Minor elements in quartz from hydrothermal-metamorphic veins in the Nether Polar Ural Province |
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| Authors: | S K Kuznetsov E N Svetova S N Shanina V N Filippov |
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| Institution: | 1. Institute of Geology, Komi Scientific Center, Ural Branch, Russian Academy of Sciences, Pervomaiskaya ul. 54, Syktyvkar, 167982, Komi Republic, Russia
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| Abstract: | Vein quartz from the Nether Polar Ural Province was examined by atomic emission spectrometry, gas chromatography, electron paramagnetic resonance, and electron microscopy. According to atomic emission spectrometric analysis, the total concentration of Al, Fe, Mg, Ti, Ca, Na, K, and other minor elements in the quartz varies from 8 to 47 ppm. The lowest concentrations of minor elements were detected in the granulated quartz. Giant-crystalline milk-white quartz is noted for higher concentrations of minor elements, including Na, K, and Ca, because it contains gas-liquid inclusions. The fine-grained quartz contains very small mineral inclusions and is thus noted for elevated concentrations of Ca, Fe, K, Mg, and Ti. Gas chromatographic data on the gas phase separated from the quartz at its heating indicate that this phase contains H2O, CO2, and other components. The H2O concentration reaches 429 ??g/g, while the CO2 content is commonly no higher than 20 ??g/g. Gas separation is at a maximum at temperatures of 100?C600°C, when gasliquid inclusions decrepitate, as is typical, first of all, of the giant-crystalline milk-white quartz. Gas separation continues at higher temperatures (below 1000°C) but is much less intense. The electron microscopic examination of quartz grains after their acid treatment indicates that the surface of these grains is covered by caverns of various morphology and size, which were produced by the partial dissolution of the quartz and the opening of its gas-liquid and mineral inclusions occurring near the surface; the inclusions were not, however, completely removed. The crystal structure of the quartz contains minor Al, Ge, Na, Li, Ti, and Fe. The lowest concentrations of Al and Ge paramagnetic centers are typical of the granulated (recrystallized) and fine-grained quartz. The giant-crystalline quartz, including its transparent varieties, and individual quartz crystals, first of all their smoky-citrine varieties, contain higher concentrations of minor elements. In the Nether Polar Ural Province, granulated quartz is potentially promising for producing especially pure quartz concentrates. The quality of the translucent coarse-to giant-crystalline quartz, which predominates in the resources and reserves, is deteriorated by gas-liquid inclusions in it and requires deep processing of the raw minerals. |
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