缅甸硬玉岩中后成合晶冠状体的含水性研究

基于多期次流体活动在硬玉岩及后成合晶冠状体的交互作用过程中发挥了至关重要的作用,采用电子探针、显微红外光谱等测试方法,从微尺度角度重点对缅甸角闪石质硬玉岩中角闪石+铬硬玉+硬玉后成合晶冠状体的成分和结构羟基赋存状态进行了研究。结果显示,参与后成合晶冠状体形成的流体组分较为复杂且形成过程是多阶段的;后成合晶冠状体的共生矿物组合不同,角闪石质硬玉岩中普遍发育角闪石+铬硬玉+硬玉化学成分环带;后成合晶冠状体中核部角闪石结构羟基含量较为均一,铬硬玉边缘至硬玉、硬玉晶粒中的结构羟基含量呈较为规律的递增趋势。核部角闪石中结构羟基均一且外层硬玉中结构羟基含量的变化规律表明缅甸硬玉岩中后成合晶冠状体的形成环境相对稳定,主要以多期次流体交代为主,未出现较大规模的动力变质作用。缅甸硬玉岩中后成合晶冠状体成分及水含量的变化规律有助于解析该地区俯冲带流体参与硬玉岩交互作用的轨迹,从而为缅甸硬玉岩的成岩机制提供一定的佐证。

A preliminary study of water content of symplectitic coronas in jadeitite in Myanmar

Based on the fact that multi-stage fluid activities play an important role in the interaction between jadeitite and symplectitic coronas, the authors focused on the study of the composition and the mode of occurrence of water in the symplectitic coronas of amphibole + chromite jadeite + jadeite in Myanmar amphibolite jadeitite from the micro scale point of view. The results show that the fluid composition involved in the formation of symplectitic coronas is complex and the formation process is of multi-stage. The paragenetic minerals of symplectitic coronas are different, the chemical composition zone of amphibole+ chromite jadeite + jadeite is widely developed in amphibolite jadeitite. In addition, the structural hydroxyl content of amphibole is more uniform in the core of symplectitic coronas, and from the edge of chromite jadeite to jadeite the structural hydroxyl content increases regularly. The change regularity of structural hydroxyl content further indicates that the formation environment of the symplectitic coronas in Myanmar jadeitite is relatively stable, which is dominated by multi-stage fluid metasomatism, without large-scale dynamic metamorphism. The evolution of the composition and water content of symplectitic coronas in Myanmar jadeitite is helpful to understanding the interaction trajectory of the fluids in the subduction zone in this area and providing some evidence for the diagenetic mechanism of Myanmar jadeitite.