新疆三塘湖盆地芦草沟组油页岩特征及成矿背景

Characteristics and Metallogenetic Background of Oil Shale in the Lucaogou Formation,Santanghu Basin,Xinjiang

石头梅地区是新疆三塘湖盆地二叠系芦草沟组油页岩的主要分布区域,为了研究其油页岩特征和成矿背景,在岩心详细观察和系统取样的基础上,识别出油页岩7层,对油页岩开展了有机碳、岩石热解、灰分、挥发份、含油率、发热量、全硫、主量元素、微量元素测试分析。结果表明,三塘湖盆地石头梅地区芦草沟组油页岩主要发育于芦二段,为特低-低硫型、高灰分、中-低品质油页岩。其有机质丰度较高,有机质类型主要为I型,有机质成熟度为低成熟;具有CaO、P_(2)O_(5)、Sr、Mo、Ag、Sb、Ge等元素富集,而Al_(2)O_(3)、K_(2)O、TiO_(2)、B、V、Ni、Rb、Th、U、Ga、Ba、Cu、Zr等元素亏损的特点。成矿背景为较稳定的构造环境,偏炎热的气候条件,半咸水-咸水盐度条件和缺氧还原环境,水深较深且水动力条件较弱的半深湖-深湖环境,同时具有较高的初始湖泊生产力和稳定的陆源碎屑输入量。与此种成矿背景相比,更温暖湿润的气候条件、更深的水体深度、更弱的水动力强度、相对高的初始湖泊生产力和陆源碎屑输入量为更有利的油页岩成矿背景。

The Shitoumei area of Santanghu Basin is the main distribution area of oil shale in Permian Lucaogou Formation.The purpose of this work was to reveal the characteristics and metallogenic background of this oil shale.In terms of detailed observations to core and systematic sampling,7 layers of oil shale were identified.analyses were conducted to examine the total organic carbon(TOC),rock-eval pyrolysis,ash,volatile,oil yield,calorific value,total sulfur,and major and trace elements.Results show that the oil shale of Lucaogou Formation in the Shitoumei area of Santanghu Basin mainly developed in the second member of the Lucaogou Formation,featured by ultra-low sulfur,high ash and medium-low quality.Its abundance of organic matter is high,with organic matter of type I and low maturity.It is characterized by enrichment of elements CaO,P_(2)O_(5),Sr,Mo,Ag,Sb and Ge,while depleted in elements Al_(2)O_(3),K_(2)O,TiO_(2),B,V,Ni,Rb,Th,U,Ga,Ba,Cu and Zr.This oil shale formed in a relatively stable tectonic environment,relatively hot climatic conditions,with brackish water and anoxic reduction,and a semi-deep to deep lake environment with deep water and low hydrodynamic conditions.At the same time,it had high initial lake productivity and stable terrigenous clastic input.Compared with this metallogenic background,humid and warmer climate,deeper water,lower hydrodynamic force,relatively higher initial lake productivity and terrigenous clastic input are the better metallogenic background of oil shale.