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Unmixing of REE-Nb enriched carbonatites after incremental fractionation of alkaline magmas in the Shaxiongdong complex, Central China

文献类型：期刊论文

作者Su, Jian-Hui5; Zhao, Xin-Fu5; Li, Xiao-Chun3,4; Hu, Wei2,5; Chen, Wei5; Slezak, Paul1
刊名LITHOS
出版日期2022-05-01
卷号416页码:18
关键词Alkaline-carbonatite complex Nb and REE mineralization Extreme fractionation Petrogenesis
ISSN号0024-4937
DOI10.1016/j.lithos.2022.106651
英文摘要Carbonatites are often temporally and spatially associated with alkaline silicate rocks. However, petrogenetic models of formation of alkaline-carbonatite complex and the related rare metal element enrichment processes are still in a matter of debate. In this study, we present detailed petrographic observations and geochemical data for the Shaxiongdong complex, consisting of meta-pyroxenite, syenite, and carbonatite in the South Qinling Belt, Central China. Meta-pyroxenite crops out as a marginal face of the complex and has higher Mg, Fe, Ti, Ca and P contents relative to syenite, consistent with a cumulate of pyroxene, magnetite, ilmenite, titanite and apatite. Syenite is the main central phase of the complex and can cut the meta-pyroxenite as dykes or veins. Both metapyroxenite and syenite show various degrees of fenitization, in which the residual syenite looks like breccia cemented by fenite. Carbonatite locally occurs as dykes of dozens of centimeters in width within syenite and meta-pyroxenite and hosts the most Nb and REE of the complex. Nb-rich minerals, e.g., pyrochlore, crystallized coeval with aegirine and apatite in carbonatite, implying a magmatic origin. In contrast, most REE minerals are spatially associated with barite and are interstitial to calcite, implying they were mainly crystallized from residual carbonatite magmas or magmatic-hydrothermal fluids. Carbonatite samples with REE mineralization have oxygen isotopes slightly higher than those of unmineralized and Nb mineralized samples, supporting the involvement of hydrothermal fluids in REE mineralization. U-Pb dating of titanite and zircon from metapyroxenite, syenite and the associated fenite yielded identical ages of ~440 Ma. Carbonatite, syenite, and meta-pyroxenite all have nearly identical Sr-Nd isotopes ((Sr-87/Sr-86)i: 0.70298 to 0.70367; epsilon Nd(t):+3.6 to +4.6), suggesting that all of these rocks were derived from the same mantle source. Fractionation modeling suggests the syenites evolve from a parental alkali basalt magma by separation of cumulate pyroxenite in the complex and finally lead to the unmixing of Nb-REE enriched carbonatites. The subsequent fractionation of carbonatite melts led to Nb and REE mineralization in the Shaxiongdong carbonatite. Niobium minerals formed at early magmatic stage, while most REE minerals likely crystallized from the late magma residuals or precipitated from magmatic-hydrothermal fluids. This genetic model can be widely applicable to other alkaline-carbonatite complexes and provides a reasonable explanation for extreme enrichment of rare metals in such rocks.
WOS关键词U-TH-PB ; NEOPROTEROZOIC TECTONIC EVOLUTION ; ISOTOPIC CHARACTERISTICS ; LIQUID IMMISCIBILITY ; TRACE-ELEMENT ; OROGENIC BELT ; SOUTH CHINA ; ZIRCON AGE ; MANTLE ; ROCKS
资助项目national key R&D pro-gram of China[2017YFC0602401] ; National Natural Science Foundation of China (NSFC)[41822203] ; National Natural Science Foundation of China (NSFC)[41972074]
WOS研究方向Geochemistry & Geophysics ; Mineralogy
语种英语
WOS记录号WOS:000799251500002
出版者ELSEVIER
资助机构national key R&D pro-gram of China ; national key R&D pro-gram of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; national key R&D pro-gram of China ; national key R&D pro-gram of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; national key R&D pro-gram of China ; national key R&D pro-gram of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC) ; national key R&D pro-gram of China ; national key R&D pro-gram of China ; National Natural Science Foundation of China (NSFC) ; National Natural Science Foundation of China (NSFC)
源URL[http://ir.iggcas.ac.cn/handle/132A11/105940]  
专题地质与地球物理研究所_中国科学院矿产资源研究重点实验室
通讯作者Zhao, Xin-Fu
作者单位1.Univ Coll Dublin, Irish Ctr Res Appl Geosci, Sch Earth Sci, Dublin, Ireland
2.No 4 Geol Team Guangxi Zhuang Auton Reg, Nanling 530033, Peoples R China
3.Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100049, Peoples R China
4.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Mineral Resources, Beijing 100029, Peoples R China
5.China Univ Geosci, Sch Earth Resources, State Key Lab Geol Proc & Mineral Resources, Wuhan 430074, Peoples R China
推荐引用方式
GB/T 7714		 Su, Jian-Hui,Zhao, Xin-Fu,Li, Xiao-Chun,et al. Unmixing of REE-Nb enriched carbonatites after incremental fractionation of alkaline magmas in the Shaxiongdong complex, Central China[J]. LITHOS,2022,416:18.
APA Su, Jian-Hui,Zhao, Xin-Fu,Li, Xiao-Chun,Hu, Wei,Chen, Wei,&Slezak, Paul.(2022).Unmixing of REE-Nb enriched carbonatites after incremental fractionation of alkaline magmas in the Shaxiongdong complex, Central China.LITHOS,416,18.
MLA Su, Jian-Hui,et al."Unmixing of REE-Nb enriched carbonatites after incremental fractionation of alkaline magmas in the Shaxiongdong complex, Central China".LITHOS 416(2022):18.

入库方式： OAI收割

来源：地质与地球物理研究所

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