津巴布韦克拉通构造变形特征分析

根据津巴布韦克拉通北部地区的构造变质特征及矿物测年数据,表明太古界地壳基底形成和演变分为两个阶段。早期约在26.7亿年,Shamva-Bindura绿岩带内发育平行层理的剪切带,在长英质片麻岩核组成的大型推覆体之间形成洋壳和火山岛弧物质的叠瓦状堆积,结果是炽热长英质和铁镁质岩层的堆积使得地壳的演变暂时达到均衡状态,岩层堆积厚度达35km。后期大约在26.0～26.2亿年炽热岩层的冷却收缩导致应变产生,沿垂直方向形成走向滑动断层带,为达到地热均衡,大面积的岩层发生熔蚀,并伴有花岗岩体底辟作用。岩层熔蚀和底辟作用产生二次临时变质作用和多种应变形态,也最终导致克拉通冷凝固化。

Mechanism of Horizontal Accretion and Stabilization of Zimbabwe Craton

Tectonic-metamorphic features and data of mineral ages in the northern area of Zimbabwe Craton,indicate two stages are divided for the formation and evolution of the Archean Basement Complex in this paper.At 2 670 Ma the shearing zones in the Shamva-Bindura greenstone belt are developed by the parallel to the bedding extending,further the imbricate stackings consisting of the oceanic and volcanic arc materials are deposited between the major thrusting nappes of the hot felsic and mafic rocks,the whole rock layers come to 35 km thick,so that the felsic and mafic crustal slices reached mechanical equilibrium.Between 2 620 and 2 600 Ma,the obviously shortening of this thick crust caused strain producing vertical strike-slip faults.To establish the equilibrium geotherm,large-scale crustal melting and diapirism were processed,which induced a second temporary metamorphic imprint and various strain patterns taken place,and led to cooling and stabilization of the craton.