Variations of Major Chemical Constituents across the Central Sierra Nevada Batholith

Abstract

Research Article| February 01, 1970 Variations of Major Chemical Constituents across the Central Sierra Nevada Batholith P. C BATEMAN; P. C BATEMAN U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar F. C. W DODGE F. C. W DODGE U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information P. C BATEMAN U.S. Geological Survey, Menlo Park, California 94025 F. C. W DODGE U.S. Geological Survey, Menlo Park, California 94025 Publisher: Geological Society of America Received: 02 Jul 1969 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1970, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1970) 81 (2): 409–420. https://doi.org/10.1130/0016-7606(1970)81[409:VOMCCA]2.0.CO;2 Article history Received: 02 Jul 1969 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation P. C BATEMAN, F. C. W DODGE; Variations of Major Chemical Constituents across the Central Sierra Nevada Batholith. GSA Bulletin 1970;; 81 (2): 409–420. doi: https://doi.org/10.1130/0016-7606(1970)81[409:VOMCCA]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 A study of 193 chemical analyses of plutonic rocks from 132 localities in the central Sierra Nevada shows convincingly that K2O decreases systematically westward and suggests that Fe2O3 and TiO2 may also decrease westward and that FeO, MgO, and CaO may increase. The ratio K2O/SiO2 obviously decreases westward across six of eight provisionally established sequences of granitic rocks. Plots of analyses of rocks from each sequence form discrete fields that are strongly elongate toward zero K2O at 40 to 45 percent SiO2. The boundaries between fields on these plots and between fields on plots of normative minerals on triangular diagrams are sharp. Compositional trends within sequences are different than the compositional changes that take place across the batholith—rocks in the western Sierra Nevada probably are not compositionally identical with rocks that are present at depth beneath the eastern Sierra Nevada.Progressive decrease of K2O in the Paleozoic and Mesozoic country rocks westward across the batholith is consistent with the anatectic model for its origin. However, it also is consistent with the hypothesis developed to explain chemical patterns in volcanic island arcs—that K2O increases toward continental land masses because of increasing depth of magma generation along landward-dipping seismic (Benioff) zones. The seismic-zone hypothesis encounters several difficulties, but it cannot be ruled out. 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.