KETERDAPATAN EMAS LETAKAN DAN IKUTANNYA DI PERAIRAN DELTA KAPUAS, PONTIANAK, KALIMANTAN BARAT

Perairan Delta Kapuas merupakan tempat yang baik bagi akumulasinya endapan letakan asal Sungai Kapuas. Permukaan dasar lautnya ditutupi oleh sedimen pasir, pasir lanauan, lanau pasiran dan lanau. Sedimen ini mengandung logam emas (Au) dan ikutannya, yaitu perak (Ag), tembaga (Cu), timbal (Pb), seng (Zn) dan timah (Sn). Kadar terendah yaitu emas berkisar 2 - 92 ppb dan tertinggi Sn < 10 - 320 ppm. Keterdapatan emas secara lateral relatif membesar ke arah bagian hulu dan secara vertikal membesar ke bagian bawah permukaan. Keterdapatan emas dan ikutannya tersebut tidak satupun dijumpai pembawa mineral bijihnya. Namun secara kualitatif keterdapatan unsur-unsur logam ini sesuai dengan hasil analisis geokimia dari percontohan "stream sediment" dan "pan concentrate" di Sungai Delta Kapuas. Primernya diduga berkaitan dengan peristiwa Batuan Terobosan Sintang yang dijumpai secara setempat di sebelah timur daerah penelitian. Delta Kapuas Waters are a good place for placer deposits accumulation originally from Kapuas River. The seafloor sediment surface are covered by sand, silty sand, sandy silt and silt. These sediments content of gold (Au) and its associate metal, such as silver (Ag), copper (Cu), lead (Pb), zinc (Zn) and tin (Sn). The lowest content of gold is approximately between 2 - 92 ppb and the highest content of tin is approximately between < 10 - 320 ppm. Laterally, the occurrence of gold is relatively higher to the upstream part and vertically higher to the deeper part of the sediment. The existence of gold (Au) and its associate metal as mentioned above could not be traced to its ore mineral. But qualitatively the existence of these metal elements are in accordance with the result of geochemical analysis of the stream sediments and concentrate pan samples in the Delta Kapuas river. Its primary source is anticipated relate to the Sintang intrusion event which occurred locally in eastern of research area.