K-rich granitoid magmatism at the Archean-Proterozoic transition in southern Jilin: Insights into the Neoarchean crustal evolution of the northeastern part of the North China Craton

Massive Neoarchean to early Paleoproterozoic K-rich granitoid rocks are widely distributed in the southern Jilin metamorphic basement terrane, which is located in the northeastern part of the North China Craton (NCC). Based on newly obtained petrological, geochemical and geochronological data, these K-rich granitoid rocks can be subdivided.into: similar to 2.50 Ga porphyritic monzogranites in the Jingyu-Tonghua area, and similar to 2.50-2.49 Ga medium grained and coarse-grained monzogranites and similar to 2.47 Ga porphyritic quartz syenites in the Huadian-Jingyu area. The similar to 2.50 Ga porphyritic monzogranites are characterized by rare earth element (REE) patterns with high (La/Yb)(N) and low (Gd/Yb)(N) ratios and weakly negative Eu anomalies, as well as zircon epsilon(Hf)(t(2)) values of +1.7 to +5.3 with T-DM(Hf) values of 2748 to 2612 Ma. These results suggest that the monzogranitic magma was produced under low-pressure conditions by partial melting of a heterogeneous crustal source, with residual plagioclase, hornblende, orthopyroxene, and clinopyroxene. The similar to 2.50-2.49 Ga medium- to coarse-grained monzogranites show low MgO and CaO contents, Mg# values of 1-42 and zircon epsilon(Hf)(t(2)) values of -0.7 to +4.6, as well as T-DM(Hf) values of 2847 to 2634 Ma. These results indicate that these rocks were also generated from partial melting of pre-existing juvenile crustal materials that were enriched in potassium by either fluid alteration or surface processes at middle to lower crustal levels. The similar to 2.47 Ga porphyritic quartz syenites have zircon epsilon(Hf)(t(2)) values of +2.8 to +5.6 and TDMHf) values of 2678 to 2571 Ma; display the highest K2O concentrations of the rocks examined in this study; are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs); have low MgO contents and Mg# values; and display strongly differentiated chondrite-normalized REE patterns with no significant Eu anomalies. These results indicate that these rocks may have been produced by partial melting of juvenile mantle-derived basaltic rocks associated with recycled K-rich metasediments in the lower crust. Combined with previous studies on the southern Jilin metamorphic basement terrane, our data indicate that the similar to 2.50-2.47 Ga K-rich granitoid rocks are products of Neoarchean intracrustal recycling. The K-rich granitoid rocks are coeval with regional amphibolite- to local granulite-facies metamorphism, which were most likely triggered by the arc-continent collision between an intra-oceanic arc system along the northwestern margin of the NCC and the ancient continental margin in southern Jilin and by the post-collisional delamination of the thickened crust. These processes led to crustal differentiation and the final stabilization of the cratonic continental crust. (C) 2018 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.