Relation between chemical composition and particle-size distribution of ores in the profile of nickeliferous laterite deposits of the Rio Tuba Mine, Philippines

Abstract

Lateritic Ni ore mined in the Rio Tuba Mine, Philippines, derived from ultramafic rock by tropical intense weathering, is generally composed of two accumulated zones, an upper laterite zone and a lower saprolite zone. These two zones are very different in appearance, mineral assemblage, chemical composition, and in other ways. A transitional zone may be seen between the upper and lower zones, but it does not develop to any appreciable thickness. Although serpentine and goethite are still predominant in the constituent minerals, other clay minerals are increasing. The transitional zone may be subdivided into three groups based on chemical composition. The behaviour of the chemical composition in this horizon indicates a complicated process of component transportation under the weathering process. In the ore, chemical components are closely related in particle size of constituent minerals. In the laterite - transitional - saprolite sequence, a common variation range and tendency in chemical composition for each particle size can be seen. However, taking samples with the same particle size the chemical composition obviously differed, representing the characteristics of the components for each zone. Concerning the correlation coefficient of the chemical components of each zone, a somewhat different inter-component relationship can be seen in these zones. These differences of correlation suggest the different complicated lateritized conditions under which they are formed.