笔石光学结构的反射率十字图解研究

STUDY OF THE REFLECTANCE CROSS-PLOT OF OPTICAL STRUCTURE OF GRAPTOLITES IN CHINA

应用反射率十字图解研究了中国部分地区下古生界地层中动物有机碎屑笔石的光学各向异性。研究结果表明 ,在成熟度较低时 ,笔石呈现双光轴中性特征 ,即Rmax-Rint≈Rint-Rmin;随成熟度的增加 ,笔石具有明显的双光轴负光性特征 ,即Rmax-Rint<Rint-Rmin,且笔石反射率椭球体变得愈扁平。利用该方法还确定了笔石中间反射率轴Rint的数值以及随热演化程度增加笔石反射率指示面的形态和变化。由此可见 ,反射率十字图解方法是研究笔石光性各向异性极为有效的方法。

The optical anisotropy of zooclast graptolite in some Paleozoic strata of China has been studied using reflectance cross-plot analysis. The cross-plots indicate that low rank samples tend to be biaxial neutral (R max -R int ≈R int -R min ) and higher rank samples are obviously biaxial negative. In addition, it can be used to determine the value of the intermediate reflectance axis (R int ), the shape and variation in the graptolite reflectance indicating surface (GRIS) with maturity. From these cross-plots, GRIS shapes for this study are found to become oblate with rank. The reflectance cross-plot analysis is a useful tool for the study of the optical anisotropy of graptolite.