Abstract The continental shelf off southern Vietnam is relatively well studied regarding the dominant transport paths of bulk and fine-grained sediments discharged by the Mekong River. Thus, this region is particularly suitable for testing the applicability of heavy mineral analysis in determining the extent and origin of the sandy fraction of continental shelf deposits supplied mainly by a large river and their distribution over the adjacent extensive shelf. The fine sand fraction of 105 sediment samples from the Mekong River Delta and neighbouring continental shelf is investigated, applying two approaches: i) considering only the transparent non-micaceous mineral assemblage and ii) considering all the identified heavy minerals. The geological complexity of the source areas and local dominance of micaceous and non-transparent heavy minerals require the inclusion of all heavy mineral components when interpreting sediment provenance and dominant transport paths. The most diagnostic heavy minerals, amphibole, chlorite, epidote, limonite, opaques, tourmaline and zircon, are used for this purpose. The investigated continental shelf can be divided into two main regions characterised by various heavy mineral assemblages, namely, SW and NE off the Mekong River Delta. The south-western region is dominated by chlorite and limonite, indicating prevailing southward sediment transport from the Mekong River, whereas the north-eastern region is characterised by amphibole, epidote, opaques, tourmaline and zircon, indicating various sources from SE Vietnam and relict sediments partly covering the continental shelf. Between the two main regions, a large mixing zone is found where sediments from all sources are present, including Mekong River sediments transported eastward.

中文翻译：

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越南东南部湄公河外大陆架的沉积物分布和来源：重矿物分析的见解

摘要 关于湄公河排放的大块细粒沉积物的主要运输路径，对越南南部大陆架的研究相对较好。因此，该区域特别适合测试重矿物分析在确定主要由一条大河流提供的大陆架沉积物的沙质部分的范围和来源及其在相邻广阔大陆架上的分布方面的适用性。研究了来自湄公河三角洲和邻近大陆架的 105 个沉积物样品的细砂部分，采用两种方法：i) 仅考虑透明的非云母矿物组合和 ii) 考虑所有已识别的重矿物。源区的地质复杂性以及云母和非透明重矿物的局部优势要求在解释沉积物来源和主要运输路径时包括所有重矿物成分。最具诊断意义的重矿物，角闪石，绿泥石，绿帘石，褐铁矿，不透明，电气石和锆石，用于此目的。所调查的大陆架可分为以各种重矿物组合为特征的两个主要区域，即湄公河三角洲的西南和东北。西南地区以绿泥石和褐铁矿为主，表明主要由湄公河向南输送沉积物，而东北地区以角闪石、绿帘石、不透明石、电气石和锆石为特征，表明来自越南东南部的各种来源和部分覆盖大陆架的残余沉积物。在两个主要区域之间，发现了一个大的混合带，其中存在来自所有来源的沉积物，包括向东输送的湄公河沉积物。