蚌埠隆起区东部变质块体的P—T条件及锆石年代学研究

摘要

Objectives:Bengbu Uplift Area is an important component section of North China Craton.However,it has been restricted for people to have a comprehensive understanding of how Bengbu Uplift Area formed and evolved due to the weakness of previous research on its metamorphic crystal basement and geochronological analysis.In this research,garnet-bearing granitic gneisses of Zhuding-Shimen Mountain region in the east Bengbu Uplift Area will be studied in order to identify the metamorphic conditions and time limits of Wuhe group.Methods:In this study,detailed petrographic,mineralogical geochemistry analysis and LA-ICP-MS zircon UPb chronology have been conducted on garnet-bearing granitic gneisses of Zhuding-Shimen Mountain region.Results:Their P—T conditions are T =736 ～ 788 ℃ and P =0.76 ～0.89GPa,which indicates that they formed under the low-pressure granulite facies condition.Zircon dating analysis has recorded the magmatic crystallization and metamorphism,for the time are 2562 ±34Ma ～ 2584 ±25Ma and 2433 ±31Ma ～ 2436 ±24Ma respectively.Conclusions:This study analyzes the garnet-bearing granitic gneisses of Zhuding—Shimen Mountain region,so that the metamorphic conditions and time limits of Wuhe group have been identified.Meanwhile,it helps to complete the regional geological data and provides basis of basement attributes of Bengbu Uplift Area.%蚌埠隆起区是华北克拉通的重要组成部分,然而前人对于蚌埠隆起结晶基底形成的变质环境和时限分析相对较为薄弱,制约了人们全面理解该隆起的形成和演化过程.因此,本文在详细的野外地质调查基础上,对在蚌埠隆起东部朱顶—石门山地区新发现的含石榴子石花岗片麻岩进行了较为细致的岩相学、矿物化学测试分析以及LA-ICP-MS锆石U-Pb定年,运用不同的温压计方法进行P—T条件估计,得出该样品温压条件为736～788℃和0.76～0.89GPa,表明其形成于低压麻粒岩相条件.锆石定年分析记录了岩浆结晶和变质两期事件,它们对应的年龄分别为2562±34 ～ 2584±25Ma和2433 ±31 ～ 2436±24Ma.