黑河流域第四纪钻孔沉积物碎屑锆石U-Pb年龄及其与北祁连造山带的形成与演化

发布时间：2018-05-02 00:20

本文选题：黑河流域 + 北祁连山　；参考：《西北大学》2017年硕士论文

【摘要】：对黑河流域从中游到下游采集的8个第四纪钻孔沉积物的碎屑锆石进行了 LA-ICP MS锆石U-Pb定年,获得了从太古代末到中生代各个时段的年龄信息,大致可分为四组:2700～1700Ma:32%;1700～650 Ma:16%;650～358 Ma:30%;358～230 Ma.:22%;包含～2450 Ma、-～1850 Ma、～950 Ma、～520 Ma、～505 Ma、～480 Ma、～450 Ma、～430 Ma、～380 Ma、～320 Ma、～295 Ma的主峰值和次峰值年龄。其中,以新元古代末-古生代年龄信息为主,占总数的一半左右,表明在这个时间段内北祁连地区发生了最强烈的岩浆作用。结合区域地质背景,源区北祁连山经历了太古宙末薄弱陆壳固结生长;古元古代早晚属于基底物质形成的主要时期(～2450 Ma、～1850 Ma),末期发生区域动力热流变质作用;中元古代陆壳改造和重熔作用;新元古代发生了重要的岩浆作用,使陆壳成熟,反映了这个时期全球性的构造-热事件,即是对同时期全球罗迪尼亚超大陆裂解事件的响应。新元古代末-中晚寒武世大陆裂解,形成北祁连早古生代洋盆(650～505 Ma);奥陶纪主要为俯冲消减作用和主动大陆边缘发展形成的沟-弧-盆体系,贯穿奥陶纪始终(480～450 Ma)在～450 Ma洋盆闭合;～430 Ma可能代表了弧后盆地发生的陆陆碰撞事件;志留纪晚期-泥盆纪早期北祁连洋壳完全消亡(～395 Ma),柴达木板块与华北板块碰撞拼合,形成北祁连造山带;研究区普遍缺失中晚泥盆世的年龄信息,源区发育泥盆纪磨拉石沉积,也表明造山作用结束。石炭纪-二叠纪主体陆内发展,边缘存在明显海西期的岩浆-热事件(～320 Ma、～295 Ma)印证了前人关于北祁连地区存在海西期事件的说法,另外本文还获得了少量印支期的年龄;中生代研究区受到特提斯洋关闭再次发生造山运动,将石炭系-三叠系均卷入到推覆和逆冲构造之中,所以研究区很少出露海西期及印支期的岩体。北祁连地区在大地构造中位于古亚洲构造体系域与特提斯构造体系域之间,其造山作用受到古亚洲洋和特提斯洋动力系统的控制,因此构造形态多样,构造活动复杂,不仅反映了完整的造山作用旋回,而且成为中国大陆的板块构造运动和大地构造演化的重要组成部分。
[Abstract]:The LA-ICP MS zircon U-Pb dating has been performed on the detrital zircon collected from 8 Quaternary borehole sediments collected from the middle reaches to the lower reaches of the Heihe River Basin. The ages from the late Archean to the Mesozoic are obtained. It can be roughly divided into four groups: 2700: 1700 Ma: 1700, 650 Ma: 16: 650 Ma: 650,358 Ma: 30U 35880 Ma .22; including 2450 Ma-1850 Ma-1850 MaU, 520 Ma-U 505 Ma, 480 Ma430 Ma / 380 Ma / 320 Ma / 295 Ma peak and a peak age of 320 Ma / 295 Ma. Among them, the information of Neoproterozoic to Paleozoic ages is dominant, accounting for about half of the total, indicating that the strongest magmatism occurred in the North Qilian region in this time period. According to the regional geological background, the North Qilian Mountains in the source area experienced the weak continental crust consolidation growth at the end of Archean, the Paleoproterozoic belongs to the main period of basement material formation in the early and late Paleoproterozoic, and the regional dynamic heat flow metamorphism occurred at the end of the period. The Mesoproterozoic continental crust was reformed and remelted, while the Neoproterozoic magmatism matured the continental crust, reflecting the global tectonic-thermal events in this period, that is, the response to the global Rhodinia supercontinent cracking event in the same period. The late Neoproterozoic and the middle and late Cambrian continents split to form the early Paleozoic oceanic basin of the North Qilian, 650,505 Mag, and the Ordovician was mainly a trench-arc basin system formed by subduction and active continental margin development. Throughout the Ordovician period, the ocean basin closed at 430Ma may represent the continental collision event in the back-arc basin, and the North Qilian oceanic crust completely disappeared from late Silurian to early Devonian, and the Qaidam plate collided with the North China plate. The formation of the North Qilian orogenic belt, the general absence of age information of the Middle and late Devonian in the study area, and the development of Devonian morlite deposits in the source area also indicate the end of orogeny. Carboniferous-Permian main continental development, with obvious Hercynian magma-thermal event of 320 Mai (295 Maa), confirms the previous theory that Hercynian event exists in North Qilian area. In addition, a small amount of Indosinian age is obtained in this paper. The Mesozoic study area was subjected to the closure of the Tethys Ocean and the orogenic movement occurred again, which involved the Carboniferous and Triassic systems in the nappe and thrust structures, so very few rocks of the Hercynian and Indosinian periods occurred in the study area. The North Qilian area is located between the paleo-Asian tectonic system tract and the Tethys tectonic system tract in the geotectonics. Its orogeny is controlled by the Paleo-Asian and Tethyan dynamic systems, so the tectonic forms are diverse and the tectonic activities are complex. It not only reflects the complete orogenic cycle, but also becomes an important part of plate tectonic movement and tectonic evolution in the Chinese mainland.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P597.3;P542

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