| 白云鄂博Fe-REE-Nb建造地球化学特征及成因：元素及同位素新证据 |
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| 引用本文： | 赖小东,杨晓勇,柳建勇.白云鄂博Fe-REE-Nb建造地球化学特征及成因：元素及同位素新证据[J].地质学报,2012,86(5):801-818. |
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| 作者姓名： | 赖小东 杨晓勇 柳建勇 |
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| 作者单位： | 1. 中国科学技术大学地球和空间科学学院,石油天然气研究中心,合肥,230026
2. 包钢(集团)公司白云鄂博铁矿,包头,014080 |
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| 基金项目： | 本文为国土资源部公益性行业科研专项“内蒙古白云鄂博铁稀土矿科学基地研究”(编号200911007-19)、科技部“973”项目(编号2012CB416602)、中国科学院知识创新项目(编号KZCX2-YW-QN509) 和国家自然科学基金项目(编号41090372、40921002)共同资助的成果。 |
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| 摘 要： | 通过野外地质观察和室内镜下研究,利用XRF和ICP-MS对白云岩及其周围的板岩的主、微量元素进行分析,同时对硫化矿化的样品开展硫同位素测试。元素测试结果显示白云鄂博Fe-REE-Nb建造白云岩既具有部分火成碳酸岩的地球化学特征,也具有部分沉积碳酸岩的地球化学特征,表明白云鄂博Fe-REE-Nb建造赋矿白云岩不是典型的火成碳酸岩或沉积碳酸盐岩。硫同位素的测试结果表明,全岩的硫同位素组成不呈塔式模型分布,出现两个比较明显的峰值,一个在0‰左右,具有深源特征;另一个在+8‰左右,明显高于幔源硫,这个结果说明其来源可能有两个:地幔和海水。赋矿白云岩中Nb随着稀土的富集也发生富集作用,但是Ta的富集作用却十分微弱,显示了成矿热液强烈富REE和Nb及贫Ta的元素地球化学特征。据元素和硫同位素结果,我们认为白云鄂博赋矿白云岩是沉积碳酸盐受地幔碳酸岩岩浆及派生的流体交代的产物,而非直接源于火山碳酸岩喷发成因。地幔深部碳酸岩岩浆及其派生的富稀土流体沿区域性深大断裂上涌与沉积碳酸盐岩进行交代作用,形成了白云鄂博独特巨大的Fe-REE-Nb矿床及区域性的稀土矿床。
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| 关 键 词： | 白云岩 地球化学 硫同位素 矿床成因 白云鄂博Fe-REE-Nb建造 内蒙古 |
| 收稿时间： | 2011/9/28 0:00:00 |
| 修稿时间： | 2011/3/22 0:00:00 |
Geochemical Features and Its Genesis of the Bayan Obo Fe-REE-Nb Formation: New Evidence from Elements and Isotopes |
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| LAI Xiaodong,YANG Xiaoyong and Liu Jianyong.Geochemical Features and Its Genesis of the Bayan Obo Fe-REE-Nb Formation: New Evidence from Elements and Isotopes[J].Acta Geologica Sinica,2012,86(5):801-818. |
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| Authors: | LAI Xiaodong YANG Xiaoyong and Liu Jianyong |
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| Institution: | Research Center for Oil and Natural Gases, School of Earth and Space Sciences, University Science and Technology of China, Hefei, 230026;Research Center for Oil and Natural Gases, School of Earth and Space Sciences, University Science and Technology of China, Hefei, 230026;Baiyunebo Mine of Baogang Group, Baotou, Inner Mongolia, 014080 |
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| Abstract: | In this study,XRF and ICP-MS methods were used to analyze major and trace elements of dolomitite and surrounding slate combined with field investigation and indoor observation.Sulfur isotopic compositions were also conducted on the samples.The results of element analyses show that the dolomitic rock in the Bayan Obo Fe-REE-Nb formation exhibits geochemical characteristics of both igneous carbonate and sedimentary carbonate,indicating that the dolomite is neither typical igneous carbonatic rock nor sedimentary carbonatic rock.Sulfur isotopic analysis show that S isotopic compositions of whole rock is characterized by normal distribution model with two distinct peaks:one at around 0‰ indicating a deep-mantle source and the other around +8‰ higher than that of mantle-derived sulfur.The results suggest two possible origins:mantle-derived and sedimentary.Niobium in ore-bearing dolomite was enriched as REE mineralization took place,but Ta enrichment was weak.This suggests that ore-forming fluid was geochemically characterized by enrichment of REE and Nb and depletion of Ta.Our element and sulfur results demonstrate that the ore-bearing dolomitic rock was the product of metasomatism of sedimentary carbonate by mantle-derived carbonatic magma but not the product of direct eruption of igneous carbonatic magma.Deep mantle-derived carbonatic magma and its REE-enriched fluid migrated along regional deep fault and metasomatised with sedimentary carbonate,resulting in the formation of the unique,giant Fe-REE-Nb deposit in Bayan Obo. |
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| Keywords: | dolomite geochemistry sulfur isotopes ore genesis Bayan Obo Fe-REE-Nb formation Inner Mongolia |
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