Zircon U-Pb age, geochemistry and Hf isotopic compositions of Shibaogou granitoid pluton in the Nannihu ore district, western Henan Province

Abstract：The Shibaogou granitoid pluton, consisting of porphyritic monzogranite and middle-fine-grained monzogranite as well as mafic magma enclaves, is located in the southern margin of the North China Craton. The zircon LA-ICPMS dating of the porphyritic monzogranite and mid-fine-grained monzogranite from this pluton yielded ages of 156±1Ma (MSWD=0.34, N=15) and 157±1Ma (MSWD=0.10, N=17), respectively. The rocks are of high K calc-alkaline series and belong to metaluminous to weak peraluminous I-type granite with A/CNK being 0.82～1.02, Na2O+K2O 7.61%～8.91% and K2O/Na2O 1.02～1.48. Their REE and trace elements are enriched in large ion lithophile elements (LREE, Rb, Ba, K and Pb), and depleted in high-field strength elements (HREE, P and Ti), with slightly negative to positive anomalies of Eu (δEu＝0.81～1.12). Zircon Hf isotopic compositions of the porphyritic monzogranite and middle-fine-grained monzogranite are mainly characterized by εHf(t) values of -22.6～-8.3 and -26.9～-12.4, and the two-stage model ages of 2.64 to 1.73 Ga and 2.91 to 1.99 Ga, respectively. Geochemistry and zircon Hf isotopic compositions show that they were derived from an ancient continental crust (probably Archean Taihua Group), with the addition of juvenile components.