| Sodic metasomatism in a dacite weathering profile in Pinxiang, Guangxi, China |
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| 作者姓名： | GU Shangyi WAN Guojiang MAO Jianquan |
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| 作者单位： | [1]Key Laboratory of Karst Environment and Geohazard Prevention （Guizhou University）, Ministry of Education, Guiyang 550003, China [2]School of Resources and Environmental Engineering, Guizhou University, Guiyang 550003, China [3]State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China |
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| 摘 要： | The Pinxiang weathering profile is well developed on Early Triassic dacite lavas of the Baisi Formation. At the top of the profile is developed a red clay zone which is characterized mineralogically by kaolinite, iron oxide minerals, quartz, and a small amount of illite, montmorillonite and vermiculite. In going downwards the red clay zone gives way to a saprolite zone in which plagioclase pseudomorphs have been well preserved although replaced by kaolinite. Beneath the saprolite zone is the saprock zone characterized by less weathering for dacite. At the bottom of the weathering profile is the parent material, dacite, which is composed mainly of plagioclase, quartz, K-feldspar and biotite which have been largely altered into chlorite owing to submarine extrusion of dacite lavas. Some layers in the weathering profile show obvious sodium enrichment and potassium depletion relative to others. In the Al2O3-(CaO* Na2O)-K2O triangular diagram, the weathering trends of these layers in the middle stage are remarkably deviated from normal ones. Both mineralogy and micro-morphology of these layers indicate such deviation resulted from sodic metasomatism of orthoclase.
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| 关 键 词： | 英安岩 化学风化 交代作用 中国 |
| 收稿时间： | 11 July 2006 |
| 修稿时间： | 2006-07-11 |
Sodic metasomatism in a dacite weathering profile in Pinxiang,Guangxi, China |
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| GU Shangyi WAN Guojiang MAO Jianquan.Sodic metasomatism in a dacite weathering profile in Pinxiang, Guangxi, China[J].Chinese Journal of Geochemistry,2007,26(4):434-438. |
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| Authors: | Gu Shangyi Wan Guojiang Mao Jianquan |
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| Institution: | Guizhou University |
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| Abstract: | The Pinxiang weathering profile is well developed on Early Triassic dacite lavas of the Baisi Formation. At the top of the profile is developed a red clay zone which is characterized mineralogically by kaolinite, iron oxide minerals, quartz, and a small amount of illite, montmorillonite and vermiculite. In going downwards the red clay zone gives way to a saprolite zone in which plagioclase pseudomorphs have been well preserved although replaced by kaolinite. Beneath the saprolite zone is the saprock zone characterized by less weathering for dacite. At the bottom of the weathering profile is the parent material, dacite, which is composed mainly of plagioclase, quartz, K-feldspar and biotite which have been largely altered into chlorite owing to submarine extrusion of dacite lavas. Some layers in the weathering profile show obvious sodium enrichment and potassium depletion relative to others. In the Al2O3-(CaO* Na2O)-K2O triangular diagram, the weathering trends of these layers in the middle stage are remarkably deviated from normal ones. Both mineralogy and micro-morphology of these layers indicate such deviation resulted from sodic metasomatism of orthoclase. |
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| Keywords: | dacite chemical weathering metasomatism Guangxi Zhuang Autonomous Region China |
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