What Happened in the Trans‐North China Orogen in the Period 2560‐1850 Ma?
What Happened in the Trans‐North China Orogen in the Period 2560‐1850 Ma?
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DOI：
10.1111/j.1755-6724.2006.tb00303.x
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发表时间：
2006-12
期刊：
影响因子：
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通讯作者：
Guochun Zhao;Liu Shuwen;M. Sun;Li Sanzhong;S. Wilde;X. Xia;Jian Zhang;Yanhong He
中科院分区：
文献类型：
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作者：
Guochun Zhao;Liu Shuwen;M. Sun;Li Sanzhong;S. Wilde;X. Xia;Jian Zhang;Yanhong He
摘要：横贯北中国造山带是一条古元古代陆-陆碰撞带，东西地块沿此拼接形成连贯的北中国克拉通。最近的地质、构造、地球化学和同位素资料表明，造山带是沿东部地块西缘的大陆边缘或日本式弧形，与西部地块之间有一个古老的大洋隔开，东部地块西缘之下的大洋岩石圈向东俯冲。2550-2520 Ma，深俯冲导致中下地壳部分熔融，产生丰富的花岗岩类岩浆，侵入地壳上部，在中低品位花岗岩-绿岩地体中形成花岗质深成岩体。2530-2520 Ma，大洋岩石圈俯冲导致地幔楔体部分熔融，导致下地壳镁铁质岩浆底侵，弧内广泛的镁铁质和次要的长英质火山作用，形成绿岩组合的一部分。广泛的镁铁质-长英质火山作用驱动的伸展作用导致了造山带中弧后和/或弧内盆地的发育。2520-2475 Ma，俯冲导致下地壳进一步部分熔融，形成大量的英云闪长花岗闪长岩(TTG)岩浆活动。此时，伴随着弧后盆地的进一步伸展，发生了幕式花岗岩浆作用，造山带内分别侵位了2360 Ma、∼2250 Ma、2110~21760 Ma和∼2050 Ma花岗岩。现代火山-沉积岩发育于弧后或弧内盆地。在2150-1920 Ma，造山带经历了几次伸展事件，可能是由于洋脊俯冲，导致镁铁质岩墙侵位，随后变质为角闪岩和中高压镁铁质麻粒岩。1880-1820 Ma，东西地块之间的大洋被俯冲完全吞没，大洋的闭合导致陆-弧-陆碰撞，导致大规模的逆冲和等斜褶皱，并将部分岩石输送到下地壳或上地幔形成麻粒岩或榴辉岩。峰期变质作用后发生折返/抬升作用，导致岩石中普遍发育不对称褶皱和辛结构。
Abstract: The Trans‐North China Orogen (TNCO) was a Paleoproterozic continent‐continent collisional belt along which the Eastern and Western Blocks amalgamated to form a coherent North China Craton (NCC). Recent geological, structural, geochemical and isotopic data show that the orogen was a continental margin or Japan‐type arc along the western margin of the Eastern Block, which was separated from the Western Block by an old ocean, with eastward‐directed subduction of the oceanic lithosphere beneath the western margin of the Eastern Block. At 2550‐2520 Ma, the deep subduction caused partial melting of the medium‐lower crust, producing copious granitoid magma that was intruded into the upper levels of the crust to form granitoid plutons in the low‐ to medium‐grade granite‐greenstone terranes. At 2530‐2520 Ma, subduction of the oceanic lithosphere caused partial melting of the mantle wedge, which led to underplating of mafic magma in the lower crust and widespread mafic and minor felsic volcanism in the arc, forming part of the greenstone assemblages. Extension driven by widespread mafic to felsic volcanism led to the development of back‐arc and/or intra‐arc basins in the orogen. At 2520‐2475 Ma, the subduction caused further partial melting of the lower crust to form large amounts of tonalitic‐trondhjemitic‐granodioritic (TTG) magmatism. At this time following further extension of back‐arc basins, episodic granitoid magmatism occurred, resulting in the emplacement of 2360 Ma, ∼2250 Ma 2110–21760 Ma and ∼2050 Ma granites in the orogen. Contemporary volcano‐sedimentary rocks developed in the back‐arc or intra‐arc basins. At 2150‐1920 Ma, the orogen underwent several extensional events, possibly due to subduction of an oceanic ridge, leading to emplacement of mafic dykes that were subsequently metamorphosed to amphibolites and medium‐ to high‐pressure mafic granulites. At 1880‐1820 Ma, the ocean between the Eastern and Western Blocks was completely consumed by subduction, and the closing of the ocean led to the continent‐arc‐continent collision, which caused large‐scale thrusting and isoclinal folds and transported some of the rocks into the lower crustal levels or upper mantle to form granulites or eclogites. Peak metamorphism was followed by exhumation/uplift, resulting in widespread development of asymmetric folds and symplectic textures in the rocks.