Modification to the crystal structure of chlorite during early stages of its dissolution
Modification to the crystal structure of chlorite during early stages of its dissolution
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DOI：
10.1007/s00269-009-0299-x
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发表时间：
2009-04
影响因子：
1.4
通讯作者：
J. Kameda;H. Sugimori;T. Murakami
中科院分区：
文献类型：
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作者：
J. Kameda;H. Sugimori;T. Murakami
研究了富镁绿泥石(斜绿泥石)的早期溶解过程，重点研究了溶解过程中颗粒边缘的结构变化。将聚焦离子束透射电子显微镜样品制备应用于在pH 3.0和25°C的流动反应系统中溶解的晶体31天。得到的硅和镁的溶解速率分别为−11.49和−11.14(logR，m o l/(m~2/S))，表明溶解是非化学计量比的。固溶样品的TEM-EDX分析表明，在最外层形成了20-50 nm厚的非晶区，化学梯度为镁，向固体表面的方向较低，并且在该非晶区中硅的含量较高。晶态材料与非晶态材料在非晶区和结晶区的界面上部分交织在一起。这些结果表明，除硅外，非晶区是由阳离子选择性浸出形成的。绿泥石的溶解可以通过形成和增厚浸出层进行，这是释放到硅溶液中的副产品，其速度比镁略慢。
Early stage processes of Mg-rich chlorite (clinochlore) dissolution were examined, focusing especially on the structural modification at grain edges during dissolution. Focused ion beam transmission electron microscopy sample preparation was applied to crystals dissolved in a flow-through reaction system at pH 3.0 and 25°C for 31 days. The obtained Si and Mg dissolution rates are −11.49 and −11.14 (logR, mol/(m2/s)), respectively, implying dissolution is non-stoichiometric. TEM-EDX analyses of dissolved samples reveal the development of 20–50-nm thick amorphous zone at an outermost rim with a chemical gradient of Mg, lower towards the solid surface, and Si enrichment in this amorphous zone. Crystalline material is partially interwoven with amorphous one at the interface between the amorphous and crystalline regions. These results indicate that the amorphous zone was produced by selective leaching of cations except for Si. Chlorite dissolution may proceed via the formation and thickening of leached layer as a by-product of release to solution of Si at slightly slower rate than Mg.