This paper discussed the petrological characteristics and coal facies of No.6 coal seam from the Haerwusu Mine, Jungar Coalfield, Inner Mongolia by using of coal petrology and geochemistry. No.6 coal facies can be div...This paper discussed the petrological characteristics and coal facies of No.6 coal seam from the Haerwusu Mine, Jungar Coalfield, Inner Mongolia by using of coal petrology and geochemistry. No.6 coal facies can be divided into 3 types, arid forest peat swamp （including two subfacies） and reed peat swamp, respectively. From bottom to top, the development of peat swamps present wavy changes, and three coal facies types appear alternately, with obvious thyme. According to the parameters, 11 secondary sequences were identified of the peat swamps of No.6 coal seam. The results indicate that the mire formed in brackish water-fresh water weak regression environment, changed in excess oxygen and poor oxygen, and reflected the characteristics of transition phase.展开更多
Petrological,mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield,northern Ordos Basin,North China,define their characteristics,ore genesis and economic int...Petrological,mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield,northern Ordos Basin,North China,define their characteristics,ore genesis and economic interest.Based on the crystalline size,two different types of kaolinite rocks,cryptocrystalline and grainy,were identified under the microscope.XRD data show that kaolinite is the predominant mineral,associated with boehmite,magnesite,anatase,pyrite,diaspore and calcite.However,high boehmite content(mean 70%)shows up in the middle layers.Kaolinite minerals present homogeneous shape and a good crystallinity(HI=0.96–1.26).Geochemical studies show that the SiO_(2)/Al_(2)O_(3)molar ratio of kaolinite is close to the theoretical value,and the contents of Na_(2)O,K_(2)O,CaO,Mg O are less,suggesting a strong chemical weathering environment.The REE and Eu anomalies show a close relationship between kaolinite and the Yinshan Oldland granite.A Ce anomaly reflects a continental sedimentary environment with shallow water.A temperature range of 26.7–34℃was calculated on the basis of the isotopic signatures(δ18O,δD)of the kaolinite rocks.All these data indicate that the formation of the kaolinite is caused mainly by the dissolution,coagulation,precipitation and recrystallization of aluminosilicate clastics in acidic conditions.The formation of boehmite in the middle layers indicates that the source rocks have changed.Boehmite is mainly formed by dehydration and compaction of an aluminum-rich colloid which transported into peat swamp during diagenesis.In addition,it formed by desiliconization of kaolinite under acidic conditions.Due to its high kaolinite content(up to 90%)and low iron mineral content(less than 1%),and good crystallinity,kaolinite deposits occurred at Haerwusu surface mine probably have great economical value in the future.展开更多
基金Supported by the Natural Science Foundation of Hebei Province （D2012402025, D2009000832）
文摘This paper discussed the petrological characteristics and coal facies of No.6 coal seam from the Haerwusu Mine, Jungar Coalfield, Inner Mongolia by using of coal petrology and geochemistry. No.6 coal facies can be divided into 3 types, arid forest peat swamp （including two subfacies） and reed peat swamp, respectively. From bottom to top, the development of peat swamps present wavy changes, and three coal facies types appear alternately, with obvious thyme. According to the parameters, 11 secondary sequences were identified of the peat swamps of No.6 coal seam. The results indicate that the mire formed in brackish water-fresh water weak regression environment, changed in excess oxygen and poor oxygen, and reflected the characteristics of transition phase.
基金supported financially by the Science and Technology Major Projects of Shanxi Province of China(grant No.20181101003)the National Key R&D Program of China(grant No.2019YFC1904903)。
文摘Petrological,mineralogical and geochemical studies carried out on kaolinite deposits in Haerwusu surface mine,Jungar Coalfield,northern Ordos Basin,North China,define their characteristics,ore genesis and economic interest.Based on the crystalline size,two different types of kaolinite rocks,cryptocrystalline and grainy,were identified under the microscope.XRD data show that kaolinite is the predominant mineral,associated with boehmite,magnesite,anatase,pyrite,diaspore and calcite.However,high boehmite content(mean 70%)shows up in the middle layers.Kaolinite minerals present homogeneous shape and a good crystallinity(HI=0.96–1.26).Geochemical studies show that the SiO_(2)/Al_(2)O_(3)molar ratio of kaolinite is close to the theoretical value,and the contents of Na_(2)O,K_(2)O,CaO,Mg O are less,suggesting a strong chemical weathering environment.The REE and Eu anomalies show a close relationship between kaolinite and the Yinshan Oldland granite.A Ce anomaly reflects a continental sedimentary environment with shallow water.A temperature range of 26.7–34℃was calculated on the basis of the isotopic signatures(δ18O,δD)of the kaolinite rocks.All these data indicate that the formation of the kaolinite is caused mainly by the dissolution,coagulation,precipitation and recrystallization of aluminosilicate clastics in acidic conditions.The formation of boehmite in the middle layers indicates that the source rocks have changed.Boehmite is mainly formed by dehydration and compaction of an aluminum-rich colloid which transported into peat swamp during diagenesis.In addition,it formed by desiliconization of kaolinite under acidic conditions.Due to its high kaolinite content(up to 90%)and low iron mineral content(less than 1%),and good crystallinity,kaolinite deposits occurred at Haerwusu surface mine probably have great economical value in the future.
