Preliminary Study on PGE Associated with Laterite of MacroAsia's Infanta Nickel Area,
Kotaro Yonezu1, Shuhei Hara1, Kosei Noda1, Jillian Gabo1,
Jaypee Juanerio2, Edna Laguerta2, Ramon Santos2 and Rogel Santos2
The nickel laterite of MacroAsia’s Infanta nickel area in Southern Palawan, Philippines was investigated in order to understand the geochemical and mineralogical association of platinum group elements (PGE) with Ni laterite. The PGE are an essential component of green technology, such as fuel cells or automobile catalysts, materials that are important in developing a sustainable society. Magmatic mafic and ultramafic rocks containing Ni and Cu are some of the possible PGE sources, especially after they are exposed to weathering. This research conducted geochemical analysis, with emphasis on PGE concentrations of the weathering profiles of the ultramafic rocks from the bedrock through saprolite and to topsoil (limonite section).
Most of the Ni laterite areas considered in this study are weathering profiles that developed from harzburgite or dunite bodies that belong to the Beaufort ultramafic complex of the Palawan Ophiolite. The Ni content of the bedrock averaged around 2700 ppm. However, the laterite profiles of test pit 2 (TP 2: 8 m depth) and test pit 3 (TP 3: 10 m depth) have concentrations of up to 2.3% and 1.8% Ni, respectively. At TP 2, the Ni concentration can be divided into two groups depending on the presence of garnierite: the upper 5 meters that lacks garnierite, and the lower part (5 meters) which contains a significant amount of garnierite. The Pt is likely to be associated with the upper zone (up to 70 ppb Pt). On the other hand, Ni concentrations at TP 3 increased with depth, whereas the Pt concentration showed nearly constant amounts for the whole pit (up to 100 ppb). As the Pt is mobilized during the weathering process and enriched by precipitation or coprecipitation, either the soil geochemistry including the pH and Eh (mobility of Pt) or the iron or nickel mineralogy (scavenging capability) may play an important role. In addition, Pd concentrations (up to 70 ppb) are well correlated with Pt, suggesting that those elements are mobilized together under certain geochemical conditions during weathering.