Rare Metals Mineralization in the Kilkile Area of Kenticha Greenstone Belt, Adola Area, Southern Ethiopia
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Date
2018-06-06
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Addis Ababa University
Abstract
Rare metal bearing pegmatite of Kilkile contains a number of economically important minerals which attract economic interest by offering rare metals (Ta, Nb, Cs, Li and others), gemstones (emerald, aquamarine, tourmaline, beryl and Others) and industrial mineral (quartz and feldspar). The present study area is located in Adola area, southern part of Kenticha belt (southern part of Ethiopia). The main objective of the study is to evaluate the geology and geochemistry and characterize the rare metal bearing pegmatite of Kilkile area. To achieve the objective, field work and laboratory studies (thin and polished section) and geochemical analysis (ICP-MS and ICP- AES) have been conducted for whole rock and muscovite chemistry. Description of the geological structures and correlation with other rare metal bearing pegmatites have also been conducted for further examination of the genesis of the Kilkile rare metals. Based on field observation the Kilkile area predominantly consists of chromite, amphibolite gneiss and schist, biotite gneiss, serpentinite, chlorite-talc-tremolite schist, granites associated with barren & rare metal bearing pegmatites. Most of the pegmatite bodies of the area are striking nearly N-S direction, not more than a km long and have less than 200m width. Fractionatiion incerases from south to north therefore rare metals like Rb, Li, Ga, Cs, and Ta concentration also increase towards north, while the Nb, Zn and Ba concentration decrease. Highly fractionated Kilkile I pegmatite plots in the zone of Ta-mineralization whereas Kilkile II and III plots in zone of Ta-prospect. REE chondrite normalized diagram shows all sample have enrichment in light rare earth element (LREE) contents relative to heavy rare earth elements (HREE) and shows negative Eu-anomaly. Kilkile rear metal bearing peraluminous granitic pegmatite is formed by partial melting of pre-existing metasedimentary rocks probably during post-Gondwana assembly, followed by hydrothermal-metasomatic enrichment of rare metals deposit. Muscovite chemistry, using Rb versus Tl and Rb versus K/Tl correlations, infers a cogenetic formation of Kilkile (I, II and III), Kenticha, Shuni and Bupo pegmatites and they are derived form same magma source most probably from Kilta Shumbela granite located on South of Kilkile III.
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Pan-African Orogeny, Neoproterozoic, Arabian Nubian Shield, Kilkile Area, Rare-Element Pegmatite, Magmatic Fractionation, Muscovite Chemistry, Ta-Mineralization