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Ca. 1318Ma A-type granite on the northern margin of the North China Craton: Implications for intraplate extension of the Columbia supercontinent

Abstract:

Identification of the Mesoproterozoic A-type Jining granite and granite porphyry, which with abundant coeval mafic dike sills and volcanic rocks on the northern margin of the Precambrian North China Craton (NCC), may suggest intraplate extension of Columbia supercontinent. Major and trace elements of the Jining granite show an affinity to A-type granites, and may reflect an intraplate rift setting (A 1-type granite). High Rb, Y, Yb, and Ta contents also show features of within-plate granites. SHRIMP zircon dating yielded concordant weighted mean 207Pb/ 206Pb ages of 1318±7Ma and 1321±15Ma, which define a Mesoproterozoic magmatic event. The zircons have negative ε Hf(t) of -3.6 to -8.6 and corresponding old T DM2 of 2330-2609Ma (mean 2436Ma), suggesting the involvement of a crustal source in the magma genesis. The Hf-in-zircon isotopic compositions are aligned along an evolution line for the average continental crust. These results suggest that the granite and granite porphyry originated from partial melting of an Archean crustal source in a within-plate anorogenic setting during the Mesoproterozoic. The discovery of this A-type granite and granite porphyry with coeval mafic sills suggests that the NCC was involved in the fragmentation of the Columbia supercontinent, and the intraplate extension of the supercontinent occurred during Mesoproterozoic, probably at ca. 1318Ma. © 2012 Elsevier B.V.