新疆色带电气石的生长过程及颜色起因研究

本文以新疆阿尔泰山地区花岗伟晶岩中的色带电气石为重点,应用X射线透射形貌技术,揭示了光学显微镜无法查明的结构缺陷,结合晶体表面微形貌观察及包裹体研究,阐明了色带电气石晶体的形成过程和生长机理。同时运用吸收光谱、穆斯鲍尔谱、红外吸收、核磁共振等谱学方法,对照光谱及化学分析、电子探针分析结果,对阿尔泰不同颜色的电气石晶体,特别是玫瑰色的颜色起因作了较全面的讨论。

GROWTH PROCESS AND ORIGIN OF COLOUR-BANDING TOURMALINE FROM XINJIANG

Chemical analysis, EPMA, optical absorption, X-ray topography, IR and Mssbauer spectroscopy were conducted on colour-banding tourmaline from Altai granitic pegmatite, Xinjiang, to investigate the mechanism of its colour change. Altai tourmaline usually has a red core enveloped by green rings. It has been observed by means of X-ray. topography that change in colour is always accompanied by abrupt change in texture.The core shows macromasaic texture but the outer rings are of lamellar texture. Optical absorption and EPMA results suggest that the difference in colour can be related to the slight variation in iron and manganese. Iron increases, while manganese decreases from the core to the outer area of the crystal. Therefore, the formation of colour bands can be attributed to the changing growth condition. According to the distribution features and homogenization temperatures of fluid inclusions in tourmaline, it can be concluded that there are two distinct growth stages separated by partial dissolution in hydrothermal process.