The Huashan and Heyu multistage granite complexes occur in the northwestern and southeastern portions of the southern margin of the North China Craton, respectively. The contamination phase monzonitic granite at top of the Hushan complex and the third stage porphyric biotite monzonitic granite of the Heyu complex yield LA-ICP-MS zircon U-Pb weighted average ages of 133.8 +/- 1.1 Ma and 134.5 +/- 1.5 Ma, respectively. These two plutons share similar geochemical features. Both of them belong to high K cal-alkaline granites, with SiO2 > 69.0%, Al2O3 > 13.0%, K2O + Na2O > 7.0%, Na2O > 3.2%, and ACNK < 1.1; obvious fractionation between LREE and HREE; high Sr contents (mostly Sr > 400 x 10(-6)) and low Y and Yb contents (Y < 18 x 10(-6), Yb < 2 x 10(-6)); slightly negative Eu anomaly (delta Eu > 0.67); and enrichment in LILE, and depletion in HFSE (Nb, Ta and Ti). This indicates the fractionation of plagioclase + hornblende + garnet + rutile assemblage from the primary magmas or residence during partial melting of magma source. Zircons of two plutons show similar Hf isotopic compositions. The epsilon(Hf)(t) values of the Huashan pluton range from -20 to -18, with t(DM2) ages between 2.1 and 1.8Ga; while the epsilon(Hf)(t) values of the Heyu pluton from -17 to -16, with most t(DM2) ages of 2.0 similar to 1.7Ga. This suggests that both plutons were formed by partial melting of the thickened lower crust (2.1 similar to 1.7Ga). In combination with the regional tectonic evolution, we argue that the crust in the study area was thickened by collisional compression or overthrusting during Jurassic and ealier lime, and then the conditions of decompression and geothermal increasing during transition from Jurassic compression to Cretaceous extension result in partial melting of the thickend lower crust, and thereby the collisional transformation-type granites such as the Huashan and Heyu complexes formed at the southern margin of the North China Craton.
