Collision zone between the Kohistan arc and the Asian plate in NW Pakistan
Collision zone between the Kohistan arc and the Asian plate in NW Pakistan
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DOI：
10.1017/s026359330001066x
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
C. Pudsey;M. Coward;I. W. Luff;R. Shackleton;B. Windley;M. Q. Jan
中科院分区：
文献类型：
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作者：
C. Pudsey;M. Coward;I. W. Luff;R. Shackleton;B. Windley;M. Q. Jan
摘要本文描述了巴基斯坦西北部吉德拉尔地区亚洲板块与科伊斯坦岛弧之间的缝合带。亚洲板块南部由两个构造单元组成，由北倾的热顺断裂分隔。西北单元由泥盆系碳酸盐岩和石英岩组成，上覆泥盆系至二叠系页岩和板岩，并有少量灰岩（伦页岩）。构造复杂，有s向逆冲和等斜褶皱。沿热顺断裂，相对未变形的热顺组可能代表糖蜜。中心单元包括向n倾斜的上古生界板岩和石英岩（Darkot群），可能与反形板岩带、火山组合的片岩和白垩纪灰岩（Chitral板岩、Koghozi绿片岩、Krinj和Gahiret灰岩）形成断裂。亚洲板块沉积物由花岗质和花岗闪长质岩体侵入，这些岩体变形不一，局部为斑岩。北缝合线混杂的火山、沉积和蛇纹岩块体在板岩基体中将亚洲板块与东南板块科希斯坦弧分开。白垩系火山岩和部分沉积物（Shamran火山岩群、Drosh组、Purit组和Gawuch组）被石英闪长岩、闪长岩和花岗岩侵入。这些中间深成岩向南进入基性层状复合体和角闪岩，代表了弧的深层。火山岩和沉积物向北倾，呈水平线理。南亚和科希斯坦的构造历史与最初弯曲的北缝合线相一致：弧的运动最初相对于亚洲向北东，随后向北西。
ABSTRACT This paper describes the suture zone between the Asian plate and the accreted Kohistan island arc in the Chitral district of NW Pakistan. The southern part of the Asian plate consists of two tectonic units separated by the N-dipping Reshun fault. The northwestern unit comprises Devonian carbonates and quartzites overlain by Devonian to Permian shales and slates with some limestones (Lun shales). Its structure is complex with S-verging thrusts and isoclinal folds. Along the Reshun fault, the relatively undeformed Reshun Formation may represent molasse. The central unit includes N-dipping Upper Palaeozoic slates and quartzites (Darkot Group), probably faulted against an antiformal tract of slates, schists derived from a volcanic assemblage and Cretaceous limestones (Chitral slate, Koghozi greenschist, Krinj and Gahiret limestones). Asian plate sediments are intruded by granitic and granodioritic plutons, variably deformed and locally porphyritic. The Northern suture melange of volcanic, sedimentary and serpentinite blocks in a slate matrix separates the Asian plate from the southeastern unit, the Kohistan arc. This comprises Cretaceous volcanic rocks with some sediments (Shamran Volcanic Group, Drosh, Purit and Gawuch Formations) intruded by aphyric diorites, tonalites and granites. These intermediate plutonic rocks pass southwards into a mafic layered complex and amphibolites representing deep levels of the arc. The volcanic rocks and sediments dip to the N and have a horizontal lineation. The structural history of southern Asia and Kohistan is consistent with an originally curved Northern suture: motion of the arc was initially to the NE relative to Asia and subsequently to the NW.