Optical anisotropy of coal from the Ruda syncline area in the upper Silesian Coal Basin (USCB) and its relation to tectonic setting

Oriented blocks and non-oriented samples were examined. True reflectance values determined on the oriented blocks are R(max) 0.94-1.02 %, R(int)=0.88=0.95 % and R(min)=0.81-0.86 % whereas on the non-oriented samples: R(bmax)=0.96 - 1.03 %, R(bint)=0.90-0.96 % and R(bmin)=0.83-0.88 %. Bireflectance amounts analogically: R(bi)=0.12=0.17 % and R(bbi) = 0.13-0.15 %. Vitrinite in all the cases reveals biaxial negative optical character. Direction of R(max) axis (azimuth 18°-38°) is concordant with the syncline axis. Deviation of R(min) axis from the vertical is usually 10-15°with SE plunge and its reorientation from perpendicular to bedding reaches 8-20°. Coalification in the study area occurred simultaneously with the formation of the Ruda syncline. Vitrinite indicatrix was formed by stress connected mostly with occurrence of the overburden or movements of the crystalline basement blocks but also due to the East-Sudetic compression.