阿尔泰造山带东段早泥盆世片麻状花岗岩岩石地球化学及年代学特征

Hronology and Petrology Characteristics of Early Devonian Gnessic Granites from East Altai Orogenic Belt

阿尔泰造山带东段识别出一套侵位于震旦系喀纳斯群和长城系苏普特岩群变质岩中的片麻状花岗岩,岩石组合为片麻状石英闪长岩、片麻状(似斑状)英云闪长岩、片麻状(似斑状)花岗闪长岩、片麻状(似斑状)二长花岗岩。岩石地球化学显示岩石具中高钾钙碱性系列花岗岩特征,形成于活动大陆边缘。锆石SHRIMP U-Pb测年表明,该套片麻状花岗岩结晶年龄为(393.7±4.4)Ma^(397.3±5.3)Ma(206Pb/238U表面年龄),属早泥盆世。该套片麻状花岗岩的厘定表明400 Ma±阿尔泰造山带存在一次规模宏大的构造岩浆热事件,同时为阿尔泰造山带400 Ma±的俯冲造山提供了新的年代学制约。

One suite of gneissic granites pluton,which emplaced in the Sinian Kanasi group metamorphic and the Mesoproterozoic Supute group complex metamorphic,consist of gneissic quartz diorite＋gneissic porphyroid tonalite＋gneissic porphyroid granodiorite ＋ gneissic porphyroid adamellite,is identified from East Altai orogenic belt.Petrochemical and geochemical characteristics of the gneissic granites show middle-K to high-K calc-alkaline series granites, which form from active continental margin.Zircon SHRIMP U-Pb dating show gneissic granites crystallization age is（393.7±4.4）Ma-（397.3±5.3）Ma（^206Pb/^238 U surface-age）,belong to the Early Devonian.Study out of the gneissic granites make clearly that there was a large- scale tectonic magmatic event in 400 Ma ± Altai orogenic belt,Simultaneously,it provides a new geochronology restriction to the 400 Ma± subduction orogenic event of the Altai orogenic belt.