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[Display omitted] • Porphyry- and epithermal-style mineralization is associated with ∼ 130 Ma magma event. • The mineralizing fluids were predominantly magmatic water with addition of meteoric water. • Metal deposition resulted from cooling, sulfidation, neutralization, and boiling of fluids. The Naozhi deposit in the Yanbian district of northeastern China contains polymetallic epithermal veins and subeconomic porphyry-style Cu mineralization within 2 km of each other. These two mineralization styles are genetically associated with 130–126 Ma andesites and dioritic–granitic intrusions. Isotopic ages determined on sericite (128.2 ± 2.9 Ma; 40Ar–39Ar plateau age) and sulfide (124.6 ± 2.7 Ma; Rb–Sr isochron) associated with the epithermal mineralization constrain the hydrothermal activity to at approximately 128 Ma. Three types of fluid inclusions, including halite-bearing, vapor-rich, and liquid-rich inclusions were trapped in quartz from porphyry-style veinlets associated with an assemblage of K-feldspar–biotite–magnetite. Based on microthermometry and the homogenization behavior of halite-bearing inclusions, they were trapped at lithostatic pressures of > 500 bars and at temperatures of ≥ 350 °C, whereas the vapor- and liquid-rich inclusions were trapped at pressures and temperatures of 110 ± 35 bars and ≤ 350 °C. Epithermal mineralization comprises four vein stages, which, from oldest to youngest, are quartz–pyrite, quartz–base metal sulfide, quartz–precious metal, and quartz–carbonate. The ore assemblage precipitated from low-salinity fluids (<10 wt% NaCl equiv.) at temperatures and pressures of ≤ 350 °C and ≤ 100 bars. The δ18O H2O (2.5 to −2.4 ‰) and δD H2O (−85 to −114 ‰) compositions of fluids related to porphyry- and epithermal-style mineralization indicate a mixture of magmatic and meteoric waters. The δ34S H2S (−3.1 to 4.5 ‰) values of fluids become isotopically heavier from the quartz–pyrite stage to the quartz–base metal sulfide stage, reflecting continuous reduction during epithermal mineralization. The mineral assemblage and chemical composition of sulfide minerals indicate a transition from oxidizing, high sulfidation porphyry-style fluids to reducing, intermediate–low sulfidation epithermal fluids, with log ƒO 2 values ranging from −31 to > −33, and log ƒS 2 values ranging from −7.0 to ≤ −13.4 during the epithermal veining stage. Metal deposition in the Naozhi magmatic–hydrothermal system resulted from cooling, sulfidation, neutralization, and boiling of predominantly magmatically sourced hydrothermal fluids that mixed with meteoric water. [ABSTRACT FROM AUTHOR]

The Talate ore field is located in the Abagong polymetallic metallogenic belt of the Altay Orogen, NW China. Lenticular ore bodies occur in the Kangbutiebao Formation, a package of intermediate-felsic marine volcanic rocks and terrigenous clastic sedimentary-carbonate rocks. Skarn alteration (mainly garnet) is present in both ore and wall rocks, especially the carbonate rocks. The mineral assemblages and cross-cutting relationships of veins allow the alteration and mineralization process to be divided into four stages. From early to late, these are the early skarn (E-skarn), the late skarn with quartz-magnetite veins (QM), the quartz-sulphide (QS) and the quartz-carbonate (QC) assemblages. Quartz crystals are important gangue minerals in the latter three stages, in which four distinct compositions of fluid inclusions are identified based on petrography, microthermometry and laser Raman microspectroscopy, namely aqueous inclusions (W-type), pure CO2 inclusions (PC-type), CO2-rich inclusions (C-type) and daughter mineral-bearing inclusions (S-type). Microthermometric data and laser Raman analyses show that the quartz crystals from the QM stage contain all four inclusion types, with the W-type being predominant. Homogenization temperatures range between 271 and 426 °C. The salinities of the W- and C-type fluid inclusions range from 0.5 to 22.4 wt.% NaCl eqv., whereas the S-type fluid inclusions in the QM stage range from 31 to 41 wt.% NaCl eqv. Daughter minerals in the fluid inclusions include halite, sylvite, pyrite and calcite. Quartz from the QS stage (main mineralization stage) contains the W-, C- and PC-type inclusions, which are homogenized at temperatures of 204-269 °C, with salinities of 0.2-15.6 wt.% NaCl eqv. Only W-type fluid inclusions have been identified in the QC stage. These yielded homogenizing temperatures of 175-211 °C and salinities of 1.1-9.9 wt.% NaCl eqv. The C-type fluid inclusions of the main (QS) mineralization stage yield trapping pressures of 107-171 MPa, corresponding to a depth of 4-6 km. The sulphur isotope values (−1.7‰ and −6.6‰) imply that the QS stage may not be directly associated with the early skarn (−7.4‰) and quartz-magnetite stages (−4.8‰ and −5.0‰), though the QS stage is probably dominated by magmatic-hydrothermal fluids. 40Ar/39Ar isotope plateau ages of 227.6 and 214.1 Ma for biotite separated from the QM and QS stages are significantly younger than the host Kangbutiebao Formation ( ca. 410 Ma). The Talate Pb-Zn(-Fe) deposit is interpreted to be an unusual skarn-type system formed in a continental collision orogeny. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The origin of stratabound deposits in the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYRB), Eastern China, is the subject of considerable debate. The Xinqiao Cu-Fe-Au deposit in the Tongling ore district is a typical stratabound ore body characterized by multi-stage magnetite. A total of six generations of magnetite have been identified. Mt1 is commonly replaced by porous Mt2, and both are commonly trapped in the core of Mt3, which is characterized by both core-rim textures and oscillatory zoning. Porous Mt4 commonly truncates the oscillatory zoning of Mt3, and Mt5 is characterized by 120° triple junction texture. Mt1 to Mt5 are commonly replaced by pyrite that coexists with quartz, whereas Mt6, with a fine-grained foliated and needle-like texture, commonly cuts the early pyrite as veins and is replaced by pyrite that coexists with calcite. The geochemistry of the magnetite suggests that they are hydrothermal in origin. The microporosity of Mt2 and Mt4 magnetite, their sharp contacts with Mt1 and Mt3, and lower trace-element contents (e.g., Si, Ca, Mg, and Ti) than Mt1 and Mt3 suggest that they formed via coupled dissolution and reprecipitation of the precursor Mt1 and Mt3 magnetite, respectively. This was likely caused by high-salinity fluids derived from intensive waterrock interaction between the magmatic-hydrothermal fluids associated with the Jitou stock and Late Permian metalliferous black shales. The 120° triple junction texture of Mt5 suggests it is the result of fluid-assisted recrystallization, whereas Mt6 formed by replacement of hematite as a result of fracturing. The geochemistry of the magnetite suggests that the temperature increased from Mt2 to Mt3 and implies that there were multiple pulses of fluids from a magmatic-hydrothermal system. Therefore, we propose that the Xinqiao stratiform mineralization was genetically associated with multiple influxes of magmatic hydrothermal fluids derived from the Early Cretaceous Jitou stock. This study demonstrates that detailed texture examination and in situ trace-elements analysis under robust geological and petrographic frameworks can effectively constrain the mineralization processes and ore genesis. [ABSTRACT FROM AUTHOR]

The Zhuangzi Au deposit in the world-class Jiaodong gold province hosts visible natural gold, and pyrite as the main ore mineral, making it an excellent subject for deciphering the complex hydrothermal processes and mechanisms of gold precipitation. Three types of zoned pyrite crystals were distinguished based on textural and geochemical results from EPMA, SIMS sulfur isotopic analyses and NanoSIMS mapping. Py0 has irregular shapes and abundant silicate inclusions and was contemporaneous with the earliest pyrite-sericite-quartz alteration. It has low concentrations of As (0-0.3 wt.%), Au and Cu. Py1 precipitated with stage I mineralization shows oscillatory zoning with the bright bands having high As (0.4-3.9 wt.%), Au and Cu contents, whereas the dark bands have low contents of As (0-0.4 wt.%), Au and Cu. The oscillatory zoning represents pressure fluctuations and repeated local fluid phase separation around the pyrite crystal. The concentration of invisible gold in Py1 is directly proportional to the arsenic concentration. Py1 is partially replaced by Py2 which occurs with arsenopyrite, chalcopyrite and native gold in stage II. The replacement was likely the result of pseudomorphic dissolution-reprecipitation triggered by a new pulse of Au-rich hydrothermal fluids. The δ34S values for the three types of pyrite are broadly similar ranging from + 7.1 to + 8.8‰, suggesting a common sulfur source. Fluid inclusion microthermometry suggests that extensive phase separation was responsible for the gold deposition during stage II mineralization. Uranium-Pb dating of monazite constrains the age of mineralization to ca. 119 Ma coincident with a short compressional event around 120 Ma linked to an abrupt change in the drift direction of the subducting Pacific plate. [ABSTRACT FROM AUTHOR]