江苏沿岸辐射沙脊物源分析——来自碎屑重矿物与锆石年代学的证据  

The Provenance Analysis of Radial Sand Ridges off the Jiangsu Coast,East China⁃Evidence from the heavy mineral compositions and zircon geochronology

作　　者：李姝睿 孙高远 茅昌平[2] 饶文波[2] LI ShuRui;SUN GaoYuan;MAO ChangPing;RAO WenBo(College of Oceanography,Hohai University,Nanjing 210098,China;School of Earth Sciences and Engineering,Hohai University,Nanjing 211100,China)

机构地区：[1]河海大学海洋学院,南京210098 [2]河海大学地球科学与工程学院,南京211100

出　　处：《沉积学报》2022年第4期931-943,共13页Acta Sedimentologica Sinica

基　　金：国家自然科学基金(42072124,41888101)。

摘　　要：辐射沙脊是分布在我国江苏沿岸南黄海浅海内陆架上的一种特殊地貌,其沉积物质来源一直广受关注。通过原位微区X荧光光谱分析、重矿物统计学以及碎屑锆石年代学等方法,对江苏沿岸辐射沙脊开展物源分析。结果表明辐射沙脊的重矿物组合为角闪石—绿帘石—铁氧化物,并且角闪石为绝对优势矿物(平均含量55.06%),其含量远大于绿帘石(平均含量20.71%)。这与长江中重矿物特征相似(角闪石平均含量46.05%,绿帘石平均含量24.69%)。碎屑锆石U-Pb年龄显示出了5个主要的年龄区间及峰值,依次为160~330 Ma(占22.89%,峰值为~200 Ma);350~550 Ma(占18.61%,峰值为~430 Ma);650~1200 Ma(占29.32%,峰值为~750 Ma);1700~2000 Ma(占10.58%,峰值为~1850 Ma)和2400~2600 Ma(占5.09%,峰值为~2500 Ma)。结合重矿物组分数据和锆石年龄谱分析,并与各潜在源区进行对比,认为辐射沙脊的碎屑重矿物特征以及锆石年龄与长江最为相近,指示长江作为辐射沙脊最主要的物质源区。此外,古黄河三角洲的沉积物显示出对江苏沿岸北部沙脊沉积具有一定的影响,而现代黄河可能对辐射沙脊最北缘提供了沉积物质,该物源分析结果反映了南黄海的海流系统在辐射沙脊搬运沉积体系中起到重要作用。A special landform⁃radial sand ridges(RSRs)is distributed on the inland shelf of the shallow sea of south Yellow Sea along the Jiangsu coast.Its sedimentary provenance is a scientific issue worthy of attention.In this study,the provenance of the RSRs was analyzed by in-situ micro-area X-ray fluorescence spectroscopy,heavy mineral analy⁃sis and detrital zircon uranium-lead(U-Pb)geochronology.The results show that the heavy mineral combination of the RSRs is amphibole-epidote-iron oxide minerals,and the content of amphibole(55.06%in average)is much high⁃er than that of epidote(20.71%in average),which is much similar to the Yangtze River(with the average content 46.05%of amphibole,and 24.69%of epidote).The detrital zircon U-Pb ages yield five significant age ranges:160⁃330 Ma(22.89%,peaking at~200 Ma),350⁃550 Ma(18.61%,peaking at~430 Ma),650⁃1200 Ma(29.32%,peaking at~750⁃800 Ma),1700⁃2000 Ma(10.58%,peaking at~1850 Ma),and 2400⁃2600 Ma(5.09%,peak⁃ing at~2500 Ma).Through comparison with the potential source area,we found a strong similarity of the heavy min⁃eral combination and zircon U-Pb ages between the RSRs and Yangtze River,indicating the Yangtze River was their major source.In addition,the sediments of the ancient Yellow River delta could have limited impacts on the coast of northern Jiangsu,while the modern Yellow River possibly only influences the northern edge of the RSRs.The prove⁃nance result constraint from this study indicates the oceanic currents of south Yellow Sea has significant influence.

关 键 词：南黄海 辐射沙脊 物源分析 重矿物 锆石U-PB年龄 

分 类 号：P512.2[天文地球—地质学]