中文摘要：

报道了华北克拉通北缘承德地区甲山正长岩的锆石U-Pb年龄及Hf同位素、主微量元素、Sr-Nd-Pb同位素组成.甲山岩体的LA-ICP-MS锆石U-Pb年龄为111～108Ma,代表岩体的结晶年龄,表明其侵位于早白垩世晚期.岩体高SiO2、K2O＋ Na2O、Al2O3、LILEs（Rb、K）和LREE,低Fe2O3T、CaO、TiO2、MgO和HFSE,具有板内裂谷岩浆岩的特征,属A型花岗岩.甲山岩体εNd（t）=-5.0～-0.9,tDM2（Nd）=0.98～1.31 Ga;εHf（t）=-2.7～＋4.3,tDM2（Hf）=0.90～ 1.33 Ga; △8/4=84.9～ 91.3,△7/4=-6.4～-4.0,（206pb/204 Pb）i=16.63～ 17.10,（207pb/204Pb）i=15.24～15.30,（208pb/204pb）i=36.54 ～ 37.20.根据野外地质观察、实验岩石学以及元素地球化学和Sr-Nd-Pb-Hf同位素示踪的综合分析,认为甲山岩体可能起源于下地壳与亏损地幔的混合源区,是华北克拉通北缘岩石圈强烈减薄、地壳伸展作用的结果.早白垩世甲山岩体形成过程中亏损地幔物质的参与指示了华北克拉通北缘岩石圈减薄和软流圈地幔上涌,记录了陆内伸展环境下与软流圈底侵作用相关的岩浆事件.

英文摘要：

The LA-ICP-MS zircon U-Pb ages and Hf isotopic data, major and trace elements and Sr-Nd-Pb iso- topic compositions are presented in this paper for the Jiashan syenite intrusive on the northern margin of the North China Craton. The Jiashan syenite intrusive was emplaced at 111--108 Ma in the Early Cretaceous peri- od. The pluton has high SiO2, KO2^＋ Na2O, Al2O3, LILEs （Rb, K） and LREE but low Fe2O3^T, CaO, TiO2, MgO and HFSE, with no Nb and Ta anomalies, suggesting intracontinental rift volcanic rocks that belong to the A-type granite, eNd（t） = - 5.0-- - 0.9, tDM2（Nd） = 0.98-- 1.31 Ga, εHf（ t ） = - 2.7～ ＋ 4.3, tDM2（Hf） = 0.90～1.33 Ga, A8/4 = 84.9～91.3, A7/4 = - 6.4～- 4.0, （206pb/204pb）i = 16.63～ 17.10, （^207pb/^204pb）i = 15.24～15.30, and （^208pb/^204pb）i = 36.54～ 37.20. According to the comprehensive analysis of the geologi- cal field observation, experimental petrology, trace element geochemistry and Sr-Nd-Pb-Hf isotopes, the authors hold that the Jiashan pluton was derived from the mixed source of the lower crust and the depleted mantle, and resulted from the crustal extension and the lithosphere thinning of the NCC. The involvement of the depleted mantle during the formation of the Early Cretaceous Jiashan syenite intrusive indicates the lithospheric thinning on the northern margin of the North China Craton and the upwelling of the asthenosphere mantle, which record- ed the magmatic events related to the asthenosphere underplating in a continental extensional environment.