大兴安岭东部花岗岩类锆石饱和温度及其地质意义

Zircon saturation temperatures of granites in eastern Great Xing'an Range,and its geological signification

通过对花岗岩锆石饱和温度的计算,求得大兴安岭东部不同时代花岗岩浆的起源温度,为探讨花岗岩的形成条件和构造背景提供重要信息。计算结果表明,大兴安岭地区早古生代花岗岩、部分晚古生代Ⅰ型花岗岩(<300 Ma)、晚古生代A型花岗岩(260～290 Ma)属于高温花岗岩,高热的产生与造山后伸展构造背景导致的软流圈上涌/幔源岩浆的底侵作用有关;部分晚古生代Ⅰ型花岗岩(>300 Ma)及侏罗纪花岗岩属于低温花岗岩,可能反映了一种有流体参与的与俯冲有关的构造背景;白垩纪I型花岗岩的锆石饱和温度与侏罗纪花岗岩基本相同,属低温花岗岩,其形成可能与流体的加入有关,流体可能来自古太平洋俯冲板片残留体;而白垩纪A型花岗岩属高温花岗岩,高热的产生可能与白垩纪时期板内伸展构造体制下岩石圈减薄导致的地幔岩浆底侵有关。

The original temperatures of different aged granites in eastern Great Xing＇an Range have been obtained by the calculation of the zircon saturation temperatures of the granites,which provided important information for discussing the forming condition and tectonic setting of the granites.The results showed that Early Paleozoic granites,Late Paleozoic I type（300 Ma） and A type（260～290 Ma）granites belonged to high temperature granites,the formation of high heat was related to asthenosphere upwelling or lower intrude action of sourcemantle caused by extensional background after orogenic activity.Late Paleozoic I type granites（300 Ma）and Jurassic granites both belonging to low temperature granites,probably show an tectonic setting associated with subduction and fluids participation.The zircon saturation temperatures of Cretaceous I type granites as the same as the Jurassic＇s,belonging to low temperature granites,and its formation was probably related to fluids participation,which maybe came from the relict of ancient Pacific Ocean subductive plate.Cretaceous A type granites belonging to high temperature granites,and the formation of high heat might be related to the lower intrude action of sourcemantle,formed by lithosphere reduction in Cretaceous extensional tectonic framework.