Fig 1.
(a) Regional location of the Junggar Basin.
(b) Simplified structural framework of the eastern Junggar Basin. (c) Simplified geological sketch of the study area, showing the distribution of CM rocks. The DEM base was derived from NASA Earth Observatory data. (d) Schematic E–W cross-section of the Shazhang Fold-Thrust Belt.
Fig 2.
Stratigraphic column of the Shazhang Fold-Thrust Belt [15].
Table 1.
Statistical results of coal petrographic identification of the B-coal seams in the Xishanyao Formation ().
Fig 3.
Field photographs of CM rocks.
(a-c) Hills and depressions formed by CM rocks. (d) Hill formed by CM rocks, more than 10 m high. (e) Brick-red clinker. (f) Upper part composed of brick-red clinker and lower part of grayish-black paralava. (g) Columnar joints developed in CM rocks. (h) Gypsum infilling within fractures of CM rocks.
Fig 4.
Thin-section micrographs of CM rock.
(a) Red clinker, quartz grains with microcracks, clay minerals coated by hematite (PPL). (b) Red clinker, quartz grains showing undulatory extinction (XPL). (c) Reddish-brown clinker, quartz grains with embayed margins, iron oxides coating or disseminated within the glassy matrix, appearing opaque (PPL). (d) Dark-gray paralava, tridymite, glass, vesicles (PPL). (e) Paralava, dendritic magnetite, radiating/fibrous intergrowths of cristobalite and mullite (PPL). (f) Paralava, rhombohedral hematite, tridymite, cordierite (PPL). Quartz, Qz; Hematite, Hem; Tridymite, Trd; Cordierite, Crd; Mullite, Mul; Glass, Gl; Vesicles, Ves.
Fig 5.
(a) clinker, (b) Paralava. Quartz, Qtz; Tridymite, Trd; Hematite, Hem; Ferrocordierite, Fe-Crd; Microcline, Mc; Albite, Ab; Pseudobrookite, Psbr.
Table 2.
Single grain zircon (U-Th)/He ages of CM rocks.
Fig 6.
Statistical summary of Mesozoic-Cenozoic tectonic activity timings [2,3,9,14,17,22,23,93,94] and CM rock ages in the orogenic belts around the eastern Junggar Basin.