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Emeralds from the Delbegetey deposit (Kazakhstan): mineralogical characteristics and fluid-inclusion study

  • E.V. Gavrilenko (a1) (a2), B. Calvo Pérez (a3), R. Castroviejo Bolibar (a3) and D. García del Amo (a1)

Abstract

The aim of this study is to provide the first detailed mineralogical and fluid-inclusion description of emeralds from the Delbegetey deposit (Kazakhstan). The characteristic features of Delbegetey emeralds are established: they have dissolution figures on crystal faces, bluish colour and distinct colour zoning; the refractive indices are ω = 1.566–1.570, ε = 1.558–1.562, and the specific gravity is 2.65±0.005, relatively low for natural emeralds; they have very small concentrations of the impurities (Fe, Mg, Na and others) typical of other emeralds, and contain Cr and V; there is a significant preponderance of vapour in fluid inclusions of all types and there is liquid-to-vapour homogenization of primary fluid inclusions (at 395–420°C). The lattice oxygen isotope composition data obtained (δ18O SMOW value of 11.3%o) situate the deposit within the range characteristic of other granite-related emerald deposits. Emerald crystallization took place in low-density (0.40–0.55 g/cm3) aqueous fluid, with the following chemical composition (mol.%): 75.6-97.4 H2O, 0.0-18.4 CO2, 0.0-0.9 CH4, and 4.06-9.65 wt.% NaCl equiv. salinity. According to the calculated isochores, the pressure of formation of the Delbegetey emeralds can be estimated at 570–1240 bar.

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Keywords

Emeralds from the Delbegetey deposit (Kazakhstan): mineralogical characteristics and fluid-inclusion study

  • E.V. Gavrilenko (a1) (a2), B. Calvo Pérez (a3), R. Castroviejo Bolibar (a3) and D. García del Amo (a1)

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