| REE Compositions of Lower Ordovician Dolomites in Central and North Tarim Basin, NW China： A Potential REE Proxy for Ancient Seawater |
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| 基金项目： | Acknowledgement The authors thank the editors and the anonymous referees for their helpful and constructive comments, and are indebted to Prof. Hao Fang and Zou Huayao with China University of Petroleum, Beijing, and Dr. Zhang Xiaolin with Peking University, for their kind helps. This research was funded by the National Basic Research Program （973 Project, No. 2005CB422103 and No. 2005CB422105）. |
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| 摘 要： | Rare earth element compositions of Lower Ordovician dolomites in the Central and Northern Tarim Basin are studied. Most dolomite samples are more or less contaminated by clay minerals. Their rare earth element compositions have been consequently changed, showing both seawater-like and non-seawater-like features. The clay contamination should be disposed before the REE data are used. Through ICP-MS and ICP-AES analyses, the REE features are well documented. The clay contamination is quantitatively determined by microscopic investigation, trace elements and REE contents. The dolomites, at least in the Tarim Basin, are thought to be pure when their total LREE contents are less than 3×10^-6. Through comparison, the pure dolomites show similarities in REE patterns but differences in REE contents with co-existing pure limestone, which indicates that dolomitization may slightly change the REE compositions. Nevertheless, whatever the change is, the pure dolomites may act as a potential REE proxy for Ordovician seawater, which would be significant for ancient massive dolomite strata that lack limestone.
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| 关 键 词： | 白云石 早奥陶世 泥土污染 塔里木盆地 稀土元素 |
REE Compositions of Lower Ordovician Dolomites in Central and North Tarim Basin,NW China:A Potential REE Proxy for Ancient Seawater |
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| Authors: | ZHANG Xuefeng HU Wenxuan JIN Zhijun ZHANG Juntao QIAN Yixiong ZHU Jingquan ZHU Dongya WANG Xiaolin XIE Xiaomin |
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| Abstract: | Rare earth element compositions of Lower Ordovician dolomites in the Central and Northern Tarim Basin are studied.Most dolomite samples are more or less contaminated by clay minerals.Their rare earth element compositions have been consequently changed,showing both seawater-like and non-seawater-like features.The clay contamination should be disposed before the REE data are used.Through ICP-MS and ICP-AES analyses,the REE features are well documented. The clay contamination is quantitatively determined by microscopic investigation,trace elements and REE contents.The dolomites,at least in the Tarim Basin,are thought to be pure when their total LREE contents are less than 3x10~(-6).Through comparison,the pure dolomites show similarities in REE patterns but differences in REE contents with co-existing pure limestone,which indicates that dolomitization may slightly change the REE compositions.Nevertheless,whatever the change is,the pure dolomites may act as a potential REE proxy for Ordovician seawater,which would be significant for ancient massive dolomite strata that lack limestone. |
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| Keywords: | dolomite REE clay contamination Tarim Basin |
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