新たなニッケル資源アワルワ鉱の探査

抄録

Awaruite is a native nickel-iron alloy (Ni₃Fe) which can occur in serpentinized ultramafic rocks and is a potential globally significant new source of nickel. Through exploration and studies on the Baptiste deposit in British Columbia, Canada, FPX Nickel Corp. (FPX; formerly First Point Minerals Corp.) has demonstrated a large-scale awaruite deposit that is an economic new nickel source for stainless steel with low CO₂ emissions. FPX has also developed a processing flowsheet to produce high purity nickel sulphate applicable for use in EV batteries. FPX and JOGMEC began a global exploration project in March, 2023, with the aim of contributing to a carbon neutral society by discovering new awaruite deposits.In general, serpentinization at low total S and low fO₂ conditions is required to generate awaruite (e.g. Frost, 1985; Britten, 2017). Decreased total sulfur can be achieved by partial melting of mantle peridotite with accompanying loss of incompatible elements, which results in creation of depleted mantle peridotite. Low fO₂ can be achieved through serpentinization of peridotite minerals: i.e. hydration reaction of olivine lowers fO₂ through the generation of H₂. Low SO₂ waters (meteoric or metamorphic) are required during serpentinization to create significant awaruite, which excludes abyssal serpentinization from preferable setting.Evans (2010) suggests that the speed of the serpentinization reaction is a controlling factor in the generation of magnetite: in the case of rapid element diffusion in higher temperature, iron can be distributed in serpentine minerals as solid solution and not contribute to magnetite formation. Our hypotheses here is that, similarly with the case of magnetite, slow diffusion might be key for having nickel not to attribute serpentine and for consequentially pronounced awaruite generation.The Baptiste deposit is hosted within the Cache Creek terrane and has geological characteristics (e.g. Britten, 2017; Milidragovic and Grundy, 2019) concordant with the theoretical ideas above. The Cache Creek terrane contains very low-T subduction metamorphic rocks evidenced by blueschist and lawsonite eclogite. Ultramafic rocks of the Baptiste deposit are highly depleted mantle peridotites in a supra-subduction zone.