干旱区生态环境知识资源中心

This paper records, for the first time, the garnierite in Wadi Dubur Neoproterozoic serpentinites from the Central Eastern Desert of Egypt. Garnierites (nepouite) occur in two types of infillings in the altered and faulted serpentinite. The Type I garnierite is Fe-richer [Mg0.26-0.71 Ni1.22-1.79 Fe1.28-3.05 Al (0.0-0.02) Si1.11-1.73 O-5(OH)(4)] showing preferential zoning, while the Type II garnierite is homogenous with higher Si and Mg [Mg0.54-0.94 Ni1.38-2.04 Fe0.38-1.29 Al (0.0-0.01) Si1.66-2.10 O-5(OH)(4)]. The serpentinization of the peridotite protolith and the associated alteration of chromite and Ni-sulfides were important for the early liberation of Ni. It is proposed that the unweathered serpentinites represent the bedrock, while the altered garnierite-bearing ones represent the saprock. The early weathering of serpentinites contemporaneous with the post-obduction tectonic activation caused in situ precipitation of Type I garnierite in veins. With the faulting repetition and progressive alteration Ni, Si, and Mg were transferred to the percolating meteoric solutions downward precipitating the Type II garnierite in gouges. Although the Dubur garnierite represents a narrow Ni-laterization, nickel ore in the Arabian Nubian Shield of the Eastern Desert of Egypt.