Geochemical constraints on the mobilization of Ni and critical metals in laterite deposits, Sulawesi, Indonesia: A mass‐balance approach. Issue 3 (12th May 2021)

• Record Type: Journal Article
• Authors: Ito, Akane; Otake, Tsubasa; Maulana, Adi; Sanematsu, Kenzo; Sufriadin, ; Sato, Tsutomu
• Is Part Of: Resource geology. Volume 71:Issue 3(2021)
• Page Start: 255
• Page End: 282
• Publication Date: 2021-05-12
• Subjects: critical metal -- Indonesia -- mass balance calculation -- nickel laterite -- supergene enrichment -- ultramafic rock; Mining geology -- Periodicals; Mining geology -- Pacific Area -- Periodicals; Mining geology -- Asia -- Periodicals; Geochemistry -- Periodicals; Environmental geology -- Periodicals; 553
• DOI: 10.1111/rge.12266
• Languages: English
• ISSNs: 1344-1698

Abstract

Abstract: Indonesia is one of the largest Ni ore producers in the world and is also expected to be an important potential source of some critical metals (e.g., Co, Sc, rare‐earth elements, and platinum‐group elements). However, few studies have examined Ni laterite deposits in this country. In this study, we investigate Ni enrichment and the potential accumulation of critical metals in four laterite profiles with varying degrees of serpentinization and weathering intensity in the Soroako and Pomalaa mining areas of Sulawesi, Indonesia. We integrate geochemical evaluation with a mass‐balance approach and mineralogical analysis to better constrain the geochemical factors influencing the mobilization of Ni during lateritization. Nickel contents in the saprolite horizon of the profiles that are strongly weathered and developed over serpentinized peridotite are higher than those that are weakly weathered and developed over unserpentinized harzburgite. The bulk Ni contents of saprolite horizons are related to Ni contents of Ni‐bearing Mg‐phyllosilicates, which suggests that Ni remobilization is the main control on Ni enrichment in the profiles. Mass‐balance calculations reveal that the amounts of gained Fe and Ni in the profiles are positively correlated. This relationship indicates that the redistribution of Ni is likely controlled by the aging of Ni‐bearing goethite (dissolution/recrystallization) involving ligand‐promoted dissolution by organic matter and/or reductive dissolution by microbial activity near the surface. Critical metals show enrichment in specific horizons. Enrichments in Co and rare‐earth elements are strongly influenced by the formation of Mn‐oxyhydroxides in the oxide zone of the profiles. In contrast, Sc, Pt, and Pd show residual enrichment patterns, with grades influenced mainly by their initial contents in bedrock. The profiles show a positive correlation between Sc and Fe, as reported for other Ni laterite deposits. Among the critical metals, Sc, Pt, and Pd contents in the studied profiles are comparable with values reported from other Ni laterite deposits worldwide. Abstract : The highest Ni enrichment was observed in the profile, where bedrock is serpentinized peridotite and the profile is highly weathered. Mineralogical and mass‐balance calculation results indicate that the amounts of gained Ni and Fe are positively correlated and a large gained amount of Fe can be an indicator of strong Ni enrichment. The dissolution of Ni‐bearing goethite by microbial activity and organic matter at or near the surface may enhance the downward remobilization and significant enrichment of Ni in the laterite profile.