利用热液金刚石压腔开展扎布耶石(碳酸锂)结晶实验的研究

Crystallization Experiment Study of Zabuyelite Using Hydrothermal Diamond Anvil Cell

花岗伟晶岩一般赋存了大量富晶体包裹体,扎布耶石（碳酸锂）是锂辉石中富晶体包裹体内的主要矿物之一,因此,扎布耶石的形成机制和温压条件对富晶体包裹体的捕获条件有重要的指示意义。本文通过热液金刚石压腔（HDAC）开展Li_2CO_3-H_2O体系的结晶实验,9组实验结果表明,扎布耶石的成核温度是550（±30）℃,大约在温度降低15℃后,晶体停止快速生长,而后缓慢生长直至在400（±50）℃完全停止生长。扎布耶石的生长主要集中在550~400℃,而与压力影响不大,处于锂辉石的稳定温度范围内,这佐证了富晶体包裹体中的扎布耶石可以是捕获流体直接结晶形成的晶体。扎布耶石开始结晶后经历了快速生长,导致包裹体内部压力降低,这可能是富晶体包裹体内存在方石英的原因之一。

The crystal-rich inclusions（CIs）are a common type of fluid inclusion in granite pegmatite.Zabuyelite is one of the main spodumene minerals which contain crystal-rich inclusions.Therefore,mechanisms for the formation and P-T conditions of zabuyelite will have important implications for the entrapment conditions of the crystal-rich inclusion.Crystallization experiments were conducted in a hydrothermal diamond anvil cell（HDAC）using Li_2CO_3-H_2O as starting materials.The results of nine experiments performed indicate that the nucleation of crystals started at 550（±30）℃,the crystals stopped quick growth when temperature decreased by 15℃,and then crystals growth was slow and stopped until temperature was at 400（±50）℃.The temperature of zabuyelite crystallization concentrate on 550~400℃ and pressure has no effect on its growth.The temperatures fall to the condition range of spodumene,further evidencing that the zabuyelite rich in crystal inclusion is the product of direct crystallization of entrapped fluid,rather than the reaction between low-density aqueous carbonic fluid and the host spodumene at the late stage of pegmatite evolution.Rapid growth of zabuyelite after nucleation resulted in decreasing of internal pressure in the crystal-rich inclusions and this might be one leading reason for the formation of cristalbalite in crystal-rich inclusion.