【作者】 李玮；

【导师】 胡健民；

【作者基本信息】 中国地质科学院 ， 构造地质学， 2007， 博士

【摘要】 本文详细的分析了准噶尔西北缘造山带中生代盆地的形成机制和构造-沉积演化,论文主要取得了以下进展:准噶尔西北缘造山带中生代沉积盆地演化过程可分为三个阶段,即三叠纪挤压拗陷盆地发育阶段、早-中侏罗世走滑伸展盆地发育阶段、晚侏罗世-白垩纪挤压拗陷盆地发育阶段。和什托洛盖盆地早-中侏罗世为走滑盆地,盆地内部发育不同的沉积体系,并显示明显的空间变化。盆地北部边缘主要发育冲积扇和扇三角洲相,而西南部则以辫状河和曲流河相为主,湖相沉积以盆地东部或东北部较为发育。砾岩中的叠瓦状砾石和砂岩中的斜层理指示,盆地北部的古水流方向为自北向南,而盆地西南部古水流则以自西向东为主。据此判断,沉积物主体应来自于盆地北部和西南部古生代褶皱山系。与和什托洛盖盆地不同,克拉玛依凹陷三叠纪古水流方向为自北西向南东,早-中侏罗世为自东北向西南方向,表明扎伊尔山-哈拉阿拉特山为其主要物源区。因此,和什托洛盖盆地与准噶尔盆地在三叠纪-侏罗纪时期为被扎伊尔山-哈拉阿拉特山所分割的不同盆地,各自发育相对独立的沉积体系。准噶尔西北缘造山带锆石裂变径迹年龄为136 Ma,磷灰石裂变径迹年龄主要集中在135-67 Ma。裂变径迹热史模拟表明准噶尔西北缘造山带中、新生代以来主要经历了两次冷却隆升事件,即晚侏罗纪-白垩纪(160-80 Ma)和晚新生代(29-9 Ma)冷却隆升事件。磷灰石-锆石矿物对法计算表明准噶尔西北缘造山带在中侏罗世-早白垩世(174-108 Ma)的视隆升速率为74.7 m/Ma。准噶尔西北缘造山带晚侏罗世-早白垩世的隆升事件,反映了准噶尔西北缘造山带沉积盆地构造属性的反转。这一时期的构造背景由早中侏罗世的伸展转换为挤压;同时亦表明,准噶尔西北缘造山带扎伊尔山一带为两侧沉积盆地的物源区。由于古特提斯洋在晚三叠世的关闭,羌塘(230-200 Ma)、拉萨(145-120 Ma)与塔里木-欧亚板块在晚三叠世-早白垩世相继拼合,导致了中亚地区板内造山作用,形成的区域构造作用控制了中亚地区中生代以来盆地的形成和演化。准噶尔西北缘中生代盆地的形成与多期区域构造环境的变化有关。三叠纪期间,由于受印支运动的影响,该地区处于区域挤压构造背景,这一时期形成的盆地性质属于挤压拗陷型盆地;早-中侏罗世时期,在区域走滑拉伸机制下形成伸展断陷盆地;准噶尔西北缘造山带晚侏罗世的隆升事件,使得区域构造环境由伸展变为挤压,形成了挤压环境下的拗陷盆地,完成了该地区中生代盆地构造属性的反转过程。更多还原

【Abstract】 This dissertation had analyzed Mesozoic basins the mechanic and tectonic evolution of Mesozoic basins in Northwestern Junggar orogenic belt. The main conclusions and progresssions in research are as following.The evolution of Mesozoic basins in Northwestern Junggar orogenic belt was divided into three stages. The early was contractive stage during Triassic; strike-slip extension played an important role during early-middle Jurassic; and extrusive depression dominanted during late Jurassic to early Cretaceous.The Heshituoluogai basin was a strike-slip extensional basin in early-middle Jurassic. There existed various depositional system and showed obvious spatial distribution. Alluvial fan and fan-delta sedimentary systems dominated the north areas of the basin; while the southwestern of the basin was composed of braided and meandering river facies; and the lacustine sediments distributed mostly in the east or northeastern of the basin. Imbricated- pebbles in conglomerate and cross-bedding in sandstone indicated that the paleocurrents in north area and southwest area were southward and eastward, respectively. The phenomenon implied the main provenance of the basin was the north and southwest late-Paleozoic folded mountains.Whereas, palaeocurrent in Kelamayi basin was different from Heshituoluogai basin’s in early Mesozoic. They were distinct basins actually.The data of granitic fission-track in northwestern Junggar indicated that the Zircon Fission-track age was 136 Ma, apatite Fission-track age were 67-135 Ma. Thermal history modeling showed that the Junggar northwestern orogeny had mostly undergone twice uplifts. The first one occurred in later Jurassic to Cretaceous (160-80 Ma); the second one occurred in later Neozoic (29-9 Ma). Uplifting velocity was about 58-22 m/Ma by thermal history modeling, and 74.7 m/Ma by Apatite-Zircon mineral pair. The uplift process in northwest Junggar denoted that structural setting had transited from extension to contraction in later Mesozoic. Zhayier Mountain offered sediments for Heshentuoluogai and kelamayi basins.Because of the closure of Tethys Ocean, Qiangtang(230-200 Ma) and Lhasa(145-120 Ma) terrances had ensuingly collided with Eurasia plate. Distant effects of these collisions induced inner-plate orogenesis and controlled forming of Mesozoic basin in Central Asia.The evolution of Mesozoic basins was closely related with the multi-stages conversion of structural setting in Northwest Junggar area. Northwest Junggar basins formed in contractive environment in Triassic firstly. At the second time, Heshentuoluogai basin was extension-faulted basin controlled by strike-slip in early-middle Jurassic. Ultimately, the uplift of northwest Junggar resulted in the reversion of these basins’structural property and formed contractive basin during late Jurassic to early Cretaceous.更多还原