摘要
物源是研究大陆架沉积物搬运过程、重建陆架古环境以及海洋砂矿资源勘查的重要信息。然而,陆架砂质沉积物普遍经历过多次搬运、分选和混合,这给物源识别带来极大的困难。南海东北部陆架砂质沉积物分布广泛,本文首次采用单矿物化学方法对其物源进行了新的解析。研究区表层砂质沉积物中电气石与角闪石为优势重矿物,两者含量呈现此消彼长的关系。电气石和石榴子石的电子探针数据显示:珠江、韩江沉积物影响海域,火成岩成因的电气石占60%左右,其主要来源为区内广泛发育的燕山期花岗岩的风化产物;莲花山断裂带和长乐−南澳断裂带附近的南海东北部沿岸小河沉积物中变质岩成因的电气石含量显著增高,最高可达70%,其来源为区内与断裂带伴生的变质岩风化物;矽卡岩成因的钙铝榴石在南澳岛以东的陆架沉积物中发现最多,这与华南陆域矽卡岩的分布区吻合。综合分析认为,重矿物的矿物化学方法可以减少分选效应的影响,利用多种矿物的矿物化学分异可以获得多维的信息,为陆架沉积物的物源判定提供便利。
The sediment provenance is important information to study on the transport process of shelf sediments,paleo-environmental changes and the formation of heavy mineral placers on the shelf.However,most shelf sediments are heavily reworked and repeatedly sorted,which cause the difficulty in indentifying their sources.This study firstly reported the work on heavy mineral provenance on the northeastern shelf of the South China Sea by using mineral chemistry,which has been proved to be a useful method to decrease the effect of hydrodynamic sorting.The provenance of shelf sediments was inferred by comparing the mineral assemblage and mineral chemical compositions of tourmaline and garnet between six marine sediment samples on the outer shelf and six offshore and coastal samples.In the study area,tourmaline and amphibole are dominant and monazite is present in some samples.Mineral chemical composition of tourmaline suggested the Zhujiang River and Hanjiang River are two dominant sediment suppliers.Sediments from the two big rivers contain abundant tourmaline from igneous rocks with the content of about 60%which are associated with widely-spreaded granitic rocks in the South China.Some small rivers distribute within the Lianhuashan and Changle-Nanao fracture zones are characterized by the high content of metamorphic tourmaline.These sediments can be traced on the northeastern shelf of the South China Sea by using chemical composition of tourmaline,suggesting small rivers are also important sediment suppliers on this studied shelf.Garnet sourced from sharn rocks is found on the eastern most shelf.The study highlights the importance of single-mineral chemistry in judging the provenance of shelf sediments which suffer from multiple sorting and have complex sources.
作者
马一开
黎刚
颜文
Ma Yikai;Li Gang;Yan Wen(Key Laboratory of Ocean and Marginal Sea Geology,Chinese Academy of Sciences/Innovation Academy of South China Sea Ecology and Environmental Engineering,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《海洋学报》
CAS
CSCD
北大核心
2020年第7期108-118,共11页
基金
国家自然科学基金(4167060123)
广东省自然科学基金(2017A030313252)
中国科学院青年创新促进会项目
广东省特支计划青年拔尖人才项目
南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0206)。
关键词
重矿物
矿物化学
物源分析
南海北部陆架
古水系
heavy mineral
mineral chemistry
provenance
the northeastern shelf of the South China Sea
paleo-drainage
