| “寨背式”离子吸附型稀土矿床多类型稀土矿化及其成因 |
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| 引用本文： | 赵芝,王登红,邹新勇.“寨背式”离子吸附型稀土矿床多类型稀土矿化及其成因[J].岩石学报,2022,38(2):356-370. |
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| 作者姓名： | 赵芝 王登红 邹新勇 |
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| 作者单位： | 中国地质科学院矿产资源研究所, 自然资源部成矿作用与资源评价重点实验室, 北京 100037;江西省地质局第七地质大队, 赣州 341000 |
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| 基金项目： | 本文受国家社会科学基金重大项目（19ZDA111）和中国地质调查项目（DD20190379）联合资助. |
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| 摘 要： | 赣南寨背离子吸附型稀土矿床产于寨背复式花岗岩体的风化壳中，自20世纪80年代发现以来一直以轻稀土型开采，近年在轻稀土型花岗岩风化壳中发现了重稀土矿。为了探讨轻稀土型花岗岩风化过程中重稀土元素的迁移、分馏和富集机制，本文选择了区内三个具有代表性的风化壳钻孔(ZK1、ZK2和ZK4)对其进行了全相和离子交换相稀土元素地球化学研究。结果显示：钻孔ZK4中离子交换相稀土含量介于14.90×10-6～835.8×10-6之间，并富集轻稀土(LREE/HREE=2.28～10.78);钻孔ZK1中离子交换相稀土含量达1470×10-6(9件样品均值),具有从轻稀土型向重稀土型过渡的配分特征(LREE/HREE=1.30～1.65),并且剖面自上而下显示轻、重稀土逐渐富集的趋势；钻孔ZK2中离子交换相稀土含量为492.4×10-6(8件样品均值),自上而下稀土配分类型从轻稀土型过渡至重稀土型(LREE/HREE=0.43～2.25),且轻稀土富集在全风化层上部而重稀土则富集在下部。三个钻孔的Nb/Ta和Zr/Hf...
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| 关 键 词： | 风化壳 全相稀土 离子交换相稀土 稀土分馏 寨背岩体 江西 |
| 收稿时间： | 2021/7/16 0:00:00 |
| 修稿时间： | 2021/11/6 0:00:00 |
The genesis and diversity of ion adsorption REE mineralization in the Zhaibei deposit, Jiangxi Province, South China |
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| ZHAO Zhi,WANG DengHong,ZOU XinYong.The genesis and diversity of ion adsorption REE mineralization in the Zhaibei deposit, Jiangxi Province, South China[J].Acta Petrologica Sinica,2022,38(2):356-370. |
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| Authors: | ZHAO Zhi WANG DengHong ZOU XinYong |
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| Institution: | MNR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China; The Seventh Geological Brigade of Jiangxi Geological Bureau, Ganzhou 341000, China |
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| Abstract: | The Zhaibei deposit, located in Dingnan County of Jiangxi Province, is hosted in regolith developed over the Zhaibei granite. It has been mined as a LREE deposit since its discovery in the 1980s. Recently, HREE ores have also been found from weathering crusts of the LREE-rich granitic rocks. In this study, REE geochemical characteristics of three representative weathering profiles (ZK1, ZK2 and ZK4) from the Zhaibei granite were analysed to reveal the migration, fractionation and enrichment of REE related to the ion-adsorption mineralisation. The result shows that the ZK4 is highly variable in its ion-exchange REE contents (14.90×10-6~835.8×10-6) with a typical LREE enrichment (LREE/HREE=2.28~10.78). The ZK1 is enriched in ion-exchange REEs (average 1470×10-6) and shows a transitional characteristic from LREE type to HREE type with LREE/HREE ranging from 1.30 to 1.65. LREEs and HREEs are enriched in the lower part of the ZK1. The ZK2 contains moderate ion-exchange REEs (average 492.4×10-6) and shows a variable REE pattern from slight LREE enrichment to depletion with LREE/HREE ranging from 0.43 to 2.25. LREEs are mainly enriched in the upper part of the ZK2 while HREEs are mainly enriched in the lower part. The ratio of Nb/Ta and Zr/Hf in the three weathering profiles is similar to that of biotite sienogranite in the transition phase of the Zhaibei granite. The biotite sienogranite also shows an REE variation pattern of LREE enrichment with an LREE/HREE ratio ranging from 1 to 5. These observations indicate that the biotite sienogranite with typical LREE-enriched pattern (LREE/HREE>3) is probably the parent rock of the ZK4. In contrast, the biotite sienogranite with LREE/HREE ranging from 1.45 to 2.56 is probably the parent rock of the ZK1 and ZK2. During the weathering, high concentrations of HREE released from the bedrock are removed from the upper part of ZK2 profile and accumulate in the lower part, leading to a high fractionation between LREE and HREE. Ultimately, the REE pattern of the profile changed from LREE type to HREE type. Compared with the ZK2, the ZK1 has a higher weathering index (CIA value) as the weathering degree increases, LREEs enriched in the upper part of the weathering crust gradually migrated downward and HREEs enriched in the lower part are mobilized and removed from the profile to the surface water, leading to a low fractionation between LREEs and HREEs. Thus, the REE pattern of the ZK1 shows a transitional type. In conclusion, HREE mineralisation could be formed by weathering of the LREE and Y-rich granitic rocks. |
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| Keywords: | Weathering crust Rare earth element Ion-exchange rare earth element Fractionation Zhaibei granite Jiangxi Province |
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