Granitoid Rocks and Mineralization from the Western Kalimantan Island : Geology and Geochemical Characteristics

The granitoid rocks of the western Kalimantan area have calc-alkaline fractionation trends that are consistent with magmas formed at volcanic arc setting. Characteristics vary slightly between samples but generally have I-type signatures. Normalized trends and tectonic comparisons for REE suggest that the granitoid rocks from the area are the crystallization product of an initial partial melting of any combination of volcanic-arc environment and active continental margins. Mineralizations are mostly associated with Cretaceous granites bodies and some are related with younger Miocene intrusive rocks which are mostly occured along the marginal parts of granite plutons. This mineralization displays both of the shallow level to deep level environments. Potential mineralizations have the highest copper grade of 26,500 ppm, zinc 369,000 ppm, lead 216,000 ppm, silver 1,580 ppm, cassiterite 31,200 ppm and manganese 10,100 ppm. Other base element nickel (Ni) and chromite (Cr) have low contents, in which the highest grade for nickel is only 20 ppm and chromite is merely 290 ppm.