The Lehman Butte project is located 15 km west of Mackay, Idaho. It is a low-Sulfidation epithermal and Carlin-style project that covers a 13 km2 zone of Au-Ag mineralized qtz-adularia(?)-clay alteration. EMX rock chip samples up to 3.1 g/t Au + 19.8 g/t Ag + As-Sb (n=35, avg.=0.185 ppm Au, 6.7 ppm Ag, max=3.1 g/t Au, 38.1 g/t Ag) were taken in qtz-adularia-clay altered lava. There is widespread, highly anomalous Au BLEG anomalies in all drainages cutting major alteration zone with minimal outcrop throughout property. Lehman Butte has an analogous bulk tonnage low-sulfidation epithermal mineralization style similar to McDonald, MT1 and Round Mountain, NV.2
Host rocks are Eocene intermediate lavas and interbedded tuffs along with underlying Mississippian Limestone. A NW to N-S trending normal fault system with likely NE-oriented secondary structures was mapped regionally. Lehman Butte has widespread clay-adularia alteration assemblages identified with ASTER, localized silicification and 0.5-1m Qtz-sulfide veins, and jasperoid in limestone on the property. A strong Au-Ag-As geochemical association and widespread Au BLEG anomalies in 6 of 14 basins cutting alteration with <5% outcrop across the property.
Bulk tonnage, near surface gold targets consist of 1) Km-scale hydrothermal alteration observed across property exhibiting anomalous Au-Ag-As geochemistry with rock chip samples up to 3.1 g/t Au + 19.8 g/t Ag + As-Sb (n=35, avg= 0.185 ppm Au, 6.7 ppm Ag, max=3.1 g/t Au, 38.1 g/t Ag), 2) permeable tuff units mapped in volcanic sequence that offer potential for shallowly concealed bulk tonnage, low-grade oxide gold mineralization similar to McDonald, MT1 and Round Mountain, NV2 and 3) basal and Paleozoic limestone that contains outcropping jasperoid anomalous in Ag-As-Sb-Hg-Tl with potential for structurally controlled Carlin-style Au mineralization beneath Eocene volcanics.
In late 2021 EMX has entered into an agreement with Hochschild Mining PLC (LSE: HOC) (“Hochschild”) for the project. The Agreement provide EMX with work commitments and cash payments during Hochschild’s earn-in period, and upon earn-in for a given project, a 4% net smelter return (“NSR”) royalty, annual advance royalty payments, and milestone payments.
1 Enders, M.S., Bartlett, M.W., Griffin, G.C., Volberding, J.E. and Young, D.P., 1995. Discovery of the McDonald gold deposit. Mining Engineering, 47(10), pp.916-921.
2 Sander, M.V. and Einaudi, M.T., 1990. Epithermal deposition of gold during transition from propylitic to potassic alteration at Round Mountain, Nevada. Economic Geology, 85(2), pp.285-311.
Note: The nearby mines and deposits mentioned above provide context for EMX’s Project, which occurs in a similar geologic setting, but this is not necessarily indicative that the project hosts similar tonnages or grades of mineralization