【摘要】 本文以天湖东岩体为例,探讨中天山澄江期片麻状花岗岩的特征及其形成机制。岩相学、岩石化学、稀土元素、微量元素和同位素研究表明,天湖东岩体是岛弧钙碱性火山—沉积岩系经原地改造的产物,其Rb-Sr等时线年龄为707.7±4.9Ma。花岗岩形成作用的动力、热力来源可能与向塔里木大陆俯冲的天山岩石圈的拆沉有关。在造山过程晚期-期后的挤压向拉张转变过程中,拆沉导致的底侵和内侵引发了地壳岩石的脱水和熔融,所产生的熔体-流体上升并将较浅层次的变质岩改造为片麻状花岗岩。变质峰期以后形成的韧性剪切带为熔体-流体的运移提供了通道。更多还原

【Abstract】 Taking the Tianhudong granite as an example, this paper investigates characteristics and genesis of the Chengjiangiangneissic granites in the Middle Tianshan Mountain areas. Studies in petrography, petrochemistry, rare earth elements, trace elementsand isotopes indicate that the Tianhudong granite, with a Rb-Sr isochron age of 707.7±4. 9 Ma, was formed by essentially in situtransformation of metamorphosed island arc calc-alkaline volcanic-sedimentary rocks. Dynamics and heat might have heen derived bydelamination of the Tianshan lithosphere which had subducted beneath the Tarim continent. In the course of tectonic conversion fromcompression to extension at late- or post-orogenic stage, underplating and intraplating induced by delamination triggered dewatering andpartial melting of crustal rocks. The resultant melts and fluids ascent and transformed the metamorphic rocks at higher levels intogneissic granites. Ductile shear zones that were formed after peak metamorphism might have provided pathways for upward transport ofmelts and fluids.更多还原