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Rb-Sr and U-Pb isotopic studies of the northeastern Idaho batholith and border zone

1978; Geological Society of America; Volume: 89; Issue: 9 Linguagem: Inglês

10.1130/0016-7606(1978)89 2.0.co;2

1943-2674

Ronald B. Chase, M. E. Bickford, Steven Elliott Tripp,

Geochemistry and Geologic Mapping

Research Article| September 01, 1978 Rb-Sr and U-Pb isotopic studies of the northeastern Idaho batholith and border zone RONALD B. CHASE; RONALD B. CHASE 1Department of Geology, Western Michigan University, Kalamazoo, Michigan 49008 Search for other works by this author on: GSW Google Scholar M. E. BICKFORD; M. E. BICKFORD 2Department of Geology, University of Kansas, Lawrence, Kansas 66045 Search for other works by this author on: GSW Google Scholar STEVEN E. TRIPP STEVEN E. TRIPP 1Department of Geology, Western Michigan University, Kalamazoo, Michigan 490083Present address: Tyler Combustion Engineering, 8200 Tyler Boulevard, Mentor, Ohio 44060 Search for other works by this author on: GSW Google Scholar Author and Article Information RONALD B. CHASE 1Department of Geology, Western Michigan University, Kalamazoo, Michigan 49008 M. E. BICKFORD 2Department of Geology, University of Kansas, Lawrence, Kansas 66045 STEVEN E. TRIPP 1Department of Geology, Western Michigan University, Kalamazoo, Michigan 490083Present address: Tyler Combustion Engineering, 8200 Tyler Boulevard, Mentor, Ohio 44060 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1978) 89 (9): 1325–1334. https://doi.org/10.1130/0016-7606(1978)89 2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation RONALD B. CHASE, M. E. BICKFORD, STEVEN E. TRIPP; Rb-Sr and U-Pb isotopic studies of the northeastern Idaho batholith and border zone. GSA Bulletin 1978;; 89 (9): 1325–1334. doi: https://doi.org/10.1130/0016-7606(1978)89 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 SocietyGSA Bulletin Search Advanced Search Abstract Border-zone rocks of the northeastern Idaho batholith have been subjected to multiphase penetrative deformation, regional metamorphism up to sillimanite-orthoclase grade, and multiple intrusion. Intrusion was accompanied by diapiric uprise of the plutonic-metamorphic complex, with extensive cataclasis and flow folding along the eastern margin of the rising gneiss dome. Normal faulting followed, with mylonitization and greenschist-grade metamorphism in local shear zones.Ages of some thermal events are estimated as follows: 85 ± 35 m.y. for a metamorphic event that affected quartzofeldspathic gneiss (Rb/Sr whole-rock line of best fit); 82 ± 10 m.y. for the emplacement of a quartz-diorite orthogneiss (estimate based on U/Pb isotopic ratios from a single zircon fraction); 66 ± 10 m.y. for the main stage of batholithic emplacement (U-Pb Concordia–lower intercept age); 46 ± 5 m.y., 42 ± 8 m.y., and 39 ± 2 m.y. for Rb/Sr isotopic equilibration late in the thermal evolution of the plutons (Rb/Sr mineral isochrons).The older dates conform generally to the range of intrusive ages assigned to the Flint Creek plutons and the Boulder batholith to the east. The younger dates reflect the igneous-hydrothermal-tectonic event of Eocene-Oligocene time which has reset K-Ar and fission-track (apatite) dates within the general Idaho batholith igneous complex.Magmas that formed the northeastern Idaho batholith were derived from, or contaminated with, older crustal material. This statement is supported by a 1,900- to 2,250-m.y. upper intercept age for batholithic zircons, some of which show euhedral overgrowths on anhedral cores, and by relatively high whole-rock Sr87/Sr86 ratios from samples with low Rb87/Sr86 ratios. 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.