吐鲁番-哈密盆地北部广泛分布下二叠统伊尔稀土组,记录了盆地形成时期的古气候、古地理、盆地演化及大地构造背景方面的许多重要信息.针对伊尔稀土组的沉积特征、盆地属性和大地构造背景研究中存在的若干争议问题,在前人研究的基础上,通过盆地分析方法,研究了早二叠世的盆地演化规律和大地构造背景.研究表明,伊尔稀土组垂向上经历了河流/冲积扇-滨浅湖-半深湖/深湖的沉积环境变化,其火山岩建造以含橄榄玄武岩、玄武安山岩及流纹岩的双峰式火山岩组合为特征,且岩石组合的展布显示火山岩比例自西向东逐渐增多,说明东部火山活动较西部强烈.同时期博格达北麓发育海相复理石建造夹少量火山岩.岩石学特征及地球化学分析显示,博格达北麓的早二叠世火山岩组合也具有双峰式特征,说明二叠纪早期博格达北麓为海相裂谷环境,博格达南麓为陆相裂谷环境.古流向呈现双向性,自博格达南北向裂谷中心汇聚.物源分析显示,吐哈盆地北缘早、中二叠世地层中的砾石成分多以安山岩与凝灰岩、流纹质等酸性火山岩为主,砂岩、硅质岩、灰岩次之,主要来自于下伏泥盆纪、石炭纪岩石.%The Early Permian Yierxitu Formation widely distributed in Turpan-Hami area of Xinjiang provides a record of paleocli-mate, paleogeography, basin and tectonic evolution in the Early Permian period. There exists much controversy concerning sedimen-tology, basin evolution and tectonic background of the Yierxitu Formation. This paper briefly reviewed previous researches on the Yierxicu Formation in Turpan-Hami area. Furthermore, on the basis of geological survey, the authors studied stratigraphy, sedimentary facies, provenance and paleocurrents of the Yierxitu Formation, and the results indicate that the Yierxitu Formation was spatially and temporally involved in an evolution of sedimentary facies from alluvial fan or river to shallow lake, semi-deep or deep lake in upward succession. Volcanic lithological associations of the Yierxitu Formation are characterized by the bimodal volcanic rock assemblages of olivine basalt, basaltic andesite and rhyolite. The distribution of lithofacies and lithological associations indicates that the volcanic constituents of the Yierxitu Formation gradually increase from west to east, which means the volcanic activities were stronger in the east than in the west. Meanwhile, marine flysch formations intercalated with volcanic rocks were developed in the northern Bogda Mountain. Petrologic characteristics and geochemistry show that, in the northern Bogda Mountain, there existed bimodal volcanic rock assemblages. Studies show that marine rift existed in the northern Bogdashan Mountain whereas a continental rift occurred in the southern Bogda Mountain. Paleocurrents show a bio-direction pattern, and currents from the northern and southern Bogda Mountain were concentrated in the central Bogda Mountain area (the center of the rift). Provenance analysis shows that conglomerate sediments of the Early and Middle Permian period in northern Turpan-Hami area are mainly composed of andesite, tufts and rhyolitic volcanics as well as sandstone, silica or limestones, suggesting that they were derived from the underlying Devonian and Carboniferous strata.
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