Neoarchean-early Paleoproterozoic crustal evolution in the Jiapigou terrane in the northeastern part of the North China Craton: Geochemistry, zircon U-Pb dating and Hf isotope constraints from the potassic granitic complex

Y Neoarchean granitic rocks are important components of Precambrian cratons, and their petrogenesis can provide constraints for understanding the evolution of continental crust. The Neoarchean potassic granites are widely distributed in southern Jilin Province, which is located in the northeastern part of the North China Craton. Newly obtained field geology observations and petrological, geochemical and geochronological data reveal that the Jiapigou potassic granitic complex is mainly composed of biotite granitic gneiss and medium- to coarse-grained granite. All the granitic gneisses and granites are high-K calcium-alkaline to shoshonite, metaluminous to peraluminous (A/CNK = 0.95-1.13; molar Al2O3/(CaO + Na2O + K2O)), enriched in LILEs and LREEs with strongly fractionated REE patterns ((La/Yb)(N) = 21-179), and depleted in Nb, Ta, Ti and P. The biotite granitic gneisses have low Rb/Sr ratios (similar to 0.06) and weak positive Eu anomalies (delta Eu = 1.26-1.51), while the granites have low Th, U and REEs and strong positive Eu anomalies (delta Eu = 7.27-16.92). The zircons of these granitic rocks generally have core-rim structures based on cathodoluminescence images and show inherited ages of 2729 +/- 10 Ma, crystallization ages of 2523 +/- 11 Ma to 2526 +/- 15 Ma, and crystallization/metamorphism ages of 2480 +/- 15 Ma to 2485 +/- 9 Ma. The zircon Hf isotope results of the medium-grained monzogranite show that the eHf(t2) values vary from -2.2 to +5.3, and the two-stage model ages (T-DM2) are 2.9-3.0 Ga. The magmatic zircons of the early Neoarchean (similar to 2.73 Ga) and the late Neoarchean (similar to 2.52 Ga) crystallized in high-temperature magmas (738-890 degrees C), whereas those of the early Paleoproterozoic (similar to 2.48 Ga) crystallized in relatively lowtemperature (646-702 degrees C) magmas. These results indicate that the Jiapigou granitic rocks were products of intracrustal recycling during the late Neoarchean and the early Paleoproterozoic. The protoliths of the Jiapigou granitic gneisses were derived from the remelting of the early Neoarchean juvenile crustal rocks in the lower crust during the late Neoarchean. Subsequently, these granitic rocks underwent amphibolite-facies metamorphism and water-fluxed melting in the early Paleoproterozoic, resulting in the association of migmatic granitic gneisses and potassic granites at the shallow crust level. The cratonization in the Jiapigou terrane involved early Neoarchean (similar to 2.73 Ga) juvenile crust growth and late Neoarchean (similar to 2.53-2.52 Ga) to the early Paleoproterozoic (similar to 2.48 Ga) intracontinental reworking.

Automated summary

The study of Neoarchean granitic rocks in the Jiapigou area of Jilin Province reveals that they are mainly composed of biotite granitic gneiss and medium- to coarse-grained granite, with high potassium and high calcium-alkaline to shoshonite characteristics. Zircon analysis suggests that these rocks formed during intracrustal recycling processes in the late Neoarchean and early Paleoproterozoic, with origins from remelting of early Neoarchean crustal rocks.