大同煤田北部中侏罗统煤中伴生元素分布特征及其地质意义
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摘要
为研究大同煤田中侏罗统煤中伴生元素地球化学特征及地质意义,应用电感耦合等离子体质谱(ICP-MS)、X射线衍射法(XRD)、光学电子显微镜和扫描电子显微镜(SEM)等测试方法分析煤田北部9个煤层中伴生元素含量和赋存特征。结果表明:煤中微量元素含量低,其有益元素(Li、Ga)含量均远低于边界品位,不具伴生成矿开发潜力,但2号煤中Co与Zn、9号煤中Tl和11-2号煤中Be等有害元素较为富集,是世界煤平均值的3倍以上,其环境影响值得关注。煤中主要矿物是高岭石与石英,高岭石主要充填在结构镜质体中,指示其同生成因,石英往往具有很好的晶型,指示其自生成因;少量的黄铁矿和方解石充填在显微裂隙中,指示其后生成因;磷灰石与有机质结合。煤中微量元素Ni和Mo可能主要以有机质结合态存在,其他元素主要赋存在无机矿物中,Si主要以石英形式存在,部分Si和Al以及Li、Cr、Ga和Nb存于黏土矿物中,Fe和Mn以及Cd、Zn、Tl赋存于黄铁矿中;Ca和Mg以及Co主要赋存在碳酸盐矿物中;P、Be、Sr和Ba可能存在磷灰石中;Rb赋存在石盐类矿物中。垂向上看,大同组存在2个沉积旋回,每个沉积旋回由下至上,水动力条件逐渐降低,水体由浅到深,陆源碎屑供给越来越少,这2个旋回间可能经历了较强的地质作用。总体看,在成煤期,随沉积作用的进行,聚煤盆地中碎屑物质输入逐渐减少,活性物质逐渐增加。
In order to study the geochemical characteristics and geological significance of associated elements in Middle Jurassic coal of Datong coalfield, the distribution and occurrence of the associated elements in 9 coal seams in the northern Datong coalfield were analyzed by inductively coupled plasma mass spectrometry(ICP-MS), X-ray diffraction(XRD), optical electron microscopy and scanning electron microscopy(SEM). The results show that the Jurassic coal in Datong coalfield has low trace element content, and beneficial elements(Li, Ga) are far lower than the boundary grade, which has no development potential. But the harmful elements such as Co and Zn in No.2 coal,Tl in No.9, and Be in No.11-2 coal are found quite enriched. Their concentration is more than 3 times the average value of the world coal. Its environmental impact deserves attention. The main minerals in coal are kaolinite and quartz. Kaolinite is mainly filled in structural vitrinite, indicating its syngenesis. Quartz often has a good crystal form, indicating its autogenesis. A small amount of pyrite and calcite is filled in the microfissures, indicating the subsequent origin; apatite is related to organic matter. Trace elements Ni and Mo in coal may exist mainly in organic matter in coal, and other elements mainly in inorganic minerals. Si mainly exists in quartz, some Si and Al, Li,Cr, Ga and Nb mainly exist in clay minerals, Fe, Mn, Cd, Zn, and Tl mainly exists in pyrite, Ca, Mg and Co mainly exist in carbonate, P, Be, Sr and Ba mainly exist in apatite, and Rb mainly exists in halite. Vertically, there are two sedimentary cycles in Datong Formation. From the bottom to the top, the water body changes from shallow to deep and the hydrodynamic condition is gradually reduced in each sedimentary cycle, therefore the supply of terrestrial material decreases. This may be related to the strong tectonic movement occurring between the two cycles. Generally speaking, in the coal-forming period, with the development of sedimentation, the input of clastic materials in the coal-accumulating basin decreased gradually, and the active materials increased gradually.
In order to study the geochemical characteristics and geological significance of associated elements in Middle Jurassic coal of Datong coalfield, the distribution and occurrence of the associated elements in 9 coal seams in the northern Datong coalfield were analyzed by inductively coupled plasma mass spectrometry(ICP-MS), X-ray diffraction(XRD), optical electron microscopy and scanning electron microscopy(SEM). The results show that the Jurassic coal in Datong coalfield has low trace element content, and beneficial elements(Li, Ga) are far lower than the boundary grade, which has no development potential. But the harmful elements such as Co and Zn in No.2 coal,Tl in No.9, and Be in No.11-2 coal are found quite enriched. Their concentration is more than 3 times the average value of the world coal. Its environmental impact deserves attention. The main minerals in coal are kaolinite and quartz. Kaolinite is mainly filled in structural vitrinite, indicating its syngenesis. Quartz often has a good crystal form, indicating its autogenesis. A small amount of pyrite and calcite is filled in the microfissures, indicating the subsequent origin; apatite is related to organic matter. Trace elements Ni and Mo in coal may exist mainly in organic matter in coal, and other elements mainly in inorganic minerals. Si mainly exists in quartz, some Si and Al, Li,Cr, Ga and Nb mainly exist in clay minerals, Fe, Mn, Cd, Zn, and Tl mainly exists in pyrite, Ca, Mg and Co mainly exist in carbonate, P, Be, Sr and Ba mainly exist in apatite, and Rb mainly exists in halite. Vertically, there are two sedimentary cycles in Datong Formation. From the bottom to the top, the water body changes from shallow to deep and the hydrodynamic condition is gradually reduced in each sedimentary cycle, therefore the supply of terrestrial material decreases. This may be related to the strong tectonic movement occurring between the two cycles. Generally speaking, in the coal-forming period, with the development of sedimentation, the input of clastic materials in the coal-accumulating basin decreased gradually, and the active materials increased gradually.
引文
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[15]DAI Shifeng,WANG Xibo,ZHOU Yiping,et al.Chemical and mineralogical compositions of silicic,mafic,and alkali tonsteins in the Late Permian coals from the Songzao coalfield,Chongqing,southwest China[J].Chemical Geology,2011,282(1/2):29-44.
[16]DAI Shifeng,REN Deyi,CHOU Chenlin,et al.Geochemistry of trace elements in Chinese coals:A review of abundances,genetic types,impacts on human health,and industrial utilization[J].International Journal of Coal Geology,2012,94:3-21.
[17]王文峰,秦勇,刘新花,等.内蒙古准格尔煤田煤中镓的分布赋存与富集成因[J].中国科学:地球科学,2011,41(2):181-196.WANG Wenfeng,QIN Yong,LIU Xinhua,et al.Distribution,occurrence and enrichment causes of gallium in coals from the Junggar coalfield,Inner Mongolia[J].Science China Earth Science,2011,41(2):181-196.
[18]KETRIS M P,YUDOVICH Y E.Estimations of Clarkes for Carbonaceous biolithes:World averages for trace element contents in black shales and coals[J].International Journal of Coal Geology,2009,78(2):135-148.
[19]代世峰,任徳贻,周义平,等.煤型稀有金属矿床:成因类型、赋存状态和利用评价[J].煤炭学报,2014,39(8):1707-1715.DAI Shifeng,REN Deyi,ZHOU Yiping,et al.Coal-hosted rare metal deposits:Genetic types,modes of occurrence,and utilization evaluation[J].Journal of China Coal Society,2014,39(8):1707-1715.
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[22]陈云云.山西平朔矿区4号煤地球化学特征及古环境意义[D].北京:中国地质大学(北京),2017.
[23]刘东娜,赵峰华,周安朝,等.大同煤田七峰山矿2号煤层若干微量元素地球化学特征[J].煤炭学报,2013,38(4):637-643.LIU Dongna,ZHAO Fenghua,ZHOU Anchao,et al.The geochemistry of trace elements in the No.2 coal seam of Qifengshan coalmine at Datong coalfield[J].Journal of China Coal Society,2013,38(4):637-643.
[24]康健.乌海石炭二叠纪煤中元素的分布规律和矿物质富集机理[D].北京:中国矿业大学(北京),2015.
[25]HAYASHI K I,FUJISAWA H,HOLLAND H D,et al.Geochemistry of approximately 1.9 Ga sedimentary rocks from northeastern Labrador,Canada[J].Geochimica Cosmochimica Acta,1997,61(19):4115-4137.
[26]HE Bin,XU Yigang,ZHONG Yuting,et al.The Guadalupian-Lopingian boundary mudstones at Chaotian(SW China)are clastic rocks rather than acidic tuffs:Implication for a temporal coincidence between the end-Guadalupian mass extinction and the Emeishan volcanism[J].Lithos,2010,119(1/2):10-19.
[27]DAI S F,HOWER J C,WARD C R,et al.Elements and phosphorus minerals in the Middle Jurassic inertinite-rich coals of the Muli coalfield on the Tibetan plateau[J].International Journal of Coal Geology,2015,144/145:23-47.
[28]陈庸勋,戴东林.山西省大同地区侏罗系的沉积相[J].地质学报,1962,42(3):65-98.CHEN Yongxun,DAI Donglin.Jurassic sedimentary facies in Datong area,Shanxi Province[J].Journal of Geology,1962,42(3):65-98.
[2]DAI Shifeng,REN Deyi,ZHOU Yiping,et al.Mineralogy and geochemistry of a superhigh-organic-sulfur coal,Yanshan coalfield,Yunnan,China:Evidence for a volcanic ash component and influence by submarine exhalation[J].Chemical Geology,2008,255(1):182-194.
[3]DAI Shifeng,ZENG Rongshu,SUN Yuzhuang.Enrichment of arsenic,antimony,mercury,and thallium in a Late Permian anthracite from Xingren,Guizhou,southwest China[J].International Journal of Coal Geology,2006,66(3):217-226.
[4]GRETA E,DAI Shifeng,LI Xiao.Fluorine in Bulgarian coals[J].International Journal of Coal Geology,2013,105:16-23.
[5]宋党育,李春辉,宋播艺,等.新密煤田裴沟矿二1煤中环境敏感元素地球化学特征[J].煤田地质与勘探,2016,44(5):28-36.SONG Dangyu,LI Chunhui,SONG Boyi,et al.Geochemistry of environment sensitive elements in the No.2-1 coal from Peigou mine,Xinmi coalfield[J].Coal Geology&Exploration,2016,44(5),28-36.
[6]胡中信.济北煤田煤中敏感性微量元素及其环境意义研究[D].徐州:中国矿业大学,2009.
[7]王文峰,秦勇,姜波,等.鄂尔多斯盆地北缘-晋北区煤中微量元素赋存特征及其洁净潜势[J].地质学报,2004,78(4):499.WANG Wenfeng,QIN Yong,JIANG Bo,et al.The occurrence characteristics and clean potential of trace elements in northern Shanxi coal from the northern margin of Ordos basin[J].Journal of Geology,2004,78(4):499.
[8]陈鹏.中国煤炭性质、分类和利用[M].北京:化学工业出版社,2007.
[9]张博.煤中有害微量元素的洁净潜势分析[J].洁净煤技术,2015,21(4):20-24.ZHANG Bo.Cleaning potentiality analysis of harmful microelements in coal[J].Clean Coal Technology,2015,21(4):20-24.
[10]刘东娜.大同双纪含煤盆地煤变质作用与沉积-构造岩浆活动的耦合关系[D].太原:太原理工大学,2015.
[11]郭万忠,程岳宏,高宇平,等.大同煤田构造特征及太原组赋煤边界[J].煤田地质与勘探,2015,43(5):1-7.GUO Wanzhong,CHENG Yuehong,GAO Yuping,et al.Structural characteristics and coal-bearing boundaries of Taiyuan Formation in Datong coalfield[J].Coal Geology&Exploration,2015,43(5):1-7.
[12]张绍鑫.大同煤田侏罗纪含煤岩系的沉积特征和沉积环境[J].山东矿业学院学报,1988,7(4):45-51.ZHANG Shaoxin.The sedimentary characters and environment of Jurassic coal measure in Datong coalfield[J].Journal of Shandong Mining Institute,1988,7(4):45-51.
[13]郝风英.大同煤田忻州窑井田大同组沉积环境及沉积旋回特征分析[J].山西煤炭,2011,31(6):38-39.HAO Fengying.Analysis on sedimentary environment and sedimentary cycle characteristics of Datong Group in Xinzhouyao mine field[J].Shanxi Coal,2011,31(6):38-39.
[14]袁远,曹代勇,林中月,等.大同煤田构造控煤特征研究[J].中国煤炭地质,2011,23(8):63-65.YUAN Yuan,CAO Daiyong,LIN Zhongyue,et al.Study on structural coal-control characteristics in Datong coalfield[J].Coal Geology of China,2011,23(8):63-65.
[15]DAI Shifeng,WANG Xibo,ZHOU Yiping,et al.Chemical and mineralogical compositions of silicic,mafic,and alkali tonsteins in the Late Permian coals from the Songzao coalfield,Chongqing,southwest China[J].Chemical Geology,2011,282(1/2):29-44.
[16]DAI Shifeng,REN Deyi,CHOU Chenlin,et al.Geochemistry of trace elements in Chinese coals:A review of abundances,genetic types,impacts on human health,and industrial utilization[J].International Journal of Coal Geology,2012,94:3-21.
[17]王文峰,秦勇,刘新花,等.内蒙古准格尔煤田煤中镓的分布赋存与富集成因[J].中国科学:地球科学,2011,41(2):181-196.WANG Wenfeng,QIN Yong,LIU Xinhua,et al.Distribution,occurrence and enrichment causes of gallium in coals from the Junggar coalfield,Inner Mongolia[J].Science China Earth Science,2011,41(2):181-196.
[18]KETRIS M P,YUDOVICH Y E.Estimations of Clarkes for Carbonaceous biolithes:World averages for trace element contents in black shales and coals[J].International Journal of Coal Geology,2009,78(2):135-148.
[19]代世峰,任徳贻,周义平,等.煤型稀有金属矿床:成因类型、赋存状态和利用评价[J].煤炭学报,2014,39(8):1707-1715.DAI Shifeng,REN Deyi,ZHOU Yiping,et al.Coal-hosted rare metal deposits:Genetic types,modes of occurrence,and utilization evaluation[J].Journal of China Coal Society,2014,39(8):1707-1715.
[20]RILEY K W,FRENCH D H,FARRELL O P,et al.Huggins.Modes of occurrence of trace and minor elements in some Australian coals[J].International Journal of Coal Geology,2012,94:214-224.
[21]ESKENAZY G M,STEFANOVA Y S.Trace elements in the Goze Delchev coal deposit,Bulgaria[J].International Journal of Coal Geology,2007,72(3/4):257-267.
[22]陈云云.山西平朔矿区4号煤地球化学特征及古环境意义[D].北京:中国地质大学(北京),2017.
[23]刘东娜,赵峰华,周安朝,等.大同煤田七峰山矿2号煤层若干微量元素地球化学特征[J].煤炭学报,2013,38(4):637-643.LIU Dongna,ZHAO Fenghua,ZHOU Anchao,et al.The geochemistry of trace elements in the No.2 coal seam of Qifengshan coalmine at Datong coalfield[J].Journal of China Coal Society,2013,38(4):637-643.
[24]康健.乌海石炭二叠纪煤中元素的分布规律和矿物质富集机理[D].北京:中国矿业大学(北京),2015.
[25]HAYASHI K I,FUJISAWA H,HOLLAND H D,et al.Geochemistry of approximately 1.9 Ga sedimentary rocks from northeastern Labrador,Canada[J].Geochimica Cosmochimica Acta,1997,61(19):4115-4137.
[26]HE Bin,XU Yigang,ZHONG Yuting,et al.The Guadalupian-Lopingian boundary mudstones at Chaotian(SW China)are clastic rocks rather than acidic tuffs:Implication for a temporal coincidence between the end-Guadalupian mass extinction and the Emeishan volcanism[J].Lithos,2010,119(1/2):10-19.
[27]DAI S F,HOWER J C,WARD C R,et al.Elements and phosphorus minerals in the Middle Jurassic inertinite-rich coals of the Muli coalfield on the Tibetan plateau[J].International Journal of Coal Geology,2015,144/145:23-47.
[28]陈庸勋,戴东林.山西省大同地区侏罗系的沉积相[J].地质学报,1962,42(3):65-98.CHEN Yongxun,DAI Donglin.Jurassic sedimentary facies in Datong area,Shanxi Province[J].Journal of Geology,1962,42(3):65-98.