Geochemical constraints on the mobilization of Ni and critical metals in laterite deposits, Sulawesi, Indonesia: A mass‐balance approach

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. Massbalance 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 rareearth 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.

Mineralogical evolution of a weathering profile in the Tagaung Taung Ni laterite deposit: significance of smectite in the formation of high-grade Ni ore in Myanmar

“…Most Ni laterite deposits develop under a humid tropical climate where intense chemical weathering leads to considerable mobilization of Ni into saprolite layers. In a typical hydrous Mg silicate deposit, serpentine is regarded as one of the main Ni-bearing minerals of the ore zone (Dublet et al 2012;Freyssinet et al 2005;Ito et al 2021). However, Ni released from primary bedrock minerals is retained in Fe-(hydr)oxides during the initial stage of chemical weathering, and this Ni is redistributed from the Fe-(hydr)oxides into serpentine in the saprolite as chemical weathering progresses (Freyssinet et al 2005;Villanova-de-Benavent et al 2017).…”

“…However, Ni released from primary bedrock minerals is retained in Fe-(hydr)oxides during the initial stage of chemical weathering, and this Ni is redistributed from the Fe-(hydr)oxides into serpentine in the saprolite as chemical weathering progresses (Freyssinet et al 2005;Villanova-de-Benavent et al 2017). This process is critical for the formation of Ni ores in saprolite (Ito et al 2021). However, it is not clear whether this process is important under different climatic conditions, such as the drier sub-tropical climate of Myanmar, because the drier conditions might produce different weathering products.…”

Determination of heavy metal elements concentration in soils and tailing sediments from lateritic nickel post-mining areas in Motui District, Southeast Sulawesi

“…One of the characteristics of laterite nickel mining is surface mining since the nickel ore will be concentrated in a saprolitic layer above the bedrock. Typically, there are four main layers in the laterite nickel profile which are (from lower to the upper or surface layer) bedrock, saprolite, limonite and top soil (overburden) (Akane et al 2021). Surface mining is conducted to extract the upper layer of laterite soil from the surface or upper to the bottom layer.…”

Indikasi Potensi Skandium Di Zona Limonit Blok Tapunopaka, Konawe Utara, Sulawesi Tenggara

“…Penggunaan skandium pada saat ini adalah 35% sebagai solid oxide fuel cell (SOFC) untuk alat elektrolisa dalam pengembangan energi berbasis hidrogen, dan 26% di bidang pertahanan dan kedirgantaraan. Skandium di Indonesia terkandung dalam laterit bauksit dari pelapukan granit [13] dan laterit nikel hasil pelapukan batuan ultramafik yaitu di Sulawesi Tenggara antara lain di Soroako dan Pomalaa [7] [8], daerah Lapopao, Sulawesi Tenggara [16]. Keberadaan skandium di Indonesia belum dipelajari secara detil [13].…”

“…Keberadaan skandium di Indonesia belum dipelajari secara detil [13]. Batuan asal laterit nikel yang mengandung skandium adalah batuan ultramafik meliputi harsburgit, dunit, piroksenit, dan lherzolit terserpentinisasi [7], wehrlit, klinopiroksenit, dan olivin orthopiroksenit [8]. Klinopiroksen yang bersifat aluminous akan menghasilkan smektit melalui proses hidrolisis dan oksidasi pada saat berlangsungnya proses pelapukan supergen, umumnya berkomposisi ferrosaponit [8].…”