摘要:
X射线荧光光谱岩心扫描(XRF Core Scanner,XRF-CS)经过20余年的发展,在多类型沉积岩心的元素分析、古环境重建、矿藏储层及丰度的勘探等领域得到了广泛应用,并展示出巨大的潜力。然而,对XRF-CS元素信号影响因素和校正的研究较为少见(特别是在国内),限制了该仪器的正确使用和数据的准确解读。本文对比分析了XRF-CS相较于传统X射线荧光光谱技术的快速、连续、无损且高分辨率的优势和特点,结果表明其测试时间仅为传统分析技术的1/10,而分辨率可高达0.02 mm;但XRF-CS的元素信号值为半定量,无法精确识别元素组成。在此基础上,归纳总结了XRF-CS“仪器”和“岩心”的影响因素、程度和效果,指出在最优化仪器设置的前提下,选取适当的扫描间隔和曝光时间可以实现XRF-CS元素信号强度和“经济性”的平衡;在扫描过程中,通过晾干和平整岩心表面,尽可能排除含水量和粒度分布对元素信号的削弱作用。此外,本文系统阐述了国际通用的Normalized Median-Scaled(NMS)模型、Log-ratio Calibration Equation(LRCE)及改进的 Multivariate Log-ratio Calibration(MLC)模型、Normalized Polynomial-scaled Calibration(NPS)和 Polynomial-Corrected Multivariate Log-ratio Calibration(P-MLC)模型,指出3种模型的校正过程和应用潜力,进而提高XRF-CS元素信号的准确性。今后,需进一步增强多类型仪器间同一因素影响效果对比分析、校正模型优化和可视化软件包开发、多种传感器搭载和“一体化”扫描、地质矿藏资源探测与评估的广泛应用等多方面的研究。
Abstract:
With more than 20 years of development, the X-ray fluorescence core scanners (XRF-CS) have been widely applied in the elemental analysis of multi-type sediment cores, the paleoenvironment reconstruction, and the exploration of mineral reservoirs and their abundance, exhibiting great potential for application. However, there is a lack of studies on the influencing factors and correction of the elemental signals output by XRF-CS (especially in China), which restricts the proper use of XRF-CS and the accurate interpretation of their data. Compared with conventional XRF techniques, XRF-CS enjoy a high processing speed (only 1/10 of the time for conventional analysis), high continuity, non-destructive scanning, and a high resolution (up to 0.02 mm). However, XRF-CS only output semi-quantitative values of elemental signals and thus fail to accurately identify the element compositions. This study summarized the influencing factors of the values of the elemental signals output by XRF-CS in terms of instruments and cores, together with the degrees of the influences. On this basis, this study proposed achieving the balance between the intensity of elemental signals output by XRF-CS and cost by selecting appropriate scanning steps and exposure time on the premise of the optimal instrument setting. This study also suggested that the influences of water content and particle sizes on elemental signals should be eliminated as far as possible by drying in the air and smoothing the core surface during the scanning. To improve the accuracy of elemental signals output by XRF-CS, this study systematically introduced three types of international common calibration models and their application potential, namely the normalized median-scaled (NMS) model, the log-ratio calibration equation (LRCE) model, the improved multivariate log-ratio calibration (MLC) model, the normalized polynomial-scaled calibration (NPS) model, and polynomial-corrected multivariate log-ratio calibration (P-MLC) model. Finally, this study proposed further enhancing research on the comparative analysis of the influence exerted by the same factor among multiple types of XRF-CS; the optimization of calibration models and development of visual software packages; the equipment of multiple sensors for integrated scanning, and the extensive applications in the exploration and evaluation of geological and mineral resources.
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