辽北太古宙岩石形成的构造背景与地壳演化

THE ARCHAEAN STRUCTURAL SETTING AND CRUSTAL EVOLUTION OF NORTH LIAONING

辽北太古宙花岗质岩石及层状变质岩系的研究表明,它们均形成于太古代的大陆边缘环境。早太古代以前(大于3000Ma),本区已发育了成分不均匀的原始地壳,后期表壳岩系沉积在这种地壳的裂谷当中并发生了麻粒岩相变质作用;大约在2800—2500Ma,发生大规模花岗质岩石侵位,形成英云闪长岩—奥长花岗岩的结晶分异趋势;太古代晚期,由于地壳的增生迥返,先存岩石发生角闪岩相变质作用和深熔作用,形成钾长花岗岩的定位,并形成钙碱性的演化趋势。在整个太古宙地质演化过程中变形作用一直贯穿始终。

Both the Archaean granitic rocks and strataform metamorphic rocks in North Liaoning were generaied in the setting of continental margin. Before the early Archaean (>3 000Ma), the chemically heterogeneous original crust had been developed. Later, supercrustal rocks deposited in the rift of the original crust, underwent a granulite facies metamorphism, and was intruded by a large--scale granitic rocks(about 2 800--2 500Ma) in which crystallization differentiation took place in the trend of tonalite--trondhjemite. At the late stage of Archaean the preexisting rocks experienced honblende--facies metamorphism and anatexis, leading to the emplacement of potashgranite and the evolution trend of cale--alkaline. During the entire geological evolution of Archaean, deformation had been existing all the time.