摘要
云开造山带广泛出露的条带-眼球状(环斑)花岗质岩石及紫苏花岗岩岩石地球化学和离子探针(SHRIMP)定年的研究表明,绝大多数为强过铝(SP)高钾钙碱性-钙碱性花岗岩,并且是高温俯冲-碰撞后构造环境形成的强过铝(SP)高钾钙碱性-钙碱性花岗岩。高钾钙碱性条带状黑云二长花岗岩、眼球状(环斑)黑云二长花岗岩到钙碱性紫苏花岗闪长岩(闪长岩)和片麻状含榴黑云二长花岗岩形成时代逐渐变新,岩浆结晶锆石SHRIMP年龄由(465±10)Ma、(467±10)Ma变为(435±11)Ma、(413±8)Ma,侵入辉长岩的Sm-Nd矿物-岩石等时线年龄为(392±53)Ma,并主要形成于俯冲-碰撞转换为碰撞后底侵-伸展的构造环境,其中紫苏花岗闪长岩(闪长岩)和片麻状含榴黑云二长花岗岩具A型花岗岩地球化学特征,侵入辉长岩的形成则标志俯冲-碰撞造山作用的结束和大陆伸展作用环境的开始。条带-眼球状(环斑)花岗岩及紫苏花岗岩中尽管存在四堡期(格林威尔)造山事件的重要信息,但它们应代表加里东期扬子板块向华夏板块俯冲-碰撞后拆沉-底侵-伸展作用构造环境岩浆岩活动的产物,并且经历了印支期的挤压抬升和伸展揭顶作用。
There are different cognitions about the genesis and ages for the banded-augen （rapakivi） granitic rock and charnockite, extensively outcroped in Yuankai region, western Guangdong Province. The study on their petrochemistry, SHRIMP dating, deformational and metamorphic structure show the most belong to the strong peraluminous high-K calc-alkaline and calc-alkalin granitoids, and were formed in post-collisional tectonic environment of high tempreture subduction-collision orogeny. The forming ages form banded biotite monzonitic granite, augen （rapakivi） biotite monzonitic granite to charnockite （enderbite, diorite） and gneissic garnet-bearing biotite monzonitic granite, whose crystallizing zircon SHRIMP ages are （465±10）Ma, （467±10）Ma, （435±11）Ma and（ 413±8）Ma respectively, became younger, and the Sm-Nd mineral-rock isochrone ages of intrusive gabbro rocks are （392±53）Ma. They were mainly formed in post-collisional delamination-underplating-exhumation tectonic environment transformed from subduction-collision, and charnockite and gneissic garnet-bearing biotite monzonitic granite with the geochemistic characterics of A-type granites. Although there was the important evidence that Sibao （Grenville ） orogenic event existed in Yunkai region, the banded-augen （rapakivi） granitoids in Yunkai orogenic belt should belong to active-continental margin magmatic rocks, which were formed in post-collisional delamination underplating -exhumation tectonic environment after Yangtze plate subduction-collision with Cathaysia plate during Caledonian and experienced the compressional uplift and extensional exhumation during Indosinian.
出处
《科学技术与工程》
2005年第17期1238-1246,共9页
Science Technology and Engineering
基金
国家自然基金(40072069)中国地质调查局(200313000041)资助
关键词
云开造山带
条带-眼球状(环斑)强过铝花岗岩
A型花岗岩
碰撞后构造环境
底侵-伸展作用
Yunkai orogenic belt banded-augen （rapakivi） strong peraluminous granitoids Atype granite post-collision tectonic enviroment delamination-underplating-exhumation
