DOI: 10.1016/j.earscirev.2020.103115
论文题名: 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
作者: Ballouard C. ; Massuyeau M. ; Elburg M.A. ; Tappe S. ; Viljoen F. ; Brandenburg J.-T.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2020
卷: 203 语种: 英语
中文关键词: 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
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. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165998
Appears in Collections: 气候变化与战略
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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
Recommended Citation:
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]. Earth Science Reviews,2020-01-01,203