Study On Geotectonics And Gold Metallogeny Of West Sarawak, East Malaysia

West Sarawak (East Malaysia), which located in the Northwest of Kalimantan island, geotectonically underwent geosynclinal, platform periods and now in diwa process. The geological and structural features of Lupar River regionhe west part of West Sarawak?represents a convergent movement that the SE oceanic crust collided with SW continental crust during Late Cretaceous to Eocene. Researches to the gold-bearing quality of sedimentary and magmatic rocks show that most of these rocks have more gold content than the average of the upper crust. Further evidences are quoted to support the view that fluids exist in shallow crust have the ability resolve some gold. Moreover, in the convergent compression, deep melting of the lower lithosphere can bring some Au and mineralization materials and move up to upper crust. Regional faults, which formed in geosynclinal and diwa periods, controlled the partial distribution of intrusions and gold mineralization belts, i.e. Bau and Sri Aman belts. Studies on different types of gold mineralization, their geological characteristics and ore deposit genesis suggest that the metallogenic materials of these gold ore deposits have both crust and upper mantle sources. An overall metallogenic system exists in porphyry to epithermal gold ore deposits, in which different types of gold mineralization were formed because magmatic fluid mingled with ground water to different degree from the center of intrusions to the distance. Gold metallogenic evolution of three periods and levels is suggested in accordance with regional geotectonic evolution in the end of this paper. When the gold-bearing formations, rock- and ore-control structures formed in geotectonic stages coupled with ore-bearing fuilds which resulted from given geotectonic system, the different types of gold mineralization were formed.