LATERITISASI PADA KOMPLEKS MELANGE AREA WAILUKUM, KABUPATEN HALMAHERA TIMUR

Abstract

This research is prompted by the presence of laterite deposit from different lithology in Wailukum Area, Buli Districts, Eastern Halmahera Region The research area is part of PT. Antam UBPN North Maluku IUP. The coordinates of research area are 412.369-413.763 mT and 89.304-88.384 mU zone 52N, and with research area of 1,4 km². This research’s objective is to determine the characteristics of laterites and bedrock in Wailukum area.. Data used in this research are DEM, LIDAR, field data and borehole data DEM and field data analysis are used to determine the topographic unit Field data analysis are used to make geological map and cross section. Geostatistical analysis on borehole data, consist of assay and drill log data (470 sample) are used to determine laterite deposit and bedrock characteristic. Based on petrography analysis, bedrock in Wailukum are serpentinite, moderately serpentinized orthopyroxenite and weakly serpentinized olivine gabbronorite. Melange complex in Wailukum consist of serpentinite, orthopiroxenite and olivine gabbronorite as a boudinage and surrounded by foliatd serpentinite as a matrix. This melange complex predicted as as result of a collisional event. Terniary SiO₂-MgO-Fe₂O₃ diagram analysis shows that type of lateritization is  dry laterites with silica deposition. Laterite deposit divided into limonite and saprolite. Topographic unit divided into hill slope and lowland basin. Landslide process in hillslope area causes thin laterite deposit. Lithology in hillslope area are divided into lithology with gabbro domination and lithology with serpentine domination. Lateritization in lithology with gabbro domination are poor lateritization and ore zone are not formed. Latertization in lithology with serpentine domination are good lateritization and ore zone are formed in saprolite and lower part of limonite. Ni is in nickeliferous serpentine which cause Ni has strong positive corellation with Co, Fe, MnO and Cr₂O₃. There is landslide accumulation in lowland basin.which cause thin laterite deposit and ore zone in limonite.