Post-rifting magmatism at the northern margin of the South China Sea: Evidenced by an ocean bottom seismometer experiment

IF 1.2 4区 地球科学 Q3 Earth and Planetary Sciences
Lu Zhang , Chen Cai , Rui Gao
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引用次数: 0

Abstract

Magmatism at continental margins is of great significance in understanding the continental rifting. We present a two-dimensional P-wave velocity model derived from an ocean bottom seismometer experiment, conducted across the middle northern continental margin of the South China Sea (SCS). The detailed velocity structures reveal significant heterogeneities extending from the continental shelf to the continent-ocean transition zone. The crust exhibits its greatest thickness below the continental shelf, measuring ∼23 km and gradually thins to ∼13 km at the distal margin. Furthermore, a narrow and distinct continent-ocean transition with only 40-km width is revealed. We also observe a high-velocity layer within the transition zone, reaching thickness of up to 4 km, characterized by P-wave velocities ranging from 7.0 km/s to 7.6 km/s in the lower crust. Based on the syn-rift melt generation using decompression melting model, we ascertain that syn-rift magmatism cannot fully account for the observed thick high-velocity layer. By integrating findings from previous geophysical and geochemical studies presenting extensive volcanic edifice on the seafloor at the northern margin, as well as ocean-island-basalt-type magmatic samples in the SCS area, we propose that post-rifting magmatism associated with the Hainan Plume may have influenced the formation of the high-velocity lower crust within the transition zone and the northern margin of the SCS can thus be recognized as magma-poor type margin.
南海北缘裂谷后岩浆活动:海底地震仪实验的佐证
大陆边缘岩浆作用对认识大陆裂陷作用具有重要意义。本文提出了一个基于海底地震仪实验的二维纵波速度模型,该模型在南海(SCS)中部北部大陆边缘进行。详细的速度结构揭示了从大陆架到陆-海过渡带的显著非均质性。地壳在大陆架以下显示出最大厚度,测量为~ 23 km,并在远缘逐渐变薄至~ 13 km。此外,还显示出一个狭窄而明显的陆-洋过渡,宽度仅为40公里。我们还观察到在过渡带内有一个高速层,厚度达4 km,其特征是下地壳的纵波速度在7.0 km/s到7.6 km/s之间。基于减压熔融模型的同裂谷熔体生成,我们确定同裂谷岩浆作用不能完全解释观测到的厚高速层。综合以往的地球物理和地球化学研究成果,在北缘海底发现了大面积的火山构造,以及南海地区的海洋-岛屿-玄武岩型岩浆样本,我们认为与海南羽流相关的裂谷后岩浆活动可能影响了过渡带内高速下地壳的形成,因此可以将南海北缘识别为岩浆贫型边缘。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Earthquake Science
Earthquake Science GEOCHEMISTRY & GEOPHYSICS-
CiteScore
1.10
自引率
8.30%
发文量
42
审稿时长
3 months
期刊介绍: Earthquake Science (EQS) aims to publish high-quality, original, peer-reviewed articles on earthquake-related research subjects. It is an English international journal sponsored by the Seismological Society of China and the Institute of Geophysics, China Earthquake Administration. The topics include, but not limited to, the following ● Seismic sources of all kinds. ● Earth structure at all scales. ● Seismotectonics. ● New methods and theoretical seismology. ● Strong ground motion. ● Seismic phenomena of all kinds. ● Seismic hazards, earthquake forecasting and prediction. ● Seismic instrumentation. ● Significant recent or past seismic events. ● Documentation of recent seismic events or important observations. ● Descriptions of field deployments, new methods, and available software tools. The types of manuscripts include the following. There is no length requirement, except for the Short Notes. 【Articles】 Original contributions that have not been published elsewhere. 【Short Notes】 Short papers of recent events or topics that warrant rapid peer reviews and publications. Limited to 4 publication pages. 【Rapid Communications】 Significant contributions that warrant rapid peer reviews and publications. 【Review Articles】Review articles are by invitation only. Please contact the editorial office and editors for possible proposals. 【Toolboxes】 Descriptions of novel numerical methods and associated computer codes. 【Data Products】 Documentation of datasets of various kinds that are interested to the community and available for open access (field data, processed data, synthetic data, or models). 【Opinions】Views on important topics and future directions in earthquake science. 【Comments and Replies】Commentaries on a recently published EQS paper is welcome. The authors of the paper commented will be invited to reply. Both the Comment and the Reply are subject to peer review.
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