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The Late Mesozoic A-type granites are widely distributed along eastern China's Lower Yangtze River Belt (LYRB). Much attention has been paid to this region's adakitic rocks and ore deposits, whereas few studies have examined A-type granites. The largest A-type granitic pluton within the Luzong basin, the Huangmeijian (HMJ) intrusion, is composed of quartz syenite, syenogranite, syenite porphyry, and a minor quartz monzonite. Syenite porphyry in the HMJ is divided into fine-grained syenite porphyry (FSP) and coarse-grained syenite porphyry (CSP) with different grain sizes, but studies on syenite porphyry are sparse. In this study, we reported a detailed study including the in situ U–Pb age and trace-element data, whole-rock major and trace elements, apatite compositions, and Sr-Nd isotopes from the HMJ pluton, with aims to further constraints on the petrogenesis, magmatic sources, and evolution, and tectonic significance of A-type granites in the LYRB. These two syenite porphyries (FSP and CSP) in HMJ intrusion were delineated by zircon U–Pb dating with the ages of 126.4 ± 4.4 Ma and 128.9 ± 0.54 Ma respectively. They have geochemical characteristics similar to those of A-type granites, with high total-alkali (10.5–10.7 wt%), HFSEs (Zr + Nb + Ce + Y = 540.4–949.4 ppm), high Ga/Al ratios (10,000 × Ga/Al = 3.88–4.57), and high whole-rock zircon saturation temperatures (832–906 °C) and high oxygen fugacity, classified as A1 type granite. The slightly enriched Sr-Nd isotope composition (87Sr/86Sr = 0.70428–0.71275, εNd(t) = −3.26 to −5.86) of the HMJ apatite with high F and Cl contents, coupled with trace element features, indicating that syenite porphyry was likely originated from metasomatized mantle-derived magma. In addition, two groups of ancient inherited zircons were observed in the FSP, implying the contribution of the old crystalline basement and Paleozoic materials in the magma source. Moreover, significant hostile Eu, Sr, and Ba anomalies and depletion of Sr and Eu in apatite suggest the fractionation of plagioclase, K-feldspar, apatite, and Fe-Ti oxides are also reflected in their elemental variations. Comprehensive discriminant analysis shows that the HMJ syenite porphyries were derived from the metasomatized mantle-derived magma mixing with ancient crustal components in the Paleo-Pacific plate roll-back and intensive lithospheric extension setting, and followed by fractional crystallization. [Display omitted] • Huangmeijian syenite porphyries were classified as A1-type granite. • Huangmeijian A-type granite is formed by melting of slightly metasomatized lithospheric mantle. • Fractional crystallization plays critical roles in controlling the compositional variation of the Huangmeijian A-type granites. • It is a product of Paleo-Pacific plate roll-back and intensive lithospheric extension setting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The independent selenides coexisting with tellurides and sulfides were discovered for the first time in the Zhaishang gold deposit. • The ore-forming materials leached from the underlying Paleozoic strata, and were affected by Indosinian magmatism. • The mineral paragenetic association shows that the redox conditions have changed from reduction to oxidation during the fluid evolution process. • The sulfur, tellurium and selenium fugacity of hydrothermal fluid of the main metallogenic stage is estimated in this paper. The Zhaishang gold deposit is characterized by Au–Sb–W paragenetic association, hosted in the Middle Devonian strata and Lower Permian strata of the Western Qinling Orogen, Central China; also found in in the mining area is a small carbonatized diorite porphyrite. Besides common sulfides, such as pyrite, arsenopyrite and chalcopyrite, some specific telluride and selenide minerals were found, and especially the first discovery of independent selenides. The assemblage pyrrhotite–arsenianpyrite–arsenopyrite suggests a relatively reducing environment for mineralization during stage II. However, the occurrence of selenides (clausthalite, tiemannite) and sulfates (barite and gypsum) represents a change of redox conditions from reduction to oxidation in stage III. On this basis, combined with the study of fluid inclusions and thermodynamic data, we evaluated the physicochemical conditions of the main metallogenic stages. the sulfur fugacity (log f S 2) did not change significantly from stage II to stage III, the selenium fugacity (log f Se 2) values were constrained to have been ≤ -13.7 in stage II, ranged from −14.8 to −9.8 in stage III, and the tellurium fugacity (log f Te 2) ranged from −14.0 to −11.2 in stage III. Moreover, the He–Ar–Pb isotopic values of sulfides suggest that ore-forming materials were dominantly of stratigraphic source but with important additions of magmatically derived hydrothermal fluid during Indosinian period. Water-rock reaction and ore-forming fluid mixed with magmatically-derived hydrothermal fluid were likely the dominant mechanisms of precipitation. Meanwhile, boiling likely played a certain role in the deposition of selenides and tellurides. [ABSTRACT FROM AUTHOR]

Abstract: Complex petrological, geochemical, and isotope studies of igneous rocks sampled from the core of parametric Maizasskaya BH-1 showed a predominance of dolerite sills, which formed earlier (~263 ± 4 Ma) than most of basalts in the basement of the West Siberian sedimentary basin and in the Siberian Platform traps (248–251 Ma). Their formation took place during the crystallization of basaltic melt in intrusive chambers existing between layers of Silurian sedimentary rocks. The petrochemical, geochemical, mineralogical, and thermobarogeochemical data show that the sills resulted from the activity of complex magmatic systems different from typical oceanic and plateau-basalt melts and related, most likely, to the formation of rift structures under the influence of mantle plume. Study of melt inclusions provided data on the conditions of generation of primary melts from mantle substratum (≤1570 ºC, depths to 105–120 km) and crystallization parameters of dolerites—1130–1155 ºC, 1.5–2 kbar. The results obtained show that the studied basalt complexes in West Siberia are genetically related to the mantle plume activity, which led to the breakup of ancient crust and rifting. Formation of oceanic crust took place in the largest rifts; the ascending magma penetrated into the enclosing ancient strata to form sills. [Copyright &y& Elsevier]

[Display omitted] • Five generation pyrite occur in four stages during its mineralization was identified. • Te is an important scavenger of Au in under the conditions of high Te fugacity. • The Te-Bi minerals vertical distribution shows upper Ag and lower Bi. • Au-Ag-Te-Bi enrichment suggests mantle-derived magmatic of ore-forming fluids/metals. • S and Te fugacity are the factors governing the formation of telluride assemblages. The Laowan Au − Ag − Te deposit (containing greater than 100 t Au), located at the center of the Qinling − Dabie orogenic belt in central China, represents a breakthrough in gold prospecting in the Tongbai district. A tunnel geological survey and microscope-based mineral identification, combined with EMPA/EDS mapping and LA-ICP-MS analysis, were used in this study to determine the mineral types present. The sequence of formation and symbiosis were determined using the Au-hosting mineral geochemical element typomorphism to provide a basis for Au enrichment and the sources of material and ore − forming fluids. The results indicate that: (1) Tellurides were widespread in the main metallogenic auriferous pyrites, consisting of petzite, calaverite, tellurobismuthite, tetradymite, volynskite, and hessite. The vertical zonation of different telluride combinations indicates that mineral distribution shows the vertical zoning characteristics of upper Ag and lower Bi. (2) Petrographic analyses indicate that 5 generations of pyrite formed during the ore-forming stage (Py1, Py2, Py3, Py4, and Py5). LA-ICP-MS analytical data showed that Py3 and Py4 were rich in Au − Ag − Bi − Te, with a correlation between gold and tellurium. Auriferous pyrites were rich in both As and Te, and the enrichment of Au was unrelated to As. Te is an important scavenger of gold, the effect of As is not obvious. (3) From 250 °C to 200 °C, log f Te 2 and log f S 2 decreased from − 13.0 to − 8.3 and − 14.7 to − 8.6 to − 15.2 to − 11.2 and − 16.7 to − 10.5, respectively. f Te 2 , f S 2 and temperature were the conditions controlling variations in the telluride combination. (4) The occurrence of tellurides, the correlation of Au − Ag − Bi − Te elements and enrichment of Te and Bi, combined with previous isotopic geochemical data, indicate that the ore-forming fluids and metals might be stemmed from the mantle-derived magmatic system, which could have provided materials, sufficient heat energy, volatiles, and components for the gold mineralisation. [ABSTRACT FROM AUTHOR]

• Average δ34S‰ of pyrite decreases from stage I (17.5) to stage II (8.7) and III (8.8). • Ore-forming fluids experienced gentle unmixing with similar and near-equilibrium physicochemical conditions. • The decouple of Au and As in pyrite was controlled by chemisorption. • Geochemistry characteristics of fluids varied from early alteration to main mineralizing periods. The microtexture, trace element characteristics and sulfur isotopic features of ore-related minerals provide important clues to trace physico-chemical conditions and source characteristics of ore formation. In this study, we investigate the Wang'ershan gold deposit in the Jiaodong gold province of eastern North China Craton where three hydrothermal stages were distinguished. Stage I is characterized by K-feldspar, sericite, quartz with minor pyrite precipitation (Py-I); sericite, quartz (Qtz-a) and pyrite (Py-II) with minor gold precipitated during stage II; and stage III involved quartz (Qtz-b), gold, and polymetallic sulfides with minor pyrite (Py-III). In situ δ34S results show a decreasing trend from 21.7 to 14.6‰ (Py-I) to 9.2–8.3‰ (Py-II) and 8.9–8.6‰ (Py-III). The Py-II and Py-III are poor in mineral inclusions and porous microtextures, and have no oscillatory composition zoning. The Co content is 1–2 order of magnitudes higher in Py-I (371.2 – 823.2 ppm, av. 597.2 ppm) than late stage pyrites (0.4 – 524.2 ppm, av. 95.4 ppm). Qtz-a show cataclastic breccia cemented by Qtz-b with little dissolution during the injection of stage III ore-forming fluids. The Al contents decrease from Qtz-a (49.0 – 426.6 ppm) to Qtz-b (18.2 – 46.8 ppm). Based on the sulfur isotope, trace element and microtextural characteristics in Py-II and Py-III, combined with previous fluid inclusion studies, we infer that the ore-forming fluids of stage II and III experienced gentle immiscibility and were suggested to be of different evolutionary stages of a single ore-forming fluid sharing common sources with similar and near-equilibrium physicochemical conditions. The trace element characteristics with lack of oscillatory compositional zoning in the two stages of quartz suggest gentle cooling with lack of any abrupt change of physicochemical conditions during fluid immiscibility. The decoupling of Au and As contents in Py-II and Py-III was likely controlled by chemisorption of gold in pyrite structure. Complex variation in geochemical features of ore-forming fluids from early alteration to main mineralization period is indicated by the large range of δ34S and Co contents in Py-I and late stage pyrites, and the differences in alteration processes. Based on a comparison of the Co/Ni, Ni and As among pyrites from the Wang'ershan gold deposit, typical porphyry deposits and orogenic gold deposits, together with the large positive deviation of δ34S relative to mantle values, we propose that ore-forming materials of the Wang'ershan gold deposit were derived from mixed sources involving magmatic hydrothermal-related and sedimentary strata-related components. [ABSTRACT FROM AUTHOR]