Characteristics and the Occurrence of ???Garnierite??? from the Soroako Nickeliferous Laterite Deposits, Sulawesi, Indonesia

摘要

An investigation of Ni-Mg hydrous silicate ores called ???garnierites??? from the Soroako nickeliferous laterite deposits has been conducted by means of optical microscopy, X ray diffractometry (XRD), and X ray fluorescence (XRF) spectroscopy with the aims at deciphering of the occurrences, mineralogy, and bulk chemical composition of garnierite. Samples were collected either from west block or Petea block. The west block is mostly occupied by unserpentinised peridotite, whereas the east block represented by Petea area is covered by moderately to highly serpentinized protolith. The field observation and microscopic analysis indicate that the garnierites in the west block occur in the three modes; i) slickensided fault coating, ii) the fracture-filled veins, and iii) matrices in conglomeratic peridotite. While in Petea area, the garnierite is only found as vein filling fractures. Results of XRD analysis exhibit that garnierite from Soroako is mainly composed of kerolite-pimellite, talc-willemseite, Ni-serpentine, and sepiolite-falcondoite series. Nickel content of the garnierite samples studied by means of XRF methods ranges from 1.8 to 19.2 wt%. The wide variation of Ni content in the analyzed garnierite samples is likely caused by the presence gangue minerals particularly of quartz/silica and trace amount of iron oxides