Petrology and Geochemistry of Scandium in Wailukum Ni Laterites, East Halmahera, Indonesia

The Wailukum area in North Maluku Province, Indonesia, is an ultramafic rock complex with a high degree of serpentinization. The mineral composition of ultramafic and mafic rocks strongly influences scandium (Sc) distribution and enrichment during lateritization. This study aims to analyze the element distribution, mineral composition, and rock identification in three types of geological materials in a lateritic profile which contains Sc, specifically bedrock, saprolite, and limonite. The analytical methods used are petrography, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). Results show that in the bedrock, Sc is mainly associated with clinopyroxene minerals such as augite and diopside. In the saprolite, Sc content decreases due to higher mobility but remains partly associated with clinopyroxene. In the limonite zone, Sc reaches maximum enrichment. Among rock types, gabbro contains the highest absolute Sc concentration (23.25 ppm in bedrock and up to 58.5 ppm in limonite), while wehrlite records the greatest enrichment ratio, with a 9.18-fold increase from bedrock to limonite. In contrast, gabbro shows the lowest enrichment ratio (2.52-fold) despite its high initial Sc content. These patterns indicate that Sc enrichment is controlled by clinopyroxene as the primary host in bedrock, its relative stability during weathering.