内蒙古北山地区阿民乌素蛇绿岩的年代学、地球化学特征及大地构造意义

内蒙古北山地区阿民乌素蛇绿岩是芨芨台子-小黄山蛇绿岩带的重要组成部分,主要由变质辉长岩和极少强蛇纹石化橄榄岩组成。变质辉长岩LA-ICP-MS锆石U-Pb年龄453±12 Ma,形成于晚奥陶世。强蛇纹石化橄榄岩MgO(36.90%~37.44%)、Ni(1980×10^-6~2232×10^-6)、Cr(2312×10^-6~2506×10^-6)含量高,而Al2O3(0.59%~1.41%)、TiO 2(0.01%~0.02%)和∑REE(0.85×10^-6~3.25×10^-6)含量低,具亏损地幔岩特征;变质辉长岩MgO(7.22.20%~11.66%)相对含量高;Al2O3(15.61%~18.79%)、TiO 2(0.20%~0.29%)、P2O5(0.01%)、K2O+Na2O(1.36%~2.43%)含量低,且K2O

Chronology, geochemical characteristics and tectonic significance of Aminwusu ophiolite in the Beishan area, Inner Mongolia

The Aminwusu ophiolite in the Beishan area,Inner Mongolia is an important part of the Jijitaizi-Xiaohuangshan ophiolite mélange belt.This rock consists of metamorphic gabbro and little serpentinized peridotite.LA-ICP-MS zircon U-Pb dating of metamorphic gabbro shows that the metamorphic gabbro formed at 453±12 Ma,i.e.,in Late Ordovician.The content of MgO(36.90%~37.44%),Ni(1980×10^-6~2232×10^-6),and Cr(2312×10^-6~2506×10^-6)in serpentinized peridotite is relative high,and the content of Al 2 O 3(0.59%~1.41%),TiO2(0.01%~0.02%)and REE(0.85×10^-6~3.25×10^-6)is relative low,showing the feature of depleted mantle.The content of MgO(7.22.20%~11.66%)in metamorphic gabbro is relative high,that of TiO 2(0.20%~0.29%),P2O5(0.01%),K2O+Na2O(1.36%~2.43%,K 2 O