Absorption correction procedures for quantitative analysis of fluid inclusions using synchrotron radiation X-ray fluorescence
Absorption correction procedures for quantitative analysis of fluid inclusions using synchrotron radiation X-ray fluorescence
复制标题
使用同步辐射 X 射线荧光定量分析流体包裹体的吸收校正程序
DOI：
10.1016/s0009-2541(97)00125-3
复制
发表时间：
1998
期刊：
影响因子：
3.9
通讯作者：
P. Populus
中科院分区：
文献类型：
--
作者：
P. Philippot;B. Ménez;P. Chevallier;F. Gibert;F. Legrand;P. Populus
使用同步辐射X射线荧光(SRXRF)分析单个流体包裹体的主要限制因素是流体和宿主材料对入射和荧光辐射的吸收的量化。从理论上讲，给定元素Z在溶液中测得的(Kα/Kβ)z强度比与被穿越材料的厚度成正比，因此可以作为吸收校正的可靠条件。为了从实验上约束(Kα/Kβ)z、宿主材料厚度与流体包裹体大小和盐度之间的关系，利用安装在D15线上的Lure(法国奥赛)光子微探针，开发了一个三步法。它们是：(1)使用已知厚度的铝和石英薄板截获从纯金属靶(Mn、Fe、Ni、Cu、Zn)发出的X射线荧光光束；(2)对含有已知浓度(∼5000 ppm)的各种金属(Mn、Ni、Zn)和盐类(0和15 wt%Nacl)的石英玻璃毛细管进行可行性测试；(3)对岩盐晶体中含有已知金属含量(∼1000ppm镍和锌)的合成流体包裹体进行确认测试。实验1的结果表明，(Kα/Kβ)z比随主体材料厚度的变化与理论预测完全一致，并且与局部分析环境(测量的重复性)无关。在实验2和实验3中，使用溶液中参比元素(锌)的(Kα/Kβ)z比率来估计所穿越的宿主材料的厚度。确定锌的X射线峰强度对应于给定的浓度，从而可以测定溶液中其他痕量金属的浓度。在这两个实验中，精密度都很高，标准偏差(1σ)在平均值的1-8%之间，但精确度可能相对较差，平均值从已知浓度的3-11%(毛细管试验)到高达17%(包合试验)。计算出的金属浓度在高于已知浓度的狭窄范围内，强烈表明用于校准锌X射线峰的锌浓度可能不同于使用SRXRF有效测量的锌浓度。为了更好地评估这一潜在的误差来源，需要了解SRXRF测量过程中的锰、镍和锌的氯化物和二氧化硅的形态。尽管如此，相对于已知浓度，结果通常好于20%(实验2)和32%(实验3)。这意味着可以使用SXRF技术定量测定单个流体包裹体中的元素浓度，而不需要精确了解包裹体的深度和几何形状。
The main limiting factor associated with individual fluid inclusion analysis using synchrotron radiation X-ray fluorescence (SRXRF) is the quantification of absorption of the incident and fluorescent radiation by the fluid and the host material. Theoretically, the measured (Kα/Kβ)zintensity ratio from a given element Z in solution is directly proportional to the thickness of material traversed and therefore could be used as a reliable term for the absorption correction. In order to constrain experimentally the relationship between (Kα/Kβ)z, host material thickness and fluid inclusion size and salinity, a three-step protocol has been developed using the LURE (Orsay, France) photon microprobe installed on line D15. These are: (1) interception of the X-ray fluorescent beam emerging from pure-metal targets (Mn, Fe, Ni, Cu, Zn) using thin plates of aluminium and quartz of known thicknesses; (2) feasibility tests on silica-glass capillaries containing known concentrations (∼5000 ppm) of various metals (Mn, Ni, Zn) and salts (0 and 15 wt.% NaCl); (3) confirmation tests on synthetic fluid inclusions containing known metal contents (∼1000 ppm Ni and Zn) hosted in halite crystals. The results of experiment 1 indicate that the evolution of the (Kα/Kβ)zratio as a function of host material thickness is in perfect agreement with theoretical predictions and is independent of the local analytical environment (reproducibility of the measurements). For experiments 2 and 3, the (Kα/Kβ)zratio of a reference element in solution (Zn), was used to estimate the thickness of host material traversed. Establishing that the X-ray peak intensity of Zn corresponds to a given concentration allowed the concentration of other trace metals in solution to be determined. In both experiments, the precision is high with standard deviations (1σ) from 1 to 8% of the mean, but the accuracy can be relatively poor with mean values ranging from 3–11% (capillary tests) to as high as 17% (inclusion tests) of the known concentrations. Tight ranges of calculated metal concentrations at values higher than the known concentrations strongly suggests that the Zn concentration used to calibrate the Zn X-ray peaks may be different from that effectively measured using SRXRF. A knowledge of Mn, Ni and Zn chloride and silica speciation during SRXRF measurements is required to evaluate better this potential source of error. Despite this, results are commonly better than 20% (experiment 2) and 32% (experiment 3) relative to the known concentrations. This implies that elemental concentrations in individual fluid inclusions can be quantitatively determined using the SXRF technique without precise knowledge of the inclusion depth and geometry.