ORIGINAL PAPER Yi Gang Xu Æ Xiao-Long Huang Æ Jin-Long Ma Yan-Bin Wang Æ Yoshiyuki Iizuka Æ Ji-Feng Xu Qiang Wang Æ Xiang-Yang Wu Crust-mantle interaction during the tectono-thermal reactivation of the North China Craton: constraints from SHRIMP zircon U–Pb chronology and geochemistry of Mesozoic plutons from western Shandong Received: 22 January 2004 / Accepted: 5 May 2004 / Published online: 7 July 2004 Ó Springer-Verlag 2004 Abstract Chronological, geochemical and Sr–Nd–Pb isotopic analyses have been carried out on the Mesozoic plutons in western Shandong with the aim of charac- terizing crustal–mantle evolution during the tectono- thermal reactivation of the craton. Detailed SHRIMP zircon U–Pb dating reveals two main periods of Meso- zoic activity with contrasting compositions. The older magmatic pulse is manifested by monzonites and mon- zodiorites from Tongshi for which zircon rims yield a concordant age of 177±4 Ma and the cores have a discordant age of ca. 2.5 Ga. Low MgO and Cr, high Na 2 O contents and especially their isotopic composi- tions ( 87 Sr/ 86 Sr < 0.7042, 206 Pb/ 204 Pb < 16.8 and  Nd 12) are consistent with derivation from late Archean–Paleoproterozoic lower crust. Relatively high HREE contents in these Jurassic plutons indicate a garnet-free source (<32 km), in contrast to the garnet- bearing source (>40 km) of the late Mesozoic high Sr and low Y granitoids from the same region. Distinctively different depths of crustal melting suggest dynamic thickening of the crust by magmatic underplating during the Jurassic and Cretaceous. The younger dioritic plu- tons from Laiwu and Yinan were emplaced at 132– 126 Ma and show relatively high MgO and Cr contents and large isotopic variability. They were likely derived from enriched lithospheric mantle source and were subjected to crustal contamination during magma evo- lution. Early Cretaceous mantle melting is coeval with the widespread late Yanshanian granitic magmatism in North China. Early Cretaceous time may correspond to a critical period when a temperature increase due to lithospheric thinning allowed the intersection of the lo- cal geotherm and the wet peridotite solidus. While some mantle-derived magmas were erupted, most were trap- ped at variable crustal depths, triggering large-scale concomitant melting of the crust. Lithospheric thinning must have continued until the late Cretaceous because of the change in the source of mafic magmas from litho- spheric to asthenospheric at that time. It is proposed that removal of the lithospheric keel beneath the North China craton may have been initiated as early as the Jurassic, but with the most intense period in the Creta- ceous between 130–75 Ma. Such a relatively long time- scale (100 Ma) emphasizes the role of thermomechanical erosion by convective mantle in lithospheric thinning beneath this region. Introduction The Archean North China craton (NCC) experienced tectono-thermal reactivation during the Mesozoic, resulting in widespread calc-alkaline magmatism (Men- zies and Xu 1998). During this event, the old, thick and refractory lithospheric keel was replaced by young and fertile asthenospheric mantle (Menzies et al. 1993; Griffin et al. 1998; Xu 2001). Recent petrogenetic studies of Mesozoic magmas have produced a wealth of infor- mation about the geochemical evolution of the mantle lithosphere beneath the NCC (Guo et al. 2001, 2003; Fan et al. 2001; Zhang et al. 2002; Yan et al. 2003; Yang et al. 2003; Xu et al. 2004a, b). Most of these studies have focused on mafic end-members such as gabbroic complexes and erupted basalts. Comparatively few studies have been conducted on the intermediate-felsic Y. G. Xu (&) Æ X.-L. Huang Æ J.-L. Ma Æ J.-F. Xu Æ Q. Wang X.-Y. Wu Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Wushan Guangzhou, PR China E-mail: yigangxu@gig.ac.cn Tel.: +86-20-85290109 Fax: +86-20-85290130 Y.-B. Wang Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, PR China Y. Iizuka Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan Contrib Mineral Petrol (2004) 147: 750–767 DOI 10.1007/s00410-004-0594-y