EI provided Geological Modeling and Mineral Resource Estimation updates in support of a Feasibility Study on SRA’s Black Butte Copper Project. The Black Butte Copper Project is located 27 km north of White Sulphur Springs, Montana, USA.
The Johnny Lee and Lowry copper deposits that comprise the Black Butte Project are considered hybrid sedimentary exhalative (SEDEX) – sediment-hosted stratabound copper (SCC) sulfide deposits.
In 1985, the Johnny Lee deposit was discovered by a joint venture between Broken Hill Proprietary Ltd. (BHP) and Cominco American Inc. (CAI), followed by the CAI discovery of Lowry in 1990.
In 2010, Tintina Resources Inc. (Tintina) acquired the mineral rights and completed resource definition drilling and a Preliminary Economic Assessment study.
In 2013, Sandfire Resources NL acquired a majority shareholding in Tintina and the company name was changed to Sandfire Resources America, Inc. (SRA). Copper mineralization at the Johnny Lee deposit is hosted by two massive sulfide units that occur at different stratigraphic levels within the sedimentary succession, referred to as the Upper Sulfide Zone and Lower Sulfide Zone.
At the Lowry deposit, copper mineralization is hosted by a succession of sub-parallel, ferruginous sediment with interbedded shale and conglomerate lithofacies.
Economically significant copper mineralization is further domained in discrete bedding-parallel areas and lower-grade halos within the main zones.