{"title":"Driven magmatism and crustal thinning of coastal southern China in response to subduction","authors":"Jinbao Su, Wenbin Zhu, Guangwei Li","doi":"10.5194/se-15-1133-2024","DOIUrl":null,"url":null,"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.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Solid Earth","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.5194/se-15-1133-2024","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
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.
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.