摘要
研究区位于北纬41°15′～42°30′,东经118°00′～121°00′范围内,属华北地台北缘,内蒙地轴之东段。太古代变质岩主要分布于3个平行的北东方向的隆起上。按岩石组合和特征,整个变质岩系被划分为建平变质杂岩和大营子群。 用锆石U-Pb法测定本区变质岩的年龄,根据4个样品的测定结果,结合本区地质特征,得出结论如下: 1.对于8H3和811两个样品中锆石测定得出的2575Ma和2579Ma的年龄,被解释为TTG岩石的形成年龄。 2.对于7Y138和8D182两个样品中锆石测得的2481Ma年龄,可解释为晚太古变质热事件高峰时的年龄。这与冀东迁西群被识别出的热事件一致。 3.本区变质岩原岩的年龄应大于2500Ma。 4.在三个隆起中的变质岩系应具有相似的发展历史。
The area studied is situated in 41°15′-42°30′N and 118°00′-121°00′E, belongs to the northern part of North China Platform and the eastern part of Inner · Mongolia geoaxis. Archean metamorphic rocks are mainly distributed in three parallel uplifts of NE direction. From east to west, they are Nulu'erhu uplift, Qilaotu uplift and Yun-wushan uplift. According to the metamorphic rock assemblages and their characteristics, Whole Archean metamorphic rocks can be subdivided into Jianping Complex and Dayingzi Croup.The U-Pb zircon method has been applied to dating metamorphic rocks in this area. Based on the four U-Pb zircon results, conbined with geological features of this area, conclusions have been made, as follows-1. Zircon discordant dating for the samples 8H3 and 811 give the ages of 2575 and 2579 Ma. They are interpreted as the formation.2. Zircon discordant dating for the samples 7Y138 and 8D182 give the ages of 2481 Ma. They can be interpreted as ages for Late Archean metamorphic event which may be correlated with the same event recognized in the Qianxi Group, eastern Hebei.3. The age of protolith of metamorphic rocks in this area should be older than 2500 Ma.4. The metamorphic rocks in three uplifts should have similar evolution history before 2500 Ma.
出处
《北京大学学报（自然科学版）》
CAS
CSCD
北大核心
1991年第2期229-237,共9页
Acta Scientiarum Naturalium Universitatis Pekinensis
关键词
锆石
U-PB年龄
太古代
辽西-赤峰
Zircon
U-Pb isotope age
TTG rocks
Archean
Western Liaoning Province-Chifeng
