A--USGS RE-OS ISOTOPIC ANALYSIS

This is a SOLICITATION NOT a pre-solicitation:Please go to Fedconnect for full details. The Minerals Team of the U.S. Geological Survey needs high-quality Re-Os isotopic analyses of whole rocks and mineral separates from one of the largest gold deposits in the world. The Homestake mine, South Dakota, has been the site of extensive geologic, geochemical, isotopic, and mineralogic studies by the author and others in the Denver office. As with many ore deposits, defining the timing of mineralization is difficult because sulfide minerals do not yield reliable radiogenic ages by conventional isotopic analyses. The Re-Os system, however, is capable of determining both the depositional age of carbon-rich sedimentary rocks and the mineralizing age of arsenopyrite, electrum, and some gangue minerals. As part of the World-class deposit-model program of the USGS, we need to contract with an outside analytical laboratory having a proven track record of investigations on mineral deposits, to provide Re-Os isotopic data and interpretations of the gold deposit at the Homestake mine. Few laboratories are capable of providing high-quality Re-Os analyses at competitive prices due to the small number of existing laboratories and the complicated nature of the analyses. In the United States there are about three such facilities; in Canada are an additional two. For our analyses, Re and Os concentrations and isotopic compositions are needed for each sample. Below we outline the specifications of work needed for material from the Homestake mine for FY 2011. See the attached document for full statement of work.