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

摘要

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 224-214 Ma with a peak at ～216 Ma. Zircon Hf isotopic compositions show that these intrusive rocks were derived from different source regions. The dioritic porphyries with the formation ages of ～216 Ma in the Zhongdian area of the southern Yidun terrane, together with the granodiorite of ～216 Ma from the Maxionggou batholith, originated from the remelting of the late Mes-oproterozoic (～1.2 Ga) juvenile continental lower crust, whereas most granitic rocks were derived from the reworking of the early Mesoproterozoic (～1.6 to 1.5 Ga) 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.