Gneiss and migmatite of Archean age in the Precambrian basement of central Wisconsin

Research Article| January 01, 1977 Gneiss and migmatite of Archean age in the Precambrian basement of central Wisconsin W. R. Van Schmus; W. R. Van Schmus 1Department of Geology, University of Kansas, Lawrence, Kansas 66045 Search for other works by this author on: GSW Google Scholar J. L. Anderson J. L. Anderson 2Department of Geological Sciences, University of Southern California, Los Angeles, California 90007 Search for other works by this author on: GSW Google Scholar Author and Article Information W. R. Van Schmus 1Department of Geology, University of Kansas, Lawrence, Kansas 66045 J. L. Anderson 2Department of Geological Sciences, University of Southern California, Los Angeles, California 90007 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1977) 5 (1): 45–48. https://doi.org/10.1130/0091-7613(1977)5<45:GAMOAA>2.0.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. Van Schmus, J. L. Anderson; Gneiss and migmatite of Archean age in the Precambrian basement of central Wisconsin. Geology 1977;; 5 (1): 45–48. doi: https://doi.org/10.1130/0091-7613(1977)5<45:GAMOAA>2.0.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 Many of the southernmost exposures of the Precambrian shield in central Wisconsin consist of gneiss, migmatite, and (or) amphibolite with associated younger intrusive tonalite and granite. Whole-rock Rb-Sr analyses and zircon U-Pb analyses show that the migmatite and gneiss formed about 2.8 b.y. ago. Ages on minerals and younger plutonic rocks indicate that the older gneiss and migmatite were intruded and locally metamorphosed during major events 1.5 to 1.9 b.y. ago.Rb-Sr data for the migmatite and gneiss indicate elevated initial 87Sr/86Sr ratios, suggesting that the migmatite and gneiss formed from crustal rocks of intermediate to granitic composition (which were themselves formed more than 3.0 b.y. ago). If this is true, then the gneissic and migmatitic rocks in central Wisconsin may represent an eastward extension of the ancient (≥3.5 b.y. old) Minnesota River Valley terrane. 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.