Geology,fluid inclusion and stable isotopes (O,S) of the Hetaoping distal skarn Zn-Pb deposit,northern Baoshan block,SW China |
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| Affiliation: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China;2. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, China;3. Wuhan Institute of Geology and Mineral Resources, Wuhan, China;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC3800, Australia;3. Centre for Exploration Targeting, Australian Research Council Centre of Excellence for Core to Crust Fluid Systems (CCFS), School of Earth and Environment, University of Western Australia, Crawley, WA 6009, Australia;4. Geological Survey of Western Australia, East Perth, WA 6004, Australia;5. Mineral Exploration Research Centre, Department of Earth Sciences, Laurentian University, Sudbury, Ontario P3E 2C6, Canada;1. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;2. School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China |
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| Abstract: | The Hetaoping zinc–lead deposit is located in the northern Baoshan block, Sanjiang region, SW China. The ore deposit comprises massive orebodies in the lower part and lenticular and vein-like orebodies in the upper part, both of which are hosted in the marbleized Upper Cambrian limestone and slate of the Hetaoping Formation. Three mineralization stages of Hetaoping skarn system have been recognized based on petrographic observation, which are pre-ore stage (pyroxene–garnet–actinolite–epidote–magnetite), syn-ore stage (sulfides–quartz–calcite–fluorite), and post-ore stage (calcite–quartz–chlorite). Andradite and hedenbergite are dominant in pre-ore garnet and pyroxene, respectively. Ore minerals consist of mainly pyrite, sphalerite, chalcopyrite, bornite and galena. Three types of fluid inclusions have been identified in Hetaoping, including primary two-phase (A type), primary three-phase (B type) and secondary two-phase (C type) inclusions. Based on fluid inclusion microthermometric study, the fluids forming the Hetaoping skarn minerals and sulfides evolved from high-moderate temperature (255–498 °C) and low-moderate salinity (5.0–18.0 wt.% NaCl equiv) in pre-ore stage, through moderate-low temperature (152–325 °C) and low salinity (0.4–14.2 wt.% NaCl equiv) in syn-ore stage, to low temperature (109–205 °C) and low salinity (0.9–10.0 wt.% NaCl equiv) in post-ore stage. The sulfide δ34S values range from 3.7 to 7.1‰ (mean = 5.2‰, n = 29), indicative of a dominantly magmatic sulfur origin. Silicate and carbonate oxygen isotopes give calculated δ18OH2O ranges of 3.9–11.1‰ in prograde stage, − 0.9 to 4.6‰ in early retrograde stage, and − 1.3 to 2.9‰ in late retrograde stage (syn-ore stage), The oxygen isotope data reveal that the prograde fluid in Hetaoping could be primarily magmatic, which has been mixed significantly with meteoric water in the late retrograde stage. Such a fluid mixing process is considered to be a key factor controlling ore precipitation. |
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