A review of the types and ore mechanism of the cobalt deposits

Cobalt is an important strategic metal of major industrial countries. In order to invoke the importance of the cobalt deposits to the strategic industries in China, this paper aims to introduce the different types of the cobalt deposits in the worldwide, to review the ore mechanism of the cobalt deposits and to propose the research directions of the future studies for the cobalt deposits. Global cobalt resources can be grouped into two deposit types: terrestrial and seafloor deposits. The major terrestrial cobalt deposits include sediment-hosted stratiform copper-cobalt, nickel-cobalt laterite, and magmatic sulfide copper-nickel deposits. Other sources include black shales hosted, skarn and replacement, metasedimentary rocks hosted, iron oxide copper-gold deposits, volcanic massive sulfides, polymetallic veins (five-element veins and other vein types), and Mississippi Valley-Type lead-zinc deposits. Seafloor cobalt-related deposits are mainly iron-manganese-cobalt nodules and crusts, which are hardly explored and productive. The detailed information of the major cobalt deposits is also listed, presenting the tonnage and grade of various types of the cobalt deposits in China. The polymetallic veins and black shales hosted types have the highest grade, and both types should be paid more attentions during the mineral exploration. For the geochemical behavior of the cobalt during the magmatic and hydrothermal environment, the partition coefficient of cobalt in the process of mantle melting under different tectonic background and water contents are relatively stable. Also, during the fractional crystallization of ultramafic-mafic magmas in the magmatic sulfide deposits, cobalt has a slight preference for olivine relative to basalt. In hydrothermal ore system, aqueous Cobalt(II) chloride complexes play a crucial role in cobalt transport and deposition, and their solubility has a close relationship with the temperature and salinity of the fluids. The debate on the genesis of various cobalt-rich deposits can be considered as the debate on the evaluation between diagenetic and superimposed processes in the ore formation. Besides some polymetallic veins, black-shale hosted, Mississippi Valley-Type lead-zinc, and iron oxide copper-gold deposits, the process of cobalt enrichment has close relationships with the ultramafic-mafic intrusions or volcanic during the magmatic processes, hydrothermal processes, or weathering. Moreover, the multiple-stage hydrothermal processes are also critical to cobalt enrichment. We suggest that the spatial-temporal distribution of different cobalt deposits in China and how their formations are related to the tectonic evolution of the craton and orogenic belt should be investigated immediately to determine the controlling geological factors in different cobalt deposits. Also, the thermodynamic properties of different cobalt-bearing speciation under different physico-chemical environments should be identified. The relationship between geodynamic processes and formation of cobalt-rich deposits needs to be considered. Finally, great attention should be paid to the study of marine iron-manganese-cobalt nodules and crusts and their proper mining technology.