http://www.sciencedirect.com/science/article/pii/S1674987111000806 |
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Authors: | Vsevolod Prokofiev Ivan Baksheev Lidiya Zorina Boris Belyatsky Vladimir Ustinov Nadezhda Krivitskaya |
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Institution: | 1. Institute of Geology of Ore Deposits, Petrography, Mineralogy & Geochemistry, Russian Academy of Sciences, Moscow, Russia;Lomonosov Moscow State University, Moscow, Russia 2. Lomonosov Moscow State University, Moscow, Russia 3. Vinogradov Institute of Geochemistry, Irkutsk, Russia 4. Institute of Precambrian Geology and Geochronology, RAS, Saint-Petersburg, Russia 5. Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, Moscow, Russia |
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Abstract: | Zoned tourmaline (schorl-dravite) in the matrix of hydrothermal explosive breccia and ore
veins in gold deposits, Chita region, Eastern Transbaikalia, Russia, are associated with Na- and K-rich
porphyry-type subvolcanic intrusives. d18O values of tourmaline from three gold deposits (Darasun,
Talatui, Teremkinskoye) are t8.3&, t7.6&, and t6.0& and calculated d18O values of fluids responsible
for the tourmalinization are t7.3&, t7.7&, and t4.2&, respectively. These data imply an igneous
fluid source, except at the Teremkin deposit where mixing with meteoric water is indicated. Wide ranges
of Fe3t
/Fetot and the presence of vacancies characterize the Darasun deposit tourmaline indicating wide
ranges of f (O2) and pH of mineralizing fluids. Initial stage tourmalines from the gold deposits of the
Darasun ore district are dravite or high mg schorl. Second stage tourmaline is characterized by oscillatory
zoning but with Fe generally increasing towards crystal rims indicating decreasing temperature. Third stage tourmaline formed unzoned crystals with xMg (mole fraction of Mg) close to that of the first stage
tourmaline, due to a close association with pyrite and arsenopyrite. From Fe3t/Fetot values, chemical composition
and crystallization temperatures, logf(O2) of mineralizing fluids ranged from ca. 25 to 20,
much higher than for the gold-bearing beresiteelistvenite association, indicating that tourmalinization
was not related to gold mineralization. |
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Keywords: | Tourmaline composition Fluid inclusions Oxygen isotopes Gold deposits Transbaikalia Russia |
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