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Guiyang, China

Cheng Y.-S.,Central South University | Cheng Y.-S.,Chinese Academy science | Hu R.-Z.,Chinese Academy science
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

In order to discuss the ore-forming material source and its characteristics, lead isotope composition and its tectonic setting were analyzed. The results indicate that the w(206Pb)/w(204Pb) of sulfide ores range from 17.478 to 18.431, with an average of 17.991 and the maximum difference of 0.953, the w(207Pb)/w(204Pb) of sulfide ores range from 15.440 to 15.717, with an average of 15.582 and the maximum difference of 0.277, the w(208Pb)/w(204Pb) of sulfide ores range from 37.556 to 38.839, with an average of 38.233 and the maximum difference of 1.283. The values of Φ, μ and w(Th)/w(U) vary from 0.592 to 0.638, 9.26 to 9.69 and 3.74 to 3.97, respectively. According to Zartman tectonic pattern, the lead isotope values project in two zones, between the upper mantle and orogenic belt and between orogenic belt and upper crust, which suggests that the ore lead is supplied by both the mantle and crust, not all by granitic magma. In addition, on the basis of Doe lead isotope diagram for discriminating tectonic setting, the values of lead isotope are characterized by concentrated distribution, between orogenic belt and upper crust mainly, which indicates that the upper crust is also one of the main lead sources and supplies lead for mineralization. The Dafulou deposit is related to orogenic tectonic event and forms in the environment of orogenic belt.

Yang Y.,Chinese Academy science | Yang Y.,University of Chinese Academy of Sciences | Ye L.,Chinese Academy science | Cheng Z.,Chinese Academy science | And 3 more authors.
Journal of Asian Earth Sciences | Year: 2013

The Hetaoping skarn type Pb-Zn deposit is located in the Baoshan-Narong-Dongzhi block metallogenic belt (BND belt), a belt between the Tengchong terrane and the Lanping basin. The deposit is hosted by marble of the upper Cambrian Hetaoping Formation and there are no outcrops of plutonic rocks present. This deposit is one of two large Pb-Zn deposits recently discovered in the BND belt. The Hetaoping deposit is a high Mn skarn. Four types of fluid inclusions were recognized in quartz from the deposit: vapor-rich inclusions (Type I), liquid-rich inclusions (Type II), pure vapor inclusions (Type III), and pure fluid inclusions (Type IV). The coexistence of Type I and Type III inclusions in Stage I (pre-ore stage) and Stage II (main ore stage) shows evidence of fluid boiling. Quartz-hosted fluid inclusions (Stage I and Stage II) display high homogenization temperatures and salinities (134-315°C; 3.7-18.6wt% NaCl equivalent) but calcite-hosted fluid inclusions in Stage III (post-ore stage) record lower homogenization temperatures and salinities (85-214°C; 0.5-5.4wt% NaCl equivalent). These data suggest a possible mixing between primary magmatic water and meteoric water. Based on chromatography data, the fluid inclusions in quartz contain abundant CO2 and O2 and subordinate CO, CH4 and C2H2+C2H4, suggesting an oxidizing environment. Based on their Na/K and Cl/SO4 ratios, fluids contained in fluid inclusions are similar to volcanic spring waters. The low Na/K ratios (0.40-1.34) of the ore-forming fluids may have resulted from interaction with a deep alkaline intermediate-acid intrusion. Hydrogen and oxygen isotope determinations on quartz from different ore stages show low δ18O and δD values relative to VSMOW (-4.3‰ to 2.3‰; -109‰ to -91‰), indicating that the ore-forming fluids were diluted by external fluid sources as the skarn system cooled. Overall, geological and geochemical interpretations suggest that the Hetaoping deposit is a distal manganese skarn Pb-Zn deposit related to concealed intrusions. © 2013 Elsevier Ltd.

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