Development characteristics and petroleum geological significance of Permian pyroclastic flow volcanic rocks in Western Sichuan Basin, SW China

PENG Hao,YIN Cheng,HE Qinglin,XIA Guoyong,LIU Yong,MA Tinghu,CHEN Kang,LIU Ran,SU Wang

Fig. 3. Microscopic characteristics of cores and thin sections of volcanic rocks in Western Sichuan Basin. (a) Gray diabase prophyrite; Well YT1; 5866.50-5866.85 m; (b) Gray dolerite; Well YT1; 5779.05-5779.32 m; (c) Gray-black basalt; Well TF8; 5267.57-5267.73 m; (d) Green-gray basalt with fractures; Well YT1; 5758.98-5759.16 m; (e) Diabase porphyrite with obvious diabasic texture; Well YT1; 5866.85 m; ×25 (+); (f) Dolerite with good lava structure and structural homogeneity; Well YT1; 5779.32 m; ×25 (-); (g) Basalt with low degree of crystallization; Well TF8; 5267.57m; ×125 (-); (h) Transition of basalt to dolerite; Well YT1; 5758.98 m; ×25 (-); (i) Dark gray pyroclastic rock with clear breccia boundary; Well TF8; 5188.42-5188.66 m; (j) Dark green-gray pyroclastic lava; Well YT1; 5645.50-5645.76 m; (k) Dark green-gray basaltic pyroclastic lava; Well YT1; 5645.76-5645.98 m; (l) Gray pyroclastic lava with breccias unevenly distributed and unclear bounded; Well TF8; 5144.10-5144.41 m; (m) Pyroclastic rock with visible pyroclastics and lithoclastics, poorly sorted; Well TF8; 5188.66 m; ×25 (-); (n) Dark green-gray pyroclastic lava with breccias which have uneven size, local long strips, obvious edge angles and disordered distribution; Well YT1; 5645.50-5645.76 m; core section (the same sample as j); (o) Dark green-gray basaltic pyroclastic lava with plastic magma clasts and rigid breccias; directional particles; Well YT1; 5645.760-5645.98 m; core section (the same sample as k); (p) Pyroclastic lava with dispersed dissolution micropores; Well TF8; 5144.41 m; ×100 (-); (q) Gray breccia-bearing tuff; Well ZJ2; 5248.42-5248.68 m; (r) Dark gray tuff; Well ZJ2; 5273.00 m; sidewall core; (s) Tuff with angular calcite clasts (stained particles); Well ZJ2; 5273.00 m; cuttings; ×200 (+); (t) Pyroclastic lava with tuffaceous mineral and dissolved micropores; Well YT1; 5645.90 m; blue casting section; ×100 (-); (u) Pyroclastic karst with dissolved pores and alternating distribution of calcite and schistose chlorite; Well TF8; 5144.41 m; ×6300; (v) Basaltic pyroclastic lava, devitrified; Well YT1; 5648.09 m; ×5000; (w) Porous basaltic magma clastic lava with intergranular dissolved pores; Well YS1; 6413.83 m; ×10 (-).