Early Paleozoic alkalic plutonism in east-central Idaho

Research Article| December 01, 1988 Early Paleozoic alkalic plutonism in east-central Idaho KARL V. EVANS; KARL V. EVANS 1U.S Geological Survey, P.O. Box 25046, M.S. 905, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar ROBERT E. ZARTMAN ROBERT E. ZARTMAN 2U.S. Geological Survey, P.O. Box 25046, M.S. 963, Denver Federal Center, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information KARL V. EVANS 1U.S Geological Survey, P.O. Box 25046, M.S. 905, Denver Federal Center, Denver, Colorado 80225 ROBERT E. ZARTMAN 2U.S. Geological Survey, P.O. Box 25046, M.S. 963, Denver Federal Center, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1988) 100 (12): 1981–1987. https://doi.org/10.1130/0016-7606(1988)1002.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation KARL V. EVANS, ROBERT E. ZARTMAN; Early Paleozoic alkalic plutonism in east-central Idaho. GSA Bulletin 1988;; 100 (12): 1981–1987. doi: https://doi.org/10.1130/0016-7606(1988)1002.3.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 SocietyGSA Bulletin Search Advanced Search Abstract U-Th-Pb analyses of zircon suites document the presence of three lower Paleozoic alkalic plutons in east-central Idaho. The igneous bodies range in composition from alkali-feldspar syenite to alkali-feldspar granite. The epizonal Arnett Creek pluton contains a morphologically bimodal suite of anhedral and euhedral zircon, which combined gives an upper intercept age on a concordia diagram of 492 ± 39 m.y. Zircon analyses from the Deep Creek pluton plot near the 500-m.y. locus on concordia, but the pattern suggests the presence of a small component of inherited radiogenic lead. Limited Rb-Sr whole-rock data for the Arnett Creek and Deep Creek plutons are compatible with an Early Ordovician age but are too imprecise to refine interpretations. Zircon from the epizonal Beaverhead pluton, for which the enigmatic Ordovician-Silurian K-Ar and Rb-Sr mineral ages have long been debated, yields an approximate age of 483 m.y.The tectonic setting of these intrusions is poorly known. The coincidence of early Paleozoic plutonism and independently documented syndepositional faulting with the coeval topographic high, known variously as the "Lemhi" or "Salmon River Arch," tentatively suggests a mutual tectonic control. Further geochronologic, stratigraphic, and especially petrogenetic studies, however, are required to evaluate this possibility. 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.