Abstract

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Title:: SHRIMP Zircon U-Pb Ages of Early Cretaceous Granites in Miyun Area of Beijing and Their Geological Significance

Author(s):: SUN Hui-yi; SHI Yu-ruo; ZHAO Xi-tao; HU Dao-gong; MA Yin-sheng; LIU Dun-yi; 1. Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China; 2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; 3. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China

Keywords:: geochronology; granite; zircon; U-Pb dating; Early Cretaceous; shear zone; emplacement; Beijing

Abstract:: SHRIMP zircon U-Pb ages of Early Cretaceous granitic and dioritic rocks from North Sihetang, South Fanzipai and Fengjiayu of Miyun area, Beijing were presented. A SHRIMP zircon age of (129±2)Ma is obtained firstly by using the SHRIMP U-Pb dating technique for North Sihetang medium-grained monzonitic granite, which represents the emplacement time of this granite. A SHRIMP zircon age of (130±1)Ma is interpreted as the emplacement time for South Fanzipai granite. Both of Fengjiayu granite and granodiorite yield the same ages of (127±1)Ma, which can be interpreted as the emplacement time of this granitoid pluton. The North Sihetang and South Fanzipai granites intrude into Sihetang thrust nappe and cut the foliation of Archean metamorphic rocks; the Fengjiayu granite and granodiorite intrude into the hanging wall of Dashuiyu-Beishicheng fault and cut the normal fault. Therefore, zircon ages of the above-mentioned granitic rocks provide geochronological constraint for the activity of Yunmengshan metamorphic core complex.