Regional variations in bulk chemistry, mineralogy, and the compositions of mafic and accessory minerals in the batholiths of California

Abstract

Research Article| June 01, 1988 Regional variations in bulk chemistry, mineralogy, and the compositions of mafic and accessory minerals in the batholiths of California JAY J. AGUE; JAY J. AGUE 1Department of Geology and Geophysics, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar GEORGE H. BRIMHALL GEORGE H. BRIMHALL 1Department of Geology and Geophysics, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1988) 100 (6): 891–911. https://doi.org/10.1130/0016-7606(1988)100<0891:RVIBCM>2.3.CO;2 Article history first online: 01 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 JAY J. AGUE, GEORGE H. BRIMHALL; Regional variations in bulk chemistry, mineralogy, and the compositions of mafic and accessory minerals in the batholiths of California. GSA Bulletin 1988;; 100 (6): 891–911. doi: https://doi.org/10.1130/0016-7606(1988)100<0891:RVIBCM>2.3.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 We define regional variations in mafic and accessory mineral assemblages and compositions and expand the current understanding of spatial variations in whole-rock geochemistry in the batholiths of California. In so doing, we gain new insights into the nature of magmatic source rocks and mechanisms of magma generation in volcano-plutonic arcs of active continental margins. Little-studied metaluminous to strongly peraluminous granites containing Fe-rich biotite with log(XMg/XFe) < -0.21 (I-SCR type; strongly contaminated and reduced I-type) typically occur in north-northwest-striking belts within pre-batholithic wall-rock terranes containing graphitic pelites in the western Sierra Nevada and Peninsular Ranges batholiths. The other pluton types (I-WC, I-MC, and I-SC; weakly, moderately, and strongly contaminated, but not reduced, I-types) range in composition from metaluminous to weakly peraluminous and form a general west-to-east progression across the batholiths defined by increasing F/OH in biotite. This correlates with the well-known petrologic sequence from quartz diorites and granodiorites on the west to quartz monzonites and granites to the east. I-WC types also occur in the central-eastern Sierra Nevada batholith, however, primarily in the vicinity of the Independence dike swarm.F/OH and Mn in biotite and amphibole increase on a regional scale from western I-WC types to eastern I-MC and I-SC types, parallel to eastward increases in incompatible elements and decreases in compatible elements in the plutons. In contrast, the belts of western I-SCR granites and eastern I-WC quartz diorites and granodiorites disrupt the regional west-to-east systematics in both mineral and whole-rock geochemistry. Spatial variations in the Al content of amphibole are regional in scale and reflect pressures of pluton crystallization. We conclude that significant, previously unrecognized complexity exists in regional geochemical systematics in the California batholiths. 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.