1. The evolution of diamond-forming fluids indicating a pre-kimberlitic metasomatic event in the mantle beneath the Mirny field (Siberian craton)
- Author
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Gubanov, Nikolai V. and Zedgenizov, Dmitry A.
- Subjects
Diamond mining ,Silicates ,Kimberlite ,Diamond crystals ,Cratons ,Diamonds ,Earth -- Mantle ,Earth sciences - Abstract
A suite of coated diamonds from the International'naya (n = 63) and Mir (n = 5) kimberlite pipes (Mirny field, Siberian craton) was studied to track the most recent metasomatic events in the sub-continental lithospheric mantle (SCLM). The diamonds consist of two contrasting domains: an older monocrystalline core, and a younger fibrous coat, the latter of which formed just prior to the kimberlite eruption. Microinclusions in the coats indicate two types of growth media: (i) dominant, silicic to low-Mg carbonatitic high-density fluids (HDFs), and (ii) minor, high-Mg carbonatitic HDFs. Eclogitic mineral inclusions were identified in the cores of the diamonds containing silicic to low-Mg carbonatitic HDFs in the coats, while peridotitic mineral inclusions were found in the cores of the diamonds with high-Mg carbonatitic HDFs in the coats. The chemistry of the high-Mg carbonatitic HDFs suggests that they originated from partial melting of a carbonated peridotite. Major components and trace-element patterns of most silicic to low-Mg carbonatitic HDFs support an eclogitic source with accessory rutile and variable ratios of CO.sub.2/H.sub.2O. In many coats, the HDFs evolve from silicic to more carbonatitic, and rarely from carbonatitic to more silicic. The scenario of both evolutionary trends could have involved the passage of peridotite-derived carbonatitic HDFs into eclogites, which triggered their partial melting, followed by the appearance of immiscible, highly silicic and Ca-rich carbonatitic fluids/melts. The immiscible fluids evolved toward a single-silicate-carbonate melt, whose cooling resulted in the precipitation of silicate minerals., Author(s): Nikolai V. Gubanov [sup.1] [sup.2], Dmitry A. Zedgenizov [sup.1] [sup.2] Author Affiliations: (1) grid.415877.8, 0000 0001 2254 1834, V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the [...]
- Published
- 2023
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