Publication Date:
2022-10-26
Description:
Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Solid Earth 124(5), (2019): 4710-4727, doi:10.1029/2018JB017080.
Description:
The southernmost Mariana margin lacks a mature island arc and thus differs significantly from the central‐north Mariana and Izu‐Bonin margins. This paper presents a new P wave velocity model of the crust and uppermost mantle structure based on a 349‐km‐long profile of wide‐angle reflection/refraction data. The active source seismic experiment was conducted from the subducting Pacific plate to the overriding Philippine plate, passing through the Challenger Deep. The subducting plate has an average crustal thickness of ~6.0 km with Vp of 7.0 ± 0.2 km/s at the base of the crust and low values of only 5.5–6.9 km/s near the trench axis. The uppermost mantle of the subducting plate is characterized by low velocities of 7.0–7.3 km/s. The overriding plate has a maximum crustal thickness of ~18 km beneath the forearc with Vp of ~7.4 km/s at the crustal bottom and 7.5–7.8 km/s in the uppermost mantle. A zone of slight velocity reduction is imaged beneath the Southwest Mariana Rift that is undergoing active rifting. The observed significant velocity reduction in a near‐trench crustal zone of ~20–30 km in the subducting plate is interpreted as a result of faulting‐induced porosity changes and fracture‐filling fluids. The velocity reduction in the uppermost mantle of both subducting and overriding plates is interpreted as mantle serpentinization with fluid sources from dehydration of the subducting plate and/or fluid penetration along faults.
Description:
Data acquisition and sample collections were supported by the Mariana Trench Initiative of the Chinese Academy of Sciences (CAS). We are grateful to the science parties and crews of R/V Shiyan 3 of the South China Sea Institute of Oceanology, CAS, for contributions to data acquisition. Constructive reviews by Robert Stern, Martha Savage, and anonymous reviewers significantly improved the manuscript. We thank Gaohua Zhu, Fan Zhang, Chunfeng Li, Zhen Sun, Zhi Wang, and Minghui Zhao for helpful discussion. The bathymetric maps were plotted using GMT (Wessel & Smith, 1995). Digital files of the velocity models and selected raw data are deposited and accessible online (at https://pan.baidu.com/s/1AbDJOgLZhYn1C‐3sg7S9Xw). This work was supported by the Strategic Priority Program of CAS (XDA13010101), CAS (Y4SL021001, QYZDY‐SSW‐DQC005, and 133244KYSB20180029), Key Laboratory of Ocean and Marginal Sea Geology, CAS (OMG18‐03), National Natural Science Foundation of China (41890813, 41676042, U1701641, 91628301, 41576041, and U1606401), and HKSAR Research Grant Council grants (14313816).
Description:
2019-10-05
Keywords:
Arc rifting
;
Plate hydration
;
Southernmost Mariana Trench
;
Seismic tomography
Repository Name:
Woods Hole Open Access Server
Type:
Article
