College of Earth Sciences, Jilin University, Changchun 130061, China

Zircon LA-ICP-MS U-Pb age and whole-rock geochemistry data are presented for the Hutouya granodiorite porphyries in Mengyin, western Shandong, to restrict its petrogenesis. The analyzed zircons exhibit oscillatory growth zoning and core-rim textures in the cathodoluminescence images and have high Th/U ratios (0.04-1.66), indicating its magmatic origin. The youngest group of magmatic zircon yields weighted mean ²⁰⁶Pb/²³⁸U age of 132±2 Ma, which represents the forming age of the granodiorite porphyries, i.e., the Early Cretaceous. The oldest group of magmatic zircon ²⁰⁷Pb/²⁰⁶Pb ages ranges from 2 398 Ma to 2 370 Ma, yielding a weighted mean age of 2 389±23 Ma, suggesting that the basement of the North China Craton should exist in the research area. Geochemically, the samples are characterized by high SiO₂ (70.38% and 64.87%), low MgO (0.60% and 1.53%) and Mg^# values (42.92 and 50.42). Moreover, they show enrichment of light rare earth elements and large ion lithophile elements (e.g. Rb, Ba and K), depletion of heavy rare earth elements and high field strength elements (e.g. Nb and Ta), positive anomaly of Pb, and negative anomaly of Ti. These results, together with previously published data, indicate that the Hutouya granodiorite porphyries were derived from partial melting of a delaminated lower continental crust and subsequent interaction with the mantle peridotites. They are consistent with the period of lithospheric thinning beneath the eastern North China Craton and may be formed in an extensional tectonic environment.

Supported by projects of the Natural Science Foundation of China (41472052) and Basic Scientific Research Foundation of Central Universities of China.