摘要
秦岭商丹构造带(商南—丹凤构造带)商南段南缘出露一套构造岩组合,其中包括变质砂岩、云母片岩、含石榴子石云母石英片岩、初糜棱岩以及糜棱岩等。岩片之间呈逆冲叠置关系、褶皱和断裂发育,其中保留大量的岩石变形—变质方面的信息。本文以含石榴子石云母石英片岩为主要研究对象,通过详细的矿物学特征研究并结合电子探针成分分析,认为其中的石榴子石为铁铝榴石,具有成分环带。利用石榴子石—黑云母地质温压计和多硅白云母地质压力计估算该区变质作用峰期温度为560～588℃,变质压力上限为0.59～0.65GPa,对应变质相为绿帘-角闪岩相到低角闪岩相,为大陆造山带环境。变形强度分析显示本区岩石变形强烈,应变椭球体呈现为三轴扁椭球状(压扁型)。利用商丹带糜棱岩中动态重结晶石英颗粒粒径计算出糜棱岩变形时的古应力差在23.93～36.70MPa之间,应变速率范围为4.47793×10-15s-1～1.36090×10-14s-1,属中等应变速率。
The southern margin of the Shangnan—Danfeng（Shang-Dan） tectonic belt is composed of a series of tectono-stratigraphic sheets,consisting of metamorphic sandstone,mica schist,garnet-bearing mica—quartz schist,phyllonite and mylonite.Thrust—nappe systems,folds and faults are well developed in this area.They retain a large number of information about deformation and metmorphsim.In this paper,the garnet-bearing mica—quartz schist is taken as the research object.According to the study on its detailed mineralogy and electronic microprobe analysis,it is proved that the garnet is almandine and has compositional zonation.The garnet—biotite geothermometer and geobarometry of Si in phengite are used to estimate the peak metamorphic temperature.The calculated metamorphic temperature is 560~588℃ and the upper limit of pressure is 0.59~0.65GPa.This metamorphic event mainly corresponds to epidote—amphibolite facies to low amphibolite facies and that is similar to the environment of continental orogenic belt.Deformation intensity analysis shows a strong deformation of rocks in this area,and the strain ellipsoid is flat-ellipsoidal（flattening）.The paleo-stress calculated with the dynamically recrystallized quartz grain size in mylonites within the Shang-Dan ductile shear zone is to be 23.93～36.70MPa and the paleo-strain rate is from 4.47793×10-15s-1 to 1.36090×10-14s-1,which belongs to medium strain-rate.
出处
《地质论评》
CAS
CSCD
北大核心
2011年第5期641-649,共9页
Geological Review
基金
国家自然科学基金资助项目(批准号40372097
40772131
41072161)
中石化基础研究项目(编号09-02)的成果
关键词
商丹构造带(商南—丹凤构造带)
变质条件
地质温压计
变形分析
Shangnan—Danfeng tectonic belt
metamorphic conditions
geothermometer and geobarometry
deformation analysis
