应用电子探针原位微区分析技术测试硅硼钠石矿物
秦玉娟，余朝丰，徐 洋，李玉文应用电子探针原位微区分析技术测试硅硼钠石矿物
秦玉娟1，2，余朝丰1，徐 洋1，李玉文1
（1.中国石油杭州地质研究院；2.中国石油集团碳酸盐岩储层重点实验室，浙江 杭州 310023）
摘 要 测试样品中的硅硼钠石矿物除了具有规则的晶体形态外，还有一种无定形类别。二者光学特征差异大，定性分析如薄片鉴定、扫描电镜(SEM)等方法在形貌上的识别难以可靠地确定它们是否同为硅硼钠石矿物。本文应用电子探针原位微区分析(EPMA)技术，针对微区进行成分分析，精确测试了该矿物。EPMA具体包括背散射电子图像(BSEI）分析技术与元素定量分析技术两种主要类型，是定性与定量分析技术的结合。测试硅硼钠石矿物要面对的主要挑战有两点：（1）硼（B）元素处于EPMA检测下限，而且无氧化物标样；（2）钠（Na）元素易迁移。针对这些检测难点，笔者采取了一系列措施，如选用氮化硼（BN）标样，避开B元素处于低位的分光晶体及加大电子束斑、延长测试时间等等。最终，在薄片分析与能谱定性分析的基础上，通过BSEI分析技术确定矿物显微结构中的均质区域，原位定量分析测试其化学成分，避免了因显微结构与成分不均造成的偏差，有力地提高了测试精度，为正确鉴定该矿物提供了可靠依据。
关键词 电子探针；原位微区；硅硼钠石
中图分类号：P757.1；P578.93 文献标识码：A doi:10.3969/j.issn.1000-6281.2016.03.005
A microarea analysis technique of EPMA to probe reedmergnerite
QIN Yu-juan1, 2，YU Chao-feng1，XU Yang1，LI Yu-wen1
(1 PetroChina Hangzhou Research Institute of Geology, Hangzhou Zhejiang 310023；2 Key laboratoryof Carbonates Reservoirs, CNPC, Hangzhou Zhejiang 310023, China)
Abstract In the samples, there are two types of reedmergneritewith different optical features: a regular one and an irregular one. Both thin section identifying and SEM (scanning electron microscope), each being a kind of qualitative analysis, are hard to confirm them as the same mineral. In this paper, we apply EPMA (electron probe microanalysis), a micro-area analysis technique, to analyze the composition aiming at the microarea, and at last we probe the mineral precisely. EPMA contains two leading techniques, one is BSEI ( a backscattered electron image) analysis, the other is element quantitative analysis. The challenges for probing reedmergnerite are like, ①element B, which being in the lowest detection limit of EPMA, and short of standard sample of oxide in our laboratory, ②element Na is prone to migrating by probed (a heating process). For these probing difficulties, we have taken some measures, e.g., choosing Boron Nitride as a standard sample; avoiding the lower limit of the spectrometer from probing B; selecting a larger beam size; increasing probing time, and etc. In the end, based on both the thin section analysis and EDS (energy dispersive spectrometer) analysis, we recognize the even area of the microstructure by the BSEI, then, probing its corresponding chemical ingredients by in-stiu element quantitative analysis. In this way, we avoid some errors caused by the uneven microstructure and ingredients. Consequently, the probing precision is effectively improved. And also it helps to correctly identify the mineral with some credible evidence supplied by the analysis.
Keywords EPMA；microarea analysis；reedmergnerite
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