| 湘西上震旦统层状硅质岩沉积环境的地球化学标志 |
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| 引用本文： | 彭军,徐望国.湘西上震旦统层状硅质岩沉积环境的地球化学标志[J].地球化学,2001,30(3):293-298. |
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| 作者姓名： | 彭军 徐望国 |
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| 作者单位： | 1. 西南石油学院博士后流动站,
2. 湘潭工学院土木系, |
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| 基金项目： | 国家自然科学基金资助项目(409700115) |
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| 摘 要： | 湘西上震旦统层状硅质岩化学成分纯净，硅质矿物平均含量95％以上，且FeO/Fe2O3比值大于1，MnO/TiO2比值为6．1，P2O5含量极低。微量元素Sr/Ba比值小于1，稀土以总量低（5．64－31．54μg/g）和铈亏损为特征。硅质岩的δ^30Si值变化在0．0‰～0.7‰之间，硅质岩中有机碳含量较高，介于0．443％－1．993％之间，Pr/Ph比值小于1。硅质岩的上述特点反映其沉积大陆边缘斜坡半深海至大洋盆地深海环境中。
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| 关 键 词： | 硅质岩 沉积环境 地球化学 震旦系 湖南 微量元素 有机碳 |
| 文章编号： | 0379－1726(2001)03－0293－06 |
| 修稿时间： | 2000年5月17日 |
Geochemical characteristics of depositional environment of the Upper Sinian bedded siliceous rocks in western Hunan |
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| PENG Jun,XU Wang-guo.Geochemical characteristics of depositional environment of the Upper Sinian bedded siliceous rocks in western Hunan[J].Geochimica,2001,30(3):293-298. |
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| Authors: | PENG Jun XU Wang-guo |
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| Abstract: | Siliceous rocks are widely distributed intrabasinal rocks, and may occur in all kinds of sedimentary environments. Some significant achievements have already been made by using sedimentary geochemical characteristics of siliceous rocks to analyze the sedimentary environment. The aims of this paper are to discuss the sedimentary environment of the Upper Sinian bedded siliceous rocks in western Hunan Province on the basis of previous studies. The ratios of FeO/Fe2O3 and MnO/TiO2 of siliceous rocks ranging from 1.13 to 7.34, 2.4 to 10, averaging 3.92 and 6.1, respectively, very low contents of P2O5 and the development of phosphatic nodule and thin bedded phosphorite interbed indicate that the rocks deposited in the marine environment with a feature of deeper water depth, deficiency of oxygen, low energy and reduction intense reduction. The ratios of Sr/Ba are much less than 1.0, reflecting that the rocks formed between deep sea and detained shallow environment. The Hf/3 Th Ta triangular diagram shows that the rocks deposited in the tectonic environment of disintegrated plate margin. The total REE contents and δ Ce values range from 5.64 μ g/g to 31.54 μ g/g and 0.4 to 0.85, averaging 15.01 μ g/g, and 0.72, respectively, manifesting that the rocks mainly formed in ocean basins of a deep sea environment to continental marginal slopes of a bathyal environment. The δ 30Si values range from 0.0‰ to 0.7‰ , averaging 0.3‰ , reflecting that the depositional environment is a transitional zone from the bathyal to the deep sea environment. The organic carbon contents and ratios of Pr/Ph ranging from 0.443％ to 1.993％ and 0.198 to 0.638, averaging 1.260％ and 0.350, respectively, and sapropel type organic matter indicate that the rocks deposited in the intense reduction environment of deeper water depth. To sum up, analyses of the depositional environment of siliceous rocks in the study area using the sedimentary geochemical characteristics yield the same conclusion that the rocks formed in environments from continental marginal slopes of a bathyal environment to oceanic basins of a deep sea environment. |
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| Keywords: | siliceous rock depositional environment geochemistry Sinian Hunan Province |
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