Research progresses and main scientific issues of strategically critical minerals in black rock series
In this paper,research progresses on the distribution and supernormal enrichment mechanism of strategically critical minerals in black rock series in recent years have been summarized,and the prospect of researches on strategically critical mineral resources has been provided.The black rock series include sedimentary strata of black shale,coal-bearing strata and carbon-rich phosphorite.Especially,critical metals which were supernormally enriched in black shale include rare metals of Se,Te,Re,Cd,Tl as well as rare and precious metals of PGE,Co and others.The supernormal enrichment of Ga and Ge,commonly occurred in coal-bearing strata,led to the formation of independent Ga/Ge deposits.The enrichment of rare earth metals and rare precious metals also occurred in coal-bearing strata.Rare earth elements,particularly medium and heavy rare earth elements,were significantly enriched in phosphorites.The strategically critical metals in black rock series were mainly derived from continental weathering products,seawater,hydrothermal fluid,and the uptake of biological organisms.In the weathering and sedimentation processes,the main mechanisms responsible for the enrichment of critical metals include the pumping effect caused by the vulcanization-reduction water column,organic matter reduction,and complexation and adsorption of organic matters,iron and manganese oxides,apatite and/or clay minerals in organic-rich sedimentary systems.The black rock series can serve as a source of ore-forming metals for the hydrothermal overprinting process,regulate the oxygen and sulfur fugacities in hydrothermal systems,thereby facilitate the formation of super-large strategically critical mineral resources.In addition,it is crucial to acknowledge that metal accumulation and dispersion behaviors within the black rock series may have significant influences on other related metallogenic systems.The supernormal enrichment of strategically critical metals in black rock series is commonly associated with anoxic-vulcanization sedimentary events in continental margin and rift basin environments.Regional geological events,such as variations of atmospheric oxygen contents,the assembly and breakup of supercontinents,changes of ocean current circulation patterns,and ocean anoxia events caused by the glaciation,and large-scale volcanic activities,are likely primary factors controlling the formation and temporal and spatial distribution of strategically critical metal deposits within black rock series.The black rock series is of a significant sub-type of rocks formed through the epigenetic weathering and sedimentation process.In the future,more attention should be paid to the importance of rocks formed through the epigenetic weathering and deposition processes,such as the black rock series,in the formation of strategically critical mineral resources,and related metallogenic theories of strategically critical minerals should be established and developed.
black rock seriesstrategically critical minerals resourcessupernormal enrichment mechanismsmetallogenic process
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