. The Main Veins produced more than 2.2 million ounces of gold and 26.9 million ounces of silver between 1998 and 2013, principally from the Colorado Grande and Gold Crown Veins. Initial development and production from the East Veins began in 2012. The third group of veins is comprised of the Queen and Trinity Veins located to the south of the existing workings and south of the regional South Owyhee Fault. They are defined by limited underground and surface drilling and there has been no mine production from them to date. The Queen Vein and Trinity Vein systems represent high-priority, near-mine exploration targets.
Mineralized material has been identified on the Main and East veins and other veins near the recently active mine workings. Active drill testing has recently taken place in these areas and has been prioritized based on ounce expectations, accessibility from existing development and geotechnical, ventilation, and hydrological considerations.