| S, C, O, H Isotope Data and Noble Gas Studies of the Maoniuping LREE Deposit, Sichuan Province, China： A Mantle Connection for Mineralization |
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| 作者姓名： | TIAN Shihong DING Tiping MAO Jingwen LI Yanhe and YUAN Zhongxin Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing Key Laboratory of Isotope Geology Ministry of Land and Resources Beijing China University of Geosci |
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| 作者单位： | TIAN Shihong,DING Tiping,MAO Jingwen,LI Yanhe and YUAN Zhongxin Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037 Key Laboratory of Isotope Geology,Ministry of Land and Resources,Beijing 100037 China University of Geosci |
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| 基金项目： | 清华大学校科研和教改项目;国家自然科学基金 |
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| 摘 要： | The Maoniuping REE deposit, located about 22 km to the southwest of Mianning, Sichuan Province, is the second largest light REE deposit in China, subsequent to the Bayan Obo Fe-Nb-REE deposit in the Inner Mongolia Autonomous Region. Tectonically, it is located in the transitional zone between the Panxi rift and the Longmenshan-Jinpingshan orogenic zone. It is a carbonatite vein-type deposit hosted in alkaline complex rocks. The bastnaesite-barite, bastnaesite-calcite, and bastnaesite-microcline lodes are the main three types of REE ore lodes. Among these, the first lode is distributed most extensively and its REE mineralization is the strongest. Theδ34Sv-CDT values of the barites in the ore of the deposit vary in a narrow range of +5.0 to +5.1‰in the bastnaesite-calcite lode and +3.3 to +5.9‰in the bastnaesite-barite lode, showing the isotopic characteristics of magma-derived sulfur. Theδ13Cv-PDB values and theδ518OV-SMOW values in the bastnaesite-calcite lode range from -3.9 to -6.9‰and from +7.3 to +9.7‰, respectively, which fall into the range of "primary carbonatites", showing that carbon and oxygen in the ores of the Maoniuping deposit were derived mainly from a deep source. Theδ13Cv-PDB values of fluid inclusions vary from -3.0 to -5.6‰, with -3.0 to -4.0‰in the bastnaesite-calcite lode and -3.0 to -5.6‰in the bastnaesite-barite lode, which show characteristics of mantle-derived carbon. TheδDv-SMOW values of fluid inclusions range from -57 to -88‰, with -63 to -86‰in the bastnaesite-calcite lode and -57 to -88‰in the bastnaesite-barite lode, which show characteristics of mantle-derived hydrogen. Theδ18OH2OV-SMOW values vary from +7.4 to +8.6‰in the bastnaesite calcite lode, and +6.7 to +7.8‰in the bastnaesite-barite lode, almost overlapping the range of +5.5 to +9.5‰for magmatic water. The 4He content, R/Ra ratios are (13.95 to 119.58×10-6 (cm3/g)STP and 0.02 to 0.11, respectively, and 40Ar/36Ar is 313±1 to 437±2. Considering the 4He increase caused by high contents of radioactive elements, a mantle-derived fluid probably exists in the inclusions in the fluorite, calcite and bastnaesite samples. The Maoniuping deposit and its associated carbonatite-alkaline complex were formed in 40.3 to 12.2 Ma according to K-Ar and U-Pb data. All these data suggest that large quantities of mantle fluids were involved in the metallogenic process of the Maoniuping REE deposit through a fault system.
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| 关 键 词： | 同位素 天然气 四川 矿化作用 |
| 收稿时间： | 2005-05-11 |
| 修稿时间： | 2005-11-11 |
S, C, O, H Isotope Data and Noble Gas Studies of the Maoniuping LREE Deposit, Sichuan Province, China: A Mantle Connection for Mineralization |
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| Authors: | TIAN Shihong DING Tiping MAO Jingwen LI Yanhe and YUAN Zhongxin Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing Key Laboratory of Isotope Geology Ministry of Land and Resources Beijing China University of Geosci |
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| Abstract: | Abstract The Maoniuping REE deposit, located about 22 km to the southwest of Mianning, Sichuan Province, is the second largest light REE deposit in China, subsequent to the Bayan Obo Fe‐Nb‐REE deposit in the Inner Mongolia Autonomous Region. Technically, it is located in the transitional zone between the Panxi rift and the Longmenshan‐Jinpingshan orogenic zone. It is a carbonatite vein‐type deposit hosted in alkaline complex rocks. The bastnaesite‐barite, bastnaesite‐calcite, and bastnaesite‐microcline lodes are the main three types of REE ore lodes. Among these, the first lode is distributed most extensively and its REE mineralization is the strongest. The δ34SV‐CDT values of the barites in the ore of the deposit vary in a narrow range of +5.0 to +5.1‰ in the bastnaesite‐calcite lode and +3.3 to +5.9‰ in the bastnaesite‐barite lode, showing the isotopic characteristics of magma‐derived sulfur. The δ13CV‐PDB values and the δ18OV‐SMOW values in the bastnaesite‐calcite lode range from ?3.9 to ?6.9‰ and from +7.3 to +9.7‰, respectively, which fall into the range of “primary carbonatites”, showing that carbon and oxygen in the ores of the Maoniuping deposit were derived mainly from a deep source. The δ13CV‐PDB values of fluid inclusions vary from ?3.0 to ?5.6‰, with ?3.0 to ?4.0‰ in the bastnaesitecalcite lode and ?3.0 to ?5.6‰ in the bastnaesite‐barite lode, which show characteristics of mantle‐derived carbon. The δDV‐SMOW values of fluid inclusions range from ?57 to ?88‰, with ?63 to ?86‰ in the bastnaesite‐calcite lode and ?57 to ?88‰ in the bastnaesite‐barite lode, which show characteristics of mantle‐derived hydrogen. The δ18OH2OV‐SMOW values vary from +7.4 to +8.6‰ in the bastnaesitecalcite lode, and +6.7 to +7.8‰ in the bastnaesite‐barite lode, almost overlapping the range of +5.5 to +9.5‰ for magmatic water. The 4He content, R/Ra ratios are (13.95 to 119.58)×10?6 (cm3/g)STP and 0.02 to 0.11, respectively, and 40Ar/36Ar is 313 ± 1 to 437 δ 2. Considering the 4He increase caused by high contents of radioactive elements, a mantle‐derived fluid probably exists in the inclusions in the fluorite, calcite and bastnaesite samples. The Maoniuping deposit and its associated carbonatite‐alkaline complex were formed in 40.3 to 12.2 Ma according to K‐Ar and U‐Pb data. All these data suggest that large quantities of mantle fluids were involved in the metallogenic process of the Maoniuping REE deposit through a fault system. |
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| Keywords: | stable isotopes noble gas mantle source Maoniuping LREE deposit Sichuan Province |
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