CHARACTERISTICS OF HEAVY MINERALS IN PEARL RIVER SEDIMENTS AND THEIR IMPLICATIONS FOR PROVENANCE

Abstract

Heavy minerals in the Pearl River sediments have excellent correlation with their source rocks.Obvious differences in heavy minerals assemblages and their diagnostic minerals have been studied in different branches of the River.The source of the river deposits can be divided into three provinces from west to east on the basis of heavy minerals assemblage types,mineral index(ATi,ZTi,ZTR) values and their correlation.The western province includes the upper reaches of the Xijiang River,where occurs a magnetite-ilmenite-zircon-leucoxene-apatite assemblage characterized by magnetite,ilmenite,apatite and chromite,indicating a provenance dominated by carbonate,with some metamorphic and basic rocks,and scarce ultrabasic and acid rocks.The middle province is located in the lower reaches of the Xijiang River,which is featured by a zircon-ilmenite-magnetite-tourmaline-leucoxene-epidote assemblage,characterized by pyroxene,leucoxene,zircon and epidote,indicating a provenance of clastic rocks and other sedimentary rocks with some metamorphic,basic and acid igneous rocks,as a mixture of local sources and the heavy minerals from upper reaches.The eastern province is the source area of the Dongjiang and Beijiang Rivers dominated by the assemblage of hornblende-tourmaline-magnetite-ilmenite-epidote-garnet characterized by hornblende,tourmaline,garnet,titanite and sillimanite,indicating a provenance of acid rocks with some metamorphic and small amount of sedimentary rocks.The results demonstrate that the characteristics of heavy minerals assemblages are useful tools to trace the provenance evolution of the Pearl River,and of significance in revealing the erosion-transportation-sedimentation pattern in the Pearl River region for source-sink comparison and analysis.