Petrogenesis of the Late Triassic Sanshilipu monzogranites in North Qinling orogenic belt

The Sanshilipu monzogranites is located in the northern margin of the South Qinling Block, with an outcrop of about 10 km 2 , and as an intrusion into Palaeozoic Danfeng ophiolitic mélange. The samples consist mainly of plagioclase, K‐feldspar, quartz, biotite, and minor titanite, apatite, magnetite, with contents of SiO 2 (61.73–68.49%), Al 2 O 3 (14.58–16.61%), K 2 O + Na 2 O (5.79–8.87%), MgO (1.07–2.91%), and low TiO 2 (0.55–0.83%), similar to those of I‐type granite. They also show high concentrations of LREE, Pb, and Sr, slightly negative Eu, but low HREE, Nb, Ta, and Y. High Sr and Sr/Y, low Y characteristics are similar to those of adakite. High precision LA‐ICP‐MS U–Pb dating and trace element analysis of zircon in the Sanshilipu granite yielded a concordant age of 205 ± 1 Ma. This age is apparently younger than the closure age of the Mian‐Lue Ocean (242–221 Ma). We propose that the Sanshilipu monzogranites formed by magma mixing of thickened lower crust and limited mantle‐derived mafic magma during post‐collision of the South China and North China blocks.