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DOI	10.1016/j.earscirev.2020.103115
	The magmatic and magmatic-hydrothermal evolution of felsic igneous rocks as seen through Nb-Ta geochemical fractionation, with implications for the origins of rare-metal mineralizations
	Ballouard C.; Massuyeau M.; Elburg M.A.; Tappe S.; Viljoen F.; Brandenburg J.-T.
发表日期	2020
ISSN	00128252
卷号	203
英文摘要	Despite Nb and Ta being considered as ‘geochemical twins’, most Ta mineral deposits are associated with muscovite-bearing peraluminous granites and related pegmatites (MPG), whereas significant Nb deposits are related to peralkaline to metaluminous A1-type granites and syenites as well as nepheline syenites. Metaluminous to peraluminous A2-type granites and syenites have a lower potential for rare-metal mineralization. The Nb/Ta ratios are highly variable within each type of rare-metal-enriched felsic igneous suite and causes of the Nb-Ta geochemical fractionation remain poorly understood. Our compilation of whole-rock geochemical data indicates that Nb/Ta ratios generally anticorrelate with Ta, and at given Ta contents the Nb/Ta ratios increase from MPG through A2-type to A1-type igneous suites. However, the Nb-Ta compositions of A1-type and silica-undersaturated felsic magmatic rocks are indistinguishable. New regression models to estimate the mineral/melt partition coefficients DNb and DTa indicate that fractional crystallization of biotite and ilmenite significantly decreases Nb/Ta, but an extreme degree of fractional crystallization is needed to explain the observed range of Nb-Ta variations in rare-metal-enriched igneous suites. Importantly, metasomatic rocks formed by the alteration of igneous suites and their country-rocks are commonly highly enriched in Ta and Nb. Their low Nb/Ta ratios suggest that magmatic-hydrothermal processes involving fluids and hydrosaline melts also play a critical role in Nb-Ta geochemical fractionation and HFSE enrichment in general. We show that the Nb-Ta compositions of the primitive end-members of rare-metal-enriched felsic igneous suites fingerprint the nature and evolution of their sources including metasomatic processes in the Earth's crust and upper mantle. © 2020 Elsevier B.V.
关键词	A-type and peraluminous granites Fractional crystallization Magmatic-hydrothermal transition Mineral/melt partition coefficients Niobium and tantalum Peralkaline complexes
英文关键词	A-type rock; felsic rock; fractional crystallization; igneous geochemistry; magmatism; melt; mineral; mineralization; niobium; partition coefficient; peralkaline rock; tantalum
语种	英语
来源期刊	Earth Science Reviews
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203628
作者单位	Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park, 2006, South Africa; Sydney Brenner Institute for Molecular Bioscience, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
推荐引用方式 GB/T 7714	Ballouard C.,Massuyeau M.,Elburg M.A.,et al. The magmatic and magmatic-hydrothermal evolution of felsic igneous rocks as seen through Nb-Ta geochemical fractionation, with implications for the origins of rare-metal mineralizations[J],2020,203.
APA	Ballouard C.,Massuyeau M.,Elburg M.A.,Tappe S.,Viljoen F.,&Brandenburg J.-T..(2020).The magmatic and magmatic-hydrothermal evolution of felsic igneous rocks as seen through Nb-Ta geochemical fractionation, with implications for the origins of rare-metal mineralizations.Earth Science Reviews,203.
MLA	Ballouard C.,et al."The magmatic and magmatic-hydrothermal evolution of felsic igneous rocks as seen through Nb-Ta geochemical fractionation, with implications for the origins of rare-metal mineralizations".Earth Science Reviews 203(2020).