准噶尔盆地阜康凹陷芦草沟组高有机碳页岩发育的古环境

Paleoenvironment of organic-rich shale from the Lucaogou Fromation in the Fukang Sag,Junggar Basin,China

准噶尔盆地是我国重要的大型含油气盆地,阜康凹陷位于准噶尔盆地东南缘,博格达山北麓,属于准噶尔盆地东部的次级凹陷。选取准噶尔盆地阜康凹陷四工河附近二叠系芦草沟组作为目标层位,探讨其有机质富集情况及古环境特征。总有机碳(TOC)分析表明,剖面上整体有机质含量介于3.67%~16.0%之间,平均值为8.50%,总体有机质含量高。微量元素在地质历史变迁过程中,物理化学条件在一定的平衡之后稳定存在,其相对含量大小的背后蕴含着古沉积环境信息。研究区的古环境,包括古盐度、古气候、古氧化还原条件、古水深、古生产力特征,经主微量元素含量及比值分析,结果显示为贫氧—次富氧、半干旱—温湿气候、水动力弱的淡水—半咸水陆相深湖湖盆沉积环境。高有机碳页岩主要是初始生产力较高造成的,古环境对有机质的富集具有积极的作用。

The Junggar Basin is a large oil-gas-bearingbasin in China,the Fukang Sag is located in the edge of the southeast of the Junggar Basin and on the north of the Bogda Mountain,which is the secondary sag in the east of the basin.We choose the Lucaogou Formation as the object that is near the Sigonghe River in the Fukang Sag to reveal the level of enrichment of the organic matter and sedimentary environment characteristics in study area.The content of organic matter in vertical profile ranged from 3.67% to 16.0% with an average of 8.5%,showing that the shale is rich in organic matter.Trace element plays a key role in unlocking paleoenvironments because of its stability.We explore the paleoenvironment through investigating paleosality,aleoclimate,paleoredox,paleoproductivity,paleo-water-depth,and paleoproductivity.Results suggest that the shale was deposited in the anoxic-suboxic,semi-arid and warm-humid,weak hydrodynamic,and fresh and semi-saline continental deep lake.High TOCin the shale is mainly caused by the primary productivity,and the paleoenvironment has a positive influence on the accumulation of organic carbon.