Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intrusion is mainly composed of a suite of gabbro-diorite. Zircons from the intrusion display euhedral-subhedral in shape and have high Th/U ratios (1.23-2.87), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating results for two samples indicate that they were formed in the Early Cretaceous, yielding weighted mean Pb-206/U-238 ages of 129 +/- 1Ma and 134 +/- 2Ma, respectively. Except for early cumulate such as sample QT-19, their SiO2 and MgO contents range from 50.12% to 56.37% and from 3.52% to 6.37%, respectively. Moreover, the gabbro-diorites are characterized by high Mg (0.54-0.63), enrichment in Na (Na2O/K2O ratios more than 1), Cr (73x10(-6)-217x10(-6)) and Ni (34x10(-6)-241x10(-6)), and intensive enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Their initial Sr-87/Sr-86 ratios and epsilon(Nd)(t) values range from 0.70962 to 0.71081 and from -16.60 to -13.04, respectively. Taken together with the Early Cretaceous high-Mg diorites and the mantle xenoliths from the Tietonggou and Jinling as well as basalts from the Fangcheng and Feixian, it is suggested that the primary magma for the Shangyu gabbro-diorites should be derived from the enriched lithospheric mantle intensively modified by continental crust. The Sr-Nd-Pb isotopic compositions for the Early Cretaceous high-Mg diorites in western Shandong display a trend of spatial variations, i.e., initial Sr-87/Sr-86, Pb-207/Pb-204 and Pb-208/Pb-204 ratios decreasing and epsilon(Nd)(t) values increasing from southeast to northwest in western Shandong, which is consistent with the tectonic model that the Yangtze Craton subducted beneath the North China Craton oriented in north-west direction in the Early Mesozoic.
