DISTRIBUTION AND SOURCES OF HEAVY MINERALS IN SURFACE SEDIMENTS IN THE SEA AREA EAST OF THE RYUKYU ISLANDS

Sediments distributed over the area east of Ryukyu Islands are enriched in volcaniclastic minerals, hornblende and Fe Mn micro-nodules. Types, characteristics and provinces of heavy minerals are closely related to some endogenetic and exogenous factors, suah as volcanism, sedimentary environment, relief and material provenance. Based on the study of types, characteristics and provinces of heavy minerals, it is preliminarily inferred that the ongoing volcaniclastic material is from Ryukyu Islands arc, which is created by the subduction of Philippine plate beneath Eurasian plate; water is the main transportation mean for heavy minerals, the abundance of which is strongly controlled by contemporaneous volcanism. Low-abun-dance hypersthene originates from volcanic rocks on adjacent ridges or seafloor plateaus such as Oki--Daito ridge, Amami ridge and Kyushu-Palau ridge, which experienced a series of processes such alteration, transportation and re-sedimentation. The abundance of volcaniclastic materials from Ryukyu Islands shows a decreasing trend southwards or southeastwards due to the obduction of seafloor plateaus; ongoing mag-matism or volcanic activity in geologic time is mainly represented by basic-intermediate magmatism. In ad-dition, Kuroshio plays a significant role in the enrichment of Fe-Mn micro-nodules.