摘要
大青山逆冲推覆构造下盘发育一套泥质板岩,它们是由二叠系泥岩、粉砂质泥岩和粉砂岩、细砂岩遭受逆冲推覆变形引起的动力变质作用改造形成的,发育一组透入性劈理构造。通过岩石薄片鉴定,沿劈理面形成绢云母、白云母和绿泥石等同构造新生矿物。对其中新生白云母矿物进行了激光微区40Ar/39Ar测年,获得了(121.6±1.6)Ma的等时线年龄。野外地质证据表明了大青山逆冲断层发生过两期逆冲推覆变形作用,早期发生在印支期,晚期发生在燕山期。(121.6±1.6)Ma年龄代表燕山期逆冲推覆事件发生时间。
There occurs a suite of argillite in the lower plate of the Daqingshan thrust nappe structure.It formed by dynamic metamorphism caused by thrust deformation of Permian mudstone,silty mudstone,siltstone and fine sandstone.A set of penetrative plate cleavages are developed in the rock.The identification of rock thin sections shows that syntectonic neogenic minerals such as sericite,muscovite and chlorite are formed along the cleavage planes.Dating of the syntectonic neogenic muscovite by the laser microprobe40Ar/39Ar method yielded a40Ar/39Ar isochron age of121.6±1.6Ma.Field geological evidence suggests that two phases of thrust deformation occurred in the Indosinian and late Yanshanian periods respectively in the Daqingshang region.The40Ar/39Ar isochron age of121.6±1.6Ma represents the age of the late Yanshanian thrust deformation event.
出处
《中国地质》
CAS
CSCD
2003年第3期293-296,共4页
Geology in China
基金
国土资源部地质大调查项目(200011300002)资助
