U PB ZIRCON AGES CONSTRAIN THE ARCHITECTURE OF THE ULTRAHIGH-PRESSUREQINLING-DABIE OROGEN, CHINA/

New SHRIMP and TIMS zircon ages, Ar-40/Ar-39 ages, and eclogite locati ons contribute significantly to our understanding of the ultrahigh-pre ssure Dabie Shan. (I) The geographic extent of the Yangtze craton that was subducted to ultrahigh pressure extends to the northern edge of t he Dabie Shan. (2) The northern half of the Dabie Shan is a magmatic c omplex, intruded over a 10-Myr interval between 137 and 126 Ma, that a ccommodated similar to 100% N-S stretching of the pre-existing collisi onal architecture. (3) Granitic orthogneisses and enclosing ultrahigh- pressure paragneisses have indistinguishable zircon populations. The p opulation of Triassic zircon ages ranges from similar to 219 to simila r to 245 Ma, leading us to question the prevailing assumption that 219 Ma zircons formed at ultrahigh pressure, and to propose instead that they reflect late retrogression at crustal pressures following the bul k of exhumation. (C) 1998 Elsevier Science B.V. All rights reserved.