GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 267-1
Presentation Time: 9:00 AM-6:30 PM


BARTH, A.P.1, WOODEN, J.L.2, TANI, Kenichiro3, COBLE, Matthew A.4, CLEMENS-KNOTT, Diane5, JACOBSON, C.E.6, RIGGS, Nancy R.7, SURPLESS, Kathleen8 and SHUKLE, John1, (1)Earth Sciences, Indiana University-Purdue University, 723 West Michigan Street, Indianapolis, IN 46202, (2)U.S Geological Survey, Menlo Park, CA 94025, (3)IFREE-JAMSTEC, IFREE-JAMSTEC, 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan, (4)Department of Geological Sciences, Stanford University, Bldg 320, 450 Serra Mall, Stanford, CA 94305-2115, (5)Department of Geological Sciences, California State University, Fullerton, 800 N. State College Blvd., Fullerton, CA 92831, (6)Earth & Space Sciences, West Chester University of Pennsylvania, West Chester, PA 19383, (7)Geology, School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011-4099, (8)Geosciences, Trinity University, One Trinity Place, San Antonio, TX 78212,

Lithophile trace element enrichment in zircons reflects melt evolutionary paths and can discriminate among potential zircon source rocks. Compilations of internally consistent, global zircon data sets (Grimes et al., 2009, 2015) show that ratios of conservative trace elements and subduction-related, non-conservative to conservative elements are useful for (1) discriminating sources in depleted (MORG) to enriched (plume) oceanic rocks and (2) defining variably enriched ‘continental’ zircon sources. In this study we utilize Hf abundances and ratios of variably non-conservative elements in zircons from arc batholithic and volcanic source rocks to devise a classification scheme for arc-derived zircons. Hf abundances in cogenetic zircon suites define fractionation-induced arrays. Discrimination of arc zircon sources relies on U/Yb enrichment across these Hf arrays that records subduction-related lithophile element enrichment from primitive oceanic arcs to continental arcs. Correlated non-conservative element enrichments define low U/Yb to high U/Yb magmatic arc zircon sources roughly analogous to low to high K arcs defined by whole rock chemistry. U/Yb and light rare earth element ratios (Ce/Gd and Ce/Yb) may record both sympathetic enrichments during melt fractionation and lithophile element decoupling due to source variations in long-lived, thermally mature arcs. We demonstrate that this discrimination of arc zircon sources is useful for defining secular magmatic variation across magma pulses and for petrologic characterization of hydrothermally altered volcanic rocks in the long-lived Sierran volcano-plutonic arc. Arc provenance characterization of populations of forearc and rear-arc detrital zircons also illuminates arc evolution through time and enhances characterization of the arc volcanic carapace and the petrologic connection between arc volcanism and plutonism.