Abstract
The Snezhnoe ruby deposit is located in the Muzkol–Rangkul anticlinorium within the Cimmerian zone of the Central Pamir. On the local scale, the deposit occurs on discrete relict bedding planes of calcitic marbles belonging to the Sarydzhilgin suite. Four ruby-bearing mineral assemblages are present within the main parts of the deposit: (1) scapolite + phlogopite + muscovite + margarite; (2) plagioclase + muscovite + margarite; (3) muscovite + phlogopite + margarite; (4) calcite. The ruby + calcite association is the most economically important, whereas the association of plagioclase + scapolite + phlogopite + muscovite is typical for the ruby-free parts of the deposit. Mica group minerals with a distinctive green color due to enhanced Cr and V concentrations are the main prospecting indicators for the ruby mineralization. The oxygen isotopic composition of the rubies is +15.3‰, a common value for crustal metamorphic and sedimentary rocks. The ratios of indicative trace elements in the rubies are Ga/Mg < 8.2, Fe/Mg < 51.2, Cr/Ga > 6.9 and Fe/Ti < 31.6. These values are characteristic for metamorphic corundum. The bulk ruby-bearing rocks have an initial 87Sr/86Sr ratio of ~0.70791 and εNd of ~−9.6, also pointing to the crustal origin of the deposit in agreement with the geological data. Ancient Al-enriched sediments are suggested to be a possible protolith for the ruby-bearing rocks. The temperature of the metamorphic processes was estimated at 760 ± 30 °C using Zr-in-rutile geothermometry. Raman mapping of rutile inclusions trapped within the ruby crystal indicates that the minimum pressure of mineralization was about one kilobar. The age determined by the Rb–Sr thermal ionization mass spectrometry of phlogopite, plagioclase and bulk rock is 23 ± 1.6 Ma, corresponding to the timing of relaxation after peak metamorphism during the Alpine–Himalayan Orogeny.
Highlights
Corundum (α-Al2 O3 ) is the aluminum end-member of the hematite group of minerals and contains a limited number of transitional elements acting as its chromophores
Corundum (α-Al2O3) is the aluminum end-member of the hematite group of minerals and to high temperature metamorphic and magmatic processes in continent–continent collision zones contains a limited number of transitional elements acting as its chromophores
Minerals were studied in petrographic thin-sections and by X-ray diffraction (XRD), while their studied in petrographic thin-sections and by X-ray diffraction (XRD), while their composition was composition was measured using electron microprobe analysis (EMPA) and laser-ablation inductively measured using electron microprobe analysis (EMPA) and laser-ablation inductively coupled coupled plasma—mass spectrometry (LA–ICP–MS)
Summary
Corundum (α-Al2 O3 ) is the aluminum end-member of the hematite group of minerals and contains a limited number of transitional elements acting as its chromophores. Ruby is assigned to the red-colored corundum variety that is due to the isomorphic substitution of Al3+ by Cr3+. Gem-quality ruby and sapphire (the blue–green–yellow-colored gem varieties of corundum) deposits are rare Minerals. 10, 478 resulting in their high economic value with annual worldwide production exceeding several billion dollars [1].1.The occasional discovery of large-scale commercial ruby deposits is related to the rarity of Introduction geological processes that produce them. Corundum (α-Al2O3) is the aluminum end-member of the hematite group of minerals and to high temperature metamorphic and magmatic processes in continent–continent collision zones contains a limited number of transitional elements acting as its chromophores. Gem-by several ([2,3,4,5,6], etc.), lessred-colored frequently in subduction areas
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