| Origin of Ore-Forming Fluids of Mississippi Valley-Type （MVT） Pb-Zn Deposits in Kangdian Area, China |
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| 引用本文： | 王奖臻,李泽琴,倪师军.Origin of Ore-Forming Fluids of Mississippi Valley-Type （MVT） Pb-Zn Deposits in Kangdian Area, China[J].中国地球化学学报,2003,22(4):369-376. |
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| 作者姓名： | 王奖臻 李泽琴 倪师军 |
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| 作者单位： | ChengduUniversityofTechnology,Chengdu610059,China |
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| 基金项目： | ThisresearchprojectwasfundedbytheNationalNaturalScienceFoundationofChina (No .4 0 1 72 0 39) |
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| 摘 要： | Analyses of fluid-inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75 - 358 and Cl/Br 67 - 394, respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the ratios ( 120 and 233 ) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the original mineralizing brine was derived from highly evapo-rated seawater with a high salinity. However, the inclusion fluids have absolute Na values of 69.9—2606.2 mmol kg^-1 and Cl values of 106.7 — 1995.5 mmol kg^-1. Most of the values are much less than those of seawater: Na, 485 mmol kg^-1 and Cl, 566 mmol kg^-1 , respectively; the salinity measured from fluid inclusions of the deposits ranges from 2.47 wt% to 15.78 wt% NaCl equiv. The mineralizing brine has been diluted. The δ ^18O and δD values of ore-forming fluids vary from -8.21‰ to 9.51‰ and from -40.3‰ to -94.3‰, respectively. The δD values of meteoric water in this region varied from - 80‰ to - 100‰ during the Jurassic. This evidenced that the ore-forming fluids are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.
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| 关 键 词： | Mississippi Valley-type Pb-Zn deposit ore fluid Kangdian area Cl-Br-Na systematics |
Origin of ore-forming fluids of Mississippi Valley-type (MVT) Pb-Zn deposits in Kangdian area,China |
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| Wang?Jiangzhen,Li?Zeqin,Ni?Shijun.Origin of ore-forming fluids of Mississippi Valley-type (MVT) Pb-Zn deposits in Kangdian area,China[J].Chinese Journal of Geochemistry,2003,22(4):369-376. |
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| Authors: | Wang Jiangzhen Li Zeqin Ni Shijun |
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| Institution: | (1) Chengdu University of Technology, 610059 Chengdu, China |
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| Abstract: | Analyses of fluid-inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75–358 and Cl/Br 67–394,
respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br
ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the
ratios (120 and 233 ) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the
original mineralizing brine was derived from highly evaporated seawater with a high salinity. However, the inclusion fluids
have absolute Na values of 69.9-2606.2 mmol kg-1 and Cl values of 106.7-1995.5 mmol kg-1. Most of the values are much less than those of seawater: Na, 485 mmol kg-1 and Cl, 566 mmol kg-1, respectively; the salinity measured from fluid inclusions of the deposits ranges from 2.47 wt% to 15.78 wt% NaCl equiv.
The mineralizing brine has been diluted. The δ18O and δD values of ore-forming fluids vary from −8. 21% to 9. 51% and from −40. 3% to −94.3%, respectively. The δD values
of meteoric water in this region varied from −80% to −100% during the Jurassic. This evidenced that the ore-forming fluids
are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb,
Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.
This research project was funded by the National Natural Science Foundation of China (No. 40172039). |
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| Keywords: | Mississippi Valley\|type Pb\|Zn deposit ore fluid Kangdian area Cl\|Br\|Na systematics |
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