3 research outputs found

    Gold Mineralization at the Maletoyvayam Deposit (Koryak Highland, Russia) and Physicochemical Conditions of Its Formation

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    Microthermometry study of fluid inclusions in quartz veins of the Maletoyvayam deposit (Koryak Highland, Russia) was carried out. This epithermal gold deposit contains unique Au compounds including maletoyvayamite, which has not been reported anywhere else. Two paragenetic mineral associations (pyrite-quartz and maletoyvayamite-quartz) with quartz of different generations corresponding to different pulses were also described. Only early generations of quartz (Q1) include ore minerals: pyrite for the first mineral assemblage, and in Au-bearing minerals, sulfosalts, bismuthinite, and others—for the second assemblage. A study on fluid inclusions in quartz showed a salinity (mainly NaCl + KCl) range from 0.2 to 4.3 wt.% NaCl eq., increasing from the first mineral association to the second due to boiling fluids. The obtained temperature variations for quartz crystallization were 295–135 °C, the fluid pressure ranged from 79 to 4 bar. On the other hand, the range of conditions obtained for the gold productive ore association is more narrow: salinity of the fluid inclusions is 4.3 wt.% NaCl eq., the temperatures vary from 255 °C to 245 °C, and the pressure from 39 to 32 bar. These physicochemical characteristics of the Maletoyvayam ore deposit greatly coincide with other HS-type epithermal deposits; however, within the Central Kamchatka Volcanic Belt it is so far the only deposit of this type reported

    Phase Evolution from Volborthite, Cu3(V2O7)(OH)2·2H2O, upon Heat Treatment

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    In the experiments on volborthite in situ and ex situ heating, analogues of all known natural anhydrous copper vanadates have been obtained: ziesite, pseudolyonsite, mcbirneyite, fingerite, stoiberite and blossite, with the exception of borisenkoite, which requires the presence of As in the V site. The evolution of Cu-V minerals during in situ heating is as follows: volborthite Cu3(V2O7)(OH)2·2H2O (30–230 °C) → X-ray amorphous phase (230–290 °C) → ziesite β-Cu2(V2O7) (290–430 °C) → ziesite + pseudolyonsite α-Cu3(VO4)2 + mcbirneyite β-Cu3(VO4)2 (430–510 °C) → mcbirneyite (510–750 °C). This trend of mineral evolution agrees with the thermal analytical data. These phases also dominate in all experiments with an ex situ annealing. However, the phase compositions of the samples annealed ex situ are more complex: fingerite Cu11(VO4)6O2 occurs in the samples annealed at ~250 and ~480 °C and quickly or slowly cooled to room temperature, and in the sample annealed at ~850 °C with fast cooling. At the same time, blossite and stoiberite have been found in the samples annealed at ~480–780 and ~780–850 °C, respectively, and slowly cooled to room temperature. There is a trend of decreasing crystal structure complexity in the raw phases obtained by the in situ heating with the increasing temperature: volborthite → ziesite → mcbirneyite (except of pseudolyonsite). Another tendency is that the longer the sample is cooled, the more complex the crystal structure that is formed, with the exception of blossite, most probably because blossite and ziesite are polymorphs with identical crystal structure complexities. The high complexity of fingerite and stoiberite, as well as their distinction by Cu:V ratio, may explain the uncertain conditions of their formation

    Phase Evolution from Volborthite, Cu<sub>3</sub>(V<sub>2</sub>O<sub>7</sub>)(OH)<sub>2</sub>·2H<sub>2</sub>O, upon Heat Treatment

    No full text
    In the experiments on volborthite in situ and ex situ heating, analogues of all known natural anhydrous copper vanadates have been obtained: ziesite, pseudolyonsite, mcbirneyite, fingerite, stoiberite and blossite, with the exception of borisenkoite, which requires the presence of As in the V site. The evolution of Cu-V minerals during in situ heating is as follows: volborthite Cu3(V2O7)(OH)2·2H2O (30–230 °C) → X-ray amorphous phase (230–290 °C) → ziesite β-Cu2(V2O7) (290–430 °C) → ziesite + pseudolyonsite α-Cu3(VO4)2 + mcbirneyite β-Cu3(VO4)2 (430–510 °C) → mcbirneyite (510–750 °C). This trend of mineral evolution agrees with the thermal analytical data. These phases also dominate in all experiments with an ex situ annealing. However, the phase compositions of the samples annealed ex situ are more complex: fingerite Cu11(VO4)6O2 occurs in the samples annealed at ~250 and ~480 °C and quickly or slowly cooled to room temperature, and in the sample annealed at ~850 °C with fast cooling. At the same time, blossite and stoiberite have been found in the samples annealed at ~480–780 and ~780–850 °C, respectively, and slowly cooled to room temperature. There is a trend of decreasing crystal structure complexity in the raw phases obtained by the in situ heating with the increasing temperature: volborthite → ziesite → mcbirneyite (except of pseudolyonsite). Another tendency is that the longer the sample is cooled, the more complex the crystal structure that is formed, with the exception of blossite, most probably because blossite and ziesite are polymorphs with identical crystal structure complexities. The high complexity of fingerite and stoiberite, as well as their distinction by Cu:V ratio, may explain the uncertain conditions of their formation
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