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

Published online by Cambridge University Press:  05 July 2018

E.V. Gavrilenko ,
B. Calvo Pérez ,
R. Castroviejo Bolibar  and
D. García del Amo
E.V. Gavrilenko*
Affiliation:
Department of Analytical Sciences, Spain's National Distance Education University (UNED), Senda del Rey 9, 28040, Madrid, Spain Spanish Gemological Institute, Victor Hugo 1, 28004 Madrid, Spain
B. Calvo Pérez
Affiliation:
Madrid School of Mines, Polytechnic University of Madrid, Ríos Rosas 21, 28003, Madrid, Spain
R. Castroviejo Bolibar
Affiliation:
Madrid School of Mines, Polytechnic University of Madrid, Ríos Rosas 21, 28003, Madrid, Spain
D. García del Amo
Affiliation:
Department of Analytical Sciences, Spain's National Distance Education University (UNED), Senda del Rey 9, 28040, Madrid, Spain
*
*E-mail: egavr@ccia.uned.es
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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.

Keywords

emeraldsDelbegeteyKazakhstanfluid inclusionsoxygen isotopes
Type
Research Article
Information
Mineralogical Magazine , Volume 70 , Issue 2 , April 2006 , pp. 159 - 173
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

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