Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups

Hulsbosch, Niels; Hertogen, Jan; Dewaele, Stijn; André, Luc; Muchez, Philippe

doi:10.1016/j.gca.2014.02.006

Cited by 156 publications

(83 citation statements)

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“…In granitic pegmatite fields reported in the literature, e.g. in Cap de Creus (northeastern Spain, Alfonso and Melgarejo, 2008;Druguet et al, 2014;Van Lichtervelde et al, 2016) or in Gatumba (central Rwanda, Hulsbosch et al, 2014;Melcher et al, 2015), the closest bodies from the sources (usually a granite) (i) are the least evolved, and (ii) contain biotite but no muscovite nor rare-element minerals (i.e. Li, B, Be, Rb, Sn, Nb-Ta… e.g.…”

Section: Potential Sources Of the Lree-rich Pgd From The Lac Okaopéo mentioning

confidence: 99%

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Unusual LREE-rich, peraluminous, monazite- or allanite-bearing pegmatitic granite in the central Grenville Province, Québec

Turlin

André-Mayer

Moukhsil³

et al. 2017

Ore Geology Reviews

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International audienceThis contribution presents an original study combining detailed mapping, petrography, whole-rock geochemistry and geochronological constraints on the recently identified LREE (Light Rare Earth Elements) occurrences associated with pegmatitic granite dykes (PGD) from the central Grenville (Lac Okaopéo region). These PGD intrude paragneisses or meta-igneous complexes with a REE mineralization hosted either in monazite-(Ce) or in allanite-(Ce) respectively. The investigated samples display peraluminous signatures and are dominated by a quartz+K-feldspar+plagioclase+biotite+monazite/allanite assemblage. Field relationships and the magmatic textures of the dykes combined with U-Pb dating of magmatic monazite grains at 1005.4±4.4 Ma and 996.7±5.3 Ma (concordant igneous ages) imply that the LREE-rich PGD were emplaced in a post-tectonic setting. Allanite-(Ce) and monazite-(Ce)-bearing PGD have ΣREE contents up to 9242 ppm and 7048 ppm, respectively. The allanite-rich assemblage is consistent with the petrographic assemblage of LREE-enriched PGD identified in the southwestern Grenville Province and elsewhere in the world, but this study constitutes the first evidence for a sole presence of monazite as LREE-bearing phase in strongly peraluminous PGD from the Grenville Province

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Section: Potential Sources Of the Lree-rich Pgd From The Lac Okaopéo mentioning

confidence: 99%

“…Li, B, Be, Rb, Sn, Nb-Ta… e.g. Hulsbosch et al, 2014;London, 2016London, , 2008 or REE mineralization (e.g. Ercit, 2005).…”

Section: Potential Sources Of the Lree-rich Pgd From The Lac Okaopéo mentioning

confidence: 99%

Unusual LREE-rich, peraluminous, monazite- or allanite-bearing pegmatitic granite in the central Grenville Province, Québec

Turlin

André-Mayer

Moukhsil³

et al. 2017

Ore Geology Reviews

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“…The parallel trends followed by the Zr/Hf and Nb/Ta Rayleigh fractionation curves (Fig. 5) are also evidences that CGM and zircon both followed magmatic fractionation trends and therefore crystallized together at the magmatic stage (Hulsbosch et al 2014). …”

Section: Dating Pegmatite Emplacementmentioning

confidence: 63%

U-Pb geochronology on zircon and columbite-group minerals of the Cap de Creus pegmatites, NE Spain

et al. 2016

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Aquesta és una còpia de la versió author's accepted manuscrit d'un article publicat a la revista Mineralogy and petrology Abstract The Cap de Creus granitic pegmatites in the eastern Catalan Pyrenees were dated using in situ U-Pb geochronology by laser ablation ICP-MS on zircon and columbite-group minerals (CGM), which are present in the different types of pegmatites from type I (K-feldspar pegmatites, least evolved) to type IV (albite pegmatites, most evolved) and therefore allow dating the different ManuscriptClick here to download Manuscript publication_text_v9. doc 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 pegmatitic pulses. In a type III pegmatite where zircon and CGM are co-genetically associated in the same sample, both minerals were dated using zircon and tantalite reference materials, respectively, to avoid laser-induced matrix-dependent fractionation. In one sample, xenotime genetically associated with zircon was also dated. Two ages were obtained for type I and three ages for type III pegmatites. Three of these 5 ages range from 296.2 ± 2.5 to 301.9 ± 3.8 Ma and are allocated to the primary magmatic stage of crystallization and therefore to the emplacement event.Two younger ages (290.5 ± 2.5 and 292.9 ± 2.9 Ma) obtained on secondary zircon and xenotime, respectively, are interpreted as late post-solidus hydrothermal remobilization. There is no age difference between type I and type III pegmatites. The mean 299 Ma primary magmatic age allows the main late Carboniferous deformation event to be dated and is also synchronous with other peraluminous and calc-alkaline granites in the Pyrenees. However, the youngest ages around 292Ma imply that tectonics was still active in Early Permian times in the Cap de Creus area. IntroductionThe Cap de Creus peninsula (NE Spain) in the easternmost end of the Pyrenean Axial Zone is a remarkable center of interest for geologists because of its well-exposed outcrops that reveal a complex tectonic, metamorphic and magmatic history. Several episodes of deformation and regional metamorphism are accompanied by calc-alkaline and peraluminous magmatism and affected a late Proterozoic series of metasediments and metavolcanics during the Variscan orogeny. An important group of mineralized granitic pegmatites is associated with these tectonic events.The study of granitic pegmatites in Europe is gaining interest because these highly fractionated rocks are important sources of industrial minerals and strategic metals such as Li and the high field strength elements Nb-Ta and Sn (Linnen et al. 2012). In Europe rare-element granitic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 ...

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“…The most evolved pegmatites belong to the Lithium-Caesium-Tantalum (LCT) family based on the rare element association, and more specifically to the rare element pegmatite class. Based on the rare element mineralogy, they include representatives of the beryl-type (beryl columbite subtype), complex-type (spodumene subtype), and albite-spodumene type [10]. The rare element pegmatite from Gatumba area has attracted different mining companies for exploitation of niobium-tantalum and tin minerals.…”

Section: Geological Settingsmentioning

confidence: 99%

“…Most deposits in Rwanda are not well developed, due to the lack of adequate geologic studies such as in the Gatumba and Gitarama areas. Some information was provided on the geochemistry of pegmatites in the area [10]. The insufficient geologic study and mineralisation relationship have made these areas less attractive to mining investors.…”

Section: Introductionmentioning

confidence: 99%

Neoproterozoic Rare Element Pegmatites from Gitarama and Gatumba Areas, Rwanda: Understanding Their Nb-Ta and Sn Mineralisation

Ndikumana¹,

Bolarinwa²,

Adeyemi³

2019

OJG

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The aim of this work was to study the petrography, geochemistry of the pegmatites, their relationship to the mineralisation in Gitarama and Gatumba areas, and current processes that occurred after the primary emplaced neoproterozoic rare element pegmatites. Previous works on pegmatites were geochemistry and geological maps which are not enough for focused exploration and mine planning. Therefore, geological, petrographic, geochemical studies of neoproterozoic rare element pegmatites of Gatumba and Gitarama areas in relation to their mineralisation were carried out. The samples were analysed for mineral assemblages by petrographic light microscope; major elements by ICP AES; trace and rare earth elements by ICP MS. Petrographic studies revealed the mineral assemblages included quartz, microcline, biotite and major muscovites, which implied that there was the process of muscovitisation occurred after the primary emplacement of pegmatites. The results of geochemical analysis revealed that the silica content (in wt%) ranges from 59.5-80.5 with an average of 67.13 (in wt%) for the weathered pegmatite in Gatumba area ,and high percentages of SiO 2 (in wt%) range 73.9-75.0 with an average of 73.15 (in wt%) for fresh pegmatite in Gitarama area. The pegmatites from Gatumba area were altered and much enriched in Rb (227-3460 ppm), Cs (2.59-24.7 ppm), Ta (2.6-268 ppm), Li (40-9224 ppm), W (240-10,000 ppm), Nb (13-517 ppm), Sn (24-8870 ppm). Their enrichment is commonly used as a marker of a magmatic-hydrothermal alteration. Conversely, the pegmatites from Gitarama area showed the low to moderate concentrations in Rb (321-337 ppm), Cs (5.47-5.62 ppm), Ta (1.3-1.6 ppm), Li (~20 ppm), W (5540-6410 ppm), Nb (3.9-4.3 ppm), Sn (28-44 How to cite this paper: de Dieu Ndiku

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Alkali metal and rare earth element evolution of rock-forming minerals from the Gatumba area pegmatites (Rwanda): Quantitative assessment of crystal-melt fractionation in the regional zonation of pegmatite groups

Cited by 156 publications

References 87 publications

Unusual LREE-rich, peraluminous, monazite- or allanite-bearing pegmatitic granite in the central Grenville Province, Québec

Unusual LREE-rich, peraluminous, monazite- or allanite-bearing pegmatitic granite in the central Grenville Province, Québec

U-Pb geochronology on zircon and columbite-group minerals of the Cap de Creus pegmatites, NE Spain

Neoproterozoic Rare Element Pegmatites from Gitarama and Gatumba Areas, Rwanda: Understanding Their Nb-Ta and Sn Mineralisation

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