Zircon geochronology and Hf isotopes of Mesozoic intrusive rocks from the Yidun terrane, Eastern Tibetan Plateau: Petrogenesis and their bearings with Cu mineralization

Abstract

Zircon U–Pb ages and Hf isotopic composition of Mesozoic intrusive rocks from the Yidun terrane were systematically investigated in order to decipher the geodynamic setting of magmatism and their relationship with Cu-polymetallic mineralization in the Eastern Tibetan Plateau. Zircon U–Pb dating results on seven granitoid rocks and four diorite samples indicate that the Mesozoic plutons from the Yidun terrane were emplaced in the period of 224–214Ma with a peak at ∼216Ma. Zircon Hf isotopic compositions show that these intrusive rocks were derived from different source regions. The dioritic porphyries with the formation ages of ∼216Ma in the Zhongdian area of the southern Yidun terrane, together with the granodiorite of ∼216Ma from the Maxionggou batholith, originated from the remelting of the late Mesoproterozoic (∼1.2Ga) juvenile continental lower crust, whereas most granitic rocks were derived from the reworking of the early Mesoproterozoic (∼1.6 to 1.5Ga) middle-lower crust. Our results, together with previous data, indicate that the collision between the Yidun and Songpan–Ganzi terranes and subsequent orogeny had been completed by the middle Triassic. A post-orogenic collapse model is proposed for the Meosozoic magmatism and related Cu-polymetallic mineralization in the Yidun terrane.