Provenance of Upper Miocene sediments in the Yinggehai and Qiongdongnan basins, northwestern South China Sea: Evidence from REE, heavy minerals and zircon U-Pb ages
Provenance of Upper Miocene sediments in the Yinggehai and Qiongdongnan basins, northwestern South China Sea: Evidence from REE, heavy minerals and zircon U-Pb ages
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南海西北部莺歌海盆地和琼东南盆地上中新统沉积物源：来自稀土元素、重矿物和锆石U-Pb年龄的证据
DOI：
10.1016/j.margeo.2015.01.007
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发表时间：
2015-03-01
期刊：
影响因子：
2.9
通讯作者：
Sun, Hui
中科院分区：
文献类型：
--
作者：
Cao, Licheng;Jiang, Tao;Sun, Hui
南海西北部的莺歌海盆地和琼东南盆地保存有大量的新生代沉积物。然而，它们的来源仍然鲜为人知。本文采用联合收割机稀土元素（BEE）地球化学、重矿物分析和碎屑锆石U-Pb年代学等方法，对晚中新世沉积物源-汇体系进行了研究。我们重建的模型表明，上中新世沉积物的供应来自非唯一的来源。海南岛主要控制着外陆架的供给，导致了相对较高的稀土元素浓度、锆石-电气石-金红石（ZTR）指数和燕山期锆石U-Pb年龄。与此相反，北方莺歌海盆地沉积物的稀土元素含量较低，并有石榴子石、磁铁矿、绿帘石、角闪石和十字石的组合，表明沿着红河断裂带的变质岩影响。尽管越南中部地区地质资料匮乏，但与莺歌海盆地中央坳陷的其他物源相比，其变质矿物少，ZTR指数相对较低。值得注意的是，琼东南盆地中央坳陷的沉积物与海南岛近海的沉积物在各物源代用指标上都有明显的区别。我们认为这些沉积物可能是从莺歌海盆地东南部通过海底峡谷搬运过来的。晚中新世的相对海平面下降和北方莺歌海盆地的构造反转共同促进了这种长距离的沉积物搬运。在琼东南盆地还发现了局部的镁铁质火山作用，其特征是Eu的富集和辉石、橄榄石矿物组合。(C)2015 Elsevier B. V.版权所有。
The Yinggehai and Qiongdongnan basins in the northwestern South China Sea preserve a large volume of Cenozoic sediments. However, their sources are still barely understood. In this paper, we combine rare earth element (BEE) geochemistry, heavy mineral analysis and detrital zircon U-Pb geochronology for samples from potential source areas and basin boreholes to explore the Late Miocene source-to-sink system. Our reconstructed model reveals that the Upper Miocene sediments were supplied from nonunique sources. Hainan Island mainly controlled the supply to the outer shelf, resulting in the relatively high REE concentration, zircon-tourmaline-rutile (ZTR) index and the Yanshanian zircon U-Pb ages. By contrast, sediments from the northern Yinggehai Basin show a lower REE concentration and the assemblage of garnet, magnetite, epidote, amphibole and staurolite, suggesting the influence of metamorphic rocks along the Red River Fault Zone. Despite the geological data shortage in Central Vietnam, it may still be distinguished from the other provenances in the Central Depression of the Yinggehai Basin where is characterized by little metamorphic minerals and the relatively low ZTR index. It is noteworthy that sediments in the Central Depression of the Qiongdongnan Basin are distinct from those offshore Hainan Island in terms of each provenance proxy. We interpret that these sediments probably were transported from the southeastern Yinggehai Basin through the submarine canyon. The relative sea level fall during the late Miocene and the structural inversion in the northern Yinggehai Basin could together facilitate this long-distance sediment transport. The local mafic volcanism is also found in the Qiongdongnan Basin, as indicated by the Eu enrichment and the mineral group of augite and olivine. (C) 2015 Elsevier B.V. All rights reserved.