Application of the revised Ti-in-zircon thermometer and SIMS zircon U-Pb dating of high-pressure pelitic granulites from the Qianlishan-Helanshan Complex of the Khondalite Belt, North China Craton

Abstract The Ti-in-zircon thermometer is a newly established, single-mineral trace element thermometer, which has been successfully used to estimate the peak and post-peak temperatures of high-grade metamorphic rocks. Here the revised Ti-in-zircon thermometer and in situ SIMS U-Pb dating are applied to detrital and metamorphic zircons of pelitic granulites from the Qianlishan-Helanshan Complex. The SIMS U-Pb results show that detrital zircons yield 207 Pb/ 206 Pb ages scattering from 2021 to 2449 Ma with a peak age of 2030 Ma, possibly sourced from felsic to intermediate igneous rocks at a relatively low temperature magmatic environment. Most metamorphic zircons yield ages of 1953 ± 15 Ma, 1954 ± 20 Ma and 1948 ± 18 Ma with Ti contents of 3.9–82.6 ppm, corresponding to metamorphic temperatures of 664–992 °C. Minor metamorphic zircons give 207 Pb/ 206 Pb ages of 1923 ± 9 Ma and Ti contents of 5.8–16.3 ppm with temperatures of 697–794 °C. These define metamorphic ages and temperature conditions at peak and post-peak metamorphic stages of pelitic granulites, respectively. Combined with previous studies, our new data establish a linking between zircon U-Pb ages and metamorphic thermal evolution. This demonstrates a ∼1.95 Ga peak temperature granulite-facies metamorphism and subsequent near-isothermal decompression process at ∼1.92 Ga, which is considered to record a ∼1.95 Ga continent-continent collisional event between the Yinshan and Ordos blocks, followed by post-orogenic exhumation at ∼1.92 Ga.