Abstract:

 Laterite nickel deposit is a hotspot of global nickel resource exploration and development, and it is also a key target of foreign mineral resource exploration for our country. The Kolonodale deposit located in Sulawesi Island in Indonesia is a typical deposit in SE Asian laterite nickel deposit belt. The deposit occurred in laterite weathering profile of ultramafic rocks. The orebearing profile can be divided into four vertical layers: the red ferric oxide layer, the yellow clay layer, the sage green ore layer and the protolith. The laterite ore occurred in the upper part of the regolith profile. The major Nibearing minerals are ferric oxyhydroxides. The silicate ore occurred in the middle and lower part of the regolith profile, forming in cracks and voids of saprolite and protolith, dominated by nepouite, willemseite and other hydrated MgNi silicates. The geochemical data show that the differentiation of elements along the profile is obvious, especially the high enrichment of Ni in the deeper layer. The migration of elements in lateritization was affected by superficial environment and geochemical activities. Fe, Al, Ti, and Cr represent the residual elements, Si and Mg belong to filtering elements and Mn, Ca, Co, and Ni are classified to the secondary rich elements. By comparison with global typical laterite nickel deposits, the Kolonodale is determined to be of the insitu silicate type. It is formed by coupling many geological and geographical factors, including the geochemical source from ultramafic rocks, the weathering force affected by rain forest climate, the filtering and precipitation channels provided by structural activities, the ore deposition space offered by good relief, and the time insurance from stable tectonic environment. This study indicates that the oreforming process of the Kolonodale deposit can be divided into three stages: The sparolite stage, the laterite stage and the secondary enrichment stage.

Key words: laterite nickel deposit, garnierite, Ni superficial geochemistry, SE Asia