Universität zu Köln

Li, Hong-Yan, Taylor, Rex N., Prytulak, Julie, Kirchenbaur, Maria, Shervais, John W., Ryan, Jeffrey G., Godard, Marguerite ORCID: 0000-0003-3097-5135, Reagan, Mark K. and Pearce, Julian A. (2019). Radiogenic isotopes document the start of subduction in the Western Pacific. Earth Planet. Sci. Lett., 518. S. 197 - 211. AMSTERDAM: ELSEVIER SCIENCE BV. ISSN 1385-013X

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Abstract

Subduction initiation is one of the least understood aspects of plate tectonics. In an effort to obtain the first in situ magmatic record of subduction initiation, the International Ocean Discovery Program Expedition 352 drilled at four sites in the inner trench wall of the Bonin Trench to recover 1.22 km of oceanic upper crust accreted within a few m.y. of subduction initiation. The two sites nearer to the trench (U1440 and U1441) yielded axial and off-axis fore-arc basalts (FAB), while those c. 15 km further from the trench (U1439 and U1442) yielded axial low-silica boninites and high-Mg andesites overlain by off-axis high-silica boninites. This study uses Hf-Nd-Sr-Pb isotope analyses from c. 50 stratigraphically representative core samples to trace the evolution of the mantle source during the brief period of FAB-through-boninite magmatism immediately following subduction initiation. Results show that: 1) the FAB have high epsilon Hf relative to epsilon Nd and were derived from variably depleted mantle of 'Indian' provenance with no detectable subduction input; 2) the axial boninites follow mixing trends between a residual FAB mantle source and a subduction component derived from shallow (amphibolite fades) melting of oceanic crust of 'Pacific' provenance; and 3) the off-axis boninites define mixing trends between a hybrid mantle wedge (residual mantle + slab melt) and an additional subduction component with lower epsilon Nd and higher (207)pb/Pb-204 that requires a significant contribution from pelagic sediment. This incoming of pelagic sediments may signify a change from an accretionary to non-accretionary margin as subduction evolves. The results thus indicate a rapidly evolving system in terms of geodynamics, magma genesis and crustal accretion immediately following subduction initiation. (C) 2019 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Li, Hong-Yan UNSPECIFIED UNSPECIFIED UNSPECIFIED Taylor, Rex N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Prytulak, Julie UNSPECIFIED UNSPECIFIED UNSPECIFIED Kirchenbaur, Maria UNSPECIFIED UNSPECIFIED UNSPECIFIED Shervais, John W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ryan, Jeffrey G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Godard, Marguerite UNSPECIFIED orcid.org/0000-0003-3097-5135 UNSPECIFIED Reagan, Mark K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Pearce, Julian A. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-135143
DOI:	10.1016/j.epsl.2019.04.041
Journal or Publication Title:	Earth Planet. Sci. Lett.
Volume:	518
Page Range:	S. 197 - 211
Date:	2019
Publisher:	ELSEVIER SCIENCE BV
Place of Publication:	AMSTERDAM
ISSN:	1385-013X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language IZU-BONIN-MARIANA; EARLY CONTINENTAL-CRUST; FORE-ARC BASALTS; EARLY HISTORY; MANTLE; ND; INITIATION; CONSTRAINTS; ELEMENT; ORIGIN Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/13514