| 滇东早寒武世梅树村期浅色粘土岩层的地球化学特征和地质意义 |
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| 引用本文： | 张俊明,李国祥.滇东早寒武世梅树村期浅色粘土岩层的地球化学特征和地质意义[J].岩石学报,1997,13(1):100-110. |
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| 作者姓名： | 张俊明 李国祥 |
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| 作者单位： | 中国科学院南京地质古生物研究所 |
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| 摘 要： | 滇东早寒武世梅树村期含磷岩系中出现的十多层浅色粘土岩层为酸性火山灰蚀变而成的变斑脱岩，它们是火山喷发事件和事件地层对比的标志。这些浅色粘土岩层中稳定微量元素Ｈｆ、Ｎｂ、Ｙ、Ｔｈ、Ｚｒ含量高于非火山成因的粘土，而Ｆｅ、Ｎｉ、Ｃｏ、Ｃｒ含量低于筇竹寺组泥岩。ＴｉＯ２／Ａｌ２Ｏ３、Ｚｒ／Ｈｆ、Ｔｉ／Ｔｈ比值属于酸性岩浆范围，球粒标准化稀土元素配分模式和具中至大的Ｅｕ负异常类似于花岗岩稀土配分模式。岩浆判别图指示了梅树村期变斑脱岩具板内花岗岩位置的亚碱性流纹岩和粗面岩岩浆亲缘性。变斑脱岩在地层序列上和区域上分布表明扬子地台西缘早寒武世初期火山活动频繁，火山喷发事件与古大陆解体和板内拉张构造运动有关。
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| 关 键 词： | 粘土岩层 地球化学 地质意义 粘土岩 浅色粘土岩层 变斑脱岩 地球化学 梅树村期 云南东部 |
Geochemistry of Light Colour Clayrock Layers from the Early Cambrian Meishucun Stage in Eastern Yunnan and Their Geological Significance |
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| Abstract: | The character of lithology, mineralogy and geochemistry demonstrates that light colour clayrock layers are volcanogenic metabentonites within phosphatic succession of the Early Cambrian Meishucun Stage in eastern Yunnan. These clayrock layers could be taken as markers for the volcanic eruption events and for the event stratigraphy correlation. Metabentonites retain high concentrations of relatively immobile trace elements, particularly Hf, Nb, Y, Th and U compared with non-volcanogenic mudstones, but contain less concentrations of Fe, Ni, Co and Cr compared with the mudstones of the Qiongzhusi Formation. TiO 2/Al 2O 3, Ti/Th and Zr/Hf ratios of the all metabentonites are characterisitic of acidic magmas. Both chondrite normalized REE distribution patterns and middle to large negative Eu anomalies of the metabentonites are similar to those of granites. Discrimination diagrams indicate that these metabentonites possibly derived from rhyolite dacite trachyte magmas in a intraplate setting. The temporal and spatial distributions of metabentonites indicate that volcanic activities occurred very frequently at the west margin of the Yangtze Platform during the Meishucun Stage. These voicanic eruption events were related to the separation of the old continent and to the extension in a intraplate settings. |
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| Keywords: | Light colour clayrock layer Metabentonite Geochemistry Meishucun stage Eastern Yunnan |
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