Abstract: The late Paleozoic diorites-granitoids emplaced into Precambrian lithological assembleges in Fengshan area, Northern Hebei province are characterized by enrichment in sodium (Na_2O/K_2O>1.0), high Sr, low Y and HREE contents, and their Sr/Y values change from 37.15 to 151.22. Most samples also show positive Eu anomalies and their Eu^* ranges from 0.92 to 1.53. LA-ICP-MS zircon dating and zircon Hf isotope analyses for samples diorite (sample JB6024) and monzogranite (sample JB6037-1) reveal that the diorite and the monzogranite were produced at 315±2.8Ma and 306.6±6Ma, respectively, namely, indicated the two late Paleozoic magmatic episodes in the Fengshan area. Whole rock petrochemistry, Sr-Nd isotopes and zircon Hf isotope indicate that the late Paleozoic Fengshan diorite was produced by the magmatic mixing between mafic magma derived from an EMI-type enriched mantle and felsic magma derived from partial melting of the ancient lower crust, and the granitoids derived from fractional crystallization of the dioritic magma that was obviously contaminated by upper crustal materials during their emplacement.

Key words: diorites and granitoids, Zircon U-Pb chronology, Sr-Nd-Hf isotopic systematics, petrogensis, Late Paleoprozoic, northern margin of the North China Craton

摘要： 冀北凤山地区侵位于前寒武纪岩石组合中的晚古生代的闪长岩-花岗质岩石，具有富Na，高Sr，低Y和重稀土元素等地球化学特征，Sr/Y在37.15～151.22之间变化,绝大多数样品均显示正Eu异常（一个样品例外），Eu^*在0.92～1.53之间变化。LA-ICP-MS锆石U-Pb同位素测年和锆石Hf同位素分析表明闪长岩（JB6024）和二长花岗岩（样品JB6037-1）分别形成于315±2.8Ma和306.6±6Ma，即该区晚古生代存在两个岩浆作用幕。地球化学、全岩Sr-Nd同位素和锆石Hf同位素研究揭示凤山晚古生代闪长岩是EMI型富集岩石圈地幔部分熔融形成的岩浆与古老下地壳部分熔融形成的长英质岩浆混合作用结果，而花岗质岩石则是闪长质岩浆发生分离结晶作用的残余岩浆同化上部地壳岩石形成的。

关键词: 闪长岩和花岗质岩石, 锆石U-Pb年代学, Sr-Nd-Hf同位素体系, 岩石成因, 晚古生代, 华北克拉通北缘