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• The Xiadian ore and alterated rock are enriched in HREE, HFSE and transition elements. • The H-O and He-Ar isotopes are similar to the local enriched mantle-derived fluids. • The Sr-Nd-Pb isotopes suggest deeply sourced fluids interacted with Neoarchaean basement. • The new data do not support fluids and metals direct release from subducted sediments. The Jiaodong Peninsula is the largest gold concentration district in China and the third largest one in the world. It covers no >0.2% of China's total landmass yet accounts for 30% of the total national gold reserves with total proved resources near 5000 t Au. One wonders where all this gold comes from. Here we present detailed whole-rock element and Sr-Nd-Pb isotope, quartz H-O isotope and pyrite He-Ar isotope geochemical data for the Xiadian gold deposit, a large Jiaojia-type gold deposit in the Jiaodong district, which furnishes new constrains on the sources of ore-forming fluids and metals. The results indicate that the ore and alterated rock have much higher HREE (e.g. Yb and Y), HFSE (e.g. Nb, Ta, Zr and Hf) and transition elements (e.g. Sc, Ti, V, Cr, Co and Ni) than the host granites but similar to the lithospheric mantle-derived lamprophyres, suggesting an enriched lithospheric mantle origin. The H-O isotopes (δD V-SMOW = −93.9‰ to −102.3‰, δ18O H2O = −0.2‰ to 1.6‰) of fluid inclusions in quartzs collected from auriferous pyrite–sericite–quartz altered rocks are distinctly different from either primary magmatic water and metamorphic water or meteoric water in the Jiaodong district but similar to the local enriched mantle-derived fluids. The He-Ar isotopes [3He/4/He = 0.58 × 10−6 to 1.90 × 10−6 (0.42–1.36 Ra), 40Ar/36Ar = 725–1358] of fluid inclusions in pyrites collected from auriferous pyrite–sericite–quartz altered rocks are also similar to the local enriched mantle-derived fluids. The ore and alterated rock have distinct Nd-Pb isotopic compositions either from the host Linglong granites or from the asthenosphere-derived mafic dikes but similar to the lithospheric mantle-derived mafic dikes. Their Sr isotopic compositions show a mix trend between the lithospheric mantle-derived mafic dikes and Neoarchaean basement. All the elemental and multiple isotopic features support a metallogenic model that the ore-forming fluids and metals were derived from the local previously enriched lithospheric mantle, and such deeply sourced fluids may have interacted with Neoarchaean basement along their flow path and mixed with a little meteoric water when they arrived high levels in the crust. [ABSTRACT FROM AUTHOR]

• We have identified hydrothermal zircons from the Xiadian gold deposit, Jiaodong. • They show homogeneous low CL-response image and have high U with low Th/U. • Direct LA-ICP-MS U-Pb dating shows the Paleocene gold mineralization. • In-situ Hf isotopes suggest lithospheric mantle-derived ore-forming fluids. The eastern North China Craton is characteristic of Mesozoic cratonic destruction and largescale gold mineralization. Previous geochronological studies by 40Ar–39Ar dating on alteration minerals such as sericite and K-feldspar and Rb–Sr and 40Ar–39Ar dating on quartz and pyrite suggested that the gold mineralization occurred in Early Cretaceous. We have identified hydrothermal zircons from the orebody and alterated rocks in the Xiadian gold deposit, Jiaodong Peninsula. These zircons contain two phase (vapor-liquid) fluid inclusions or enclose hydrothermal alteration minerals such as sericite. They show homogeneous low CL-response image and have high U with low Th/U, and also show enriched and flatter normalized LREE pattern with high La and low (Sm/La) N and Ce/Ce* relative to magmatic zircons. Their petrographical, textural and compositional features strongly suggest that they mainly crystallized from the hydrothermal fluids during the pyrite–sericite–quartz alteration that was closely related to the gold mineralization. Direct LA-ICP-MS U-Pb dating on such hydrothermal zircons indicates that the gold mineralization in the Xiadian deposit mainly occurred during the Paleocene and underwent a prolonged metallogenic process (68.7–56.7 Ma), most likely commenced at the end of Cretaceous and lasted at the end of Paleocene. In-situ Hf isotopic compositions of the hydrothermal and inherited zircons suggest that the ore-forming fluids might have been derived from an enriched lithospheric mantle, followed by interacting with Archean metamorphic basement during ascent. Such a gold mineralization event might have been associated with the early Cenozoic uppermost lithospheric thinning in eastern North China Craton. It has important implications for further understanding the geneses and the geodynamics of gold deposits in the whole eastern North China Craton. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluids from all paragenetic stages show magmatic signatures. • Discrete pulses of magmatic fluids for both prograde and retrograde skarn stages. • Fluid cooling serves as the principal factor for Cu precipitation. • Fluid-rock reaction may exert a secondary influence on sulfide precipitation. Skarn deposits are significant sources of copper, yet there are different understandings on their fluid evolution and precipitation mechanism due to lack of direct constraints on fluid compositions of mineralization process. Here, we present a detailed reconstruction of fluid evolution history from the pre-ore prograde stage through the syn -ore retrograde stage to the post-ore stage of the Chuankeng deposit in the North Wuyi area, South China, based on fluid inclusion microthermometry and LA-ICP-MS analysis of typical minerals from three stages. The pre-ore fluids trapped in pyroxene have higher homogenization temperatures (450–550 ℃), higher salinities (31.9–51.5 wt% NaCl equiv), but lower concentrations of Cu (∼556 ppm) than syn -ore fluids (338–465 ℃, 31.3–38.9 wt% NaCl equiv, ∼3247 ppm Cu). The post-ore fluids show lower temperatures (139-163℃), salinities (1.1–6.5 wt% NaCl equiv), and low concentrations of Cu (<387 ppm). Fluids of all paragenetic stages have high K/Na and Rb/Na ratios, exhibiting signatures of magmatic hydrothermal fluids. Mixing of the magmatic fluids with meteoric waters of lower temperature and salinity occurred at the final post-ore stage, thus it is not related to Cu mineralization. As the temperature descends from 445 ℃ to 340 ℃, the Cu/(Na + K) ratios of syn -ore fluids diminish exponentially, manifesting fluid cooling within a certain temperature may be an important factor controlling Cu mineralization. Concomitantly, a moderate negative correlation between the Ca/(Na + K) ratios and Cu/(Na + K) ratios of syn -ore fluids suggests that fluid-rock interaction do have some impact on copper contents. Additionally, the Cu/(Na + K) ratios of syn -ore fluids in quartz are an order of magnitude higher than those of pre-ore fluids, and it is proposed that during the initial retrograde stage—the onset of mineralization—the magma chamber released fluid pulse with higher copper contents. Based on these findings, the fluids of pre-ore prograde stage and syn -ore retrograde stage are distinct magmatic fluid pulses, and copper-rich fluids, thermal cooling within a specific temperature range and fluid-rock reaction are suggested to be key factors controlling metal enrichment in skarn copper systems. [ABSTRACT FROM AUTHOR]

Abstract: The behavior of boron and its isotopes in fluid-dominant processes and hydrothermal alteration of granites is examined using fresh and altered granite samples from the Qitianling granite and associated hydrothermal tin deposits in South China. Boron concentrations are highest in the fresh granite (37ppm) and depleted as a result of two stages of fluid mobility and fluid–rock interaction within the granite. Constraints provided both by δ 11 B and δ 18 O data suggest that the first stage was related to exsolution of aqueous fluids from the granite magma at a temperature of >450°C. This was followed by further boron depletion in the granite by hydrothermal circulation of meteoric water at lower temperatures (~350°C) and low water/rock ratios. The sensitivity of coupled boron and oxygen isotope systematics to these processes suggests that they can provide valuable constraints on of fluid mobility in granite and associated mineralization. [Copyright &y& Elsevier]