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标题：A perspective view of origins and occurrences of Niobium-Tantalum, Tin and Tungsten mineralisation in Rwanda
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作者：Jean de Dieu Ndikumana ; Franck Wilfried Nguimatsia Dongmo ; Anthony Temidayo Bolarinwa 等
期刊名称：International Research Journal of Earth Sciences
电子版ISSN：2321-2527
出版年度：2018
卷号：6
期号：1
页码：20-29
语种：English
出版社：International Science Community Association
摘要：Rwanda is geologically situated in the Karagwe Ankole Belt, centre east Africa. Karagwe Ankole Belt (KAB) is separated from Kibara Belt (KIB) by a Paleoproterozoic Rusizian terrane and they both form mesoproterozoic orogenic belts of Central Africa. The KAB, which spans Rwanda, Burundi, Southwestern Uganda and Northwestern Tanzania, and the KIB together host a large metallogenic province that is composed of numerous rare -metal ore deposits mineralised in niobium-tantalum(Nb-Ta), tin(Sn) and tungsten(W).The part of the KAB located in Rwanda contains the bulk of cassiterite, columbite-tantalite, and wolframite. These ore minerals have been termed 3Ts and occur in Nb-Ta-Snpegmatites, W-Sn hydrothermal quartz vein deposits and Sn greisens, which are components of one composite metallogenic system related to the granite generation (G4-granite or fertile granite) that occurred at 986±10Ma. The composition of hydrothermal fluid is H2OCO2CH4N2NaCl, and this fluid is characterized by the low to moderate salinity (2.7-14.2 eq. wt.% NaCl), high pressure (~100MPa), and the mesothermal temperature (~300°C). The isotopic composition of the fluids indicated that the mineralised quartz veins are much more likely to be formed from the fluid mainly subjected to metamorphic processes, in equilibrium with magmatic rocks (G4 granite) from which the present precipitated metals were remobilised and got deposited in favoured preferential sites, within metasedimentary rocks, under structural and lithological controls. This paper owes the brief on the current status of views about the mineralisation of 3Ts in Rwanda.
关键词：Karagwe-Ankole belt;Kibara belt;cassiterite;columbite-tantalite;wolframite;Rwanda