黄土中石英的含量与结晶度指数的测定

DETERMINATION OF QUARTZ CONTENT AND CRYSTALLINITY INDEX FROM LOESS SAMPLES

碎屑石英是风成黄土最主要的组成矿物,其结晶度指数与粉尘源区石英的母岩类型有关,其含量则可用于估算风尘通量变化进而恢复源区的干旱化历史。通过详细的探讨,揭示了测试条件及数据处理方法对石英含量和结晶度指数估算的可能影响。结果表明:(1)测量石英结晶度指数时扫描的步长和速度有别于测量石英含量时的参数设置;(2)数据处理时,先对数据进行人工手动扣除背景,结晶度指数要依据衍射图谱67.74°处和67.85°处的峰谷值进行估算,而石英含量的估算主要依据衍射图谱中20.9°处石英峰与28.4°处硅粉峰;(3)石英结晶度指数需要反复压片测量多次取平均值。

Clastic quartz is the main mineral component of the eolian loess.The Crystallinity Index（CI） of clastic quartz is related to the type of mother rock,and the quartz content（QC） can be used to estimate the dust flux change so as to restore the desertification history of the source area.The paper discussed in details the testing conditions and data processing methods,and the errors they may cause to the estimation of QC and CI.It is concluded that（1） The scanning step size and speed should be different when CI and QC are measured separately;（2） Before the data processing,the background should be deducted manually.CI was estimated by the diffraction peak value at 67.74° and the diffraction valley value at 67.85°,and the estimation of QC mainly depends on the diffraction quartz peak value at 20.9° and diffraction silicon peak value at 28.4°;（3） CI should be the average of repeated measurement by pressed methods.