中国煤中氮同位素组成特征初步研究  

Preliminary Study on the Characteristics of Nitrogen Isotopic Compositions in Chinese Coals

作　　者：程晨[1,2] 赵峰华 任德贻[1,2] 苗雪娜[1,2] CHENG Chen;ZHAO Fenghua;REN Deyi;MIAO Xuena(College of Geoscience and Surveying Engineering,China University of Mining ＆ Technology,Beijing,100083;State Key Laboratory of Coal Resources and Safe Mining,China University of Mining ＆ Technology,Beijing,100083)

机构地区：[1]中国矿业大学(北京)地球科学与测绘工程学院,北京100083 [2]中国矿业大学(北京)煤炭资源与安全开采国家重点实验室,北京100083

出　　处：《地质学报》2018年第9期1959-1969,共11页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41372164);国家留学基金(编号CSC201506430017)联合资助成果

摘　　要：本文采用Dumas燃烧法测定了部分中国煤样的氮同位素组成(δ^(15 )N),并结合文献数据和煤样品的地质背景初步探讨了影响煤中氮同位素组成的因素。研究表明:(1)中国煤的δ^(15 )N值介于+1.4‰^+5.1‰之间,与世界其他地区煤的δ^(15 )N值范围(+0.3‰^+5.4‰)相吻合;同一煤层剖面分层煤样(煤级相似)的δ^(15 )N值具有非均质性特征,最大可达2.5‰。(2)煤的δ^(15 )N值是煤变质作用、沉积环境等多种因素耦合作用的结果。变质作用对煤的δ^(15 )N值的影响主要包括原始煤级、变质程度(煤级)和煤变质作用类型;沉积环境对煤的δ^(15 )N值的影响包括成煤植物的氮源以及沼泽介质的物理化学条件和微生物活动性等因素。(3)就煤变质作用(煤级)而言,中国煤的δ^(15 )N值随煤级升高呈现增高的趋势,到无烟煤又有所降低,这是煤中氮同位素稳定性差异的结果。在高级烟煤阶段(贫瘦煤)之前,随煤级升高稳定性较差的14 N优先脱除,δ^(15 )N值增高,增高幅度约1‰。在高级烟煤至初级无烟煤阶段,煤中剩余的14 N已趋于稳定,随煤级升高,部分不稳定15 N优先脱除,δ^(15 )N值降低。在无烟煤阶段,随煤级升高,14 N和15 N同步脱除,δ^(15 )N值几乎不变。在不考虑含氮地质流体影响的情况下,深成变质作用和接触变质作用对煤中δ^(15 )N值的影响应相似。(4)就沉积环境而言,形成于海陆过渡相的中高硫煤/高硫煤的δ^(15 )N值最高,形成于陆相的特低硫煤和低硫煤的δ^(15 )N值次之,而形成于碳酸盐岩台地相的超高有机硫煤的δ^(15 )N值最低,这主要与沉积环境中成煤植物的氮源以及泥炭化作用阶段植物有机质降解程度的差异有关。一般以富集15 N的海水硝酸盐为氮源的成煤植物形成的煤(海陆过渡相中高硫煤/高硫煤)较以相对亏损15 N的大气氮为氮源的成煤植物形成的煤(陆相特低硫煤和低硫煤)要富集15 N。当成煤母In this study,nitrogen isotopic compositions（δ15 N）of a series of Chinese coals were determined using Dumas combustion method to preliminarily figure out the factors affecting nitrogen isotopic compositions in coals,combined with previous results and geological background of coal deposits.The study shows that（1）The δ15 N values of Chinese coals range from ＋1.4‰ to ＋5.1‰,within the range of δ15 N values（＋0.3‰ ＋5.4‰）of coals from other regions in the world.The δ15 N values within the same coal profiles display heterogeneous characteristic,with the maximum of 2.5‰.（2）The δ15 N values in coals are controlled by multiple effects including coal metamorphism and sedimentary environment,in which the former involves the effects of original coal grades,metamorphic grades and types,and the latter contains the effects of nitrogen sources of coal-forming plants as well as physical-chemical conditions and microbial activities of swamp medium.（3）In terms of coal metamorphism,the δ15 N values of Chinese coals increase with increasing coal grade（about 1‰）but decrease at anthracite,which reflects the difference in the stability of two nitrogen isotopes.Before transforming into high rank bituminous coal,the δ15 N values increase along with the preferential removal of 14 N.Between high rank bituminous coal and low rank anthracite,the δ15 N values decrease first and keep stable to high rank anthracite,due to the preferential removal of unstable 15 N in this stage but synchronous elimination of 14 N and 15 N after this stage.Regardless of N-containing geological fluid,hypozonal metamorphism and contact metamorphism should have the same effect on the δ15 N values in coals.（4）As for sedimentary environment,the coals from transition facies with medium-high and high inorganic sulfur content show higherδ15 N values than the coals from lacustrine and fluvial facies with ultralow and low sulfur content,and the lowest coalsδ15 N values are showed in coals from carbonate platform facie

关 键 词：中国 煤 氮同位素 煤变质作用 沉积环境 成煤时代 

分 类 号：TQ533[化学工程—煤化学工程]