Ni enrichment associated with Fe isotope fractionation in Ni laterite deposits, Sulawesi Island, Indonesia

摘要

Ni laterite deposits, formed by intense chemical weathering of ultramafic rocks under tropical to subtropical climate, are important resources of Ni and potential targets for other critical metals (e.g. Co, Sc, PGE) (Aiglsperger et al. 2016). Ni laterite deposits are well developed in modern and ancient tropical to subtropical regions, such as New Caledonia, Western Australia, and Southeast Asia, including The Philippines and Indonesia, which have been the major Ni supply sources in recent years. However, only a few studies have been conducted for Ni laterite deposits in these countries. In order to understand chemical weathering processes involving enrichment of Ni and other critical metals, we investigated the geochemistry and Fe isotopic compositions of 4 Ni laterite profiles developed on peridotites with different degrees of serpentinisation in the Soroako and Poma-laa areas, Sulawesi Island, Indonesia. The major and minor element concentrations were analyzed by XRF and ICP-MS, the mineralogical compositions were obtained by XRD. Fe isotopes were analyzed by MC-IGP-MS (RIHN, Kyoto) after acid digestion with HNO_3+HF and HC1 in a stainless bomb and purification using anion exchange column.