辽宁鞍山地区东山杂岩带3.3~3.1 Ga期间的岩浆作用——锆石SHRIMP U-Pb定年

3.3-3.1 Ga magmatism in the Dongshan Complex, Anshan area, Liaoning, China: Evidence from SHRIMP U-Pb zircon dating.

摘要: 报道了鞍山地区东山杂岩带奥长花岗岩和二长花岗岩的锆石SHRIMP U-Pb年龄。中粗粒奥长花岗岩中岩浆锆石的年龄为3329 Ma ± 22 Ma (MSWD=9.6)，存在年龄为3687~3784 Ma的残余锆石。细粒奥长花岗岩和二长花岗岩中岩浆锆石的年龄分别为3141 Ma ± 8 Ma (MSWD=1.5)和3142 Ma ± 5 Ma (MSWD=0.35)。研究表明，约~3.3 Ga和3.1 Ga是鞍山地区2个重要的地壳演化阶段。

Abstract: This paper reports SHRIMP U-Pb zircon ages of granitoids from the Dongshan Complex in the Anshan area, where there are Archean rocks with ages ranging from 3.8 to 2.5 Ga. A medium-coarse-grained trondhjemite sample has a 207Pb/206Pb weighted mean age of 3329 ± 22 Ma (MSWD=9.6) on magmatic zircons, with inherited zircons of 3687-3784 Ma. Magmatic zircons from fine-grained trondhjemite and adamellite samples have weighted mean 207Pb/206Pb ages of 3141 ± 8 Ma (MSWD=1.5) and 3142 ± 5 Ma (MSWD=0.35), respectively. The ~3.3 Ga medium-coarse grained trondhjemite was formed by anatexis of 3.8 Ga trondhjemiteic rocks. The 3.14 Ga fine-grained trondhjemite is considered to be a veinlet emanated from the nearby Lishan trondhjemite body with the same age. The 3.14 Ga adamellite cuts the fine-grained trondhjemite and is derived from continental material. Combined with early researches, it is indicated that ~3.3 Ga and ~3.1 Ga are two important crustal evolution stages in the Anshan area.