| Geochemistry of Platinum Group and Rare Earth Elements of the Polymetallic Layer in the Lower Cambrian, Weng’an, Guizhou Province |
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| 作者姓名： | FU Yong WU Chaodong GUAN Ping QU Wenjun CHEN Jiafu |
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| 作者单位： | Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China;Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China;Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China;National Research Center of Geoanalysis, Beijing 100037, China;Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China |
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| 基金项目： | This study was supported by grants from the Key Project of Chinese Ministry of Education (no.: 104004) and the National Natural Science Foundation of China (no.: 40839907). |
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| 摘 要： | Abstract: The black shales of the Lower Cambrian Niutitang Formation in Weng’an, on the Yangtze platform of south China, contain voluminous polymetallic sulfide deposits. A comprehensive geochemical investigation of trace, rare earth, and platinum group elements (PGE) has been undertaken in order to discuss its ore genesis and correlation with the tectono-depositional setting. The ore-bearing layers enrich molybdenum (Mo), nickel (Ni), vanadium (V), lead (Pb), strontium (Sr), barium (Ba) , uranium (U) , arsenic (As), and rare earth elements (REE) in abundance. High uranium/thorium (U/Th) ratios (U/Th>1) indicated that mineralization was mainly influenced by the hydrothermal process. The dU value was above 1.9, showing a reducing sedimentary condition. The REE patterns showed high enrichment in light rare earth elements (LREE) (heavy rare earth elements (HREE) (LREE/HREE=5–17), slightly negative europium (Eu) and cerium (Ce) anomalies (dEu=0.81–0.93), and positive Ce anomalies (dCe=0.76–1.12). PGE abundance was characterized by the PGE-type distribution patterns, enriching platinum (Pt), palladium (Pd), ruthenium (Ru) and osmium (Os). The Pt/Pd ratio was 0.8, which is close to the ratios of seawater and ultramafic rocks. All of these geochemical features suggest that the mineralization was triggered by hydrothermal activity in an extensional setting in the context of break-up of the Rodinian supercontinent.
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| 关 键 词： | geochemistry polymetallic layer hydrothermal activity Lower Cambrian |
| 收稿时间： | 2/4/2009 12:00:00 AM |
| 修稿时间： | 3/3/2009 12:00:00 AM |
Geochemistry of Platinum Group and Rare Earth Elements of the Polymetallic Layer in the Lower Cambrian,Weng'an,Guizhou Province |
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| Authors: | FU Yong WU Chaodong GUAN Ping QU Wenjun and CHEN Jiafu |
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| Institution: | Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China;Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China;Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China;National Research Center of Geoanalysis, Beijing 100037, China;Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, Peking University, Beijing 100871, China |
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| Abstract: | The black shales of the Lower Cambrian Niutitang Formation in Weng'an, on the Yangtze platform of south China, contain voluminous polymetallic sulfide deposits. A comprehensive geochemical investigation of trace, rare earth, and platinum group elements (PGE) has been undertaken in order to discuss its ore genesis and correlation with the tectono‐depositional setting. The ore‐bearing layers enrich molybdenum (Mo), nickel (Ni), vanadium (V), lead (Pb), strontium (Sr), barium (Ba), uranium (U), arsenic (As), and rare earth elements (REE) in abundance. High uranium/thorium (U/Th) ratios (U/Th>1) indicated that mineralization was mainly influenced by the hydrothermal process. The δU value was above 1.9, showing a reducing sedimentary condition. The REE patterns showed high enrichment in light rare earth elements (LREE) (heavy rare earth elements (HREE) (LREE/HREE=5–17), slightly negative europium (Eu) and cerium (Ce) anomalies (δEu=0.81–0.93), and positive Ce anomalies (δCe=0.76–1.12). PGE abundance was characterized by the PGE‐type distribution patterns, enriching platinum (Pt), palladium (Pd), ruthenium (Ru) and osmium (Os). The Pt/Pd ratio was 0.8, which is close to the ratios of seawater and ultramafic rocks. All of these geochemical features suggest that the mineralization was triggered by hydrothermal activity in an extensional setting in the context of break‐up of the Rodinian supercontinent. |
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| Keywords: | geochemistry polymetallic layer hydrothermal activity Lower Cambrian |
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