辽东岫岩-凤城地区早白垩世侵入岩的年代学、地球化学特征及地质意义

EARLY CRETACEOUS INTRUSIVE ROCKS IN XIUYAN-FENGCHENG AREA,EASTERN LIAONING:Geochronology,Geochemistry and Geological Implication

对辽东岫岩-凤城地区秦家岭花岗闪长岩和红旗岭石英闪长岩进行了年代学和地球化学研究.LA-ICP-MS锆石U-Pb测年获得秦家岭花岗闪长岩年龄加权平均值为127.5±0.9 Ma,红旗岭石英闪长岩年龄加权平均值为126.5±0.8 Ma,均形成于早白垩世.岩石地球化学分析结果表明,秦家岭花岗闪长岩SiO_(2)含量70.40%~72.28%,A/CNK和A/NK值分别为0.99~1.06和1.44~1.61,轻稀土相对富集,亏损Ba、Sr等大离子亲石元素和Nb、P、Ti等高场强元素,相对富集Rb、Th、La、Nd、Hf等元素,锆石饱和温度变化区间为755~816℃,属于过铝质I型花岗岩,为下地壳部分熔融形成;红旗岭石英闪长岩SiO_(2)含量56.42%~57.22%,A/CNK和A/NK值分别为1.04~1.09和1.70~1.83,Eu负异常明显,亏损Sr、Nb、Ta、Ti、P,富集Ba、Rb、K、Zr、Hf、Th等元素,物质来源为壳源并有少量幔源成分加入.秦家岭花岗闪长岩和红旗岭石英闪长岩形成于辽东地区早白垩世伸展拉张环境,与华北克拉通遭受破坏、岩石圈减薄密切相关.

The paper studies the geochronology and geochemistry of Qinjialing granodiorite and Hongqiling quartz diorite in Xiuyan-Fengcheng area,eastern Liaoning Province.The LA-ICP-MS zircon U-Pb dating yields the weighted average ages of 127.5±0.9 Ma for Qinjialing granodiorite and 126.5±0.8 Ma for Hongqiling quartz diorite,both of which were formed in the Early Cretaceous.The lithogeochemical analysis results show that the content of SiO_(2) in Qinjialling granodiorite is 70.40%-72.28%,with the A/CNK and A/NK values of 0.99-1.06 and 1.44-1.61,respectively.The granodiorite is characterized by relatively enriched LREEs,depleted LILEs(Ba and Sr)and HFSEs(Nb,P and Ti),and enriched Rb,Th,La,Nd,and Hf,with the zircon saturation temperature ranging from 755℃ to 816℃,belonging to peraluminous I-type granite,formed by the partial melting of lower crust.The content of SiO_(2) in Hongqiling quartz diorite is 56.42%-57.22%,with the A/CNK and A/NK values of 1.04-1.09 and 1.70-1.83,respectively.The quartz diorite is characterized by obvious negative Eu anomaly,depleted Sr,Nb,Ta,Ti and P,and enriched Ba,Rb,K,Zr,Hf and Th.The source material is derived from the crust with minors of mantle-derived component.The Qinjialing granodiorite and Hongqiling quartz diorite were formed in the Early Cretaceous extensional environment of eastern Liaoning,which are closely related to the destruction of North China Craton and lithospheric thinning.