REE-Nb MINERALIZATION IN TRACHYTES AND RHYOLITES OF THE KHULAM VOLCANO-PLUTONIC COMPLEX, NORTH CAUCASUS
The paper presents the first data on the composition of REE and Nb mineralization in the Middle Jurassic moderately alkaline felsic and moderately acid rocks of the Khulam volcano-plutonic complex at the territory of Kabardino-Balkaria, central part of Northern Caucasus. The igneous rocks of the Khu...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
South Urals Federal Research Center of Mineralogy and Geoecology UB RAS
2021-12-01
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| Series: | Минералогия |
| Subjects: | |
| Online Access: | https://journal.mineralogy.ru/wp-content/uploads/2021/12/2021_7_4_2.pdf |
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| Summary: | The paper presents the first data on the composition of REE and Nb mineralization in the Middle Jurassic moderately alkaline felsic and moderately acid rocks of the Khulam volcano-plutonic complex at the territory of Kabardino-Balkaria, central part of Northern Caucasus. The igneous rocks of the Khulam Complex (intrusive and subvolcanic facies) belong to the contrasting differentiated bimodal association: (gabbro + basaltic trachyandesite) – (trachyte + rhyolite). Their main petrological and geochemical characteristics and ore mineralization are discussed. The trachytes and rhyolites of the Khulam Complex exhibit the high contents of Zr (up to 3100 ppm), Nb (up to 400 ppm), and ΣREE (>1000 ppm), which are caused by specific process of fractional crystallization of magmatic melts of elevated alkalinity during the formation of acid and moderately acid rocks. The Nb mineralization includes ilmenorutile and Nb-bearing brookite; REE minerals are monazite-(Ce), REE-bearing fluorapatite and REE fluorocarbonates of the bastnasite–vaterite homologous series. Monazite has magmatic origin and its formation is related to the enrichment of residual magmas in incompatible elements during fractional crystallization. The fluorocarbonates and ilmenorutile formed later as a result of autometamorphism and low-temperature hydrothermal alteration of felsic rocks. |
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| ISSN: | 2313-545X 2782-2044 |