沁水盆地霍州矿区石炭-二叠纪煤中微量元素地球化学特征及沉积环境分析

Geochemical characteristics and sedimentary environment analysis of trace elements in Carboniferous-Permian coal in Huozhou Area,Qinshui Basin

利用工业分析及光学显微镜对沁水盆地石炭-二叠系煤中水分、灰分、挥发分、全硫以及显微组分进行测定,运用电感耦合等离子体质谱(ICP-MS)分析了沁水盆地霍州矿区石炭-二叠系煤中微量元素包括稀土元素的含量、分布特征和地球化学特征。利用元素地球化学参数探究了研究区的煤系地层的沉积环境,古盐度,氧化还原环境和古气候。结果表明:沁水盆地中南部煤的灰分产率、水分含量、挥发分以及含硫量分别为11.19%、1.02%、14.02%及1.27%,为低中灰-中硫煤,镜质体反射率为1.14%,为低变质程度烟煤。与中国煤相比,煤中微量元素含量整体处于亏损状态,仅有Cu(Cc=1.39)、Sr(Cc=1.35)和Zr(Cc=1.04)轻微富集(Cc为浓集系数),太原组煤中微量元素含量略大于山西组煤中微量元素。稀土元素分布范围2.44~164.11μg/g,平均为73.28μg/g,小于中国煤,略高于世界煤,煤中稀土元素Yb(Cc=2.81)轻微富集,Y(Cc=7.19)富集,其余都相对亏损。稀土元素配分模式呈右倾“V”字型,为轻稀土富集型,存在Eu负异常,Ce微弱负异常,说明稀土元素的物源来自陆源碎屑,海水并没有造成Ce的亏损。w(Sr)/w(Ba)、w(V)/w(V+Ni)和w(Sr)/w(Cu)平均值分别为6.50、0.74和7.57,表明了沁水盆地霍州矿区石炭-二叠系整体属于海相沉积环境,水体环境呈现缺氧环境,石炭-二叠系成煤环境处于温湿气候。山西组CaO/(MgO×Al_(2)O_(3))平均值为0.055,明显低于太原组平均值1.55,表明从太原组到山西组气温有所降低。

The moisture,ash,volatile matter,total sulfur and micro-components of the Carboniferous-Permian coal in Qinshui Basin were determined by industrial analysis and optical microscope,and the Qinshui Basin was analyzed by inductively coupled plasma mass spec⁃trometry(ICP-MS).The content,distribution and geochemical characteristics of trace elements including rare earth elements in Carbonif⁃erous-Permian coal in Huozhou area of Qinshui Basin were analyzed.The depositional environment,paleo-salinity,redox environment and paleoclimate of coal-measure strata in the study area were explored using elemental geochemical parameters.The results show that the ash yield,moisture content,volatile matter and sulfur content of the coal in the central and southern Qinshui Basin are 11.19%,1.02%,14.02%and 1.27%,respectively.The rate is 1.14%,which is low metamorphic bituminous coal.Compared with Chinese coal,the con⁃tent of trace elements in coal is depleted as a whole,only Cu(Cc=1.39),Sr(Cc=1.35)and Zr(Cc=1.04)are slightly enriched.The content of trace elements in coal of Taiyuan formation is slightly greater than trace elements in Shanxi coal.The distribution range of rare earth elements is 2.44-164.11μg/g,with an average is 73.28μg/g,which is smaller than that of Chinese coal and slightly higher than that of world coal.The rare earth element Yb(Cc=2.81)in the thin coal is slightly enriched,Y(Cc=7.19)is enriched,and the rest are relatively depleted.The rare earth element distribution pattern is right-leaning"V"shape,which is a light rare earth enrichment type,with Eu negative anomaly and Ce weak negative anomaly,indicating that the source of rare earth elements comes from terrigenous debris,and seawater does not cause Ce loss.The average values of w(Sr)/w(Ba),w(V)/w(V+Ni)and w(Sr)/w(Cu)are 6.5,0.74 and 7.57,respectively,indicating that the Carboniferous-Permian in the Huozhou area of Qinshui Basin as a whole belongs to a marine sedimentary environment,and the water environment is anoxic environment,the Carboniferous-Permian coal-forming environment is in a warm and humid climate.The average value of CaO/(MgO×Al_(2)O_(3))in Shanxi Formation is 0.055,which is significantly lower than that of Taiyuan Formation's average of 1.55,indicating that the temperature has dropped from the Taiyuan Formation to the Shanxi Formation.