Driven magmatism and crustal thinning of coastal southern China in response to subduction

IF 3.2 2区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Jinbao Su, Wenbin Zhu, Guangwei Li
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引用次数: 0

Abstract

Abstract. The late Mesozoic igneous rocks along the coastal South China Block (SCB) exhibit complex parental sources involving a depleted mantle, subducted sediment-derived melt, and melted crust. This period aligns with the magmatic flare-up and lull in the SCB, debating with the compression or extension in coastal region. Our study employs numerical models to investigate the dynamics of the ascent of underplating magma along the Changle–Nan'ao Belt (CNB), simulating its intrusion and cooling processes while disregarding the formational background. The rheological structure of the lithospheric mantle significantly influences magma pathways, dictating the distribution of magmatism. This work reveals that the ascent of magma in the presence of faults is considerably faster than in the absence of faults, and contemporaneous magmatic melts could produce different cooling and diagenetic processes. Additionally, the influence of pre-existing magma accelerated the emplacement of underplating magma. The magma beneath the fault ascended rapidly, reaching the lower crust within 20 million years, with a cooling rate of approximately ∼ 35 °C Myr−1. Conversely, the thickened magma took 40–50 million years to ascend to the lower crust, cooling at a rate of ∼ 10 °C Myr−1. In contrast, magma without thickening and fault would take a considerably longer time to reach the lower crust. The ascent of magma formed a mush-like head, contributing to magmatic circulation beneath the crust and decreasing crustal thickness. Multiphase magmatism increases the geothermal gradient, reducing lithospheric viscosity and promoting underplating magma ascent, leading to magmatic flare-ups and lulls. Our findings suggest that the Cretaceous magmatism at different times in the coastal SCB may be associated with the effects of lithospheric faults under similar subduction conditions. Boundary compression forces delay magma ascent, while rising magma induces a significant circulation, decreasing the crustal thickness of the coastal SCB. This study provides new insights into the complex interplay of magmatic processes during subduction, emphasizing the role of lithospheric structure in shaping the temporal and spatial evolution of coastal magmatism.
华南沿海俯冲驱动的岩浆活动和地壳减薄
摘要华南地块沿岸中生代晚期火成岩表现出复杂的成因,包括贫化的地幔、俯冲沉积物衍生的熔体和熔融的地壳。这一时期与华南地块的岩浆爆发和沉寂相一致,与沿岸地区的压缩或延伸存在争论。我们的研究采用数值模式研究了长乐-南澳带的下伏岩浆上升动力学,模拟了岩浆的侵入和冷却过程,同时忽略了形成背景。岩石圈地幔的流变结构对岩浆路径有重大影响,决定了岩浆活动的分布。这项工作揭示了存在断层时岩浆的上升速度比不存在断层时要快得多,同时代的岩浆熔体可能产生不同的冷却和成岩过程。此外,先期存在的岩浆的影响也加速了板下岩浆的喷发。断层下的岩浆迅速上升,在2000万年内到达下地壳,冷却速度约为∼ 35 °C Myr-1。相反,增厚的岩浆需要 4000 万至 5000 万年才能上升到下地壳,冷却速度为 ∼ 10 °C Myr-1。相比之下,没有增厚和断层的岩浆需要更长的时间才能到达下地壳。岩浆上升过程中形成了泥状岩浆头,促进了地壳下的岩浆循环,减小了地壳厚度。多相岩浆活动增加了地热梯度,降低了岩石圈粘度,促进了板下岩浆上升,导致岩浆爆发和岩浆沉积。我们的研究结果表明,南中北沿海不同时期的白垩纪岩浆活动可能与类似俯冲条件下岩石圈断层的影响有关。边界压缩力延迟了岩浆的上升,而上升的岩浆引起了显著的环流,减小了沿岸华南板块的地壳厚度。这项研究为了解俯冲过程中岩浆过程的复杂相互作用提供了新的视角,强调了岩石圈结构在塑造沿岸岩浆活动的时空演变过程中的作用。
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来源期刊
Solid Earth
Solid Earth GEOCHEMISTRY & GEOPHYSICS-
CiteScore
6.90
自引率
8.80%
发文量
78
审稿时长
4.5 months
期刊介绍: Solid Earth (SE) is a not-for-profit journal that publishes multidisciplinary research on the composition, structure, dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. The journal invites contributions encompassing observational, experimental, and theoretical investigations in the form of short communications, research articles, method articles, review articles, and discussion and commentaries on all aspects of the solid Earth (for details see manuscript types). Being interdisciplinary in scope, SE covers the following disciplines: geochemistry, mineralogy, petrology, volcanology; geodesy and gravity; geodynamics: numerical and analogue modeling of geoprocesses; geoelectrics and electromagnetics; geomagnetism; geomorphology, morphotectonics, and paleoseismology; rock physics; seismics and seismology; critical zone science (Earth''s permeable near-surface layer); stratigraphy, sedimentology, and palaeontology; rock deformation, structural geology, and tectonics.
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