Abstract:

The large-scale gold mineralization in Jiaodong Peninsula occurred in 125-110 Ma. Coincided with the mineralization period, the Early Cretaceous the Dazeshan and Tianzhushan plutons  are distributed in the eastern margin of the North China craton. Based on the studies of the petrography, geochemistry, zircon LA-ICP-MS U-Pb dating, and Lu-Hf isotopic constitution, in this paper, the petrologic classification, forming age, magmatic source, petrogenesis and tectonic dynamic background are discussed. The Dazeshan and Tianzhushan plutons are characterized by w(Na₂O) >3.68, 1.0δEu=0.49-0.64). They are a set of weakly peraluminous high potassium calc-alkaline rocks, showing the characteristics of I-type granites. The LA-ICP-MS zircon U-Pb ages of the Dazeshan and Tianzhushan plutons are (120±1) and (112±2) Ma, respectively. They are the late Early Cretaceous magmatic rocks of the Mesozoic in Jiaodong, and the products of different evolution stages of the same period. Their zircon εHf(t) values are －15.3-－10.7 and －21.8-－14.1, respectively, and the two-stage Hf model ages (TDM2) vary in the range of 2.15-1.86 Ga and 2.55-2.07 Ga, respectively. According to their petrology, geochemistry and Lu-Hf isotopic constitution, combined with the results of previous studies, the authors believe that the Dazeshan and Tianzhushan granites are the products of lithospheric thinning and intracontinental extension, and the diagenetic materials are mainly derived from the partial melting of the ancient crustal materials with the addition of some mantle materials. In the early stage, the Dazeshan pluton was formed at the same time as a large number of dark dykes in the Jiaodong area, and more mantle materials were added, which led to the decrease of the two-stage Hf model ages of the Dazeshan pluton.

Key words: Dazeshan plutons')">

Dazeshan plutons, Tianzhushan plutons, granite, geochemistry, zircon U-Pb age, Lu-Hf isotope,
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