吉南大荒沟──板石沟地区早前寒武纪变质变形作用及地壳演化

    EARLY PRECAMBRIAN METAMORPHISM,DEFORMATION AND CRUSTAL EVOLUTON IN THE DAHUANGGOU-BANSHIGOU AREA,SOUTBERN JILIN

    • 摘要: 本区早前寒武纪地壳曾经历了三期区域变质和变形作用:中太古宙最早期是上壳岩系沉积的形成,后来在2.605Ga时发生角闪岩相区域变质作用,至晚期是英云闪长岩的侵位,并伴生有韧性剪切变形;晚太古宙时期,上壳岩系和英云闪长岩于2.538Ga前后发生低角闪岩相变质,在晚期出现NE向韧性剪切变形事件;至早元古宙时期,早期是黑云钾长花岗岩侵入活动,大约在2.380Ga时发育了绿片岩相变质,并发生二次浅层次的NW与NE向剪切变形作用。以上三期地质事件均表现为变形作用滞后于变质作用,每期都具有不同矿物组合、不同方向和规模的韧性剪切变形特点。

       

      Abstract: In the earliest Middle Archean supracrustal rocks were formed.Then amphibolite faciesn1etamorphism happened at 2.605 Ga B. P. Later tonalite was intruded,accompanied by duc-tile shear deformation. In the Late Archean supracrustal rocks and tonalite underwent low am-phibolite facies metamorphism around 2.538 Ga B.P. and later there occurred an event of NE-directed ductile shear deformation. In the Early Proterozoic,K-feldspar granite was intrudedand then it underwent greenschist facies metamorphism at about 2.380 Ga;besides there alsooccurred two events of NW and NE shear deformation. The above three phases are character-ized by different mineral assemblages and shear deformations of different directions and scales.

       

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