玉尔吐斯组黑色页岩是塔里木盆地寒武系盐下最具有潜力的烃源岩之一,普遍认为其沉积于统一、相似的沉积环 境(斜坡相),而作者的研究结果与上述结论不符.为了探讨两套在岩石矿物组合方面完全不同的黑色岩系分布规律和成因,并重建其各自的沉积模式,本文对研究区12条剖面进行了详细描述、测量,从沉积学特征、岩矿鉴定入手,结合扫描电子显微镜、X-衍射、地球化学等分析手段,着重研究了库勒剖面和于提希剖面两套黑色岩系的沉积学特征和地球化学特征差异.沉积层序、岩石矿物组合、微量元素富集系数、氧化还原敏感元素比值(V/(V+Ni)、V/Cr、U/Th)、REE+Y配分模式、有机质含量以及饱和烃色谱特征分析结果表明:两套黑色页岩均为有机质高度富集的,处于热成熟生油阶段的海相优质烃源岩(干酪根类型Ⅱ1-Ⅱ2型,第一套黑色页岩TOC均值为5.37％,第二套TOC均值为1.46％),均沉积于海水氧化-还原分层的还原环境,但各自的空间展布规律和控制因素差异较大.建立了热液喷流缺氧模式和斜坡缺氧沉积模式:第一套黑色页岩主要沉积于第一个旋回海侵高峰期水体较深、沉积速率较高的内缓坡,其发育主要受热液喷流活动、微生物活动以及氧化还原条件影响,分布范围广,台内厚,缓坡带薄,靠近台内或台地内部热液喷流中心的裂洼陷主要控制着该套黑色页岩的展布,成烃生物以底栖藻类、细菌为主,少量浮游藻类为辅;而第二套黑色页岩主要沉积于第二旋回海侵初期水体不断变深的中-外缓坡低能带,其发育主要受古生产力、氧化还原条件以及古地形(斜坡陡缓)控制,分布范围局限,外缓坡带厚度较稳定,靠近台内不发育,成烃生物以浮游藻类为主,微生物和低等水生生物为辅,其发育条件则在台缘中-外缓坡更为有利.%It is generally believed that the black shale of Yurtusi Formation,one of the most potential hydrocarbon source rocks under Cambrian gypsum-salt bed in Tarim Basin,Northwest China,deposited in a uniform and similar sedimentary environment (slope facies),however,the results of the study are inconsistent with the above conclusions.In order to investigate the distribution and origin analysis of two black rock series observed in outcrop with completely different association of rock and mineral,and reconstruct respective depositional models,we conduct a detailed description and measurement of 12 profiles in the study area,from the perspective of sedimentology characteristics and identification of rock and minerals,combining with the methods of scanning electron microscope,XRD,and geochemical analysis,and focus on the study of the sedimentary and geochemical characteristic differences of two black rock series in Kule and Yutixi profiles.Sedimentary sequence,rock mineral assemblage,microelement enrichment coefficient,redox sensitive element ratio (V/(V + Ni),V/Cr,U/Th),REE + Y distribution pattern,organic matter content and saturated hydrocarbon chromatographic characteristics show that both sets of black shales,highly enriched in organic matter,are marine high-quality source rocks at the stage of thermal mature oil generation (kerogen type:Ⅱ 1-Ⅱ 2;mean TOC of the first black shale:5.37％,mean TOC of the second black shale:1.46％),depositing in the reductive environment of seawater oxidation-reduction stratification,but the differences of their spatial distribution and control factors are larger.And then according to the conclusions above we establish two deposition models:one is the hydrothermal jet hypoxia model,and the other is the slope hypoxia model The first black shale (thick in platform,thinn in platform margin),which is deposited in the inner ramp rifted sag with relatively deep water and high deposition rate during the period of transgressive peak (the first cycle),mainly controlled by hydrothermal exhalative activities,microbial processes and redox conditions,is wildly distributed and dominated by rifted sags in the center of the hydrothermal field near the platform or in the platform.Hydrocarbon-forming organisms of the first black shale are dominated by benthic algae,bacteria,supplemented by a small amount of planktonic algae,and its condition of development is more favorable in platform sag.While,the second black shale (stable and thick in outer ramp,pinch-out in the inner of platform),which is deposited in low energy zone of outer ramp with deepening water during the period of early transgressive (the second cycle),mainly controlled by paleoproductivity,redox conditions and paleotopography (slope gradient),is locally distributed.Hydrocarbon-forming organisms of the second black shale are dominated by the phytoplankton,supplemented by microbes and lower hydrobiont,and its condition of development is more favorable in outer ramp of platform margin.
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