Spatial-Temporal Distribution, Geological Characteristics and Ore-Formation Controlling Factors of Major Types of Rare Metal Mineral Deposits in China

Rare metals including Lithium(Li),Beryllium(Be),Rubidium(Rb),Cesium(Cs),Zirconium(Zr),Hafnium(Hf),Niobium(Nb),Tantalum(Ta),Tungsten(W)and Tin(Sn)are important critical mineral resources.In China,rare metal mineral deposits are spatially distributed mainly in the Altay and Southern Great Xingán Range regions in the Central Asian orogenic belt;in the Middle Qilian,South Qinling and East Qinling mountains regions in the Qilian-Qinling-Dabie orogenic belt;in the Western Sichuan and Bailongshan-Dahongliutan regions in the Kunlun-Songpan-Garze orogenic belt,and in the Northeastern Jiangxi,Northwestern Jiangxi,and Southern Hunan regions in South China.Major ore-forming epochs include Indosinian(mostly 200-240 Ma,in particular in western China)and the Yanshanian(mostly 120-160 Ma,in particular in South China).In addition,Bayan Obo,Inner Mongolia,northeastern China,with a complex formation history,hosts the largest REE and Nb deposits in China.There are six major rare metal mineral deposit types in China:Highly fractionated granite;Pegmatite;Alkaline granite;Carbonatite and alkaline rock;Volcanic;and Hydrothermal types.Two further types,namely the Leptynite type and Breccia pipe type,have recently been discovered in China,and are represented by the Yushishan Nb-Ta-(Zr-Hf-REE)and the Weilasituo Li-Rb-Sn-W-Zn-Pb deposits.Several most important controlling factors for rare metal mineral deposits are discussed,including geochemical behaviors and sources of the rare metals,highly evolved magmatic fractionation,and structural controls such as the metamorphic core complex setting,with a revised conceptual model for the latter.

Carbon neutrality needs a circular metal-energy nexus

Carbon neutrality requires systematic transformations of both energy and metal systems.These transformations are not isolated but rather interlinked and interdependent,such that trade-offs between different strategies exist.Herein,we explore the critical interlinkages between energy and metal systems and further propose a circular metal-energy nexus to advance global coordinated actions towards a carbon-neutral future.

Coal measure metallogeny:Metallogenic system and implication for resource and environment

Coal,coal measure gas,coal conversion to oil and gas,and coal-based new materials are reliable guarantees for stable energy supply and economic and social development in China.The coal-dominated resource endowment and the economic and social development stage determine the irreplaceable position of coal resources in the energy system.Coal measure resources,including aggregated or dispersed solids,liquid and gaseous multitype energies,and metal as well as nonmetallic minerals,are the products of multisphere interaction and metallogenetic materials generation,migration,and accumulation.Coal measures record rich deep-time geological information of transitional and terrestrial peat bogs,which is a crucial carrier to reveal ecosystem evolution,significant organic carbon sequestration,atmospheric O_(2)/CO_(2)variation,and wildfire events.Coal measure evolution is accompanied by the migration and transformation of various materials during diagenesis-metamorphism,forming differentiated coal compositions besides properties and various mineral resources in its adjacent strata.The enrichment condition,occurrence state,and separation potential are the premise for level-by-level use and efficient development of coal measure resources.Coal measure metallogeny is based on the metallogenic system of multiple energy and mineral resources in coal measures and their environmental effects.Fully understanding coal measure metallogeny is beneficial for promoting the coal transition from fuel to raw materials and strengthening its attribute of multiple mineral resources.The metallogeny comprises various aspects,including:(1)the symbiosis mechanism,co-exploration and co-mining conditions of various resources;(2)the source-sink system of ore-forming materials;(3)the differential carbon accumulation and hydrogen enrichment effect;(4)organic(coal and hydrocarbon)and inorganic(mineral)interactions;and(5)combination of minerals naturally enrichment during the metallogenic process and artificial enrichment during the ore processing process.The coal measure metallogeny belongs to the geoscience disciplines,and studies the types,formation,distribution,enrichment mechanisms,evaluation methods,and development strategies of resources related to coal measures.The key scientific problems include geological records related to mineral enrichment processes,metallogenic mechanisms,resource distribution,occurrence evaluation,and accurate development.Developing coal measure metallogeny is significant in improving the critical mineral metallogenic theory,revealing various deep-time earth systems and realizing the national energy transformation and high-quality development.

Super-enrichment of lithium and niobium in the upper Permian Heshan Formation in Pingguo,Guangxi,China

The upper Permian Heshan Formation in Pingguo,Guangxi,China,is strongly enriched in lithium(Li)and niobium(Nb).The lower bauxite layer contains 0.02–0.04 wt.%Nb_(2)O_(5)(averaging 0.035 wt.%),and the overlying clay rock layer contains 0.06–1.05 wt.%Li_(2)O(averaging 0.44 wt.%),both of which exceed the cut-off grades for independent Li and Nb deposits and are therefore highly prospective.In this study,a preliminary discussion of the genesis of the Li and Nb enrichment is presented to serve as a reference for the investigation,evaluation,and prospecting for clay-and sedimentary-type Li and Nb ores in other regions.The preliminary conclusions are that:(1)The bauxite ore contains abundant anatase,which positively correlates with the whole-rock concentrations of TiO_(2) and Nb,indicating that the Nb is hosted mainly in the anatase;(2)the cookeite content in the clay rock positively correlates with the whole-rock Li concentration,indicating that cookeite is the main carrier mineral of Li,and its genesis can be attributed to reactions between clay minerals(e.g.,pyrophyllite and illite)and Li-Mg-rich underground brine or pore water and groundwater in coastal areas;and(3)provenance analysis of immobile elements(Al,Ti,Nb,Ta,Zr,Hf,and rare earth elements)suggests distinct sources for the Nb-rich bauxite and the overlying Li-rich clay rocks,with the bauxite and Nb originating largely from alkaline felsic rocks in the Emeishan Large Igneous Province,and the clay rocks being derived from peraluminous or moderately fractionated felsic rocks associated with Permian Paleo-Tethyan magmatic arcs.

Scavenging and release of REE and HFSE by Na-metasomatism in magmatic-hydrothermal systems

Exploitable or potentially exploitable deposits of critical metals,such as rare-earth(REE)and high-field-strength elements(HFSE),are commonly associated with alkaline or peralkaline igneous rocks.However,the origin,transport and concentration of these metals in peralkaline systems remains poorly understood.This study presents the results of a mineralogical and geochemical investigation of the Na-metasomatism of alkali amphiboles and clinopyroxenes from a barren peralkaline granite pluton in NE China,to assess the remobilization and redistribution of REE and HFSE during magmatic-hydrothermal evolution.Alkali amphiboles and aegirine-augites from the peralkaline granites show evolutionary trends from sodic-calcic to sodic compositions,with increasing REE and HFSE concentrations as a function of increasing Na-index[Na^(#),defined as molar Na/(Na+Ca)ratios].The Na-amphiboles(i.e.,arfvedsonite)and aegirine-augites can be subsequently altered,or breakdown,to form hydrothermal aegirine during late-or post-magmatic alteration.Representative compositions analyzed by insitu LA-ICPMS show that the primary aegirine-augites have high and variable REE(2194-3627 ppm)and HFSE(4194-16,862 ppm)contents,suggesting that these critical metals can be scavenged by alkali amphiboles and aegirine-augites.Compared to the primary aegirine-augites,the presentative early replacement aegirine(Aeg-I,Na^(#)=0.91-0.94)has notably lower REE(1484-1972)and HFSE(4351-5621)contents.In contrast,the late hydrothermal aegirine(Aeg-II,Na^(#)=0.92-0.96)has significantly lower REE(317-456 ppm)and HFSE(6.44-72.2 ppm)contents.Given that the increasing Na^(#)from aegirine-augites to hydrothermal aegirines likely resulted from Na-metasomatism,a scavenging-release model can explain the remobilization of REE and HFSE in peralkaline granitic systems.The scavenging and release of REE and HFSE by Na-metasomatism provides key insights into the genesis of globally significant REE and HFSE deposits.The high Na-index of the hydrothermal aegirine might be useful as a geochemical indicator in the exploration for these critical-metals.