Abstract
Trace element compositions of orthopyroxene antecrysts sampled during the proto-arc phase of magmatism along the Izu-Bonin-Mariana arc
p.226
IAVCEI 2023 Scientific Assembly
2023
Abstract
The Izu-Bonin-Mariana intraoceanic arc system was generated following subduction initiation along the proto-Philippine Plate-Pacific Plate boundary 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 including both fore-arc basalt and boninite extrusives. Boninite volcanism persisted along the margin until c. 45 Ma, constituting the proto-arc phase of magmatism. Primitive boninite products sampled by on-land surveys, oceanic dredging/diving, and DSDP/ODP/IODP drilling are similar; dominated by orthopyroxene macrocrysts (+ or -olivine) set in a glassy matrix. Boninites are subdivided into low silica- (LS-) and high silica boninites (HSBs). LSB erupted before 51.3 Ma and were followed by HSB eruptions along the entirety of the tectonic margin lasting from 51.3 to c. 46-43 Ma. As volcanism migrated away from the trench, extrusive rocks became dominated by “normal” arc volcanics.
Here we detail the compositions of orthopyroxene macrocrysts separated from HSBs and derivative high-magnesium andesite rocks recovered from the Mariana fore-arc (near Guam), Chichi-jima, Ani-jima, 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). Orthopyroxene H concentrations for these samples are similar, ranging from 83-151 μg/g H2O. Major element and trace transition metal (Sc, V, Ni, Cr, Co) concentrations in orthopyroxene were used to delineate relationships between the sub-volcanic reservoirs sampled at each locality and across time during the proto-arc phase of magmatism. Orthopyroxene macrocrysts were last equilibrated with trace element rich melts with similar carrier melt compositions, establishing a laterally continuous geochemical reservoir. This reservoir was
consistently hydrous and produced HSB volcanism for c. 7 Myr during proto-arc magmatism owing to the consistent migration of hydrous melts to the nascent arc.
Details
- Title: Subtitle
- Trace element compositions of orthopyroxene antecrysts sampled during the proto-arc phase of magmatism along the Izu-Bonin-Mariana arc
- Creators
- Daniel Coulthard - Menlo SchoolGeorg F. ZellmerRaimundo BrahmTakeshi KuritaniMark K. ReaganNaoya SakamotoTakashi SanoKenichiro TaniHisayoshi Yurimoto
- Resource Type
- Abstract
- Publication Details
- p.226
- Conference
- IAVCEI 2023 Scientific Assembly
- Publisher
- International Association of Volcanology and Chemistry of the Earth's Interior
- Alternative title
- IAVCEI 2023 book of abstracts
- Language
- English
- Date published
- 2023
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984790974002771
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