Paleoproterozoic tectonic evolution from subduction to collision of the Khondalite Belt in North China: Evidence from multiple magmatism in the Qianlishan Complex

This study presents detailed petrology, major and trace element chemistry, Sr-Nd isotope, and in-situ zircon U-Pb dating and Hf-O isotopes on granites from the Qianlishan Complex of the Khondalite Belt in North China. Zircon SIMS U-Pb data indicate three episodes of Paleoproterozoic magmatism at ca. 2.06 Ga, 1.95 Ga and 1.92 Ga. Of those, the ca. 2.06 Ga hornblende monzogranites and fine-grained potassic granites display typical features of A-type granite, represented by metaluminous affinity, high FeOT/MgO ratios (3.29-5.63), and high Ga/Al and Zr + Nb + Ce + Y values with high zircon saturation temperatures (916-1000 degrees C). Moreover, they have positive zircon epsilon Hf values of +0.29 to +5.01 and homogenous delta O-18 values of 5.11-5.87 parts per thousand, probably derived from the partial melting of talc-alkaline granitoids without addition of supracrustal rocks. The ca. 1.95 Ga garnet-bearing granites contain peraluminous minerals of garnet and muscovite and have high ASI index (>1.1) and delta O-18 values (7.14-9.18 parts per thousand), indicating S-type granite. Their negative whole-rock epsilon Nd(t) values (-2.87 to -2.81) and zircon epsilon Hf(t) values (-4.06 to +1.29) suggest a source of ancient supracrustal rocks. The ca. 1.92 Ga coarse-grained potassic granites present metaluminous and magnesian signatures of I-type granite, including low A/CNK and FeOT/MgO ratios. Their negative epsilon Hf(t) values (-5.00 to -1.64) and homogenous delta O-18 values (5.20-6.00%) suggest that the original magma was derived primarily from enriched lower crust. The results, combined with regional geology and previous studies, establish a prolonged magmatic-metamorphic evolution of the Khondalite Belt from subduction to collision, involving ca. 2.3-2.0 Ga subduction-related arc magmatism, ca. 1.95 Ga syncollisional high-pressure high-temperature crustal anatexis, and ca. 1.92 Ga post-collisional magmatism and synchronous ultrahigh temperature metamorphism.

Automated summary

This study provides detailed information on the petrology, geochemistry, and isotopic composition of granites in the Khondalite Belt in North China, revealing different episodes of magmatism through Paleoproterozoic time. The findings contribute to a better understanding of the geological evolution of the region.