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The Baiyun gold deposit is a medium-sized deposit in northeastern Hubei around the southern margin of the Tongbai-Dabie metallogenic belt. However, its genesis has not been determined. The metallogenic process of the Baiyun gold deposit can be divided into three stages: quartz + feldspar, quartz + native gold + electrum + polymetallic sulfides, and quartz + pyrite + calcite + iron dolomite + illite. In this study, LA-ICP-MS was used for in situ trace element and isotope analyses in the main and late ore stage hydrothermal sulfides to evaluate the genesis and evolution of ore-forming fluids. Gold is positively correlated with Ag, Cu, Pb, Zn, and Te and the Co/Ni ratio is greater than 1. The S isotope values of Py1 and Py2 are −0.23–3.04‰ and 1.27–6.09‰, respectively. As mineralization progressed, S isotope values increased. In situ S isotope values of the two types of galena symbiotic with pyrite in the main metallogenic stage are 2.97–3.47‰. In situ Fe isotopic values of pyrite are −0.05–0.82‰; values in the two stages are similar without significant fractionation. We inferred that the Baiyun gold deposit formed via magmatic mineralization related to the subduction of the Pacific Plate during the Yanshanian. [ABSTRACT FROM AUTHOR]

The Baiyun gold deposit is a medium-sized deposit in northeastern Hubei around the southern margin of the Tongbai-Dabie metallogenic belt. However, its genesis has not been determined. The metallogenic process of the Baiyun gold deposit can be divided into three stages: quartz + feldspar, quartz + native gold + electrum + polymetallic sulfides, and quartz + pyrite + calcite + iron dolomite + illite. In this study, LA-ICP-MS was used for in situ trace element and isotope analyses in the main and late ore stage hydrothermal sulfides to evaluate the genesis and evolution of ore-forming fluids. Gold is positively correlated with Ag, Cu, Pb, Zn, and Te and the Co/Ni ratio is greater than 1. The S isotope values of Py1 and Py2 are −0.23–3.04‰ and 1.27–6.09‰, respectively. As mineralization progressed, S isotope values increased. In situ S isotope values of the two types of galena symbiotic with pyrite in the main metallogenic stage are 2.97–3.47‰. In situ Fe isotopic values of pyrite are −0.05–0.82‰; values in the two stages are similar without significant fractionation. We inferred that the Baiyun gold deposit formed via magmatic mineralization related to the subduction of the Pacific Plate during the Yanshanian.

The Huaishuping gold deposit is located in the Xiong'ershan Mountains of the Qinling-Dabie Orogen of central China. The mineralisation is structurally controlled and hosted by faulted rhyolite, quartz andesite, volcaniclastic rocks and volcanic breccia assigned to the Jidanping Formation towards the top the Palaeoproterozoic Xiong'er Group. The deposit has a resource of around 32 t with an average grade of 5.5 g/t Au. Alteration at the deposit progressed from an early K-feldspar–quartz–pyrite assemblage through quartz–pyrite–gold, quartz–base-metal sulfides, to a late-stage assemblage of quartz–carbonate. The δ34S (V-CDT) values for pyrite in the ore range from − 13.3 to + 1.6‰. The calcite has C-isotopes ranging from − 6.1 to + 2.5‰ (V-PDB) and O-isotopes from + 10.6 to + 15.8‰ (V-SMOW). The δ18O quartz ranges from 10.5 to 15.1‰, and the δD values for fluid inclusions in quartz range from − 93 to − 76‰. The δ56Fe value for the mineralisation varies between 0.1 and 0.5‰ with corresponding δ57Fe values between 0.2 and 0.7‰. The isotope systematics indicates that the hydrothermal fluids were derived from metamorphic fluid, but the source of gold remains uncertain. Re–Os dating of molybdenite yields a date of 202 ± 8 Ma interpreted as the age of the gold mineralisation. This age is consistent with the Triassic onset of extensional tectonics following the collision between North and South China. [ABSTRACT FROM AUTHOR]

There are a wide range of magmatism and mineralization in the Yunkai area of South China during the Late Yanshanian Period, including the newly discovered Michang, Youmapo, Sanchachong and Songwang porphyry-skarn W-Mo deposits. In this study, we obtained zircon U-Pb ages of the ore-bearing biotite granites and their mafic enclaves from 88±1 to 110±1 Ma. Zircons from the granites show Hf isotopic compositions with negative εHf(t) values of -5.9 to -0.6 and calculated Hf model ages (TDM2) of 1.5-1.2 Ga; indicating that the Middle Proterozoic crustal materials may have provided an important source for the magmatic rocks in this district during the Late Yanshanian Period, whereas zircons from the mafic enclaves show positive εHf(t) values of 1.3 to 10.1 with younger Hf model ages (TDM2) of 0.5-1.1 Ga, suggesting a mantle component may have involved in the granitic magma generation. Sulfur isotope study of the sulfide minerals from the W-Mo deposits show a narrow δ34S distribution with most data ranging from -4.2‰ to 5.2‰. In addition, this study reports the first Fe isotopic compositions of pyrite in the W-Mo deposits, which show a uniform distribution range with the values near zero (δ56Fe=0.16‰-0.58‰, average 0.35‰; δ57Fe=0.02‰-0.54‰, average 0.48‰). These data indicate that the ore-forming materials may come from the deep-sourced granitic magma, and the mineralizations show a close relationship with the granitic magmatism during the Late Yanshanian Period. Combining with previous results, we suggest that there is a widespread porphyry-skarn W-Mo mineralization in the Yunkai area during the Late Cretaceous (80-110 Ma), which has a close relationship with the Late Yanshanian magmatism that may have formed during the rollback of the subducted Pacific Plate. [ABSTRACT FROM AUTHOR]

[Display omitted] • δ34S change is related to f O 2 decrease and sediment addition. • There are two S-Fe sources, one is alkaline magma, the other is 56Fe or 32S-rich sediment. Carbonatite-related rare earth element (REE) deposits are the most significant source of REEs worldwide. The processes of REE precipitation, enrichment, and mineralization remain controversial. The Cenozoic Mianning–Dechang (MD) REE belt, located in Sichuan Province, southwestern China, comprises one giant (Maoniuping), one large (Dalucao), and two small–medium (Muluozhai and Lizhuang) deposits. These deposits provide a continuous record of fluid evolution, and thus are ideal for investigating the processes of REE mineralization in carbonatite-related REE deposits. Given that sulfate (i.e., barite and celestite) and sulfide (i.e., pyrite and galena) minerals crystallized and precipitated in the pegmatitic to hydrothermal stages, respectively, the REE minerals formed later than the sulfate minerals. However, the formation sequence of the sulfide minerals and bastnäsite is unclear, although both pyrite and bastnäsite formed in the late hydrothermal stage. We used S isotope data for sulfate and sulfide minerals and Fe isotope data for pyrite to investigate the composition and evolution of ore-forming fluids during the magmatic–hydrothermal stages. The sulfate minerals have positive δ34S CDT values (+3.2‰ to +8.3‰), and the sulfide minerals have negative δ34S CDT values (−13.5‰ to − 5.6‰) in the four REE deposits. In the Maoniuping deposit, δ34S CDT values for barite from the pegmatitic stage (+4.7‰ to +5.7‰) are higher than for barite from the hydrothermal stage (+4.1‰ to +4.5‰), which indicate that hydrothermal activity led to relative enrichment in isotopically light S. The δ34S CDT values for barite (+3.2‰ to +5.5‰) are lower than for celestite (+6.2‰ to +7.2‰) from the pegmatitic stage in the Dalucao deposit. The δ34S CDT values for galena (−13.5‰) are also lower than for pyrite (−13.5‰ to −7.2‰) from the hydrothermal stage in the Guangtoushan section. In general, δ34S CDT values change from positive to negative values (+8.3‰ to −16.4‰) as the fluids evolved from the pegmatitic to hydrothermal stages, which can be attributed to a decrease in oxygen fugacity (f O 2) and addition of sediment containing isotopically light S. Iron isotopic compositions of pyrite from the hydrothermal stage show significant variations (δ56Fe IRMM-014 = −0.03‰ to +0.65‰ for the Maoniuping deposit; −0.14‰ to 0.00‰ for the Dalucao deposit; +0.05‰ to +0.35‰ for the Lizhuang deposit), and are higher than those for the carbonatites (δ56Fe IRMM-014 = −0.47‰ to −0.17‰). These data indicate there are two sources of Fe in the MD REE belt, which are the carbonatite–nordmarkite magma and 56Fe-rich sediment. Paleozoic–Mesozoic volcanic–sedimentary and Mesozoic clastic and carbonate rocks are exposed in the MD REE belt. In general, the S–Fe isotope data, along with geological and petrographic observations, indicate that the REE minerals formed later than the sulfate minerals, and the S–Fe were derived from both carbonatite magma and sediment containing isotopically light S and heavy Fe. [ABSTRACT FROM AUTHOR]