| 西藏斯弄多地区岩帽地质地球化学特征:林子宗群火山岩中成矿的指示 |
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| 引用本文： | 杨宗耀,唐菊兴,张乐骏,赵晓彦,郎兴海,张崇海.西藏斯弄多地区岩帽地质地球化学特征:林子宗群火山岩中成矿的指示[J].地球科学,2020,45(3):789-803. |
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| 作者姓名： | 杨宗耀 唐菊兴 张乐骏 赵晓彦 郎兴海 张崇海 |
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| 作者单位： | 1.西南交通大学地球科学与环境工程学院, 四川成都 611756 |
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| 基金项目： | 国家自然科学基金项目41772075国家重点研发计划项目2018YFC0604105 |
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| 摘 要： | 岩帽作为重要的找矿标志，长期以来却没有引起广泛关注，阻碍了勘查工作.在斯弄多地区对与不同矿化类型相关的岩帽进行岩石学、岩相学和全岩地球化学分析，其中斯弄多红色岩帽与铅锌成矿作用相关，窝弱黑色岩帽与金银成矿作用相关，而马尔地村白色岩帽目前未见明显相关矿化.镜下特征和岩石学特征表明斯弄多地区3种类型岩帽具大量石英晶屑，多呈致密块状，其次为多孔状石英.全岩地球化学显示，斯弄多红色岩帽SiO2含量>90%，主要由石英组成，Pb含量为288.75×10-6~4 769.16×10-6，Zn含量为34.34×10-6~332.70×10-6；马尔地村白色岩帽则含更多的铝硅酸盐矿物，不具成矿元素异常；窝弱黑色岩帽含富钾类蚀变矿物，K2O含量为0.26%~2.58%，Au含量为80.21×10-9~360.74×10-9.斯弄多地区岩帽均由硅质酸性流体交代晶屑凝灰岩形成，铅锌成矿作用使岩帽Be元素富集，具Ce负异常；窝弱金银成矿作用使岩帽V、Rb、Mo和Cs富集，具Yb正异常；马尔地村岩帽面积大，粘土蚀变矿物发育，其深部可能存在斑岩型矿体.
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| 关 键 词： | 岩帽 林子宗群火山岩 地球化学 金矿 铅锌矿 |
| 收稿时间： | 2019-03-02 |
Geological and Geochemical Characteristics of Lithocaps in Sinongduo Area,Tibet: Implications for the Mineralization in Linzizong Group Volcanic Rocks |
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| Abstract: | Lithocap, as an important indicator for exploration, has not attracted widespread attention for a long time, hindering the exploration work.Three types of lithocaps related to different mineralization styles in Sinongduo area are sampled for petrology, microphysiography and whole rock geochemistry analysis in which Sinongduo red lithocaps correspond to Pb-Zn mineralization, while Woruo black lithocaps are of Au-Ag mineralization, and Maerdi white lithocaps display no obvious mineralization. Microscopic and petrological characteristics show that three types of lithocaps in the Sinongduo area have many quartz fragments which are composed of massive quartz and vuggy quartz. The whole rock geochemistry data show that Sinongduo red lithocaps contain over 90% of SiO2, and are mostly composed of quartz. The Pb contents are 288.75×10-6-4 769.16×10-6, and the Zn is 34.34×10-6-332.70×10-6. The Maerdi white lithocaps are rich in aluminosilicate minerals and show none metallogenic elements anomaly. The contents of K2O (0.26%-2.58%) in Woruo black lithocaps indicate that there are many potassium-rich altered minerals, and the contents of Au are 80.21×10-9-360.74×10-9. In conclusion, the forming processes of lithocaps can be explained as the ascending siliceous acid fluid reacting with the crystal tuff. Pb-Zn mineralization tends to result in enrichment of Be and a negative anomaly of Ce in chondrite normalized REE patterns. In contrast, Au-Ag mineralization benefits V, Rb, Mo and Cs and Ce, and there is a positive anomaly of Yb. In addition, the large amount of clay minerals in the biggest Maerdi white lithocap could be an implication for porphyry at depth. |
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