准噶尔盆地北部石炭系富火山物质烃源岩地球化学特征

Geochemical characteristics of source rocks rich in volcanic material of Carboniferous in northern Junggar Basin

准噶尔盆地北部乌伦古地区石炭系发育一套巨厚的混杂有火山物质、岩性复杂的暗色岩系。笔者以乌参1井为例,通过系统的薄片鉴定,依据火山物质、碎屑物质的含量把石炭系暗色岩系划分为4类岩性组合,自下而上凝灰质含量逐渐增加。综合应用薄片观察、地球化学测试等资料分析了富火山物质烃源岩的形成环境,认为石炭纪乌伦古地区为多岛弧的构造环境,受火山活动旋回期次的影响,沉积物中火山物质含量发生规律性变化。提出火山喷发初期混杂有火山物质的泥岩(凝灰质泥岩)形成于还原、水体分层、偏酸性的环境中,有机质丰度高,有机质类型以混合型为主,具有较高的生烃潜力。

There developed a set of very thick dark rock series mixed with volcanic material in Carboniferous in Wulungu area,northern Junggar Basin.The abundance and type of organic matter indicate that the dark rock series have the potential to be source rocks.Taking Well Wucan 1 as an example,the dark rock series were divided into four types of lithological association according to the contents of volcanic and clastic materials through systematic thin section identification,and the content of tuffaceous matter gradually increases from the bottom to the top.Based on thin section observation and the data of geochemical analysis,the formation environment of the source rocks rich in volcanic materials is analyzed.It is considered that Wulungu area was located in a multi-island arc tectonic environment in Carboniferous,and the content of volcanic materials in the sediments changes regularly due to the influence of volcanic activity cycle.It is suggested that the tuffaceous mudstone which developed in the environment of reduction,water stratification,and acidity in the early stage of volcanic eruption,has high hydrocarbon generation potential with high TOC and kerogen typeⅠ-Ⅱ.