鞍山东山风景区3.8～2.5Ga古老岩带的同位素地质年代学和地球化学  

Geochronology and Geochemistry of 3. 8-2. 5 Ga Ancient Rock Belt in the Dongshan Scenic Park, Anshan Area

作　　者：万渝生[1] 宋彪[1] 刘敦一[1] 李惠民[2] 杨淳[1] 张巧大[1] 杨崇辉[1] 耿元生[1] 沈其韩[1] 

机构地区：[1]中国地质科学院地质研究所 [2]中国地质调查局天津地质矿产研究所,300170

出　　处：《地质学报》2001年第3期363-370,共8页Acta Geologica Sinica

基　　金：地质行业科学技术发展基金(编号HY979816);国土资源部重点基金(编号DKD2001020-3和9501116);国家自然科学基金(编号49473172)

摘　　要：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。In the Dongshan Scenic Park of Anshan area, there is an ancient rock belt occurring as a huge enclave in the Lishan trondhjemite of 3. 1 Ga and consisting predominantly of 3. 8 Ga banded gneiss. Also found in the belt are phlogopite tremolite schist, biotite (-bearing) plagioclase amphibolite, dioritic gneiss, meta-quartz dioritic rock, fine-grained trondhjemite, adamellite, pegmatitic vein. Some of them, such as the meta-quartz dioritic rock, seem to be residual as enclaves in the 3. 8 Ga banded gneiss. The zircons from the dioritic gneiss, meta-quartz dioritic rock and adamellite (type I) yield discordia upper intercept ages of 3. 45 ± 0. 28 Ga,3. 65± 0. 06 Ga and 3. 10 ± 0. 07 Ga, respectively. The amphibolite, trondhjemite and adamellite (type II) give 207Pb/ 206Pb evaporation ages of 3. 3 Ga, 3. 2 Ga and 2. 6 Ga, respectively. Combined with the geochemical characteristics of the rocks, the main conclusions can be drawn that in the Anshan area there might be >3. 8 Ga crustal material, and the geological bodies of different origins and ages are not jointed together by late tectonism, but the result of long-period geological evolutions.

关 键 词：年代学 地球化学 地壳演化 太古宙 鞍山 东山风景区 同位素 

分 类 号：P597[天文地球—地球化学]