复杂变质带褶皱形态判定新方法——变斑晶包裹物迹线应用研究  

A new method for ascertaining the shape of isoclinal folds in multiply-deformed metamorphic zone:The application of porphyroblast inclusion trails

作　　者：曹汇[1,2] 许志琴[1] 李化启[1] 蔡志慧[1] 许翠萍[1] 

机构地区：[1]大陆构造与动力学国家重点实验室,中国地质科学院地质研究所,北京100037 [2]澳大利亚詹姆斯库克大学地球科学学院

出　　处：《岩石矿物学杂志》2013年第5期751-760,共10页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目(41202153);国土资源公益性行业科研专项(201211093);中国地质科学院地质研究所中央级公益性基本业务费专项基金(J1101)

摘　　要：经历了复杂多期变形的片岩和片麻岩地区,褶皱形态及形成时代的判定是变质岩构造地质过程研究的难点之一。变斑晶内包裹物迹线记录了区域变质变形作用历史过程,可为通过野外露头观测难以确定的复杂褶皱形态判定提供新的研究途径。本文以美国科罗拉多州阿肯色河Texas Creek地区为例,尝试运用垂直于5期面理弯切轴的定向薄片中叠加面理(变斑晶包裹物迹线)由水平到竖直和由竖直到水平的几何形状变化,确定研究区内一个存在争议的复杂褶皱形态为背形,并推断该褶皱形成于区域内第1期变斑晶生长过程(约为1500 Ma)中。It is usually difficult to ascertain the shape of folds in multiply-deformed high-grade metamorphic gneisses and schists. If such rocks contain porphyroblasts, a new approach is possible because of the way through which porphyroblast grew was affected by crenulation versus reactivation of compositional layering. Isoclinally folded rocks in Texas Creek, Arkansas River region of Central Colorado contain relics of fold hinges; neverthe- less, it is very difficult to ascertain whether they are antiforms or synforms because of the effects of younger re- folding and the locally truncated nature of coarse compositional layering. Using the asymmetry of overprinting foliations relative to the five FIA sets in this region, the authors have revealed that an isoclinal fold, which was previously interpreted as a synform, is actually an antiform, which was developed during the first stage of por- phyroblast growth （around 1 500 Ma）.

关 键 词：褶皱形态 变斑晶 变斑晶包裹迹线 面理弯切轴 

分 类 号：P542[天文地球—构造地质学]