Conference proceeding
Hydrogen concentrations of orthopyroxenes sourced from Izu-Bonin-Mariana proto-arc boninites quantified via ion microprobe
American Geophysical Union Fall Meeting, Vol.2021
American Geophysical Union 2021, fall meeting
12/2021
Abstract
The Izu-Bonin-Mariana intraoceanic arc system was generated following subduction initiation along the western edge of the Pacific Plate beginning c. 52 Ma. During the subsequent 2 Myr, abundant crust was generated at a suprasubduction zone ridge, a majority of which is preserved in the modern forearc as forearc basalt-boninite extrusives. Focused boninite volcanism persisted in this locality until at least c. 45 Ma and constitutes the proto-arc phase of magmatism. Many studies of these samples have revealed that the melts generated here differentiated in a shallow crustal setting. We observe that first-order features of primitive boninite products sampled by on-land surveys, oceanic dredging/diving, and ODP/IODP drilling are similar; dominated by pyroxene minerals (+ or - olivine) set in a glassy matrix with neither hydrous nor aluminous phases present. Orthopyroxene H concentrations for samples recovered from the Mariana fore-arc (Guam), Muko-jima Island Group, the submarine portion of the Bonin Ridge and the nearby trench slope (sampled by Shinkai 6500 diving and IODP Expedition 352, respectively), and the Izu fore-arc (sampled during ODP Leg 125) are similar, ranging from 83-151 mu g/g H (sub 2) O with core analyses having lower concentrations than rim analyses. Crystallization temperatures inferred using Ca-in-orthopyroxene thermometry and are c. 1100 degrees C for all orthopyroxene core analyses.Based on these data, orthopyroxene crystallized from shallow (crustal) water under-saturated melts. Melt H (sub 2) O concentrations for each reservoir are estimated using partitioning data recovered from Chichi-jima orthopyroxene-melt inclusion pairs and range from c. 2.4-4.2 wt.% in the Mariana fore-arc, c. 3.2-4.3 wt.% for the Muko-jima Island Group, c. 3.1-4.3 wt.% for samples recovered from the submarine Bonin Ridge, and c. 2.9-3.7 wt.% in the Izu fore-arc, demonstrating along-arc similarity in magmatic H (sub 2) O concentrations and stable magmatic conditions during the proto-arc period.
Details
- Title: Subtitle
- Hydrogen concentrations of orthopyroxenes sourced from Izu-Bonin-Mariana proto-arc boninites quantified via ion microprobe
- Creators
- Daniel Coulthard - Massey UniversityGeorg F. ZellmerRaimundo BrahmTakeshi KuritaniMark K. ReaganNaoya SakamotoTakashi SanoKenichiro TaniHisayoshi Yurimoto
- Resource Type
- Conference proceeding
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2021
- Conference
- American Geophysical Union 2021, fall meeting
- Publisher
- American Geophysical Union
- Alternative title
- AGU 2021 fall meeting
- Language
- English
- Date published
- 12/2021
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984442222202771
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