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The Chen'er gold deposit hosted in the Precambrian Taihua Supergroup metamorphic rocks is one of the typical gold deposits in the Xiaoqinling region along the southern margin of the North China Craton. The metallic mineral assemblage in this deposit includes sulfides, tellurides, native gold, electrum, and native bismuth. The telluride minerals are composed of calaverite, petzite, hessite, altaite, joseite; except for hessite and matildite, the other tellurides and native bismuth are first reported in this study. Fluid inclusion studies in the auriferous quartz reveal three types: aqueous, aqueous–carbonic, and carbonic inclusions. The homogenization temperatures range from 184 to 364°C, and salinities are in the range of 1.74‐ to 11.47‐wt.% NaCl equiv. At temperatures of 275°C, the logfTe2 and logfS2 of the fluid are estimated as −16.13 to −8.19 and −12.74 to −4.80, respectively, and at temperatures of 305°C, the pH and logfO2 of the fluid are estimated as 3.61 to 5.69 and −34.31 to −27.81, respectively. It is inferred that Au(HS)2− and Au(HS)0 are the predominant gold‐bearing complexes, and tellurium was transported as Te22−. Based on thermodynamic models of logfO2(g) versus pH, we suggest that the precipitations of native gold and electrum in the early and main mineralization stages are different, with the oxygen and hydrogen isotope values of auriferous quartz suggesting mixing of magmatic water with meteoric water. [ABSTRACT FROM AUTHOR]

• Silver occurs as argentite, pyrargyrite and invisible silver in tetrahedrite. • The ore-forming fluids were mainly of magmatic origin. • Mixing of hydrocarbon and ore-forming fluids resulted in the precipitation of Ag. The recently discovered Erdaokan Ag-Pb-Zn deposit is located in the Duobaoshan gold-copper metallogenic belt in the eastern part of the Central Asian Orogenic Belt. The ore-bodies occur mainly as veins hosted in the breccia. Three stages of mineralization, including early magnetite-quartz-pyrite, middle silver-sulfide-bitumen-quartz and late carbonate stages, were recognized. Here we report results from electron microprobe analysis (EPMA), S-Pb-H-O isotopes and fluid inclusions studies to gain insights into the salient characteristics of the ore mineralization and mechanism of silver precipitation. The silver occurs mainly as argentite, pyrargyrite and invisible silver in the tetrahedrite grains, in which Ag, Fe and As isomorphically substituted Cu, Zn and Sb, respectively. The homogenization temperatures of fluid inclusions in the early, middle and late stage mineralisation range from 96 to 179 °C, 78 to 178 °C, and 98 to 191 °C, respectively. The fluid salinities vary from 0.35 to 5.54 wt.%NaCl equiv. The δ34S values of the pyrite and galena show a range from −0.97‰ to +9.31‰. 206Pb/204Pb vary from 18.0125 to 18.1864, 207Pb/204Pb, from 15.561 to 15.081, and 208Pb/204Pb, from 38.0445 to 37.6979, with a mean of 18.0298, 15.5125 and 37.7281 respectively. The δD and δ18O water values of the quartz from the ore body range from −119.1‰ to −109.7‰ and −4.64‰ to 1.98‰, respectively. Based on these results, we argue that the ore-forming fluids were derived from a magmatic source, with fluid mixing as the dominant mechanism for silver precipitation, involving hydrocarbon fluid interaction as inferred from the presence of bitumen in the ore. [ABSTRACT FROM AUTHOR]

• Fluid mixing might dominantly govern the precipitation and deposition of ore-forming materials. • The Rb-Sr dating of pyrite, calcite and quartz indicate that the deposit was formed at 114.6 ± 1.2 Ma. • There are great prospecting potentials in the deep northwest part of the deposit. The Yongxin gold deposit is one of the prominent gold deposits in the Duobaoshan gold-copper metallogenic belt within the eastern domain of the Central Asian Orogenic Belt. The deposit has recently been discovered therefore, its genesis and economic significance remain unknown. Here, we present the results of pyrite thermoelectricity, fluid inclusion and H-O-Rb-Sr isotopic studies of different minerals with a view to decipher ore genesis and ore prospecting in the Yongxin gold deposit. The Rb-Sr isotopic composition of pyrite, quartz and calcite indicate that the deposit was formed at 114.6 ± 1.2 Ma. Fluid inclusions and H-O isotopic studies show that the Yongxin gold deposit was formed at shallow depth, with relatively low ore-forming temperatures (120–355 °C), low-medium salinity (0 wt% to 10 wt%), and low-moderate density (0.6–1.0 g/cm3). The ore-forming fluids were mainly magmatic which mixed with meteoric water triggering the precipitation of ore-forming materials. We trace the evolution of the ore fluids from deeper levels in the northwest part of the deposit to shallower levels in the southeast. The thermoelectricity parameter values (Xnp) of pyrite range from −188 to −85 and the values of erosional or exhumation level (γ) range from 97% to 71% with an average of 79.4%, suggesting that the existing ore-body is the lower part of the deposit (79.4% of the ore-body has already been eroded). Thermoelectricity of pyrite shows a vertical distribution in the axial direction without significant change in the Xnp values, indicating that the ore body extends further. Combined with the pyrite thermoelectric coefficients in different altitudes, we predict gold potential for the ores at further depth depending on the continued presence of the N-P type pyrite. Our mineralogical mappings also suggest a prospecting potential in the two zones at depth beneath the northwestern part of the deposit. [ABSTRACT FROM AUTHOR]