Tectonic framework and Mesozoic magma distribution in the South China Block. a Tectonic and topographical map of the South China Cluster. The blue dashed lines indicate the position of the CT profiles (AA, BB, CC′, DD′, and EE′). Solid red lines outline major tectonic units (eg, Yangtze massif, Cathaysia massif, Triassic Qinling-Dabie orogen, and Proterozoic Jiangnan orogen) and major faults (JSF: Jiangshan-Shaoxing fault; TLF: Tanlu fault; ZDF: Zhenghe fault -Dabu). SCB: Sichuan Basin; JHB: Jiang’an Basin; NCB: North China Cluster. B The spatio-temporal distribution of astronomical magmas in the South China Massif. The names of tectonic units and faults are the same a. The solid circles show the locations of mafic rocks from different phases, while the colored squares show different phases of granite and igneous isotopes. There is an outward expansion trend for the distribution of late Mesozoic felsic rocks. credit: Nature Communications (2023). DOI: 10.1038/s41467-023-37855-5
A research team led by Professor Zhang Haijiang of the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences and Professor Hu Zengqian of the Chinese Academy of Geosciences has revealed the earthquake-imaged lithosphere unloading and controls over the Central Lithospheric Province in southern China using a new joint seismic overturning algorithm. The study has been published in Nature Communications.
Based on the latest developed joint seismic reflection algorithm, the researchers used the seismic body wave travel time, surface wave scattering data and receiver function to determine a high-resolution shear wave velocity model for the lithosphere in southern China. They found that there is a high-velocity anomaly in the asthenosphere at a depth of less than 90 kilometers.
These high-velocity deflections can be explained as lithosphere clumps that began to disintegrate at 180–170Ma, which were subsequently heated by the deep mantle and returned to their previous position. Large-scale degassing triggered lithosphere metamorphism, resulting in lithosphere thinning and an adiabatic bulge in the asthenosphere. Then, the lithosphere stretched and the overlying crust melted, forming a rocky province in southern China.
As shown by geochemical analysis, large amounts of water and heat from the convective mantle were required to cause degassing. As a result, abundant granitic and mafic rocks were formed, which explains the formation of igneous rocks and mineral deposits.
This study proposed a new understanding of the formation mechanism of the Central Magma Province in southern China, which helps to understand Paleo-Pacific plate dynamics and large-scale mineralization during the late Mesozoic in southern China. It also provides new ideas for the establishment of the deep process of the lithosphere and the connection between shallow magma and mineralization.
more information:
Haijiang Zhang et al, Seismic-photographed lithosphere unloading and controls over the central lithographic province of southern China, Nature Communications (2023). DOI: 10.1038/s41467-023-37855-5
Provided by the University of Science and Technology of China
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