陕西省咸阳市彬长矿区胡家河4号煤有机地球化学特征

Organic Geochemical Characteristics of the Hujiahe No.4 Coal in the Binchang Mining Area,Xianyang,Shaanxi Province

富惰质组煤成因机制是目前的研究热点,其有机地球化学特征对探究富惰质组煤的古沉积环境和演化过程具有重要意义。本文以陕西省咸阳市胡家河4号煤为研究对象,运用有机化学抽提、族组分分离、气相色谱-质谱联用(GC-MS)等方法,分析了富惰质组煤的有机地球化学特征。结果表明,胡家河4号煤的有机质丰度高,饱芳比较低;正构烷烃呈单峰型分布,中-高碳数占优势,具有轻微的奇碳优势;姥植比(4.67)较高,姥鲛烷丰度高;萜烷中藿烷具有明显优势,Ts/(Ts+Tm)值为0~0.133;规则甾烷中C29>C28>C27,呈反“L”型;芳烃中以萘、菲系、氧芴系列为主;1,2,5-三甲基萘含量较高,惹烯具有明显优势,二苯并呋喃含量高于芴;多环芳烃中苝的优势明显。以上特征表明,胡家河4号煤的有机质处于低热成熟阶段,其母质来源以陆生高等植物为主并有少量低等水生生物混入,形成于弱还原偏氧化的干燥陆相淡水泥炭沼泽环境。

In order to investigate paleo-sedimentary environment and evolution process of the Jurassic inertinite-rich coal from the Hujiahe mine in the southern margin of the Ordors basin,the organic geochemical characteristics of the coal were studied.The results showed that the Jurassic inertinite-rich coal had a high abundance of organic matter,characterized by the unimodal pattern of n-alkanes and the slight predominance of odd carbons.The average ratio of Pr/Ph of the Hujiahe Mine was 4.67.Hopane was predominant in terpenes and ratios of Ts/(Ts+Tm)were between 0 and 0.133.In terms of regular steranes,the relative abundance of C29 was highest,followed by C28 and then C27,showing an inverted“L”type.The Jurassic inertinite-rich coal was characterized by high abundances of naphthalene,phenanthrene and fluorene,relatively high abundance of 1,2,5-TMN,retene and oxyfluorene.The advantage of perylene in polycyclic aromatic hydrocarbons was remarkable.Based on analyses of multiple hydrocarbon indicators,it can be concluded that the organic matter of Hujiahe No.4 coal had a low thermal maturity degree,and that was formed in a weakly reduced and partially oxidized terrestrial freshwater peat bog environment,and that was originated mainly from terrestrial higher plants and mixed with a small amount of lower aquatic organisms.