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Yi-Gang Xu
Yi-Gang Xu
Academician Chinese of Science, Professor
State Key Laboratory of Isotope Geochemistry and CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Science
Academician Chinese of Science, Professor
State Key Laboratory of Isotope Geochemistry and CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Science
Guangzhou
China

Articles

Geology
  • Date submitted
    2022-12-01
  • Date accepted
    2023-01-19
  • Online publication date
    2023-05-18
  • Date published
    2023-12-25

Inclusions of diamond crystals in the tourmaline of the schorl-uvite series: problems of genesis

Article preview

The mineralogical and geochemical features of diamond-bearing tourmaline crystals (schorl-uvite series) from garnet-clinopyroxene rocks of the Kumdy-Kol deposit (Northern Kazakhstan) have been studied in detail. The formation of the main rock-forming minerals (garnet + K-bearing clinopyroxene) occurred in the diamond stability field at 4-6 GPa and 950-1000 °C. Crystallization of K-bearing clinopyroxene at these parameters is possible in the presence of an ultra-potassic fluid or melt formed because of crustal material melting in subduction zones. Tourmaline crystals (up to 1 cm) containing diamond inclusions perform veins crosscutting high-pressure associations. The composition of individual zones varies from schorl to uvite within both a single grain and the sample as a whole. The potassium content in this tourmaline does not exceed 0.1 wt.% K2O, and the isotopic composition of boron δ11B varies from –10 to –15.5 ‰, which significantly differs from the previously established isotopic composition of boron in maruyamaite crystals (δ11B 7.7 ‰ in the core and –1.2 ‰ in the rim) of the same deposit. Analysis of the obtained data on δ11B in the tourmalines from the diamond-grade metamorphic rocks within the Kumdy-Kol deposit suggests the existence of two boron sources that resulted in crystallization of K-bearing tourmaline crystals (maruyamaite-dravite series) and potassium-free tourmalines of the schorl-uvite series.

How to cite: Korsakov A.V., Mikhailenko D.S., Zhang L., Xu Y.-G. Inclusions of diamond crystals in the tourmaline of the schorl-uvite series: problems of genesis // Journal of Mining Institute. 2023. Vol. 264. p. 833-841. EDN UMQOXK