祁漫塔格造山带——青藏高原北部地壳演化窥探

发布时间：2018-10-29 12:35

【摘要】：祁漫塔格是东昆仑造山带的一个分支,位于青藏高原中北部,夹持于柴达木盆地和库木库里盆地中间,向西被阿尔金走滑断裂错段。从元古代到早中生代,由于受到多期、多阶段大洋俯冲和关闭影响,导致不同地体间发生碰撞拼贴和大陆增生过程,并由此引发一系列的岩浆事件。祁漫塔格造山带内发育新元古代花岗岩(1000~820 Ma)是对Rodinia超大陆形成的响应。以阿达滩和白干湖逆冲断裂为界,划分为南、北祁漫塔格两地体。北祁漫塔格地体作为活动大陆边缘,发育大量的早古生代与俯冲有关的花岗岩和VA型蛇绿岩;南祁漫塔格地体最初为洋内俯冲形成的原始大洋岛弧,发育早古生代SSZ型蛇绿岩、岛弧拉斑玄武岩和钙碱性火山岩。随着持续俯冲,年轻岛弧伴伴随地壳加厚转变为成熟岛弧。南、北祁漫塔格地体间的碰撞(弧-陆碰撞)可能发生在晚志留世(422Ma),并持续到早泥盆世(398Ma)。在此期间(422~389Ma),南祁漫塔格地体内发育一系列同碰撞型花岗岩;北祁漫塔格地体内发育一系列的大洋岛弧花岗岩。南祁漫塔格作为外来地体,碰撞拼贴对于大陆边缘、大陆增生意义重大。之后,南、北祁漫塔格地体进入后碰撞环境并发育一系列板内花岗岩。此外,伸展导致造山带垮塌,发育中泥盆统磨拉石建造。碰撞使得海沟后退,海沟阻塞导致俯冲减弱甚至停止,因而产生了石炭-二叠纪(357~251 Ma)岩浆活动缺口。古特提斯祁漫塔格洋的最终关闭可能始于晚二叠世,使得库木库里微板块拼贴于大陆边缘;碰撞抬升导致缺失上二叠统-中三叠统地层。早中三叠世(251~237 Ma)由于碰撞,俯冲大洋板片回转,之后断离,软流圈地幔物质沿岩石圈地幔通道上涌,使得新生下地壳部分熔融;到了晚三叠世,大规模岩石圈地幔和下地壳物质拆沉,导致古老地壳物质发生熔融,形成了一系列后碰撞背景下的钙碱性和碱性花岗岩。
[Abstract]:Qimantag is a branch of the East Kunlun orogenic belt, located in the central and northern part of the Qinghai-Tibet Plateau, located between the Qaidam basin and the Kumukuli basin, and is located westward by the fault of the Altyn strike slip fault. From Proterozoic to early Mesozoic, the collision collage and continental accretion occurred between different terraces due to the influence of multi-stage and multi-stage ocean subduction and closure, and caused a series of magmatic events. The development of Neoproterozoic granites (1000 ~ 820 Ma) in the Qimantage orogenic belt is a response to the formation of the Rodinia supercontinent. The Ardatan and Baigan Lake thrust faults are divided into south and north Qimantag bodies. As the active continental margin, the North Qimantag terrane developed a large number of early Paleozoic subduction-related granite and VA ophiolite. The South Qimantage terrane was originally a primitive oceanic island arc formed by subduction of the ocean, and developed early Paleozoic SSZ ophiolite, island arc tholeiite and calc-alkaline volcanic rocks. With continuous subduction, young island arcs are accompanied by crustal thickening to mature island arcs. The collision between the South and North Qimantag terrains (arc-continent collision) may take place in the late Silurian (422Ma) and last until the early Devonian (398Ma). During this period (422~389Ma) a series of concollision granites were developed in the South Qimantag and a series of oceanic island arc granites were developed in the North Qimantag. South Qimantag as an alien terrane, collision collage is of great significance to continental margin and continental accretion. Later, the south and north Qimantag terrains entered the post-collision environment and developed a series of intra-plate granites. In addition, the extension caused the orogenic belt to collapse, and the developing Devonian molded rock formation. The collision caused the trench to recede and the blocking of the trench led to the weakening or even stopping of the subduction resulting in a gap in Carboniferous Permian magmatic activity. The final closure of the PaleoTethys Qimantag Ocean may have started in the late Permian, which led to the collage of the Kumukuri microplate on the continental margin, and the collision uplift resulted in the absence of the Upper Permian and Middle Triassic strata. In the early Middle Triassic (251C 237 Ma), the subduction oceanic plate rotated due to collision, then broke off, and the asthenospheric mantle material upwelled along the lithospheric mantle channel, which led to the partial melting of the new lower crust. By the late Triassic, large scale lithospheric mantle and lower crust materials desunk, resulting in the melting of ancient crustal materials and the formation of a series of calc-alkaline and alkaline granites in the background of post-collision.
【作者单位】：中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;北京大学地球与空间科学学院;中国地质调查局西安地质调查中心;青海省第三地质矿产勘查院;长安大学地球科学与资源学院;
【基金】：国土资源部公益性行业科研专项经费项目(编号:201411025) 中国地质调查局地质调查项目(编号:1212011085528);中国地质调查局高层次地质人才培养计划(编号:201309) 青年地质英才计划(编号:201112)资助的成果
【分类号】：P313

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