ORIGINAL PAPER Yi-Gang Xu Æ Jin-Long Ma Æ Xiao-Long Huang Yoshiyuki Iizuka Æ Sun-Lin Chung Æ Yan-Bin Wang Xiang-Yang Wu Early Cretaceous gabbroic complex from Yinan, Shandong Province: petrogenesis and mantle domains beneath the North China Craton Received: 29 December 2003 / Accepted: 28 June 2004 / Published online: 28 September 2004 Ó Springer-Verlag 2004 Abstract Sensitive high resolution ion microprobe (SHRIMP) zircon U–Pb ages, geochemical and Sr-Nd- Pb isotopic data are reported for the gabbroic complex from Yinan (Shandong Province) with the aims of characterizing the nature of the Mesozoic mantle be- neath the North China Craton. The Yinan gabbros contain alkali feldspar and biotite, and are characterized by moderate Mg#, high SiO 2 , low FeO and TiO 2 con- tents and a strong enrichment of light rare earth ele- ments [(La/Yb) n =11–50], but no Eu anomaly. They have low Nb/La (0.07–0.29), radiogenic 87 Sr/ 86 Sr (0.710) and unradiogenic  Nd (t)(15 to 13). These ‘‘crustal fingerprints’’ cannot be attributed to crustal contami- nation, given the lack of correlation between isotopic ratios and differentiation indices and the unreasonably high proportion of crustal contaminant (>20%) re- quired in modeling. Instead, compositional similarities to contemporaneous basalts from nearby regions imply that the Yinan gabbros were not significantly affected by crystal cumulation. Isotopic data available for the Mesozoic mafic magmas reveal two distinct mantle do- mains beneath Shandong. While the EM1-like domain (with low 87 Sr/ 86 Sr) is confined to western Shandong, the mantle beneath eastern Shandong is dominated by EM2-type (with high 87 Sr/ 86 Sr) affinities. This aerial distinction suggests that the EM2-like signature of the Yinan gabbros may have been inherited from westerly- subducted Yangtze crust during the Triassic North China-South China collision. Emplacement of the Yinan gabbros (127 Ma) is likely affiliated with the widespread and protracted extension during the late Mesozoic in this region. Keywords Geochemistry Æ Zircon U–Pb age Æ Gabbros Æ Mantle Æ North China Craton Introduction The geology of the North China Craton (NCC) has received much attention not only because it is one of the oldest continental nuclei in the world (up to 3.8 Ga; Jahn et al. 1987; Liu et al. 1992), but also owing to the presence of a variety of mafic magmas of different ages. Geochemical characterization of these mantle-derived magmas, particularly the Paleozoic diamondiferous kimberlites and Cenozoic basalts and their entrained xenoliths, has been used to investigate mantle evolution in this region (e.g., Fan and Menzies 1992; Menzies et al. 1993; Griffin et al. 1998; Menzies and Xu 1998; Fan et al. 2000; Xu 2001; Zhang et al. 2002). The general scenario that has emerged from these studies is that the thick, old, cold and refractory lithospheric keel (preserved at least until the Palaeozoic) has been replaced by a thin, young, hot and fertile mantle. Better understanding of this process is of great importance, not only for deep dynamics and regional geology investigations (Menzies and Xu 1998), but also for exploration of mineral re- sources (e.g., Yang et al. 2003). It has been proposed that the lithospheric destruction must have taken place during the late Mesozoic, probably owing to the loss of physical integrity of the craton as a result of the Triassic collision between the North China and Yangtze blocks (Xu 2001; Gao et al. 2002; Zhang et al. 2002). Never- theless, the timing and nature of this event still remain Y.-G. Xu (&) Æ J.-L. Ma Æ X.-L. Huang Æ X.-Y. Wu Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Wushan Guangzhou, People’s Republic of China E-mail: yigangxu@gig.ac.cn Tel.: +86-20-85290109 Fax: +86-20-85290130 Y. Iizuka Institute of Earth sciences, Academia Sinica, Taipei, Taiwan S.-L. Chung Department of Geosciences, National Taiwan University, Taipei, Taiwan Y.-B. Wang Institute of Geology, Chinese Academy of Geological Sciences, 100037 Beijing, P.R. China Int J Earth Sci (Geol Rundsch) (2004) 93: 1025–1041 DOI 10.1007/s00531-004-0430-7