Provenance of heavy mineral deposits on the northwestern shelf of the South China Sea, evidence from single-mineral chemistry

A study of heavy mineral geochemistry has been carried out in order to examine the potential sources of heavy mineral deposits within surficial sediment on the northwestern shelf of the South China Sea. Tourmaline, amphibole and garnet from six samples near the coast and eleven samples on the shelf were analyzed by an electron microprobe. Chemical varieties of tourmaline and amphibole indicate that the Pearl River is the main supplier of sandy sediments on the eastern shelf within a 100 km radius west of the paleo-deltas. Sandy sediments on the western shelf are mainly sourced from the Jian River and the Wanquan River. Heavy mineral placers on the middle and outer shelves are mainly derived from reworking of the paleo Pearl River deltas. Heavy mineral placers in the west are mainly sourced from the small rivers and are distributed in the sandy deposits near the coasts. This study demonstrates that the occurrence of heavy mineral placers on wide continental shelf is mainly determined by the sediment supply and marine processes during transgressions.