蒸发岩矿物单个流体包裹体成分测定方法研究进展

Advances in Chemical Composition Determination of Individual Fluid Inclusions Trapped within Evaporite Minerals

蒸发岩矿物流体包裹体,作为古卤水地球化学信息的有效载体,在反演古海洋、古湖泊成矿物质来源、水文地球化学演化过程中都具有十分重要的作用,其提取和分析技术一直备受盐矿学者重视。综述了近年来盐类矿物单个流体包裹体成分测定的主要方法,包括微钻—超微分析法、激光剥蚀电感耦合等离子体质谱法、扫描电镜—能谱法及激光拉曼光谱法,对其测试流程、应用范围、分析精度及优缺点进行了对比和总结;提出了多种方法交叉结合的应用思路,以满足包裹体多元素定量分析的要求,并对其应用前景提出了建议。

Fluid inclusions preserved within evaporite minerals, the reliable recorder of geochemical informa- tion of paleo-brines, play an important role in tracing the source of ore-formation material and reconstructing the hydro-geochemical evolution history of paleo-sea/lake. Salt-mine geologists have paid more attention to extractive and determinative techniques. In this paper, the authors summarized recent progresses in the chemical analysis techniques of individual fluid inclusions, including Ultra-micro-chemical Analysis （UMCA） , Laser Ablation Induc- tively Coupled Plasma-Mass Spectrometry （LA-ICP-MS）, Scanning Electron Microscopy with an Attached Energy Dispersive Spectrometer（ SEM-EDS） and Laser Raman Microspectroscopy （LRM）, and their determinative proce- dure, application area, analysis accuracy, advances and disadvances. The traditional Ultra-micro-chemical Analysis can be used to determine the concentration of K, Mg, Ca, and SQ, but not the concentration of sodium or chloride in the fluid inclusions. Futhermore, this fluid inclusion extraction requires relatively large inclusions which likely formed during recrystallization. The uncertainty of the UMCA method is typically 10% - 17% with 2 - 3 parallel test. The LA- ICP-MS method is able to analyse small individual inclusions （〉10 p.m） successfully with a wide range of ions, including major elements, low concentrations of minor and trace irons. The analytical error of this technique is 4% - 20%. However the test results can only be reported as ionic ratios because the volume of an in- clusion is unknown prior to analysis. The SEM-EDS technique can produce precise measurements of much smaller individual fluid inclusions （ 〉15 μm） with precision of 〈10%. The detection limits for the SEM-EDS are typically on the order of 0.1 wt% to 1.0 wt%. The ESEM-EDS method is similar to SEM-EDS method, and the major differ- ence is the instrument used for analysis. The precision of ESEM-EDS analysis is between 3% and 6% and the de- tection limits are 0.1 wt% for all the major irons except Na, which is 0.5 wt%. The Laser Raman Microspectros- copy method is unique nondestructive among all the techniques. It can be used to determine what covalent bonded complexes such as sulfate and bicarbonate. In order to obtain quantitative multi-element analysis data of fluid inclu- sions, the cross-comparison method of diverse measuring techniques was proposed in the future application.