South Bullfrog Gold Project
Bullfrog Mining District, Nye County, Nevada
- Epithermal gold exploration project centrally located in the Bullfrog district between Augusta’s Bullfrog and Reward projects and AngloGold’s Silicon and North Bullfrog projects
- 488 unpatented mining claims (9,899 acres) with numerous historic workings and a large area of alluvial cover concealing favorable geology
- Geophysical surveys (mag/rad, IP, gravity), geochemical surveys, and remote sensing have highlighted several highly prospective target areas for drill testing
The South Bullfrog project is located in the Mojave desert of southwestern Nevada adjacent to the town of Beatty, approximately 100 miles northwest of Las Vegas. Access is via interstate 95 and a well developed network of roads and tracks on U.S. Bureau of Land Management ground. Elevations range from 3300 to 4700 feet with sparse desert vegetation predominantly creosote bushes.
Zacapa acquired the South Bullfrog project through claim staking in 2020. Historic gold exploration and development in the Bullfrog district began in 1904 and saw rapid development in the early 20th century but only sporadic activity thereafter with most production coming from the Montgomery-Shoshone mine (112,000 oz Au; 1.7 km west of the South Bullfrog claims). In 1986 exploration around the Montgomery-Shoshone mine discovered the Bullfrog deposit near a small inactive narrow vein mine. The Bullfrog deposit went into production in 1989 and was ultimately acquired by Barrick Gold, who also redeveloped the historic Montgomery-Shoshone mine and also produced from a small open pit at Bonanza Mountain. In total these deposits produced 28.8 Mt at 2.52 g/t gold and 2.7 g/t silver, for 2.33 Moz gold and 2.49 Moz silver. Corvus Gold was active in the district from 2006 to 2021, defining a number of deposits and exploration targets, including the Mayflower deposit < 2 km northwest of Zacapa’s claims. Corvus was acquired by AngloGold Ashanti in 2021. AngloGold has been advancing Corvus’ North Bullfrog and Silicon projects to mine development. In 2022 AngloGold also purchased Coeur Mining’s land holdings in the district and is working on developing the Merlin deposit, which is contiguous with what were Corvus’ Lynnda Strip and Coeur’s C-horst discoveries. Kinross and Augusta Gold are also actively exploring in the district, with Augusta working to reopen the Bullfrog and Reward mines. Little is known about prior exploration on the Zacapa’s South Bullfrog project area, but numerous historic workings and several apparent drill pads indicate that some exploration has taken place.
The project area occurs in the southwestern Great Basin within the southern part of the Walker Lane mineral belt in the Southwestern Nevada Volcanic Field (SWNVF). Folded and thrust faulted Late Proterozoic to Late Paleozoic metamorphic and sedimentary rocks are overlain by a thick pile of Miocene (~15-7.5 Ma) volcanic and minor sedimentary rocks associated with the SWNVF. Volcanic rocks are dominated by ash flow tuffs and breccias from a cluster of nearby calderas, with lesser rhyolite domes and flows. The Walker Lane mineral belt is well known for its abundance of epithermal gold and silver deposits.
Much of the South Bullfrog project area is concealed beneath young alluvial cover. In areas to the west and southeast exposed rocks consist predominantly of Miocene volcanically derived tuff and breccias along with rhyolite. Mapped stratigraphic units range from 11.6 Ma Rainer Mesa tuff to 10.3 Ma Rainbow Mountain Sequence. Alteration occurs along high-angle fault zones up to several meters wide and most commonly consists of silicification (chalcedony, opal, quartz), clay (kaolinite, smectite, illite) and iron-manganese oxides.
Gold mineralization in the Bullfrog district has a strong structural control, occurring along steeply dipping faults and fractures of various orientations and disseminated in adjacent wallrocks. Known ages of gold mineralization range from 13 Ma to 10 Ma. Faults appear to have focused hydrothermal fluids resulting in two styles of gold-silver-bearing deposits: 1) high-grade fissure veins and associated stockwork zones; and 2) low-grade disseminated or replacement deposits within altered volcanic rocks, predominately tuff.
Deposits in the Bullfrog district are predominantly of the low-sulfidation epithermal variety with gold and silver occurring in quartz-calcite veins with minor pyrite and adularia, typically within a halo of quartz-kaolinite-alunite alteration where near surface. Some deposits (e.g. Silicon) display an apparent fluctuation in fluid chemistry between high-sulfidation magmatic condensate derived advanced argillic alteration and low-sulfidation, quartz-calcedony-calcite-adularia associated with gold deposition
- Longtail – small window through alluvial cover into strongly altered tuff. Soil geochemistry suggests a larger zone of anomalous Au, Hg, and As coincident with a large magnetic low.
- Shingleback – numerous faults displaying varying degrees of alteration. The most extensive is the NE-SW trending Basalt Fault zone which aligns with a strong IP-resistivity anomaly and magnetic low. Notice of intent accepted by BLM and ready for drilling.
- Bottom’s Up – zones of elevated As, Sb, and Hg in surface geochemistry associated with silicified outcrops.
- Sledge – large N-S trending structure with several other subsidiary and cross fault zones displaying varying degrees of alteration, silicification, and local bladed calcite with strongly elevated Hg and As geochemistry.
- SE Block – broad zones of alteration with locally anomalous geochemistry.
PERMITTING AND ESG
- Permitting at South Bullfrog is conducted through the U.S. Bureau of Land Management.
- A Notice of Intent has been accepted for four drilling locations at the Shingleback target.
- A second Notice of Intent is in preparation for three drilling locations at the Longtail target with a decision anticipated in mid-February 2023.
Bartos, P., Doyle, M., Nicholson, D., and Thompson, T., 2022, Exploration, geology, alteration, and mineralization of the Silicon Gold Prospect, Greater Bullfrog Hills – Bare Mountain District, Nye County, Nevada: Geological Society of Nevada Symposium, 25 p.
Connors, K.A., Weiss, S.I., and Noble, D.C., 1998, Geologic Map of the Northeastern Bullfrog Hills and Vicinity, Southern Nye County, Nevada, Nevada Bureau of Mines and Geology, Map 112, scale 1:24,000.
Coolbaugh, M.F., Pace, D., Craig, L.D., Bedell, R.L., and Miller, M.S., 2020, The Silicon Gold Project, Nye County, Nevada: Prospect generation methods leading to initial recognition, acquisition, and characterization: Geological Society of Nevada Symposium, p. 1027-1041.
Cornwall, H.R. and Kleinhampl, F.J., 1961, Geologic Map of the Bare Mountain Quadrangle, Nevada: U.S. Geological Survey, GQ-157, scale 1:62,500.
Cornwall, H.R., and Kleinhampl, F.J., 1964, Geology of the Bullfrog quadrangle and ore deposits related to the Bullfrog Hills caldera, Nye County, Nevada, and Inyo County, California: U.S. Geological Survey Professional Paper 454-J, 25 p.
Eng, T., Boden, D.R., Reischman, M.R., and Biggs, J.O., 1995, Geology and Mineralization of the Bullfrog Mine and vicinity, Nye County, Nevada, in Coyner, A.R. and Fahey, P.L., eds., Geology and Ore Deposits of the American Cordillera, Symposium proceedings, Reno, Geological Society of Nevada, Vol. 1, pp. 353-399.
Johnson, K.L., 2021, NI 43-101 Technical Report Mineral Resource Estimate, Bullfrog Gold Project – Nye County, Nevada: Tetra Tech for Augusta Gold Corp., 106 p.
Maldonado, F., and Hausback, B.P., 1990, Geologic map of the northeast quarter of the Bullfrog 15-minute quadrangle, Nye County, Nevada: U.S. Geological Survey Miscellaneous Investigations Map I-2049, scale 1:24,000.
Ransome, F.L., Emmons, W.H., and Garrey, G.H., 1910, Geology and Ore Deposits of the Bullfrog District, Nevada: U.S. Geological Survey Bulletin 407, 130 p.
Simmons, S.F., White, N.C., and John, D.A., 2005, Geological characteristics of epithermal precious and base metal deposits: Society of Economic Geologists 100th Anniversary Volume, p. 485-522.
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