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摘要
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 Pb-207/Pb-206 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 degrees C. Minor metamorphic zircons give Pb-207/Pb-206 ages of 1923 +/- 9 Ma and Ti contents of 5.8-16.3 ppm with temperatures of 697-794 degrees 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 similar to 1.95 Ga peak temperature granulite-facies metamorphism and subsequent near-isothermal decompression process at similar to 1.92 Ga, which is considered to record a similar to 1.95 Ga continent-continent collisional event between the Yinshan and Ordos blocks, followed by post-orogenic exhumation at similar to 1.92 Ga.
- 出版日期2016-5
- 单位中国科学院地质与地球物理研究所兰州油气资源研究中心; 中国科学院地质与地球物理研究所; 中山大学
