Thermal maturity assessment of the Upper Triassic to Lower Jurassic Nampo Group, mid‐west Korea: Reconstruction of thermal history

摘要: Thermal maturity of the Upper Triassic to Lower Jurassic Nampo Group, a sediment-fill Chungnam Basin located in central western part South Korea, was assessed by illite crystallinity measurement and sandstone microtexture analysis. The Group consists fluvio-lacustrine deposit bearing meta-anthracitic coals over-thrusted basement rocks. Sandstones are characterized down sequence increasing crystallinity, from anchizone epizone, which is strongly suggestive burial heating. Deep-burial diagenesis deformation evidenced well-developed pressure solution textures, whose intensity tends increase sequence, ductile lowermost strata. On basis result measurement, maximum paleo-temperature total depth estimated be ca 340°C 10 km, respectively; these conditions good agreement with observed features. absence strata younger than around suggests that deep caused tectonic crustal loading. overload because over-thrusting occurred during Daebo orogeny, closely related orthogonal subduction Izanagi Plate beneath East Asian continent. Subsequent hydrothermal alteration disturbed thermal pattern, resulting anomalously high meta-anthracitization.