| 杨万涛.云南沾益小米戛磷矿渔户村组磷块岩地球化学特征及成因分析[J].地质与勘探,2021,57(5):1028-1039 |
| 云南沾益小米戛磷矿渔户村组磷块岩地球化学特征及成因分析 |
| Geochemistry and genesis of phosphate rocks in the Yuhucun Formation of the Xiaomiga deposit, Zhanyi District, Yunnan Province |
| 投稿时间：2020-12-03 修订日期：2021-01-11 |
| DOI：10.12134/j.dzykt.2021.05.008 |
| 中文关键词: 渔户村组 磷块岩 地球化学特征 小米戛磷矿 沾益 云南 |
| 英文关键词: Yuhucun Formation, phosphate rocks, geochemical characteristics, Xiaomiga phosphate deposit, Zhanyi District,Yunnan Province |
| 基金项目:中国地质调查调局“云南待补、务德、李子沟、得德卡幅1:5万区域地质矿产综合调查”(编号：12120115041601)资助 |
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| 中文摘要: |
| 小米戛磷矿是云南曲靖沾益地区新发现的矿床。本文对该矿床渔户村组磷块岩的主量、微量和稀土元素地球化学特征进行研究，探讨沾益渔户村组磷块岩的成磷环境和成磷物质来源。研究表明小米戛磷矿磷块岩富SiO2(28.50%~51.47%)、CaO(20.21%~31.31%)、P2O5(15.48%~25.42%)。磷块岩中Ba、Sr、Cu、Pb、Zn、V、Mo等元素富集，显示生物聚磷作用。磷块岩的Sr/Ba=0.10~1.40，U/Th比值大于1(1.35~4.15)，表明磷块岩的形成可能有热液活动的参与。磷块岩稀土元素总量较高(148.84×10-6~232.16×10-6)，经北美页岩标准化的稀土配分模式曲线近水平，但LREE/HREE=2.96~5.37，显示一定程度的轻稀土元素富集，进一步暗示磷矿的形成受热水沉积成矿作用与生物成矿作用共同控制。磷块岩中U元素高度富集(富集系数平均值8.84)，V/Cr=1.08~3.01(平均值为2.12)，Ceanom=-0.50~-0.35，介于-0.5与-0.1之间，表明磷块岩形成于次氧化环境。综上所述，在早寒武世渔户村期的潮坪-泻湖环境，磷质沉积物发生胶结作用形成初始磷矿层；后期生物繁盛，生物遗体中所含的磷被大量地分解，不同深度的大量含磷物质伴随上升洋流进一步改造初始磷矿层，最终成矿。 |
| 英文摘要: |
| The Xiaomiga phosphate deposit is a newly discovered resource in Zhanyi District, Qujin, Yunnan Province. This work studies the major and trace elements and REE geochemistry of phosphate rocks and explores the formation environment and source for phosphorite in the Yuhucun Formation of this deposit. Research shows that the phosphate rocks are rich in SiO2 (28.50%~51.47%), CaO (20.21%~31.31%), and P2O5 (15.48%~25.42%). They also have high content of Ba, Sr, Cu, Pb, Zn, V, and Mo, implying biological accumulation. The ratio of Sr/Ba is 0.10~1.40 and that of U/Th is 1.35~4.15, indicating hydrothermal fluid was involved in mineralization. The rocks are highly rich in U element (the average of the enrichment coefficient is 8.84). The ratio of V/Cr is 1.35~4.15 with an average 2.12, implying that the phosphate rocks formed in an anoxic sedimentary environment. The REE content of the rocks is relatively high (148.84×10-6~232.16×10-6), and the NASC normalized REE pattern is close to the level, but the ratio LREE/HREE is 2.96~5.37, which shows a certain enrichment in LREE. The REE signature also indicates that phosphate mineralization is the result of both hydrothermal sedimentation and the biological effect. The value of Ceanom is -0.50~-0.35, much less than -0.1 and greater than -0.50, further supporting that the phosphate rocks formed in an anoxic environment. In summary, during the tidal-lagoon environment in Early Cambrian Yuhucun period, cementation of phosphorous sediments caused the initial phosphate mineralization. In the later stage, there was a lot of life in the ocean. The phosphorus in biological remains was decomposed in large quantities, and the upwelling of ocean current brought a large amount of phosphorous material from different depths, further reforming the original phosphate layer and finally leading to mineralization． |
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