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

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。

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.