U-Pb and Sm-Nd ages for the Stillwater Complex and its associated sills and dikes, Beartooth Mountains, Montana: Identification of a parent magma?

Abstract

Research Article| November 01, 1990 U-Pb and Sm-Nd ages for the Stillwater Complex and its associated sills and dikes, Beartooth Mountains, Montana: Identification of a parent magma? W. R. Premo; W. R. Premo 1U.S. Geological Survey, M.S. 963, Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar R. T. Helz; R. T. Helz 2U.S. Geological Survey, M.S. 959, National Center, Reston, Virginia 22092 Search for other works by this author on: GSW Google Scholar M. L. Zientek; M. L. Zientek 3U.S. Geological Survey, West 920 Riverside Avenue, Spokane, Washington 99201 Search for other works by this author on: GSW Google Scholar R. B. Langston R. B. Langston 4Stillwater Mining Company, HC 54-Box 365, Nye, Montana 59061 Search for other works by this author on: GSW Google Scholar Author and Article Information W. R. Premo 1U.S. Geological Survey, M.S. 963, Federal Center, Denver, Colorado 80225 R. T. Helz 2U.S. Geological Survey, M.S. 959, National Center, Reston, Virginia 22092 M. L. Zientek 3U.S. Geological Survey, West 920 Riverside Avenue, Spokane, Washington 99201 R. B. Langston 4Stillwater Mining Company, HC 54-Box 365, Nye, Montana 59061 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (11): 1065–1068. https://doi.org/10.1130/0091-7613(1990)018<1065:UPASNA>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation W. R. Premo, R. T. Helz, M. L. Zientek, R. B. Langston; U-Pb and Sm-Nd ages for the Stillwater Complex and its associated sills and dikes, Beartooth Mountains, Montana: Identification of a parent magma?. Geology 1990;; 18 (11): 1065–1068. doi: https://doi.org/10.1130/0091-7613(1990)018<1065:UPASNA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Seven analyses from two samples of the Lower Banded series of the Stillwater Complex, Montana, yielded a U-Pb zircon-baddeleyite age of 2705 ±4 Ma. A more precise age of 2704 ±1 Ma is obtained if we regress only five of seven analyses. In either case, the age is in very good agreement with the previously reported Sm-Nd mineral isochron age of 2701 ±8 Ma for a gabbro from the Lower Banded series.Noncumulate mafic sills and dikes that immediately underlie the Stillwater Complex are separated into five compositional groups. U-Pb zircon ages for a group 1 gabbronorite (2711 ±1 Ma) and a group 3 mafic norite (2703 ±10 Ma) are comparable to previously reported U-Pb zircon ages for a group 1 diabase (2713 ±3 Ma) and a group 4 high-Ti norite (2712 ±3 Ma). Although group 2 high-Mg gabbronorite and group 6 olivine gabbro have not yet yielded significant amounts of zircon, baddeleyite, or sphene, mineral separates from group 2 ielded a four-point Pb-Pb internal isochron age of 2704 ±25 Ma, and separates from group 6 yielded a Sm-Nd internal isochron age of 2706 ±64 Ma, indicating that these groups are at least contemporaneous with intrusion of the Stillwater Complex.These results indicate that groups 1 and 4 of the associated sills and dikes are perhaps slightly older than the complex and that groups 2, 3, and 6 may be coeval with it, supporting the idea that these three groups are the best candidates for a Stillwater parent magma, a conclusion previously presented on the basis of detailed mineralogic and geochemical evidence. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.