TY  - JOUR
A1  - Ishizuka, Osamu
A1  - Hickey-Vargas, Rosemary
A1  - Arculus, Richard J.
A1  - Yogodzinski, Gene M.
A1  - Savov, Ivan P.
A1  - Kusano, Yuki
A1  - McCarthy, Anders
A1  - Brandl, Philipp A.
A1  - Sudo, Masafumi
T1  - Age of Izu-Bonin-Mariana arc basement
JF  - Earth & planetary science letters
N2  - Documenting the early tectonic and magmatic evolution of the lzu-Bonin-Mariana (IBM) arc system in the Western Pacific is critical for understanding the process and cause of subduction initiation along the current convergent margin between the Pacific and Philippine Sea plates. Forearc igneous sections provide firm evidence for seafloor spreading at the time of subduction initiation (52 Ma) and production of "forearc basalt". Ocean floor drilling (International Ocean Discovery Program Expedition 351) recovered basement-forming, low-Ti tholeiitic basalt crust formed shortly after subduction initiation but distal from the convergent margin (nominally reararc) of the future IBM arc (Amami Sankaku Basin: ASB). Radiometric dating of this basement gives an age range (49.3-46.8 Ma with a weighted average of 48.7 Ma) that overlaps that of basalt in the present-day IBM forearc, but up to 3.3 m.y. younger than the onset of forearc basalt activity. Similarity in age range and geochemical character between the reararc and forearc basalts implies that the ocean crust newly formed by seafloor spreading during subduction initiation extends from fore-to reararc of the present-day IBM arc. Given the age difference between the oldest forearc basalt and the ASB crust, asymmetric spreading caused by ridge migration might have taken place. This scenario for the formation of the ASB implies that the Mesozoic remnant arc terrane of the Daito Ridges comprised the overriding plate at subduction initiation. The juxtaposition of a relatively buoyant remnant arc terrane adjacent to an oceanic plate was more favourable for subduction initiation than would have been the case if both downgoing and overriding plates had been oceanic. (C) 2017 The Authors. Published by Elsevier B.V.
KW  - subduction initiation
KW  - Izu-Bonin-Mariana arc
KW  - arc basement
KW  - Ar-40/Ar-39 age
Y1  - 2017
U6  - https://doi.org/10.1016/j.epsl.2017.10.023
SN  - 0012-821X
SN  - 1385-013X
VL  - 481
SP  - 80
EP  - 90
PB  - Elsevier
CY  - Amsterdam
ER  -