Unraveling the link between magma and deformation during slow seafloor spreading

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Yanghui Zhao , Weiwei Ding , Gianreto Manatschal , Xiaodong Wei , Hanghang Ding , Zhengyi Tong , Jingyan Zhao
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Abstract

Detachment faulting related to oceanic core complexes (OCCs) has been suggested to be a manifestation of slow seafloor spreading. Although numerical models suggest OCCs form under low magma supply, the specific interaction between magmatism and tectonic faulting remains elusive. This paper examines seismic observations detailing the spatiotemporal interactions between magmatism, high-angle faulting, and detachment faulting at a slow-spreading mid-ocean ridge in the West Philippine Basin. We identified a magma-rich spreading phase, indicated by a magmatic top basement and oceanic crust with shallow-penetrating high-angle normal faults. An axial valley reveals an along-strike transition from magmatically-dominated to highly tectonized oceanic crust over a distance of 70 km. Two older OCCs with concave-down fault geometries and a younger OCC with steep-dipping faulting suggest sequential detachments with the same polarity. Our findings suggest: (1) slow seafloor spreading alternates between high-angle faulting with a relatively high magma supply and detachment faulting with a limited magma supply; (2) sequential development of younger detachments in the footwall of its predecessor leads to an asymmetric split in the newly accreted crust; and (3) the life cycle of OCC ends with high-angle faults that overprint the detachment and act as magma pathways, sealing the OCC. Our study captures the dynamic interaction between high-angle and detachment faults and their concurrent and subsequent relationship to magmatic systems. This reveals that strain distribution along strike is critical to OCC formation, thus enriching our understanding beyond conventional considerations such as spreading rates and melt budgets at mid-ocean ridges.

揭示缓慢海底扩张过程中岩浆与变形之间的联系
与大洋核心复合体(OCCs)有关的剥离断层被认为是缓慢海底扩张的一种表现形式。尽管数值模型表明 OCC 是在岩浆供应量较低的情况下形成的,但岩浆活动与构造断层之间的具体互动关系仍然难以捉摸。本文通过地震观测,详细分析了西菲律宾盆地一个缓慢扩张的大洋中脊的岩浆活动、高角度断层和剥离断层之间的时空相互作用。我们确定了一个岩浆丰富的扩张阶段,岩浆顶部基底和大洋地壳与浅穿透高角度正断层表明了这一阶段。一个轴向山谷显示了从岩浆主导到高度构造化洋壳的沿走向过渡,距离为 70 千米。两个较老的 OCC 断层呈凹陷向下的断层几何形状,一个较年轻的 OCC 断层呈陡倾的断层形状,这表明具有相同极性的连续剥离。我们的研究结果表明:(1) 缓慢的海底扩张在岩浆供应量相对较高的高角度断层和岩浆供应量有限的剥离断层之间交替进行;(2) 较年轻的剥离断层在其前身的底壁依次发展,导致新增生地壳的非对称分裂;(3) OCC 的生命周期以覆盖剥离断层并作为岩浆通道的高角度断层结束,从而封闭了 OCC。我们的研究捕捉到了高角度断层和剥离断层之间的动态相互作用,以及它们与岩浆系统的同时和后续关系。这揭示了沿走向的应变分布对 OCC 的形成至关重要,从而丰富了我们对大洋中脊扩张速率和熔融预算等传统考虑因素之外的认识。
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
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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