固阳花岗-绿岩地体 ~2.5Ga岩浆作用与地壳增生机制

There was a strong tectonic thermal event at ~ 2.5 Ga in the North China craton(NCC), and the understanding of this event is controversial. The granite-greenstone terrane is an important unit of the Archean basement. Due to the low degree of metamorphism and deformation, making the granite-greenstone terrene a optimal object for studying the magmatism and continental crust growth in Archean. Guyang granite-greenstone terrane is located at western NCC, and composed of volcanic-sedimentary series and intermediate-acid intrusive bodies. There are abundant types of rocks in granite-greenstone terrane, including komatiite-high Fe tholeiite assembly, adakite-Nb rich basalt-Mg andesite assembly, TTG gneiss, sanukitoid and so on. All these types of rocks contemporary formed at ~ 2.5 Ga, and document a strong magmatism event in this time completely. For this application, We will carry systematic work on the petrology, geochemistry and chronology of the samples from Guyang granite-greenstone terrane, in order to understanding related to the evolution, the sources and the formation time of the magmas in the ~2.5 magmatic events in this area. Combined with other geological data in the region, We want to clarify the tectonic setting of the ~ 2.5 Ga magmatism. Moreover, Based on these work, we will discuss the continental curst growth and evolution in the western NCC.

华北克拉通～2.5Ga存在强烈构造热事件，对这期事件的认识存在很多分歧。花岗-绿岩地体是太古宙地壳的重要单元，由于变质变形程度较低，使其成为研究太古代岩浆作用及陆壳增长的最佳对象。固阳花岗-绿岩地体位于华北克拉通西部，由火山－沉积岩系及相关的中酸性侵入岩体组成，发育丰富的岩石类型，包括科马提岩-高Fe拉斑玄武岩、埃达克岩-富Nb火山岩-Mg安山岩、TTG、高镁闪长岩等，这些岩石集中形成于～2.5Ga，完整的记录了一期强烈的岩浆作用热事件。此项目拟对上述岩石进行系统的岩石学、地球化学和年代学研究，以了解相关的岩浆过程、岩浆源区的物质组成、形成时代及相互关系，并进一步结合该地区其他地质资料，理清~2.5Ga岩浆作用的构造背景。在此基础上探讨华北克拉通西部晚太古代经历的地壳增生及相关的构造过程。

固阳花岗-绿岩地体做为华北克拉通西部最重要的前寒武基底岩石组合，是研究阴山地块演化的理想区域。本项目选择花岗-绿岩地体为主要研究对象，通过进行细致的野外大比例尺填图、岩石地球化学（包括全岩主微量和Nd同位素、锆石Hf同位素）及年代学研究，查明固阳绿岩带的岩石成因及外围中酸性侵入体，结合该地区相关地质资料，探讨晚太古代阴山地块的地质演化历史。并取得以下几点认识：（1）固阳绿岩带可能记录了早期地球的构造体制的转化；（2）绿岩带层序由下至上具有特有的演化趋势；（3）识别出一套具有低负εHf(t)值石英闪长岩体（+1.3 ~ -7.2），可能形成于下地壳的重熔，可能有俯冲背景有关。本项目的研究成果对于早前寒武纪地壳演化及板块体制的起源具有重要意义，并在国际地学权威期刊上发表SCI论文5篇，EI一篇。