Silicic melt evolution in the early Izu-Bonin Arc recorded in detrital zircons; zircon U-Pb geochronology and trace element geochemistry for Site U1438, Amami Sankaku Basin

Online Access: Get full text
http://abstractsearch.agu.org/meetings/2016/FM/V13C-2858.html
Author(s): Barth, A. P.; Tani, K.; Meffre, Sebastien; Wooden, J. L.; Coble, M. A.
Author Affiliation(s): Primary:
Indiana University Purdue University Indianapolis, Earth Sciences, Indianapolis, IN, United States
Other:
National Museum of Nature and Science, Japan
ARC Centre of Excellence in Ore Deposits, Australia
Stanford University, United States
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Understanding the petrologic evolution of oceanic arc magmas through time is important because these arcs reveal the processes of formation and the early evolution of juvenile continental crust. The Izu-Bonin (IB) arc system has been targeted because it is one of several western Pacific intraoceanic arcs initiated at ∼50 Ma and because of its prominent spatial asymmetry, with widespread development of relatively enriched rear arc lavas. We examined Pb/U and trace element compositions in zircons recovered at IODP Site 351-U1438 and compared them to regional and global zircon suites. These new arc zircon data indicate that detrital zircons will yield new insights into the generation of IB silicic melts and form a set of useful geochemical proxies for interpreting ancient arc detrital zircon provenance. Project IBM drilling target IBM1 was explored by Expedition 351 at Site U1438, located in the proximal back-arc of the northern Kyushu-Palau Ridge (KPR) at 27.3°N. A 1.2 km thick section of Paleogene volcaniclastic rocks, increasingly lithified and hydrothermally altered with depth, constitutes a proximal rear arc sedimentary record of IB arc initiation and early arc evolution. The ages and compositions of U1438 zircons are compatible with provenance in one or more edifices of the northern KPR and are incompatible with drilling contamination. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic KPR melts. The abundances of selected trace elements with high native concentrations provide insight into the petrogenesis of U1438 detrital zircon host melts, and may be useful indicators of both short and long-term variations in melt compositions in arc settings. The U1438 zircons are slightly enriched in U and LREE and are depleted in Nb compared to zircons from mid-ocean ridges and the Parece-Vela Basin, as predicted for melts in a primitive oceanic arc setting with magmas derived from a highly depleted mantle source. Close age and geochemical affinity of U1438 detrital zircons to igneous zircons in Eocene leucotonalite from the partially exhumed intrusive suite at Komahashi-Daini Seamount in the northernmost KPR suggests that these zircons also can yield insight into the link between silicic volcanism and evolving tonalitic intrusions in the Paleogene IB Arc.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Cores; Expedition 351; Geochemistry; IODP Site U1438; International Ocean Discovery Program; Izu-Bonin Arc; Marine sediments; North Pacific; Northwest Pacific; Pacific Ocean; Sediments; Trace elements; West Pacific
Coordinates: N272300 N272301 E1341907 E1341905
Record ID: 2017062826
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States