In order to better understand the early continental evolution of the Anshan area, one of the typical Precambrian distribution areas of the North China Craton, the geochronology and REE composition of the zircons from the meta-argillo-arenaceous rock occurred as enclave in 3.1 Ga Lishan trondhjemite are studied by using SHRIMP II ion microprobe. It is indicated that the Paleoarchaean is a very important continental formation period in the Anshan area and 3.2 Ga can be regarded as the boundary between the Paleoarchaean and Mesoarchaean.
鞍山东山风景区古老岩带呈巨型包体存在于立山奥长花岗岩(3.1Ga)中,其主体为条带状片麻岩(3.8Ga)。此外还有金云母透闪石岩、(含)黑云斜长角闪岩、闪长质片麻岩、变石英闪长质岩石、细粒奥长花岗岩、二长花岗岩、伟晶岩脉等。测定了部分岩石的锆石年龄,其中变石英闪长质岩石(A9604)为3.65Ga(Wan et al.,1999),闪长质片麻岩(A9317)为3.5Ga、二长花岗岩(类型Ⅰ,A9605)为3.1Ga、黑云斜长角闪岩(A0019)为3.3Ga、细粒奥长花岗岩(A0017)为3.2Ga、二长花岗岩(类型Ⅱ,A0020)为2.6Ga。有关岩石的地球化学组成特征在文中也进行了简要介绍。在此基础上,提出了该古老岩带的地质同位素年代演化序列,认为鞍山地区不同时代、不同成因地质体空间上共存是该区长期地质演化的结果,而不是后期构造作用把它们拼合到一起的。鞍山地区很可能存在>3.8Ga的古老地壳岩石。
