WEI Shou-shu1,2,3, MA Ling-ya1,3, LIANG Xiao-liang1,3, JI Shi-chao1,2,3, LI Shang-ying1,2,3, ZHU Jian-xi1,3, CHEN Qing-ze1,3, HE Hong-ping1,2,3*
(1. CAS Key Laboratory of Mineralogy and Metallogeny, Guangdong Provincial Key Laboratory of Mineral Physics and Materials, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;
2. University of Chinese Academy of Sciences, Beijing 100049, China;
3. Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China)
Abstract: In this paper, the effect of Al3+ on the dissolution/transformation process of biotite has been studied by using the X-ray diffraction, Fourier infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and Mo？ssbauer spectroscopy. Especially, the mineralogical characteristics of the transformation products and the transformation mechanism of biotite in solutions with different concentrations of Al3+ were emphatically analyzed. The results show that protons produced through the hydrolysis of Al3+ in solutions had accelerated the dissolution and transformation of biotite. When the solutions have low concentrations of Al3+ (0.01－0.10 mol/L), a small amount of protons, produced by the hydrolysis of Al3+, contributed slightly to the dissolution of lamellar structure of biotite, with main transformation products including vermiculite, hydrobiotite, and chlorite. The preferentially dissolved Fe congregated into the nucle which had adsorbed the dissolved Si to have formed the spherical nanoparticles with core-shell structure and the well-crystallized hematite. When the solutions have high concentrations of Al3+ (0.30－0.60 mol/L), Al3+ a large amount of protons, produced by the hydrolysis of Al3+, obviously accelerated the dissolution of biotite, with the main transformation products including kaolinite and weakly crystallized iron oxides. The concentration of Al3+ can change obviously the dissolution rate of biotite and the corresponding transformation products, thus can affect the weathering process of biotite.
Keywords: Biotite; dissolution; aluminum; transformation mechanism
ACTA MINERALOGICA SINICA Vol. 41, No.1, 2021, page 85-94