Geochemical variation of subducting Pacific crust along the Izu-Bonin Arc system and its implications on the generation of arc magmas

Author(s): Durkin, K.; Castillo, P.; Abe, Natsu; Kaneko, R.; Straub, Susanne M.; Garcia, E. S. M.; Yan, Q.; Tamura, Yoshihiko
Author Affiliation(s): Primary:
Scripps Institution of Oceanography, Geosciences Research Division, La Jolla, CA, United States
University of California San Diego, La Jolla, CA, United States
Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
Niigata University, Niigata, Japan
Lamont Doherty Earth Observatory, Palisades, NY, United States
State Oceanic Administration, First Institute of Oceanography, Qingdao, China
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Subduction zone magmatism primarily occurs due to flux melting of the mantle wedge that has been metasomatized by the slab component. The latter is enriched in volatiles and fluid-mobile elements and derived mainly from subducted sediments and altered oceanic crust (AOC). Subduction input has been linked to arc output in many studies, but this relationship is especially well documented in sedimented arc-trench systems. However, the Izu-Bonin system is sediment-poor, therefore the compositional and latitudinal variations (especially in Pb isotopes) of its arc magmas must be sourced from the subduction component originating primarily from the AOC. Pb is a very good tracer of recycled AOC that may contribute 50% or more of arc magma Pb. Izu-Bonin arc chemistry suggests a subduction influx of Indian-type crust, but the subducting crust sampled at ODP Site 1149 is Pacific-type. The discrepancy between subduction input and arc output calls into question the importance of the AOC as a source of the subduction component, and raises major concerns with our understanding of slab input. During the R/V Revelle 1412 cruise in late 2014, we successfully dredged vertical fault scarps at several sites from 27.5 N to 34.5 N, spanning a range of crustal ages that include a suggested compositional change at ≈125 Ma. Major element data show an alkali enrichment towards the north of the study transect. Preliminary incompatible trace element data (e.g. Ba, Zr and Sr) data support this enrichment trend. Detailed mass balance calculations supported by Sr, Nd, Hf and especially Pb isotope analyses will be performed to evaluate whether the AOC controls the Pb isotope chemistry of the Izu-Bonin volcanic arc.
Year of Publication: 2015
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Chemical composition; Cores; Geochemistry; Izu-Bonin Arc; Leg 185; Marine sediments; North Pacific; Northwest Pacific; ODP Site 1149; Ocean Drilling Program; Pacific Ocean; Sediments; West Pacific
Coordinates: N312030 N312030 E1432100 E1432100
Record ID: 2016066770
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