2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 6
Presentation Time: 9:15 AM


LEECH, Mary L., Department of Geosciences, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132-4163, WEBB, Laura E., Department of Earth Sciences, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244-1070 and YANG, T.N., Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China, leech@sfsu.edu

New U-Pb SHRIMP dating of zircon from the ultrahigh-pressure (UHP) Sulu terrane, eastern China, records three events in the evolution of the orogen. Relict zircon cores and mantles preserve protolith ages between 700 and 790 Ma, reflecting the Yangtze craton affinity of the Sulu terrane and supporting other evidence indicating that the suture between the Yangtze and Sino–Korean cratons lies along the Yantai–Qingdao–Wulian fault zone (see Hacker et al., in review). Late Jurassic to Early Cretaceous ages from a pegmatite vein near the suture probably reflect early melting related to a widespread magmatic event that affected the northern margin of the Dabie–Sulu belt. Peak UHP and retrograde metamorphism in the Middle to Late Triassic (~230 to 200 Ma) is recorded in zircon mantles and rims; cathodoluminescence imaging, grain morphology, and U-Th-Pb and REE chemistry cannot distinguish between UHP and retrograde zircon growth. Comparison of high-temperature thermochronology for the Sulu and Dabie–Hong'an areas suggests that peak UHP metamorphism in Sulu took place at ca. 230 Ma, post-dating Dabie–Hong'an by 10 m.y.; this age disparity has implications for collision–subduction–exhumation models for the entire Qinling–Hong'an–Dabie–Sulu orogen and suggests that Sulu was a separate UHP slab that was never adjacent to Dabie.