Combined XRF, XRD, SEM-EDS, and Raman Analyses on Serpentinized Harzburgite (Nickel Laterite Mine, New Caledonia): Implications for Exploration and Geometallurgy

Different techniques have been combined to determine the crystallography and the chemical composition of serpentinized harzburgite sampled in a drill core coming from the lower part of the New Caledonia ophiolite. Specifically, this serpentinized harzburgite is the common bedrock of most of the nickel laterite mines in New Caledonia. Most of the minerals present in serpentinized harzburgite were analyzed by Raman spectroscopy and XRD. In this study, Raman spectroscopy has been applied for the first time to estimate the nickel content in lizardite, forsterite, talc, and goethite. The analyses confirm that the major serpentine minerals show two varieties: (1) Ni-bearing lizardite and (2) Ni-free lizardite. Furthermore, Ni-rich forsterite, enstatite, Ni-rich talc, sepiolite, periclase (MgO), and quartz were detected. Additionally, Raman spectroscopy evidence minor phases not detected by XRD: anatase, rutile, pyrite, hematite, chromite, magnesiochromite, and Ni-rich goethite. Our results show that the Ni substitution is only present in lizardite exhibiting turbostratic-stacking disorder. This finding has potential for being used as an exploration tool using short-wave-infrared spectroscopy online or as a portable instrument, and for defining geometallurgical parameters for processing these complex ores.