~1.77 Ga A-type granite and dark enclaves in the North Qinling Orogenic Belt: Constrains on the tectonic affinity between the North Qinling Orogenic Belt and the North China Craton

The Hudian gneissic monzonitic granite with lentoid dark enclaves and foliated mafic dykes was exposed in the western segment of the North Qinling Orogenic Belt (NQOB). It has long been considered as an intrusion into the Kuanping Complex, the northernmost component of the NQOB. LA–ICP–MS zircon dating yields consistent formation age of ca. 1.77 Ga for the granite and dark enclaves and the same metamorphic age of ca. 400 Ma for the granite and the mafic dykes. The formation age of ca. 1.77 Ga of the Hudian pluton is much older than the deposition age ( The granite is low in Al2O3, CaO, MgO and Mg# high in SiO2, Na2O + K2O, Fe2O3T, Zr and 10,000*Ga/Al, and displays slightly right dipping “gull-wing” shaped rare earth element patterns, agreeing well with the features of A-type granites; the dark enclaves are basalt-andesitic rocks and show characteristics of crust-contaminated continental within-plate basaltic rocks, all suggesting a tectonic setting of extension. The major and trace element compositions of the Hudian monzonitic granite and its dark enclaves and the zircon eHf (t) values (−12.1 to −7.1) of the Hudian monzonitic granite all show strong comparability to the 1.75–1.8 Ga A-type granites and coeval intermediate-basic rocks of the Xiong’er Group in the southern North China Craton (NCC), indicating that the Hudian pluton maybe initially formed in the southern NCC. Considering the absence of obvious 1.75–1.8 Ga detrital zircon records in the Kuanping Complex, and the common metamorphic age of ca. 400 Ma in the Kuanping Complex and Hudian pluton as well as other units of the NQOB, we propose that the NCC has no affinity to the NQOB and the Hudian pluton was involved in the NQOB during the collision between the southern NCC and the NQOB at ca. 400 Ma.