松散沉积物和沉积岩非球形碎屑长轴微组构的定量方法(英文)

THIN SECTION METHOD FOR QUANTITATIVE MICROFABRIC STUDY OF NONSPHERICAL LONG AXES IN LOOSE SEDIMENT AND SEDIMENTARY ROCK

以往利用碎屑的延性特征研究沉积碎屑的微组构时,未充分考虑方位角、倾角和切角等的关系,有时得出的结论不可靠。本文通过理论解析,讨论了用薄片法研究非球形碎屑长轴微组构的问题、在满足一定的倾角、真长短轴长度比值和视长短轴长度比值的条件下,水平切片上的视长轴方位可代表真长轴方位。优势方位明显,平均倾角可用平均优势方位的余弦与垂直切片上平均视倾角的正切之积,或者用平均优势方位的正弦与横向切片上的平均视倾角的正切之积来估算。球度、真长短轴和视长短轴长度比值越大,而倾角越小,那么方位量测的系统误差就越小。量测倾角用的垂直或横向切片与优势方位的夹角越小,倾角量测的系统误差也越小。

The thin section method for the quantitative microfabric study of nonspherical elongate fragments in friable sediments is discussed theoretically. The orientation of the apparent long axis on a horizontal thin section can be represented as the azimuth of the true long axis under certain conditions of plunge, the ratio n of true long axis to short axis and the ratio k of apparent long axis to short axis. If the preferred orientation is appparent, the average plunge can be calculated approxmately by the product of the cosine of the average azimuth and the tangent of the average apparent plunge on vertical thin section or the product of the sine of the average azimuth and the tangent of the average apparent plunge on transverse thin section. If the spherity, the n and k values are high and the plunge is low, then the measuring accuracy is high. The smaller the included angle of the thin section for measuring apparent plunge with the preperred orientation, the higher the measuring accuracy.