Magmatic Response to Subduction Initiation: Part 1. Fore-arc Basalts of the Izu-Bonin Arc From IODP Expedition 352

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dc.identifier.uri Shervais, John W. Reagan, Mark K. Haugen, Emily Almeev, Renat R. Pearce, Julian A. Prytulak, Julie Ryan, Jeffrey G. Whattam, Scott Godard, Marguerite Chapman, Timothy Li, Hongyan Kurz, Walter Nelson, Wendy R. Heaton, Daniel Kirchenbaur, Maria Shimizu, Kenji Sakuyama, Tetsuya Li, Yibing Vetter, Scott K. 2019-06-26T12:21:09Z 2019-06-26T12:21:09Z 2019
dc.identifier.citation Shervais, John W.; Reagan, Mark K.; Haugen, Emily; Almeev, Renat R.; Pearce, Julian A. et al.: Magmatic Response to Subduction Initiation: Part 1. Fore-arc Basalts of the Izu-Bonin Arc From IODP Expedition 352. In: Geochemistry Geophysics Geosystems 20 (2019), Nr. 1, S. 314-338. DOI:
dc.description.abstract The Izu‐Bonin‐Mariana (IBM) fore arc preserves igneous rock assemblages that formed during subduction initiation circa 52 Ma. International Ocean Discovery Program (IODP) Expedition 352 cored four sites in the fore arc near the Ogasawara Plateau in order to document the magmatic response to subduction initiation and the physical, petrologic, and chemical stratigraphy of a nascent subduction zone. Two of these sites (U1440 and U1441) are underlain by fore‐arc basalt (FAB). FABs have mid‐ocean ridge basalt (MORB)‐like compositions, however, FAB are consistently lower in the high‐field strength elements (TiO2, P2O5, Zr) and Ni compared to MORB, with Na2O at the low end of the MORB field and FeO* at the high end. Almost all FABs are light rare earth element depleted, with low total REE, and have low ratios of highly incompatible to less incompatible elements (Ti/V, Zr/Y, Ce/Yb, and Zr/Sm) relative to MORB. Chemostratigraphic trends in Hole U1440B are consistent with the uppermost lavas forming off axis, whereas the lower lavas formed beneath a spreading center axis. Axial magma of U1440B becomes more fractionated upsection; overlying off‐axis magmas return to more primitive compositions. Melt models require a two‐stage process, with early garnet field melts extracted prior to later spinel field melts, with up to 23% melting to form the most depleted compositions. Mantle equilibration temperatures are higher than normal MORB (1,400 °C–1,480 °C) at relatively low pressures (1–2 GPa), which may reflect an influence of the Manus plume during subduction initiation. Our data support previous models of FAB origin by decompression melting but imply a source more depleted than normal MORB source mantle. eng
dc.language.iso eng
dc.publisher Washington, DC : American Geophysical Union (AGU)
dc.relation.ispartofseries Geochemistry Geophysics Geosystems 20 (2019), Nr. 1
dc.rights CC BY 4.0 Unported
dc.subject Forearc basalts eng
dc.subject Izu‐Bonin forearc eng
dc.subject Joides Resolution eng
dc.subject ophiolites eng
dc.subject subduction initiation eng
dc.subject Geology eng
dc.subject Basalt eng
dc.subject Geochemistry eng
dc.subject Ophiolite eng
dc.subject Subduction eng
dc.subject Geophysics eng
dc.subject Arc (geometry) eng
dc.subject.ddc 550 | Geowissenschaften ger
dc.subject.ddc 551 | Geologie, Hydrologie, Meteorologie ger
dc.title Magmatic Response to Subduction Initiation: Part 1. Fore-arc Basalts of the Izu-Bonin Arc From IODP Expedition 352
dc.type article
dc.type Text
dc.relation.issn 1525-2027
dc.bibliographicCitation.issue 1
dc.bibliographicCitation.volume 20
dc.bibliographicCitation.firstPage 314
dc.bibliographicCitation.lastPage 338
dc.description.version publishedVersion
tib.accessRights frei zug�nglich

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