长江口和东海内陆架黏土矿物与黏土粒级碎屑矿物构成及物源指示意义

Clay minerals and detrital minerals in clay fraction from the Changjiang River estuary and inner continental shelf of the East China Sea and their provenance indication

黏土矿物以及黏土粒级碎屑矿物颗粒细小、搬运距离远,是进行长江口及浙闽内陆架泥质区多物源示踪的良好指标。本研究利用改进的黏土矿物XRD(X射线衍射分析)预处理方法,制作了供多面XRD衍射分析的方形样品,实现了部分黏土矿物种的鉴定,结合黏土粒级中碎屑矿物鉴定,探讨了长江口及内陆架沉积物来源。研究表明:长江口及内陆架表层沉积物中的黏土矿物种属包括伊利石(含2M1、2M2两个多型)、高岭石、珍珠陶土、斜绿泥石以及弹性绿泥石,非黏土矿物主要有石英、钾长石、斜长石、白云石、铁白云石、方解石以及硬石膏。依据黏土矿物、黏土粒级碎屑矿物空间分布差异把长江口及东海内陆架划分为两个物源区:长江口及内陆架北部物源区、内陆架南部物源区,前者受废黄河物质影响,后者受浙闽中小河流物质影响。本研究表明来自苏北废黄河的沉积物不仅跨过了长江冲淡水进入长江水下三角洲,而且一直向南达到浙闽泥质区的北部。

Clay minerals and detrital minerals in clay fraction can be transported long distance due to small sizes,making them good indicators for multi-provenance tracing in the muddy areas of the Changjiang(Yangtze)River estuary and its adjacent areas.Based on an improved clay mineral XRD pretreatment method,the main clay mineral species and detrital minerals in clay fraction were specified.The distributions of clay minerals and non-clay minerals in the areas,and the sources and sinks of sediment in the Changjiang River estuary and the inner continental shelf were explored.The results show that the types of clay minerals in the surface sediments in the Changjiang River estuary and inner continental shelf included illite(containing 2M1 and 2M2),kaolinite,nacrite,clinochlore,and cronstedtite,whereas non-clay minerals in clay fraction included mainly quartz,potassium feldspar,plagioclase,dolomite,iron dolomite,calcite,and anhydrite.Based on the spatial distribution differences of clay minerals and non-clay minerals,the study areas could be divided into two provenance areas:the first is the northern area covering the Changjiang River estuary and the northern part of the inner continental shelf;and the second is the southern area covering the southern part of the inner continental shelf.Provenances in the former area are dominated by Changjiang River originated materials,with a few from the abandoned Huanghe(Yellow)River delta;while the latter are also dominated by Changjiang River originated materials,but with a certain amount of material from regional small-medium-sized rivers in Zhejiang and Fujian provinces.These results reveal that sediments from the abandoned Huanghe River delta in the northern Jiangsu coastal zone could transport cross the Changjiang River estuary and reach the northern part of the inner continental shelf.