环境噪声层析成像和波梯度法揭示的阿拉斯加俯冲系统层状各向异性和异常岩浆活动机制

IF 3.9 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Zhijin Liu, Chuntao Liang, Feihuang Cao, Xingli Fan, Chunmei Chen
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引用次数: 0

摘要

地震各向异性可以为俯冲带动力学研究提供有价值的约束条件。本研究通过环境噪声层析成像和波浪梯度法,建立了阿拉斯加230 km以下的高分辨率三维方位各向异性横波速度模型。该模型揭示了与俯冲构造有关的层状各向异性模式。随着深度的增加,阿留申弧前区域横波快速方向相对于海沟趋势呈现出海沟平行、海沟正向、海沟平行和海沟正向的变化。这种各向异性模式可能分别归因于上覆北美板块的裂缝或断层走向、俯冲驱动的地幔楔角流、俯冲太平洋板块的预先存在的构造以及板块下地幔的夹带流。弧后地幔楔体的各向异性随深度的变化反映了俯冲引起的角流,这是由于俯冲板块几何形状的变化而改变的。此外,该模型还对阿拉斯加俯冲系统的异常岩浆活动提供了新的认识。三维等面清晰地显示了迪纳里火山裂谷(DVG)下相对较高的地幔楔速度,表明了雅库塔板块平板俯冲的相对干燥和寒冷的地幔楔。岩浆源的缺乏很可能导致了DVG。Wrangell火山场(WVF)具有与阿留申-太平洋俯冲系统相似的深度各向异性特征,为Wrangell板块的存在提供了额外的证据。WVF的形成可能是弗兰格尔板块边缘环形地幔上涌和弗兰格尔板块脱水导致的熔融共同作用的结果。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Mechanisms for Layered Anisotropy and Anomalous Magmatism of Alaska Subduction System Revealed by Ambient Noise Tomography and the Wave Gradiometry Method
Seismic anisotropy can provide valuable constraints for the study of subduction zone dynamics. This study presents a high-resolution 3-D azimuthally anisotropic shear wave velocity model down to 230 km beneath Alaska via ambient noise tomography and wave gradiometry method. The model reveals layered anisotropy patterns related to subduction tectonics. The shear wave's fast directions in the Aleutian fore-arc region exhibit trench-parallel, trench-normal, trench-parallel, and trench-normal variation relative to the trench trend with increasing depth. This anisotropic pattern may be attributed to the strike of fractures or faults in the overlying North American plate, subduction-driven mantle wedge corner flow, preexisting fabrics in the subducting Pacific Plate, and entrained flow in the sub-slab mantle, respectively. The depth-dependent anisotropy pattern in the back-arc mantle wedge reflects subduction-induced corner flow, altered by the subducting slab's changing geometry. Moreover, the model provides new insights into the anomalous magmatism in the Alaskan subduction system. The 3-D isosurface clearly shows the relatively high mantle wedge velocities beneath the Denali Volcanic Gap (DVG), suggesting a relatively dry and cold mantle wedge for the flat-slab subduction of Yakutat slab. The absence of a magma source likely caused the DVG. The Wrangell Volcanic Field (WVF) is characterized by a similar depth-dependent anisotropy pattern to the Aleutian-Pacific subduction system, providing additional evidence for the presence of Wrangell Slab. The formation of WVF may be the result of combined effects of toroidal mantle upwelling around the edge of the Wrangell Slab and melting due to dehydration of the Wrangell Slab.
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来源期刊
Journal of Geophysical Research: Solid Earth
Journal of Geophysical Research: Solid Earth Earth and Planetary Sciences-Geophysics
CiteScore
7.50
自引率
15.40%
发文量
559
期刊介绍: The Journal of Geophysical Research: Solid Earth serves as the premier publication for the breadth of solid Earth geophysics including (in alphabetical order): electromagnetic methods; exploration geophysics; geodesy and gravity; geodynamics, rheology, and plate kinematics; geomagnetism and paleomagnetism; hydrogeophysics; Instruments, techniques, and models; solid Earth interactions with the cryosphere, atmosphere, oceans, and climate; marine geology and geophysics; natural and anthropogenic hazards; near surface geophysics; petrology, geochemistry, and mineralogy; planet Earth physics and chemistry; rock mechanics and deformation; seismology; tectonophysics; and volcanology. JGR: Solid Earth has long distinguished itself as the venue for publication of Research Articles backed solidly by data and as well as presenting theoretical and numerical developments with broad applications. Research Articles published in JGR: Solid Earth have had long-term impacts in their fields. JGR: Solid Earth provides a venue for special issues and special themes based on conferences, workshops, and community initiatives. JGR: Solid Earth also publishes Commentaries on research and emerging trends in the field; these are commissioned by the editors, and suggestion are welcome.
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