A PRELIMINARY STUDY ON THE HEAVY MINERALS IN THE SURFACE SEDIMENT IN THE ESTUARY OF THE PEARL RIVER AND ITS ADJACENT COAST

Surface sediments in the Pearl River and its adjacent coast are finegrained deposits with low contents of heavy minerals,which mainly consist of igneous minerals such as hematite,zircon,ilmenits,touermaline,amphi-bole,niobite-tantalite and a small amount of altered minerals such as epi-date,diopside and garnet,etc.Based on the variation in the combination and content of heavy minerals as well as their differen tdepositional positions,six areas over which they are distributed may be identified.There is a law governing the components content and shape characteristics of the heavy minerals as well as the plane distribution of these characteristics.This law depends on the energy conditions of the sediment size and the various depositional environments.In the estuary-the nearshore shallow waters at a depth of 5m,there are distinct river tidal and wave actions,which result in an area with high content of heavy minerals.Being sorted under high energy conditions of sea water,the heavy minerals here are characterized by the isometric,well round shape and frosted-glass-like appearance.The source of the heavy minerals may be traced to ternigenoccs clastic deposits or to the deposits of recent origins off the islands and continental coasts.Owing to the complexity of the variations in the hydrologic conditions,one cannot determine the source distance simply by the roundness of the minerals.