Geochemical Composition Of Late Paleozoic Coal And Black Shale From Eastern Ordos Basin,China

To investigate petrological,mineralogical and geochemical composition of studied coal and shale,samples of black shale,Nos.2,3+4,and 5 Coal from Hedong Coalfield and No.5 Coal from Junger Coalfield were collected from Hedong Coalfield and Junger Coalfield located in eastern Ordos basin,China,using SEM,XRD,ICP-MS,ICP-CCT-MS,DMA-80 and ISE methods.1.Nos.3+4 Coal samples from Hedong Coalfield have low ash yield,medium volatile,low sulfur content,No.5 Coal samples have high ash yield,medium volatile,low moisture,super low-sulfur content(average on 0.40%).Shale samples from Hedong Coalfield were characterized by high TOC content(1.10~6.39%),high Ro values(2.85 on average)and low permeability(0.57% on average).2.Mineral composition in samples were detected by SEM and XRD.Quartz and clay minerals were main constituents in studied coal and shale samples.Coal samples of Nos.3+4 Coal from Hedong Coalfield and No.5 Coal from Junger Coalfield had high kaolinite and quartz concentrations.Shale samples from Hedong Coalfield had high quartz concentration.Other minerals could only be detected in several samples.3.Major elements concentration showed regional diversity in coal and shale samples from studied areas.No.5 Coal samples from Junger Coalfield had extremely high SiO2,Al2O3 concentrations,with averaging 51.7%,42.42%,respectively,SiO2/Al2O3 value was 1.22.Nos.3+4 Coal samples from Hedong Coalfield have average SiO2,Al2O3 concentration with their means of 49.83%?38.98%,respectively.Shale samples in Shanxi formation had higher SiO2 concentration(58.76%)than in Taiyuan formation(51.62%)and had similar Al2O3 concentrations.Other major elements had low contents in studied samples.4.Trace elements concentrations were suggested by concentration coefficients(CC).Li and Bi were enriched in shale samples from Hedong Coalfield,Li and Zr were enriched in Nos.3 and 5 coal samples from Hedong Coalfield.No.5 coal samples from Junger Coalfield were enriched in Li,Be,F,Sc,Ga,Se,Zr,Nb,In,Hf,Ta,Pb,and U.Trace elements concentrations decreased from north to south in studied areas.5.Coal and shale samples had same sediments origin,felsic rocks,that were indicated by Al2O3-TiO2,TiO2/Zr and Th/Sc-Zr/Sc values.In addition,quartz contents increased and clay concentrations decreased from north to south in studied shale samples,suggesting sediments in studied samples were from Yinshan upland.6.Coal faces and elemental indicators suggested coal and shale in Taiyuan and Shanxi formations were deposited in transition-continental facies,with stable water condition.Hedong Coalfield had more stable sedimentary environment than Junger Coalfield.