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ISOTOPIC ANALYSIS OF ZIRCON SOURCES SOUGHT The US Geological Survey (USGS) is conducting market research to determine the availability of qualified businesses capable of providing services on U-Pb iso... ISOTOPIC ANALYSIS OF ZIRCON SOURCES SOUGHT The US Geological Survey (USGS) is conducting market research to determine the availability of qualified businesses capable of providing services on U-Pb isotopic analysis of zircon by CA-ID-TIM as described in the Statement of Work. This sources sought announcement is not a request for quote or proposal and the Government is not committed to award of a purchase order or contract pursuant to this announcement. The information resulting from this market research is simply for planning purposes to assist the Government in determining its acquisition strategy. The Government will not pay for any costs incurred in the preparation of information for responding to this notice. Statement of Work I. GENERAL INFORMATION A. Introduction The USGS Geology, Minerals, Energy, and Geophysics (GMEG) Science Center requires U-Pb chemical abrasion isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) analyses of zircon and baddeleyite separates collected from the Stillwater Complex in Montana. These analyses will support on-going research being conducted for critical commodity studies of mineralized rocks in the complex. B. Background U-Pb CA-ID-TIMS analyses performed on zircon and baddeleyite minerals are used to determine highly precise ages of igneous rocks. For this project, the precise age determination of individual layers of igneous rock within the Stillwater Complex help constrain the crystallization history and the origin of the igneous rocks that host the PGE-rich sulfide mineralization in the J-M Reef deposit. C. Definitions/Applicable Documents The primary use of the U-Pb CA-ID-TIMS method is to date age Zr-minerals in igneous rocks. Highly precise determinations of 207Pb/206Pb isotopic ratios with 2 sigma errors of ~0.01% can be achieved by analyzing multiple, concordant, and internally corrected for U and Pb fractionation, U-Pb data that correspond to 2 sigma age errors of <~200,000 years for rocks that are billions of years old. These age determinations are precise enough to distinguish the crystallization age of individual layers in layered mafic intrusions. Reviews of the CA-ID-TIMS method and its application to layered intrusions can be found in the following review papers: ¿ Condon, D. J., Schoene, B., McLean, N. M., Bowring, S. A., & Parrish, R. R. (2015). Metrology and traceability of U-Pb isotope dilution geochronology (EARTHTIME Tracer Calibration Part I). Geochimica et Cosmochimica Acta, 164, 464¿480. https://doi.org/10.1016/j.gca.2015.05.026 ¿ Gerstenberger, H., & Haase, G. (1997). A highly effective emitter substance for mass spectrometric Pb isotope ratio determinations. Chemical Geology, 136(3¿4), 309¿312. https://doi.org/10.1016/S0009-2541(96)00033-2 ¿ Jaffey, A. H., Flynn, K. F., Glendenin, L. E., Bentley, W. C., & Essling, A. M. (1971). Precision measurement of half-lives and specific activities of U235 and U238. Physical Review C, 4(5), 1889¿1906. https://doi.org/10.1103/PhysRevC.4.1889 ¿ Mattinson, J. M. (2005). Zircon U-Pb chemical abrasion (¿CA-TIMS¿) method: Combined annealing and multi-step partial dissolution analysis for improved precision and accuracy of zircon ages. Chemical Geology, 220(1¿2), 47¿66. https://doi.org/10.1016/j.chemgeo.2005.03.011 ¿ Scoates, J. S., & Wall, C. J. (2015). Geochronology of layered intrusions. In B. Charlier, O. Namur, R. Latypov, & C. Tegner (Eds.), Layered Intrusions (pp. 3¿74). Springer Geology. ¿ T.E.Krogh. (1973). A low-contamination method for hydrothermal decomposition of zircon and extraction of U and Pb for isotopic age determinations. Geochimica et Cosmochimica Acta, 87, 485¿494. D. Scope In collaboration with the Stillwater Mine and East Boulder Mine, we have collected five samples for whole-rock major, minor, and trace element geochemistry, polished thin section, and heavy mineral separation. Based on igneous rock texture, we have collected samples most prospective to contain Zr minerals for age determination. The samples were selected to test the hypothesis that the stratigraphic sequence of the layers does not obey the law of superposition. Sampling focuses on rocks in and around the layer that is being mined for platinum and palladium. II. WORK REQUIREMENTS A. Technical Requirements 1. Work Requirements/Products The USGS will provide 7 samples or mineral separates from samples to the laboratory manager. The laboratory manager (and assistants) will perform the necessary rock crushing, heavy liquids, and magnetic mineral separation to collect zircon and baddeleyite; chemically abrade zircon and baddeleyite to remove metamict rims; perform ID-TIMS analyses; acquire and reduce the data. 2. Criteria for acceptance of Product The criteria required for acceptance of the product include descriptions of the sample processing, analytical methods used to acquire data, data reduction methods used to calculate sample ages and age errors with sufficient detail appropriate for publication in a peer-reviewed journal. B. Deliverables 1. Characteristics for work product described in II.A.1. The data provided to the USGS will include age calculations and U-Pb data reduction. 2. Delivery dates Depending on lab schedules, the work for five samples will be completed within a year from the award of the contract. Digital data can be transferred to the USGS by email or other electronic data delivery. Leftover mineral separates will be returned to the USGS after work is complete. III. SUPPORTING INFORMATION A. Place of Performance Contractor¿s facility. B. Period of Performance Approximately 60 days of lab time, performed within a year from the award of the contract. C. Government Furnished Property (GFP): None. D. Special Considerations 1. Key personnel qualifications The person performing the analyses must have experience collecting zircon and baddeleyite, chemically abrading the minerals, and successfully collecting the isotopic data from mafic and ultramafic rocks found in layered igneous intrusions¿as shown by being author or coauthor on several peer- reviewed scientific reports or journal papers. Examples of layered intrusions include the Bushveld Complex, South Africa; and the Niquelandia layered intrusion, Brazil; as well as numerous other felsic, mafic, and ultramafic intrusions from all around the world. 2. Data Rights, Safety, Environment: None 3. Security/Privacy: None