地质成岩成矿演化过程的太赫兹光谱研究

Terahertz spectroscopic characteristics of the geological diagenetic and metallogenic evolution

流体包裹体是研究矿物演化的重要手段之一.不同温度条件下生长的石盐矿物中,其流体包裹体中的个体形态、数量与大小不同,流体包裹体是反映成矿流体的成分、温度和压力的最直接证据.本文利用太赫兹时域光谱系统对石盐体系进行了检测,根据样品的吸收系数变化建立了石盐矿物在温度环境下的演化模型,总结出石盐矿物的成岩过程:即早成岩期、晚成岩期和近似变质阶段,采用XRD和包裹体显微镜测试为辅助手段进行分析,并通过理论模拟进一步验证了演化模型的正确性,实现了利用太赫兹技术对地质成岩成矿演化过程的评价.

The study of fluid inclusion is an important tool and method in mineral evolution research. The shape, number and size of fluid inclusions in halite crystals grown at different temperatures are different and can directly show the composition, temperature and pressure of the ore-forming fluids. Terahertz time-domain spectroscopy（THz-TDS） has been used to probe the inclusion of individual of the halite rock, exhibiting different spectral signals in the terahertz band. The relationship between absorption coefficient and temperature exhibited the nonlinear features at different frequencies, a fitted regression curve can present accordingly and the evolutionary regime of halite rock（early diagenetic phase, late diagenetic phase and approximate metamorphic phase） can be indicated by the absorption coefficient in the THz region. Furthermore, XRD and optical microscope as supplementary methods provide more information for us to understand the evolutionary regime of halite rock. The results show that under low temperature, the inclusion of individual is less but relatively large, arranged in relatively loose; at higher temperatures, the inclusion of individual were more, substantially along or parallel to the crystal surface, but individual size is relatively small. The present study of identification based on THz-TDS was in good agreement with X-ray diffraction（XRD） and optical microscopes, and the evolution is validated by theoretical simulations suggesting that the terahertz technology can act as a non-destructive, contact-free tool for the evolution of the geological diagenetic and metallogenic research. THz-TDS can be used as a complementary method for composition and characteristic analysis of ore-forming fluids in geological diagenetic research, realizing a lead in evolution of rock reservoir diagenetic systems study.