TRACE ELEMENT GEOCHEMISTRY OF SEDIMENTS IN QIONGDONGNAN AREA, THE SOUTH CHINA SEA, AND ITS IMPLICATIONS FOR GAS HYDRATES

In order to study the geochemical characteristics of trace elements and their implications for gas hydrate, marine sediment samples were systematically collected from the Qiongdongnan area of the South China Sea.The major and trace elements as well as the TOC of the sediments are analyzed, upon which the redox condition, redox-sensitive elements and their TOC correlation are adopted to describe the geochemistry characteristics of sediments.The results indicate that Sr, Pb, Th, U, Zn, Cu and Mo are enriched in the sediments comparing to the average of upper crust.Systematic variations in Th/U, V/Cr values further indicate that the sediments are under a more reducing condition, and as the results, Mo and U are enriched.Some sediment samples have already dropped into the sulfide zone, leading the enrichment of redox-sensitive elements such as Mo and U, owing to the dissociation of gas hydrate and methane fluxes coming from deeper sediments.Therefore, the existence of the sulfide zone and Mo and U enrichment in sediments may have the significance to trace the gas hydrates in deep.