Extension of orogenic belts and upwelling of asthenosphere:the example of Hinggan-Mongolian orogenic belt

There were mighty advances in continental lithosphere study last decade. It is recognized that asthenosphere, which is marked by low-velocity seismic wave, is not only unlike that of ocean in continuity and uniformity, but also not suitable to continent as the concept of mechanical decoupling zone. The depth and reflection characters of the top of asthenosphere vary in different regions within a continent. Instead of the passive response to plate divergence, asthenosphere plays a very active role in continental dynamics,

大兴安岭北段新巴尔虎右旗韧性剪切带的发现及其地质意义

大兴安岭北段新发现一条韧性剪切带--新巴尔虎右旗韧性剪切带。根据野外露头观测,该韧性剪切带为左行-逆断层性质。韧性剪切带内变形的最年轻地质体为早三叠世花岗闪长岩,其被侏罗系覆盖,且下侏罗统柴河组未发生韧性变形。通过SHRIMP锆石U-Pb测年,得出早三叠世花岗闪长岩的年龄加权平均值为249.3±4.1 Ma,结合野外地质关系,将新巴尔虎右旗韧性剪切带变形时代归属于中-晚三叠世。根据区域构造演化分析,认为其形成于蒙古-鄂霍茨克洋三叠纪晚期向额尔古纳地块南向俯冲的活动大陆边缘构造背景。通过区域韧性断裂对比,认为新巴尔虎右旗韧性剪切带为额尔古纳河-阿龙山NE向韧性变形域的南部延伸。新巴尔虎右旗韧性剪切带的发现为研究区域韧性变形构造及兴蒙造山带构造演化提供了基础资料。

内蒙古苏尼特左旗晚石炭世花岗岩地球化学特征及其意义

内蒙古苏尼特左旗晚石炭世花岗岩位于兴蒙造山带中的二连—贺根山断裂带南侧,属中亚造山带的一部分,研究该花岗岩能够对兴蒙造山带晚古生代构造演化提供新的证据。该地区的粗中粒花岗闪长岩为一套高钾钙碱性花岗岩,岩浆经历了较彻底的分异演化,分离结晶程度高。LREE轻度富集,HREE轻度亏损,具中等程度的Eu负异常。岩浆岩成因类型为Ⅰ型花岗岩,为破坏性活动板块边缘(板块碰撞前)花岗岩,指示西伯利亚板块和华北板块在研究区于(晚)石炭世开始碰撞。