摘要
太行山太古宙变质杂岩中富铝片麻岩主要分布在湾子岩系的底部,常常与大理岩密切伴生或者以似层状体产于花岗质片麻岩中。依据岩石结构和反应关系将变质作用分为早期、中期和晚期三个阶段。早期矿物组合为Gt(石榴石)+St(十字石)+Pl(斜长石)+Ms(白云母)+Bi(黑云母)+Ru(金红石)+Qz(石英)±K-fs(钾长石);中期矿物组合为Gt+Ged(铝直闪石)+Bi+Pl+Ilm(钛铁矿)+Co(刚玉)+Sil1(毛发状夕线石)+Qz+K-fs±Ms;晚期矿物组合为Hc+K-fs+Sil2(针柱状夕线石)。矿物温度压力计和内部一致性热力学计算结果表明早期矿物组合形成于680℃和0.8GPa左右,刚玉、铝直闪石和毛发状夕线石组合形成于730℃~750℃和0.7GPa左右的很窄的P-T范围内,夕线石和尖晶石矿物组合的形成温度与前一组合相似或略高,压力偏低。在P-T空间上上述矿物组合的演化构成了一条近等温减压(ITD型)的PTt轨迹。
Al rich gneisses in Taihang mountain Archean metamorphic complex are mainly distributed in the lower part of Wanzi stratified rock series and the gneisses usually associate together with various marbles or occurrence by stratified bodies in granitic gneisses. Depending on textural and metamorphic reaction relationships of rocks, we divide the evolution of their metamorphism into three stages.Mineral assemblage in the early stage is garnet + staurolite + plagioclase +muscove+ biotite + quartz + rutile±K feldspar; mineral assemblage in the middle stage is garnet + gedrite + sillimanite 1(hair sill)+biotite +corundum± quartz + plagioclase + ilmenite+K feldspar; mineral assemblage in the later stage is hercynite+sillimanite 2(needle sill)+K feldspar. Through garnet biotite thermometry and internally consistent thermodynamic calculation, we get that garnet, stourolite and rutile assemblage formed at 680℃ and 0 8 GPa, corundum and gedrite present mineral assemblage at a little P T space of 730℃~750℃ and about 0 7 GPa; The temperature of sillimanite and hercynite present mineral assemblage are a little higher than that of second association, yet pressures are less than one of second assemblage. The evolution of above mineral assemblages and P T conditions constructs a clockwise ITD type P T tpath.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1997年第3期303-312,共10页
Acta Petrologica Sinica
基金
国家自然科学基金
关键词
变质岩
杂岩
片麻岩
富铝
变质作用
Archean
Al rich gneisses
metamorphism
PTt trajectory
Taihang mountain