石盐中流体包裹体在古气候研究中的应用进展

摘要

蒸发岩沉积在地质历史上分布十分广泛。其中的石盐属于广温相矿物，其内部捕获的流体包裹体记录了大量石盐沉积时的古温度信息。石盐中流体包裹体的冷冻测温法已经广泛应用于包裹体均一温度的测定。通过该方法，目前已经初步建立了包裹体记录的均一温度与古气温的关系，即石盐中纯液相原生流体包裹体均一温度最大值与卤水结晶温度符合，与最大平均气温关系密切，且形成于卤水底层“人”字型晶石盐中的流体包裹体记录的温度信息更能代表较长时间尺度的古气温变化等。除此以外，成岩作用对于石盐中流体包裹体的温度记录的影响也被广泛讨论，尽管石盐矿物中流体包裹体可能发生变形以及热再平衡等一系列的变化，但“人”字型结构的原生石盐晶体特征以及石盐颗粒云雾状环带中呈负立方体形状的流体包裹体为原生包裹体等一系列识别标志的建立，为我们利用石盐中流体包裹体进行古温度的研究提供了很好的样品基础。通过对石盐中原生流体包裹体最大均一温度测试，已经得到了一些现代盐湖以及古代盐类沉积时的环境温度信息，并在古气温波动方面也展示了一定前景。尽管石盐中流体包裹体在古气候研究中取得了初步成果，但仍存在一些亟待解决的问题：如除最大均一温度的其它温度数据代表的环境温度意义问题；通过对盐类地质剖面进行连续的包裹体测温建立高分辨率定量古温度变化记录等，也尚未有大量文章报道。我国盐类资源分布广泛，石盐包裹体测温技术的应用，对于盐类发育地区古气候环境定量化信息提取具有十分重要的意义。%The evaporation sediments distributes widely in the geological history.The halite is eurythermic mineral.The fluid inclusions in it record a lot of paleotemperature information.The freezing method of the fluid inclusion in the halite is applied in measuring the homogenization temperature widely.By this method,the relation between the homogenization temperature of the fluid inclusion and the paleotemperature are learned preliminarily, including the maximum value of the homogenization temperature from the pure liquid primary fluid inclusions is consistent with the crystallization temperature of the brine,and is closely related with the maximum mean air temperature;the temperature information from the fluid inclusion of the halite with the “Λ”shape crystal which deposits in the bottom of the brine may reflect the paleotemperature fluctuation in the long time scale.Besides,the affection of the diagenesis on the paleoclimate record of the fluid inclusion is discussed widely.Though the fluid inclusion in the halite may deform and undergo thermal balance again,a series of identifying features set the foundation of the paleotemperature research,such as the “Λ”shape of the original halite crystal and the primary inclusions with the native cube shape in the cloud-like zone of the salt crystal and so on.By measuring the maximum homogenization temperature of the original fluid inclusion in the halite,it reveals the some environment temperature message from the modern salt lake and the ancient salt sediment,and shows the research prospects in the aspect of the paleotemperature fluctuation.Though the paleoclimate research on the fluid inclusion of the halite has got the primary harvest,it still exists the critical problems,including the circumstance means of the other temperature data except for the maximum homogenization temperature and how to build the high resolution and quantitative paleotemperature fluctuation curve by measuring the maximum homogenization temperature of the fluid inclusion from the salt geological profile successively.The salt resource in China distributes widely.The application on the thermometry of the salt inclusion is significant for extracting the quantitative information of the climate and environment from the inner salt lake.