旋转载物台显微镜下矿物定量及其精确性研究

Study on Accuracy of Quantitative Analysis of Minerals under Rotating Stage Microscopy

光学显微镜矿物定量方法简单、结果可靠,被广泛应用于工艺矿物学和岩矿鉴定工作中。"线测法"测试速度快,效率高,并且适用于细粒矿物颗粒,在应用中占有重要的地位。但是常规的测试线具有方向同一性的特征,不能很好地处理待测矿物颗粒"择优取向"的问题。针对该问题,本文阐述了一种通过旋转载物台进行镜下矿物定量的方法。主要工作原理为:系列圆周线穿切各待测矿物颗粒截线长度比等于其体积比。主要测试过程为:转动载物台一周,测定待测矿物颗粒与视域周边相交的各段圆周截线所占的包含角之和(’K)。观测一定数量的视域(N),计算质量百分含量(W)=[(’K/(N×360)]·(δ/Δ)×100%。经理论分析,并对方铅矿、闪锌矿和磁铁矿光片进行了检验,结果表明:旋转载物台矿物定量工作量低、简单易行、精度较高,与传统"线测法"测试结果差值小于±5%,并且可以有效地解决待测矿物颗粒"择优取向"对测试结果的不利影响。

Mineral quantitative analysis by optical microscope is simple and reliable,and has been widely used in process mineralogy and rock-mineral determination. The line measurement method is fast and efficient,and is suitable for fine-grained mineral particles, which plays an important role in the application. However, the conventional test line has the characteristics of directional identity, and cannot deal with the problem of‘preferential orientation＇of the analyzed mineral particles. To solve this problem,a new mineral quantitative method by rotating the platform of an optical microscope was conducted. The main principle is that the length ratio of the circular cutting lines of different mineral particles is equal to their volume ratio. The main test process of the method is as follows： rotating the objective table for a circle and testing the angles（ΔK） that the circular cutting line contained,which is intersected by the mineral particles and the visual field under the microscope. By testing a certain number of visual fields（ N） and calculating weight percentage（ W）,the percent content is acquired by the equation W = [（ΣΔK/（ N × 360） ]·（ δ/Δ） × 100%. After theoretical analysis,the galena,sphalerite,and magnetite thin sections were examined. The results show that the new mineral quantitative method is simple,accurate,and the difference value of the test results is less than ± 5% compared with the conventional line measurement method. In addition,this method can be used to effectively solve the negative effect of ‘preferential orientation＇on the test results.