燕山中段走滑断裂中辉绿岩脉的SHRIMP U-Pb年龄和Ar-Ar年龄
SHRIMP U-Pb and Ar-Ar ages of the dolerite dyke along a strike-slip fault in the middle segment of Yanshan
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摘要: 燕山中段东西向走滑断裂的活动时代一直存在争议，对侵入断层中的辉绿岩脉的直接测年可以给出一个年龄上限。侵入密云-喜峰口断裂中的辉绿岩脉的锆石SHRIMP U-Pb和角闪石Ar-Ar测年发现，锆石U-Pb年龄为290~125Ma，没有一个谐和年龄；角闪石Ar-Ar坪年龄为123.5Ma±1.5Ma。Ar-Ar年龄与最年轻的锆石U-Pb年龄一致，代表了辉绿岩脉的冷却年龄，是断裂活动时代的上限。分散的锆石U-Pb年龄，均为继承年龄，与燕山造山带5次岩浆活动的时代对应。
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关键词:
- 燕山 /
- 走滑断层 /
- 辉绿岩 /
- SHRIMP 锆石U-Pb测年 /
- 角闪石Ar-Ar测年
Abstract: There exists controversy concerning the time when the EW-trending strike-slip faults were active in the middle segment of Yanshan. Direct dating of the dolerite dyke that intruded in the fault might give the upper limit of the age. Secondary High Resolution Ion Microprobe U-Pb (SHRIMP U-Pb) and Ar-Ar dating of the dolerite dyke in the Miyun-Xifengkou fault belt yielded zircon SHRIMP U-Pb ages of 290-125Ma and hornblende Ar-Ar plateau ages of 123.5±1.5Ma. The Ar-Ar ages, which are consistent with the youngest U-Pb age, represent the cooling age of the dyke and set an upper limit of the active age of the fault. The scattered U-Pb ages are all inherited zircon ages which correspond to five regional magmatic episodes of the Yanshan orogenic belt.-
Keywords:
- Yanshan /
- strike-slip fault /
- dolerite /
- SHRIMP zircon U-Pb dating /
- hornblende Ar-Ar dating
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