Models of the rapid post-rift subsidencein the eastern Qiongdongnan Basin,South China Sea: implications for the development of the deep thermal anomaly
Models of the rapid post-rift subsidencein the eastern Qiongdongnan Basin,South China Sea: implications for the development of the deep thermal anomaly
复制标题
南海琼东南盆地东部裂谷后快速沉降模型：对深部热异常发育的启示
DOI：
10.1111/bre.12179
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发表时间：
2016
期刊：
影响因子：
3.2
通讯作者：
Hehua Xu
中科院分区：
文献类型：
--
作者：
Xiaobin Shi;Haiyan Jiang;Jun Yang;Xiaoqiu Yang;Hehua Xu
琼东南盆地是南海被动陆缘北方最大的新生代裂陷盆地之一。众所周知，自晚中新世以来，大约在同裂谷阶段结束后10 Ma，该盆地表现出快速的热沉降。然而，详细的分析表明，在10.5Ma以后，存在着同裂陷沉降亏损和裂后快速沉降两个阶段的异常沉降特征。热流资料表明，中央坳陷区的热流为70-105 mW·m ~ 2，明显高于盆地东部的热流（85 mW·m ~ 2）。本文利用地热过程、岩石圈减薄过程和沉积过程耦合的数值模型，分析了异常沉降模式的成因。不同实例的数值分析表明，基于同裂陷序列的地壳伸展因子bs小于观测到的地壳伸展因子bc，如果岩石圈在同裂陷阶段（21 Ma以前）以bc减薄，则可以较准确地预测现今基底深度。进一步的分析不支持21 Ma以后地壳减薄的说法，这表明同裂谷沉降与地壳伸展因子bc预测的沉降相比是亏损的。在中央坳陷带观测到的高热流值是由3-5 Ma左右的岩浆注入加热造成equivalently.at，这种加热作用对盆地东部的影响大于西部，而晚第三纪岩浆活动可能是由深部热异常提供的。我们的研究结果表明，同裂谷沉降亏损和快速裂谷后沉降的原因可能是相关的。同裂陷沉降亏损可能是由于较温暖的软流圈物质的流入和研究区下方的小规模热上涌的动力支持造成的，这种动力支持可能在裂后早期持续了约10 Ma，裂后快速沉降可能是随着深部热源的衰减或移走而失去动力支持的结果。.以及软流圈的快速冷却.我们认为，裂谷后的过量沉降弥补了同裂谷沉降的不足，深部热异常可能影响了晚渐新世以来的琼东南盆地东部。occurs.to
The Qiongdongnan Basin is one of the largest Cenozoic rifted basins on the northern passive margin.of the South China Sea. It is well known that since the Late Miocene, approximately 10 Ma after the.end of the syn-rift phase, this basin has exhibited rapid thermal subsidence. However, detailed analysis.reveals a two-stage anomalous subsidence feature of the syn-rift subsidence deficit and the wellknown.rapid post-rift subsidence after 10.5 Ma. Heat-flow data show that heat flow in the central.depression zone is 70–105 mW m.2, considerably higher than the heat flow (85 mW m.2 in the.eastern basin. We used a numerical model of coupled geothermal processes, lithosphere thinning.and depositional processes to analyse the origin of the anomalous subsidence pattern. Numerical.analysis of different cases shows that the stretching factor bs based on syn-rift sequences is less than.the observed crustal stretching factor bc, and if the lithosphere is thinned with bc during the syn-rift.phase (before 21 Ma), the present basement depth can be predicted fairly accurately. Further analysis.does not support crustal thinning after 21 Ma, which indicates that the syn-rift subsidence is in.deficit compared with the predicted subsidence with the crustal stretching factor bc. The observed.high heat flow in the central depression zone is caused by the heating of magmatic injection equivalently.at approximately 3–5 Ma, which affected the eastern basin more than the western basin, and.the Neogene magmatism might be fed by the deep thermal anomaly. Our results suggest that the.causes of the syn-rift subsidence deficit and rapid post-rift subsidence might be related. The syn-rift.subsidence deficit might be caused by the dynamic support of the influx of warmer asthenosphere.material and a small-scale thermal upwelling beneath the study area, which might have been persisting.for about 10 Ma during the early post-rift phase, and the post-rift rapid subsidence might be the.result of losing the dynamic support with the decaying or moving away of the deep thermal source,.and the rapid cooling of the asthenosphere. We concluded that the excess post-rift subsidence occurs.to compensate for the syn-rift subsidence deficit, and the deep thermal anomaly might have affected.the eastern Qiongdongnan Basin since the Late Oligocene.