Origin of the penecontemporaneous sucrosic dolomite in the Permian Qixia Formation, northwestern Sichuan Basin, SW China

LU Feifan,TAN Xiucheng,ZHONG Yuan,LUO Bing,ZHANG Benjian,ZHANG Ya,LI Minglong,XIAO Di,WANG Xiaofang,ZENG Wei

Fig. 2. Macroscopic and microcosmic features of Md1 and Md2 in the Qixia Formation of northwestern Sichuan Basin. (a) Well D6, 7743.58 m, Qi-1 Member, core sample (The black arrows indicate up and down, similarly hereinafter), dark red stripe in very finely to finely crystalline dolomite (Md1); (b) Well D6, 7743.58 m, Qi-1 Member, Md1, Planar-polarized light (PPL); (c) Well D6, 7743.58 m, Qi-1 Member, no light or dark red light of dolomite in cathodoluminescence; (d) Well D6, 7740.06 m, Qi-1 Member, core sample, dolomite with gray-dark red bands, the dark red fabric is Md1, the light gray fabric is medium-coarse crystal sucrosic dolomite (Md2), with multiple layers of near-horizontal gravel fragments (indicated by green arrow); (e) Well D6, 7740.06 m, Qi-1 Member, scouring surface with bioclastic dolomite above and finely crystalline dolomite below, PPL; (f) Well D6, 7740.06 m, Qi-1 Member, karrens cutting matrix dolomite, and karst filling dolomite in the karren (Kfd), PPL; (g) Changjianggou section, Qi-2 Member, light gray Md2; (h) Changjianggou section, Qi-2, semi-autochthonous Md2, with turbid core and bright rim structure, stained cast thin section, PPL; (i) Changjianggou section, Qi-2 Member, no light or dark red light of dolomite core and red light of dolomite edge in cathodoluminescence.