柴达木盆地北缘鹰峰环斑花岗岩体的岩相学特征  

Petrography Feature of Yingfeng Rapakivi Granite Body in North Margin of Qaidam Basin

作　　者：胡能高[1] 申文环[1] 王晓霞[2] 孙延贵[3] 蔡欢欢[1] 陈云杰[1] 

机构地区：[1]长安大学地球科学与国土资源学院,陕西西安710054 [2]中国地质调查局发展研究中心,北京100073 [3]青海省地质调查院,青海西宁810012

出　　处：《地球科学与环境学报》2006年第4期1-9,共9页Journal of Earth Sciences and Environment

基　　金：国家自然科学基金项目(40372043)

摘　　要：野外调查表明，鹰峰环斑花岗岩体形成于中元古代，位于柴北缘构造带，呈透镜状夹持在剪切带间。同时代侵入的还有辉绿岩墙和石英闪长岩-奥长花岗斑岩脉，构成双峰式岩石组合。该环斑花岗岩多具无奥环结构，卵形钾长石球斑十分发育，其体积分数多在50％～60％，粒径多在2～3cm，常以多晶集合体出现，出溶作用十分强烈。基质结构有中粗粒、细粒和显微文象结构等。石英、钾长石都具两个或多个世代，黑云母多结晶较晚，按矿物定量分类多属石英正长岩和石英二长岩类。与典型环斑花岗岩相比，该岩体有出露面积小，岩石类型单调，球斑含量大，大小较均匀且为多晶集合体，出溶作用强烈，基质结构多样，变质变形明显等特征。这些特征部分起因于加里东期的改造，部分是该地区元古代岩浆作用个性的表现。According to field investigation, the Yingfeng rapakivi granite is formed in mid Proterozoic and located between shear belts as a lentiform in the structural belt of north margin of Qaidam basin. There are also diabase dyke and quartz diorite digoclase trondhjemite vein of the same time, which show a character of bimodal magmatic association. In the granite body, pyterlitic texture is very common, and, ovoid megacrystal composed by K-feld- spars which has a megacryst eontent of 50% to 60%, size about 2 cm to 3 cm, aggregation of several crystals and very intense exsolution effect is very developed. In matrix, mediumrcoarse grains, fine grains and micrographic texture are the main texture. Quartz and K-feldspar can be divided into two generations, but biotite crystallized later. According to the content of minerals, they belong to quartz syenite and quartz monzonite. Compared with the typical rapakivi granite, Yingfeng complex is characterized by smaller exposing area, monotonous rock types, larger megacryst content, even megacryst size, diversified matrix texture, and obvious deformation and metamor phism. These characters may be caused mainly by the reforming in Caledonian period and partially by the magmatic effect of mid-Proterozoic in this area.

关 键 词：环斑结构 环斑花岗岩 鹰峰岩体 柴北缘构造带 中元古代 

分 类 号：P588.121[天文地球—岩石学]