Cobalt occurrence and metallogenetic regularities of Songjiashan cobalt-iron deposit in Zhongtiaoshan of Shanxi Province
The Songjiashan cobalt-iron deposit is located in the central part of the"Tongshan skylight"on the southeastern edge of the Zhongtiaoshan area,and the ore-bearing rocks are mainly volcanic-sedimentary rock series of the Jiangdaogou Formation of the Paleoproterozoic Songjiashan Group.The cobalt-iron ore body is controlled by the lithology of the strata and is distributed in a SN strike.Metal minerals mainly include magnetite,pyrite,chalcopyrite,carrollite and linnaeite,while non-metallic minerals mainly include quartz,calcite,sericite and chlorite.The ore structures mainly comprise massive,banded,disseminated,bulk and veined.The pyrite and chalcopyrite were mostly distributed in disseminated and veined ores.The alteration of surrounding rocks mainly includes silicification,sericitization,pyritization,carbonation and chloritization.The formation of cobalt-iron ore bodies mainly includes three periods,namely,sedimentation,metamorphism and hydrothermal processes.Microscopic observation of ores,scanning electron microscopy and electron probe analysis of sulfides indicate that cobalt element is mainly hosted in carrollite,linnaeite and pyrite.The characteristic element Co/Ni ratio of pyrite is mostly between 100 and 1000,with several ratios less than 100,indicating that the formation of sulfides should be mainly related to hydrothermal processes.In-situ sulfur isotope composition of sulfides δ34S is between 12‰ and 16‰,which is lower than those of the Proterozoic seawater sulfate(15‰～20‰).It can be seen that thermochemical sulfate reduction(TSR)plays an important role in the process of seawater sulfate reduction.Comprehensive research shows that the formation of cobalt-rich ore bodies in the Songjiashan deposit is attributed to the original volcanic-sediments,cobalt-containing metamorphic fluids filling and metasomatism along the foliation structure during the orogenic stage.In the late orogenic period,there was also a superposition of hydrothermal mineralization.Therefore,it is suggested that the genetic type of the Songjiashan deposit belongs to the sedimentary-hydrothermal superimposed cobalt-iron deposit.
Cobalt occurrencePaleoproterozoicSedimentary-metamorphic sedimentary rock depositsSongjiashan cobalt-iron depositsZhongtiaoshan area
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