有序钠长石向高岭石的转化：对“小册子”形态的启示,ACS Earth and Space Chemistry

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有序钠长石向高岭石的转化：对“小册子”形态的启示
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2022-03-21 , DOI: 10.1021/acsearthspacechem.2c00030
Shangying Li _{1,

2,

3} , Hongping He _{1,

2} , Xiaoliang Liang _{1,

2} , Qi Tao _{1,

2} , Shichao Ji _{1,

2} , Meijun Yang _{1,

2} , Yilin He _{1,

2,

4} , Qingjin Zeng _{1,

2,

4} , Yiping Yang _{1,

2} , Jianxi Zhu _{1,

2,

4}

Affiliation

长石的高岭化广泛存在于各种地质环境中，包括风化和热液环境。然而，这种矿物转化和高岭石形成的机制仍然不清楚。本研究在水热条件下进行了有序钠长石向高岭石的转变实验，以揭示所涉及的转变机制以及具有“小册子”形态的高岭石聚集体的形成机制。所获得的结果表明，由于有序钠长石中 Al-O _{4四面体的构型和连接与 Al-O}₂ (OH) ₄的构型和连接显着不同，转变过程是由完全溶解-再结晶机制造成的。高岭石中的八面体片。在前体钠长石的溶解过程中，Si 可能先于 Al 从钠长石结构中释放出来。随后，四配位铝 (Al ^IV ) 将逐步转化为六配位铝 (Al ^VI)通过水化作用，有利于高岭石的形成。对于大粒径钠长石，蚀变产物是具有“小册子”形态的高岭石聚集体，由钠长石溶解过程中生成的Al和Si中间组分附着，随后高岭石片晶或层状结晶堆积而成。最有可能沿着钠长石裂隙达到微米高度。然而，“小册子”高岭石聚集体的结晶度和层堆叠顺序较低。这些发现为更好地理解长石转化为高岭石以及在自然和实验条件下形成具有“小册子”形态的高岭石聚集体提供了见解。

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Transformation of Ordered Albite into Kaolinite: Implication for the “Booklet” Morphology

Kaolinization of feldspars is widespread in various geological environments including weathering and hydrothermal environments. However, the mechanisms of such mineral transformation and kaolinite formation remain obscure. In this study, the experiments of the transformation of ordered albite into kaolinite were carried out under hydrothermal conditions to reveal the transformation mechanism involved and the formation mechanism of kaolinite aggregates with a “booklet” morphology. The obtained results demonstrated that a complete dissolution–recrystallization mechanism is responsible for the transformation process since the configurations and linkages of Al–O₄ tetrahedrons in ordered albite are significantly different from those of the Al–O₂(OH)₄ octahedral sheets in kaolinite. During the dissolution of precursor albite, Si might be released from the structure of albite prior to Al. Subsequently, four-coordinated Al (Al^IV) would be progressively converted into six-coordinated Al (Al^VI) through hydration, which is beneficial to the formation of kaolinite. For albite with a large particle size, the alteration products were kaolinite aggregates with a “booklet” morphology, which were formed by the attachment of generated intermediate components of Al and Si during the dissolution of albite and subsequent crystallization of kaolinite platelets or layers stacking up to a micron height most likely along the albite cleavages. However, the crystallinity and layer stacking order of the “booklet” kaolinite aggregates were low. These findings provide insights for a better understanding of the transformation of feldspars into kaolinite and the formation of kaolinite aggregates with a “booklet” morphology under both natural and experimental conditions.

更新日期：2022-03-21

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