ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    李平, 高晓峰, 吕鹏瑞, 朱小辉, 陈隽璐. 祁连山–柴北缘地区岩浆活动的时空分布、成因演变及构造岩浆演化[J]. 西北地质,2023,56(4): 283-317.
    引用本文: 李平, 高晓峰, 吕鹏瑞, 朱小辉, 陈隽璐. 祁连山–柴北缘地区岩浆活动的时空分布、成因演变及构造岩浆演化[J]. 西北地质,2023,56(4): 283-317.
    LI Ping, GAO Xiaofeng, LÜ Pengrui, ZHU Xiaohui, CHEN Junlu. Spatial–Temporal Distribution, Petrogenetic Evolution and Tectono–Magmatic Evolution in Qilian Mountains and Northern Margin of Qaidam[J]. Northwestern Geology,2023,56(4): 283-317.
    Citation: LI Ping, GAO Xiaofeng, LÜ Pengrui, ZHU Xiaohui, CHEN Junlu. Spatial–Temporal Distribution, Petrogenetic Evolution and Tectono–Magmatic Evolution in Qilian Mountains and Northern Margin of Qaidam[J]. Northwestern Geology,2023,56(4): 283-317.

    祁连山–柴北缘地区岩浆活动的时空分布、成因演变及构造岩浆演化

    Spatial–Temporal Distribution, Petrogenetic Evolution and Tectono–Magmatic Evolution in Qilian Mountains and Northern Margin of Qaidam

    • 摘要: 祁连山及邻区广泛出露有形成于不同时代、具有复杂成因类型的侵入岩类,它们记录了祁连山、柴北缘和宗务隆构造带多阶段、多期次的构造岩浆事件。根据侵入岩的空间展布情况、年代学时空格架和岩石成因类型,祁连山–柴北缘地区的侵入岩浆活动主要可分为3个阶段:前寒武纪(2.47 Ga~561 Ma)、早古生代—泥盆纪(517~360 Ma)、中晚二叠世—三叠纪(271~210 Ma)。①前寒武纪花岗岩(2470~561 Ma)的形成记录了区内古老大陆的聚合、离散过程及北祁连洋的开启。②自前寒武纪末期洋盆打开以来,祁连山和柴北缘地区在517~359 Ma形成有大量的侵入岩类,祁连山、柴北缘和宗务隆地区自中泥盆世以来开始明显的显示出相对独立的构造–岩浆演化过程。其中,自517 Ma以后,祁连山地区形成有俯冲成因地球化学特征的花岗岩、埃达克质岩石和碱性花岗类,与区内同期火山岩一同构成弧盆系的火山–侵入岩组合;中南祁连在奥陶纪(452~444 Ma)和早志留世初(431 Ma)广泛形成的强过铝质S型碰撞成因花岗岩与晚奥陶世出现的磨拉石沉积建造,表明了祁连山碰撞造山事件发生于晚奥陶世—早泥盆世(452~431 Ma)阶段;柴北缘地区可能于463 Ma左右已经开始进入碰撞–后碰撞造山阶段,略早于祁连山地区。440~425 Ma阶段,大量高Mg中性侵入岩和具有正εNd(t)、εHf(t)值同位素特征的埃达克质岩类,与430~420 Ma阶段的A型花岗岩,共同代表了中–南祁连后碰撞造山伸展作用。至泥盆纪,祁连山和柴北缘地区岩浆作用显示相对独立的构造演化进程。祁连地区该阶段侵入岩浆活动开始急剧减弱,北祁连少量形成于409~402 Ma阶段的A型花岗岩、中南祁连386 Ma的辉绿岩岩墙和老君山组山间磨拉石的出现,为祁连山在中泥盆世开始由后碰撞造山转为陆内伸展作用的地质记录;柴北缘地区在402~367 Ma折返及后续造山过程中发育有高Sr、低Y型花岗岩,且几乎同期形成有少量板块拆离成因的A型花岗岩(413~391 Ma)。晚泥盆世牦牛山组陆相砾岩–裂谷系火山岩建造,及早—中泥盆世至晚二叠世宗务隆山南缘–隆务峡、兴海–赛什塘–苦海等地断续出露的镁铁、超镁铁质岩石,可能与相对广泛的陆内裂解事件及宗务隆洋的形成、演化有关。③中晚二叠世—三叠纪(271~210 Ma),祁连山全区花岗岩浆活动仍较为微弱,但宗务隆构造带在中生代构成一期显著而特有的岩浆活动期。晚二叠世—早三叠世花岗岩形成于宗务隆洋向南的俯冲环境,240~220 Ma阶段的花岗岩与西秦岭地区碰撞–后碰撞成因花岗岩显示有相似的地球化学特征。至215 Ma,宗务隆地区A型花岗岩的发现标志了宗务隆构造带及邻区已全部进入了陆内造山阶段,整个秦–祁整个地区主造山期已经结束。三叠纪以后(<201 Ma),祁连山和柴北缘地区几乎无侵入岩浆活动。

       

      Abstract: Types of intrusions with different formation ages are widely exposed in Qilian Mountains and its adjacent areas, which record multi–stage tectono–magmatic events in Qilian Mountains, Northern Margin of Qaidam and Zongwulong tectonic belt. According to the spatial distribution, chronological framework and petrogenetic types, the intrusive magmatism in Qilian–Northern Margin of Qaidam region can be divided into three stages: Precambrian (2470~561 Ma), Early Paleozoic to Devonian (517~360 Ma), and Middle–Late Permian to Triassic (271~210 Ma). ① The Precambrian granites (2470 Ma~561 Ma) recorded the process of convergence and dispersion of ancient continents and the opening of the North Qilian Ocean. ② Since the opening of the Sinian ocean basin, a large number of intrusions have been formed between 517 and 359 Ma in Qilian Mountains and the Northern Margin of Qaidam. Since the Middle Devonian, the Qilian Mountains, the Northern Margin of Qaidam and the Zongwulong region have began to shown relatively independent tectonic–magmatic evolution process. Since 517 Ma, granitoids with geochemical characteristics of slab subduction, adakitic rocks and alkaline granites have been formed in Qilian Mountains, together with the volcanic rocks formed in the same period can constitute a volcanic–intrusive rock association of the arc–basin system. The strongly peraluminous S–type collision–related granites widely formed in the Ordovician (452~444 Ma) and Early Silurian (431 Ma) in Central and Southern Qilian, and the molasse sedimentary formation occurred in the Late Ordovician, indicate that the Qilian collision orogenic event occurred during the Late Ordovician and Early Devonian (452~431 Ma). In addition, the Northern Margin of Qaidam may have entered the collision–post–collision orogenic stage at ca. 463 Ma, slightly earlier than that of Qilian Mountains. In 440~425 Ma stage, a large number of high Mg neutral intrusive rocks, adakitic rocks with positive εNd(t) and εHf(t) values and the A-type granites formed during 430 Ma and 420 Ma, represent the post-collision orogenic extension of Central and Southern Qilian. To the Devonian, Qilian Mountains and the Northern Margin of the Qaidam Basin showed some differences for tectonic and magmatic evolution and have relatively independent evolution processes. The intrusive magmatism began to weaken sharply in Qilian Mountains. The occurrence of a small amount of A–type granite formed at 409~402 Ma in North Qilian, diabase dikes at 385.9Ma in Central and Southern Qilian and molasses in Laojunshan Formation is a geological record of Qilian Mountains from post–collision to intra–continental extension in the Middle Devonian. In Northern Margin of Qaidam, high Sr and low Y–type granites were developed during 402~367 Ma, and a small amount of A–type granite (413~391 Ma) was formed by slab broken–off almost at the same time. In addition, the continental conglomerate and rift–related volcanic rocks in Late Devonian Maoniushan Formation, and the ultramafic–mafic rocks intermittently exposed at southern Zongwulong–Longwu Gorge, Xinghai–Saishitang–Kuhai during the Early–Middle Devonian and the Late Permian may be related to the intracontinental extension and the evolution of Zongwulong Ocean. ③ From the Middle and Late Permian to Triassic (271~210 Ma), the granitic magma in Qilian Mountains is still weak. However, the Zongwulong belt formed a distinct and unique magmatic activity period in the Mesozoic. The Late Permian–Early Triassic granite was formed in the southward subduction of the Zongwulong Ocean. The geochemical futures of granites formed at ca. 240~220 Ma is similat to that of the collision or post–collision granite in Westeren Qinling. By 215 Ma, the discovery of A–type granite in Zongwulong belt marked them and its adjacent areas had all entered the intra–continental stage, and the main orogenic stage of the whole Qinling–Qilian region had ended. After the Triassic (<201 Ma), the magmatic activity in Qilian mountains and the northern margin of Qaidam was weakly.

       

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