scholarly journals Coupled dissolution–precipitation reactions of tennantite-tetrahedrite minerals in the Darasun gold deposit (Eastern Transbaikalia, Russia)

2019 ◽  
Vol 61 (6) ◽  
pp. 38-57
Author(s):  
N. G. Lyubimtseva ◽  
N. S. Bortnikov ◽  
S. E. Borisovsky ◽  
O. V. Vikent’eva ◽  
V. Yu. Prokofiev
Keyword(s):  
Gold Deposit ◽  
Negative Correlation ◽  
Crystallization Temperature ◽  
Miscibility Gap ◽  
Sharp Drop ◽  
Initial Stage ◽  
Eastern Transbaikalia ◽  
Fluid Cooling ◽  
Precipitation Reactions ◽  
Complete Transformation

Heterogeneous rhythmic-zonal aggregates of tennantite-IV replaced partly or completely early homogeneous Zn-tetrahedrite-I and euhedral (Fe-Zn)-tennantite-I crystal were found in ores of the Darasun gold deposit. Different replacement stages of fahlore were observed. It initiates at grain boundaries and is terminated by a complete transformation into pseudomorphic newly formed (Zn-Fe)-tennantite-IV aggregates rimed with Zn-tetrahedrite-IV. These aggregates associated intimately with bournonite and galena and their deposition initiated the pseudomorph formation. EMPA revealed that (Fe-Zn)-tetrahedrite richer in As relative to Zn-tetrahedrite-I was deposited at initial stage. Tennantite with wide variation in Sb/(Sb + As) and Fe/(Fe + Zn) ratios predominantes in heterogenous zonal aggregates of (Fe-Zn)-tetrahedrite-tennantite-IV. A negative correlation between the Sb/(Sb + As) and Fe/(Fe + Zn) was found in these minerals. In each site at the contact between Zn-tetrahedrite-I and newly formed (Fe-Zn)-tetrahedrite-tennantite-IV a miscibility gap between As and Sb a sharp drop in the Sb/(Sb + As) ratio and an increase in Fe/(Fe + Zn) ratio occur. Sharp saw-shape boundaries between Zn-tetrahedrite-I and tennantite-IV and voids in newly formed aggregates are considered to be evidence for couple dissolution-precipitation reactions. The dissolution was initiated due disequilibrium between Zn-tetrahedrite-I and an undersaturated fluid resulted from deposition of galena and bournonite. Precipitation of tetrahedrite-tennantite-IV occurred under oscillation in Sb/(Sb + As) and Fe/(Fe + Zn) ratios due to the metal and semimetal contents in the fluid. Crystallization temperature of zonal-heterogenous tennantite-IV aggregates was calculated by sphalerite-fahlore geothermometer which shows (134161) 20 С. Instability of early Zn-tetrahedrite-I resulted from fluid cooling, decreasing in fluid salinity, changing in tetrahedrite and tennantite solubility due to an evolution of migration conditions of semimetals.

Coupled Dissolution–Precipitation Reactions of Tennantite–Tetrahedrite Minerals in the Darasun Gold Deposit (Eastern Transbaikalia, Russia)

2019 ◽  
Vol 61 (6) ◽  
pp. 530-548
Author(s):  
N. G. Lyubimtseva ◽  
N. S. Bortnikov ◽  
S. E. Borisovsky ◽  
O. V. Vikent’eva ◽  
V. Yu. Prokofiev
Keyword(s):  
Gold Deposit ◽  
Eastern Transbaikalia ◽  
Precipitation Reactions

Fülöppite Pb3Sb8S15 from the Darasun Volcanogenic–Plutonogenic Gold Deposit (Eastern Transbaikalia)

2020 ◽  
Vol 75 (6) ◽  
pp. 616-620
Author(s):  
E. M. Spiridonov ◽  
N. N. Krivitskaya ◽  
I. A. Bryzgalov ◽  
N. N. Korotaeva ◽  
K. N. Kochetova
Keyword(s):  
Gold Deposit ◽  
Eastern Transbaikalia

Disseminated ores of the Darasun gold deposit (Eastern Transbaikalia) and their genesis

2008 ◽  
Vol 422 (1) ◽  
pp. 1025-1027 ◽  
Author(s):  
V. Yu. Prokof’ev ◽  
N. S. Bortnikov ◽  
A. V. Volkov ◽  
I. A. Baksheev ◽  
L. D. Zorina
Keyword(s):  
Gold Deposit ◽  
Eastern Transbaikalia

Metasomatites of the Kara gold deposit (Eastern Transbaikalia)

2007 ◽  
Vol 48 (11) ◽  
pp. 901-912 ◽  
Author(s):  
Z.I. Kulikova ◽  
A.M. Spiridonov ◽  
L.D. Zorina
Keyword(s):  
Gold Deposit ◽  
Eastern Transbaikalia

Evolution of Al2O3 Scale Formed on Ni-Al-Pt Alloy in Atmospheres Containing Water Vapor

2011 ◽  
Vol 696 ◽  
pp. 132-137 ◽  
Author(s):  
Mitsunari Auchi ◽  
Shigenari Hayashi ◽  
Toshio Narita ◽  
Shigeharu Ukai
Keyword(s):  
Water Vapor ◽  
Cyclic Oxidation ◽  
Oxidation Behavior ◽  
Mass Gain ◽  
Oxidation Time ◽  
Dry Air ◽  
Initial Stage ◽  
Oxidation Stage ◽  
Pt Alloy ◽  
Complete Transformation

High temperature cyclic oxidation behavior of γ'-base Ni-25Al-10Pt (in at.%) alloy was investigated at 1000°C in air with and without 30vol.%H2O. The oxidation mass gain during the initial stage of oxidation was similar in both atmospheres, but the oxidation rate in air+H2O was lower in the longer steady-state oxidation stage. Metastable Al2O3, which formed during the initial stage of oxidation, transformed completely after about 100hr of oxidation in dry air. The transformation to α-Al2O3also occurred in air+H2O, but complete transformation to α-Al2O3was not observed during the oxidation time in the present study. θ-Al2O3grains remained for longer on the α-Al2O3layer in air+H2O and became significantly coarser with oxidation time. The present results indicate that water vapor delays the metastable to α-Al2O3phase transformation, and decreases the growth rate of α-Al2O3.

scholarly journals Study of melting and crystallization process of CsPbBr3 by differential thermal analysis

2019 ◽  
pp. 29-34
Author(s):  
A. I. Kanak ◽  
L. M. Kanak ◽  
S. V. Solodin ◽  
O. V. Kopach
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Crystallization Temperature ◽  
Melting Process ◽  
Endothermic Effect ◽  
Quartz Ampoule ◽  
Heating Rates ◽  
X Ray ◽  
Initial Stage ◽  
Melting And Crystallization

The crystalline CsPbBr3 was synthesized from CsBr (6N) and PbBr2 (5N) by the mechanochemical method with further fusion in quartz ampoule at 640-650 °С. After synthesis, the structure and chemical composition of the obtained material was confirmed by energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis. The melting and crystallization of the obtained perovskite were investigated by the differential thermal analysis (DTA) with heating/cooling rates of 1, 5 and 10 °C/min. Measurements were carried on the self-constructed DTA-setup with S-type thermocouples in the range of 450-590 °C. Each cycle of heating/cooling was repeated three times to confirm the accuracy of the results obtained. A decrease in the melting point from ~ 568.1 °C to ~ 566.2 °C was demonstrated with an increase in the heating rate from 1 °C/min. up to 10 °C/min. respectively. Probably, it's due to the approach to equilibrium conditions of phase transformations at lower heating rates. We recorded an additional-endothermic effect during CsPbBr3 melting. This may indicate a complex process of melting the compound. The thesis of a two-stage melting mechanism of CsPbBr3 perovskite with an initial stage of fragmentation of the crystalline structure and subsequent dissolution of crystalline phase residues is proposed. It is reported that with increasing of the melt heating above a certain "critical" temperature (579-585 °C), its homogenization occurs, and the crystallization temperature is set at 540-550 °C for the heating/cooling rate of 1 ° C/min. and 538-543 °C for the rate of 5-10° C/min. All obtained data confirm the assumption of a two-step melting process of CsPbBr3 perovskite, and the relatively constant crystallization temperature after a critical point of overheating may also indicate a certain structure of the melt of the compound with short-range order in the arrangement of the structural units of the compound in the liquid phase.

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