The thermal imprint of continental breakup during the formation of the South China Sea
The thermal imprint of continental breakup during the formation of the South China Sea
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DOI：
10.1016/j.epsl.2019.115972
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发表时间：
2020-02
影响因子：
5.3
通讯作者：
M. Nirrengarten;G. Mohn;A. Schito;S. Corrado;L. Gutiérrez-García;S. Bowden;F. Despinois
中科院分区：
文献类型：
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作者：
M. Nirrengarten;G. Mohn;A. Schito;S. Corrado;L. Gutiérrez-García;S. Bowden;F. Despinois
大陆岩石圈的伸展导致软流圈上涌、等温线升高、减压熔融，最终导致海底扩张。这些环境中上覆沉积有机质的热成熟度预计会因这些过程而明显改变，但这仍然受到很大的限制，而且在数量上尚未进行探索。国际海洋发现计划（IODP）第367-368次考察在中国南海（SCS）北方边缘的大陆洋过渡带（COT）取芯沉积物。从两个设置在中国东南COT，我们测量和模拟热成熟度前/同裂谷后的沉积物利用一系列的热成熟度参数。各种热流演化的情况进行了调查，与显着的跳跃对应于不同的沉积包的沉积物的热成熟度。为了与热成熟度的观测结果相匹配，人们发现，较深的、可能是裂谷前的沉积物在最初破裂期间被加热到高达200 °C的温度。要使较深的沉积物达到这一温度，就需要在较浅的深度给予大量的额外热量（例如，至少暴露于岩浆侵入或火山作用的地下表现的远场效应）。裂谷后沉积物具有较低的热成熟度，这可能是由于有限的埋藏和缺乏后期裂谷后岩浆活动。通过与其它大陆边缘实例的比较，突出了控制热演化及其记录的一些参数。
The stretching of continental lithosphere results in asthenospheric upwelling, raising of isotherms, melting during decompression and eventually seafloor spreading. The thermal maturity of overlying sedimentary organic matter from these settings would be expected to be distinctly altered by these processes, however this is still poorly constrained and quantitatively unexplored. International Ocean Discovery Program (IODP) Expeditions 367–368 cored sediments at the Continent Ocean Transition (COT) on the Northern Margin of the South China Sea (SCS). From two settings at the South East China COT we measured and modelled thermal maturity in pre-/syn- to post-rift sediments making use of a range of thermal maturity parameters. Various heat-flow evolutionary scenarios were investigated, with notable jumps in thermal maturity for sediments corresponding to different depositional packages. In order to match observations of thermal maturity, it was found that the deeper and likely pre-rift sediments were heated to temperatures as high as 200 °C during initial breakup. Achieving this temperature for the deeper sediments requires that significant additional heat be imparted at shallow depths (e.g. exposure to at least the far-field effects of a magmatic intrusion or subsurface expressions of volcanism). The post-rift sediments have lower thermal maturities which are likely due to limited burial and the absence of late post-rift magmatism. The comparison of the SE China COT with other margin examples highlights some parameters controlling the thermal evolution and its record.