鄂尔多斯盆地东胜煤田侏罗系煤中元素地球化学特征及其古环境意义OA北大核心CSTPCD

This study investigated the geochemical characteristics and sedimentary paleoenvironment of the Yan'an Formation from borehole No.6-5 in the Xinibulage exploration area of the Dongsheng coalfield,Ordos basin. Proximate and ultimate analyses,an X-ray fluorescence spectrometer (XRF),and an inductively coupled plasma-mass spectrometer (ICP-MS) were employed to determine the major and trace element compositions of coal. The results showed that coal samples from different seams exhibit low moisture content,(extra) low ash yield,extremely low sulfur content (with organic sulfur being the primary form),and medium to high volatile matter yield. Major elements are predominantly SiO2 and Al2O3,followed by CaO,Fe2O3,and Na2O. Trace element enrichment varies among seams:coal 3# is enriched in Cr,Zr,Nb,Ta,and Th,with slight enrichment in V,Cu,Zn,Ga,Y,Ba,Yb,Hf,W,Pb,and U;coal 4# is enriched in Sb and slightly enriched in Ba,Be,and Co;coal 5# shows slight enrichment in Be and Co;and coal 6# exhibits slight enrichment in Cr and V. Rare earth element analysis indicates that coal 3# and 6# are characterized by heavy rare earth element enrichment,while coal 4# and 5# are enriched in medium/heavy rare earth elements. All coal seams display a positive Eu anomaly. Inertinite is the dominant maceral in all seams,with coal 4# exhibiting the lowest inertinite content. Sedimentary paleoenvironmental reconstruction suggests that all coal seams formed in predominantly oxidative environments. Coal 3#,5#,and 6# likely originated in oxidative,acidic,oxygen-rich to sub-oxygen-rich,and hydraulically weak dry forest swamp facies. Coal 4# experienced fluctuating conditions,alternating between oxidative,acidic,oxygen-rich to sub-oxygen-rich,and hydraulically weak dry forest swamp facies,and reducing,alkaline,highly fluctuating water body environments characteristic of anoxic to extremely hypoxic moist forest swamp facies.