黑龙江省柳树河盆地始新统八虎力组油页岩元素地球化学特征及沉积环境

Geochemistry characteristics and sedimentary environment of oil shale from the Eocene Bahuli Formation in Liushuhe Basin,Heilongjiang Province

黑龙江省柳树河盆地始新统八虎力组发育多层油页岩。通过对油页岩样品元素地球化学分析测试,研究了其常量元素、微量元素和稀土元素特征,分析了油页岩沉积环境。研究结果表明,常量元素以富Al2O3、Fe和Ca O,贫Si O2、Mg O、Na2O和K2O为特征,微量元素总体上表现出不同程度的亏损特征,稀土元素总量平均为140.7×10-6,表现出轻稀土元素轻度富集特征。稀土元素具有较为一致的变化趋势,表明油页岩沉积时物源和沉积环境较为稳定。Mn/Ti值表明油页岩组成物质的搬运距离随着时间变化经历了远→近→远的变化,反映水体深度经历了深→浅→深的变化。Sr/Cu值和Rb/Sr值表明油页岩沉积时为相对炎热干旱的环境。Sr/Ba值反映当时为炎热干旱气候条件下的过渡相咸水湖泊沉积环境。V/(V+Ni)值、δEu和有机碳含量表明油页岩沉积时处于缺氧的还原沉积环境中。总体上,柳树河盆地油页岩发育于炎热干旱气候、咸水、缺氧条件下的湖泊沉积环境中。

Several layers of oil shale were developed in the Eocene Bahuli Formation of Liushuhe Ba_sin,Heilongjiang Province.Based on the characteristics of major,trace and rare earth elements,sedi_mentary environment of oil shale was analyzed.In the oil shale of Bahuli Formation of Liushuhe Basin, major elements are characterized by rich in Al2 O3 ,Fe and CaO,and poor in SiO2 ,MgO,Na2 O and K2 O;trace elements are generally depleted in different degree,and the amount of rare earth elements （ΣREE） averages 1 40.7＆#215;1 0 -6 ,which show mild enrichment of light rare earth elements.Relatively con_sistent change trend of rare earth elements indicates that the provenance and sedimentary environment were relatively stable.The ratio of Mn /Ti shows that the transported distance of material composed oil shale ex_perienced changes from far to near,then to far,which reflects that the depth of water changed from deep to shallow,then to deep.The ratios of Sr /Cu and Rb /Sr indicate that the climate was relatively hot and dry.The ratio of Sr /Ba reflects the salt water lake at that time.The ratios of V /（V ＋Ni）,δEu and the content of organic carbon show that the oil shale was developed in the anaerobic reducing sedimentary envi_ronment.As a whole,the oil shale in Liushuhe Basin was developed in the lake with the condition of hot and dry climate,salt water and anaerobic reduction.