Distribution,characteristics and significances of burnt rocks in northern China
Shi Zhi-Qiang1, Wang Mei-Ling1, Chen Bin2
1 Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China; 2 School of Geography and Environment,Liaocheng University,Shandong Liaocheng 252000,China
Abstract：Burnt rocks are widely distributed in many sedimentary basins located in the northern China that are bounded by Kunlun mountain-Qinling-Dabie mountain. However,few studies have focused on the origin,age and geological significance of these kinds of metamorphic rocks. Based on our field investigation,four distribution modes of the burnt rocks are found: (1)large area distribution,(2)linear distribution along the mountain range alignment,(3)distribution along the river incised-valley and(4)covered by the Quaternary loess. These burnt rocks were mainly caused by the self-ignition of Jurassic and Carboniferous-Permian coals. Various burnt rocks developed in the burnt rock area on different levels. The vitrified structure,whitened structure,lava structure,residual structure,pore structure,columnar jointing structure,breccia structure,fissure structure and filling minerals are often found in these burnt rocks. The burnt rocks are mainly red,mixed with brown,black and steel-gray colors. The typical high temperature minerals as cristobalite,tridymite,cordierite,sekaninaite and mullite are common in these burnt rocks. The active tectonic movements and arid climate in northwestern China triggered the formation of burnt rocks since the Miocene. The relationship between the palaeotectonic,palaeoclimate,palaeo-wildfire and the coal self-ignition,however,has been seldomly studied. Such information implied from the formation of burnt rocks should be paid more attention in the future work.
Shi Zhi-Qiang,Wang Mei-Ling,Chen Bin. Distribution,characteristics and significances of burnt rocks in northern China[J]. JOPC, 2021, 23(6): 1067-1081.
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