Halloysite-to-kaolinite transformation by dissolution and recrystallization during weathering of crystalline rocks
Halloysite-to-kaolinite transformation by dissolution and recrystallization during weathering of crystalline rocks
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DOI：
10.1180/claymin.2012.047.3.08
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发表时间：
2012-09-01
期刊：
影响因子：
1.5
通讯作者：
Hatta, T.
中科院分区：
文献类型：
--
作者：
Inoue, A.;Utada, M.;Hatta, T.
本研究是对日本山阴地区石英闪长岩的深层风化剖面以及来自印度和斯里兰卡的两个红土样品进行的，为支持结晶岩石风化过程中埃洛石到高岭石转变的溶解和重结晶机制提供了令人信服的证据。在所有研究的样品中，管状埃洛石在高岭石之前通过长石的溶解和溶液中的沉淀而形成。早期形成的管状埃洛石的晶体尺寸分布的特征是具有正不对称性的对数正态曲线。当风化剖面中水的活性降低时，埃洛石和针铁矿开始脱水，这引发了埃洛石溶解。高岭石的异质成核发生在脱水埃洛石管的边缘和收缩孔中。在高岭石的早期生长阶段，基质埃洛石和产物高岭石之间保持了b*(埃洛石)//b*(高岭石)的拓扑关系。结果，由于在自然开放系统中间歇性供应相对于埃洛石不饱和的溶液，早期形成的埃洛石在很长一段时间内以同类相食的方式转变为高岭石。
The present study, which was carried out on a deep weathering profile of quartz diorite in the San'in district, Japan, along with two lateritic samples from India and Sri Lanka, provides convincing evidence supporting the dissolution and recrystallization mechanism for the halloysite-to-kaolinite transformation during weathering of crystalline rocks. In all the samples studied, tubular halloysite formed prior to kaolinite via the dissolution of feldspars and precipitation from solution. The crystal size distribution of tubular halloysite formed early was characterized by a lognormal curve having a positive asymmetry. When the activity of water decreased in the weathering profile, halloysite as well as goethite began to dehydrate, which acted as a trigger for dissolving halloysite. The heterogeneous nucleation of kaolinite took place on the edges and in the shrinkage pores of dehydrated halloysite tubes. The topotactic relationship of b*(halloysite)//b*(kaolinite) was kept between the substrate halloysite and the product kaolinite in the incipient growing stages of kaolinite. As a consequence, early formed halloysite transforms to kaolinite in a cannibalistic manner over a long period of time, owing to the intermittent supply of solution undersaturated with respect to halloysite in natural open systems.