摘要
本文报道了鞍山地区3.8Ga(锆石SHRIMP年龄)变质石英闪长岩中磷灰石SHRIMP U-Th-Pb定年结果。32个数据点207Pb/206Pb加权平均年龄为3007±22Ma,被解释为磷灰石的重结晶年龄。这一结果与该区存在约3.0Ga强烈岩浆构造热事件相吻合。虽然该区3.0Ga以后发生了一系列重要的陆壳增生和构造热事件,但磷灰石样品未获得任何年轻于3.0Ga年龄。磷灰石的重结晶温度为400～500℃之间。由此推论,鞍山地区的3.8Ga古老岩石自3.0Ga以后一直处于上部地壳,再没有到过15km以下的地壳深部。
An apatite sample separated from the 3.8 Ga （ zircon SHRIMP U-Th-Pb age） meta-quartz-diorite sample in Anshan area has been dated using SHRIMP Ⅱ. 32 analyses yielded a ^207Pb/^206Pb weighted mean age of 3007 ± 22 Ma that is interpreted as the age of recrystallization of the apatite during the very intense thermo-tectonic events at 3.0 Ga in the Anshan area. In the Anshan area a series of crustal addition and other thermo-tectonic events took place after 3.0 Ga, however, no younger than 3.0 Ga apatite has been found in the 3.8 Ga old rock in the area so far. It is generally believed that the recrystallization temperature of apatite is between 400℃ and 500℃. Therefore it seems that the 3.8 Ga old rock in the Anshan area has always been staying in the upper lithosphere and never went down to the depth greater than 13 km since 3.0 Ga.
出处
《地质论评》
CAS
CSCD
北大核心
2007年第1期120-125,共6页
Geological Review
基金
国土资源部北京离子探针中心资助的成果
