Burnt rocks(combustion metamorphic rocks)are widely distributed in northern China,and may be associated with the genesis of sandstone-type uranium deposits.However,few studies have considered the microscopic mineralogical characteristics of burnt rocks,and their geological significance has often been ignored in the relevant research.Highly developed burnt rocks are widely available in the Jurassic coal seam strata in the Liuhuanggou area of Xinjiang,China.This study investigates the color,structure,petrology,and mineralogy of burnt rocks in the region by using field observations and analyses of thin petrographic sections of samples based on scanning electron microscopy and electronic probes.We found that the degree of high-temperature metamorphosis of different kinds of burnt rocks led to them having different colors,ranging from bright red(such as brick red,red ochre,and purple-red)to black and steel gray.The burnt rock predominantly had porcelain,slag,and brecate structures.The results of microscopic examinations showed that the structure of the original rock had been damaged to varying degrees.We analyzed samples collected from Xishan Baituyao in the wild by using an electronic probe.The results showed that SiO2 was the main component of the burnt rock,with content in the range of 35.43％～99.83％,with an average of 75.73％.The secondary ingredients included Al2O3,CaO,Na2 O,K2O,FeO,MgO,MnO,and BaO,and were presumed to be aluminosilicate minerals related to the composition of the original rock.The original rocks had undergone different degrees of high-temperature metamorphism such that part of minerals in them had recombined to produce new types of minerals,including cordierite,iron iolite,mullite,and mica.The morphology of the minerals had also changed by varying degrees,and included condensation edge,rheology of quartz plastic,and a worm-like structure.The pyrothermal sandstone mode of mineralization of uranium ore may be suitable for its enrichment in the Liuhuanggou area,and needs to be researcher further.
维普
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