Layered mafic sill complex beneath the eastern Snake River Plain: Evidence from cyclic geochemical variations in basalt

Abstract

Research Article| May 01, 2006 Layered mafic sill complex beneath the eastern Snake River Plain: Evidence from cyclic geochemical variations in basalt John W. Shervais; John W. Shervais 1Department of Geology, Utah State University, Logan, Utah 84322-4505, USA Search for other works by this author on: GSW Google Scholar Scott K. Vetter; Scott K. Vetter 2Department of Geology, Centenary College, Shreveport, Louisiana 71104-1188, USA Search for other works by this author on: GSW Google Scholar Barry B. Hanan Barry B. Hanan 3Department of Geological Sciences, San Diego State University, San Diego, California 92182-1020, USA Search for other works by this author on: GSW Google Scholar Author and Article Information John W. Shervais 1Department of Geology, Utah State University, Logan, Utah 84322-4505, USA Scott K. Vetter 2Department of Geology, Centenary College, Shreveport, Louisiana 71104-1188, USA Barry B. Hanan 3Department of Geological Sciences, San Diego State University, San Diego, California 92182-1020, USA Publisher: Geological Society of America Received: 25 Sep 2005 Revision Received: 13 Dec 2005 Accepted: 19 Dec 2005 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2006) 34 (5): 365–368. https://doi.org/10.1130/G22226.1 Article history Received: 25 Sep 2005 Revision Received: 13 Dec 2005 Accepted: 19 Dec 2005 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation John W. Shervais, Scott K. Vetter, Barry B. Hanan; Layered mafic sill complex beneath the eastern Snake River Plain: Evidence from cyclic geochemical variations in basalt. Geology 2006;; 34 (5): 365–368. doi: https://doi.org/10.1130/G22226.1 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 The eastern Snake River Plain in southern Idaho, western United States, is characterized by 1–2 km of Pleistocene to late Pliocene basalt overlying rhyolite caldera complexes. Cyclic variations in the chemical composition of basalts from 1136 m of scientific drill core show that the parent magmas of these lavas evolved by crystal fractionation at shallow to intermediate crustal depths, punctuated by episodic recharge with more primitive compositions and assimilation of adjacent wall rock. We have identified 10 upward fractionation cycles and four reversed cycles; assimilation of sialic crust was limited and mainly affects the oldest basalts, which directly overlie rhyolites. We infer that the crystal fractionation and/or recharge cycles took place in a series of sill-like intrusions at intermediate crustal depths that now form a layered mafic intrusion that underlies the eastern Snake River Plain at depth. This layered sill complex is represented by the ∼10-km-thick "basaltic sill" that has been imaged seismically at ∼12–22 km depth. The association of this mid-crustal sill complex with geochemical fractionation cycles in basalt supports the concept that exposed layered mafic intrusions may be linked to overlying basalt provinces that have since been removed by erosion. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.