Magmatic Response to Subduction Initiation, Part II: Boninites and Related Rocks of the Izu‐Bonin Arc From IOPD Expedition 352

Authors

John W. Shervais, Utah State University
Mark K. Reagan, University of Iowa
Marguerite Godard, Université de Montpellier
Julie Prytulak, University of Durham
Jeffrey G. Ryan, University of South FloridaFollow

Document Type

Article

Publication Date

1-2021

Keywords

boninite, IODP Expedition 352, Izu‐Bonin‐Mariana forearc, JOIDES Resolution, ophiolites, Sites U1439, U1442, subduction initiation

Digital Object Identifier (DOI)

https://doi.org/10.1029/2020GC009093

Abstract

International Ocean Discovery Program Expedition 352 to the Izu‐Bonin forearc cored over 800 m of basement comprising boninite and boninite‐series lavas. This is the most extensive, well‐constrained suite of boninite series lavas ever obtained from in situ oceanic crust. The boninites are characterized as high‐silica boninite (HSB), low‐silica boninite (LSB), or basaltic boninite based on their SiO₂‐MgO‐TiO₂ relations. The principal fractionation products of all three series are high‐Mg andesites (HMA). Lavas recovered >250 meters below seafloor (mbsf) erupted at a forearc spreading axis and are dominated by LSB and HMA. Lavas recovered fromoff‐axis and are dominated by HSB. The axial and off‐axis lavas are characterized by distinct chemostratigraphic trends in their major, trace, and isotopic compositions. The off‐axis lavas are chemically similar to boninite from the type locality at Chichijima, with concave‐upward rare earth elements patterns. In contrast, the more abundant axial lavas have distinctly light rare earth element‐depleted patterns and represent a new, previously unsampled precursor to the Chichijima‐type boninite lavas. Petrogenetic modeling suggests that the axial lavas formed by fluxing of refractory mantle (likely the residue from forearc basalt extraction), with amphibolite‐facies melt derived from subducting altered oceanic crust. The upper, off‐axis lavas require an additional component of sediment‐derived melt in addition. Both models are consistent with previously published isotopic data.

Comments

Full list of authors: John W. Shervais, Mark K. Reagan, Marguerite Godard, Julie Prytulak, Jeffrey G. Ryan, Julian A. Pearce, Renat R. Almeev, Hongyan Li, Emily Haugen, Timothy Chapman, Walter Kurz, Wendy R. Nelson, Daniel E. Heaton, Maria Kirchenbaur, Kenji Shimizu, Tetsuya Sakuyama, Scott K. Vetter, Yibing Li, Scott Whattam

Rights Information

This work is licensed under a Creative Commons Attribution 4.0 License.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Geochemistry, Geophysics, Geosystems, v. 22, issue 1, art. e2020GC009093

Scholar Commons Citation

Shervais, John W.; Reagan, Mark K.; Godard, Marguerite; Prytulak, Julie; and Ryan, Jeffrey G., "Magmatic Response to Subduction Initiation, Part II: Boninites and Related Rocks of the Izu‐Bonin Arc From IOPD Expedition 352" (2021). School of Geosciences Faculty and Staff Publications. 2308.
https://digitalcommons.usf.edu/geo_facpub/2308