首页|Unveiling Nb-Ta mineralization processes:Insight from quartz textural and chemical characteristics in the Songshugang deposit,Jiangxi Province,South China
Unveiling Nb-Ta mineralization processes:Insight from quartz textural and chemical characteristics in the Songshugang deposit,Jiangxi Province,South China
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Unveiling Nb-Ta mineralization processes:Insight from quartz textural and chemical characteristics in the Songshugang deposit,Jiangxi Province,South China
The Songshugang deposit is a large Ta-Nb deposit in South China,with Ta-Nb mineralization associ-ated genetically with the granite and pegmatite.A diversity of quartz from topaz-albite granite,quartz-mica pegmatite,quartz-feldspar pegmatite,and quartz-fluorite pegmatite at Songshugang was studied by CL and LA-ICP-MS in order to constrain enrichment mechanisms of Nb and Ta and to find geochemical indicators of quartz for rare metal deposits.Cathodoluminescence image illuminates a canvas of com-plexity,the quartz from topaz-albite granite,quartz-mica pegmatite,quartz-feldspar pegmatite,and quartz-fluorite pegmatite,exhibits numerous dark CL streaks,patches,and a series of healed fractures.These textures suggest that the rocks were fractured because of deep crustal pressure,and underwent later hydrothermal metasomatism and quartz filling.The quartz from quartz-fluorite pegmatite present limited patches or fractures but distinct growth bands,indi-cating that the melt fluid composition during the formation of quartz at this stage varies greatly and is less affected by mechanical fragmentation.The LA-ICP-MS analysis of quartz shows that there is a positive correlation between Al and Li in the quartz from topaz-albite granite,quartz-mica pegmatite,quartz-feldspar pegmatite,to quartz-fluorite pegmatite,indicating that Al mainly enters the quartz lat-tice through charge compensation substitution mechanism with Li.However,our data deviate from the theoretical Li:Al mass ratio of～1:3.89 in quartz,indicating that there may be competition between H+and Li in a water-rich magmatic environment.The quartz from topaz-albite gran-ite is enriched in K and Na elements,and the quartz from quartz-fluorite pegmatite is enriched in fluorite with a low Ca content in quartz,further elucidating that these rocks were subjected to hydrothermal metasomatism.From topaz-albitite granite to quartz-fluorite pegmatite,Al,Li and Ge content and Al/Ti,Ge/Ti,Sb/Ti ratios in quartz gradually increased,but Ti content gradually decreased,reflecting the high evolution of magma,which can enrich rare metal ele-ments.Based on the characteristics of quartz CL textures and trace elements in topaz-albite granite,quartz-mica pegmatite,quartz-feldspar pegmatite,and quartz-fluorite pegmatite,combined with the albitization and K-feldspa-thization of rocks,it is suggested that the Nb-Ta minerali-zation in Songshugang may be influenced by the combined action of magmatic crystallization differentiation and fluid metasomatism.By comparing the quartz in the Songshugang pluton with the quartz in the granite type and pegmatite type rare metal deposits recognized in the world,the Songshu-gang pegmatite share similarities with the LCT-type peg-matite.Combined with previous studies,the Ge/Ti＞0.1 and Ti＜10 ppm,as well as Al,Li,Ge,Sb,K,Na contents and Al/Ti,Sb/Ti ratios in quartz have the potential to be a power-ful exploration marker for identifying granite-like pegmatitic Nb-Ta deposits in other places.
Hengsong Zhang、Shaohao Zou、Xilian Chen、Deru Xu、Zhilin Wang、Yongwen Zhang、Hua Wang
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State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China
School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China
Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education,School of Geosciences and Info-Physics,Central South University,Changsha 410083,China
Jiangxi Mineral Resources Guarantee and Service Center,Nanchang 330025,Jiangxi,China
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Nb-Ta deposit Quartz Cathodoluminescence LA-ICP-MS Trace elements Magma-hydrothermal evolution
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