New U-Pb sensitive high-resolution ion microprobe (SHRIMP) dating of zircon from the ultrahigh-pressure Sulu terrane, eastern China, records three events in the evolution of the orogen. Peak ultrahigh-pressure and retrograde metamorphism in the Middle to Late Triassic (ca. 230–200 Ma) is recorded in zircon mantles and rims; cathodoluminescence imaging, grain morphology, and U-Th-Pb and rare earth element chemistry cannot distinguish between ultrahigh-pressure and retrograde zircon growth. Comparison of high-temperature thermochronology for the Sulu and Dabie–Hong'an areas suggests that peak ultrahigh-pressure metamorphism in Sulu took place at ca. 230 Ma, postdating 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 ultrahigh-pressure slab that was never adjacent to Dabie. 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. 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.

There are three sutures in the Qinling-Dabie-Sulu orogen in the Tongbai–Xinxian (northern Hong'an)–northern Dabie area: the Silurian Sino-Korean craton–Erlangping intra-oceanic arc suture, the Silurian Erlangping arc–Qinling unit (microcontinent) suture, and the Early Triassic Qinling unit–Yangtze craton suture. We resolve the controversy regarding the age of the Sino-Korean craton–Yangtze craton collision by recognizing that there was Paleozoic collision between the Qinling unit and the Sino-Korean craton and Mesozoic collision between the Qinling unit and the Yangtze craton. The Qinling unit constitutes a long and narrow microcontinent that extends through the Qinling-Dabie area and probably into the Sulu area. Its common characteristics are the Mesoproterozoic (ca. 1.0 Ga) Jinningian orogeny, ca. 0.8–0.7 Ga arc formation and rifting, and Late Silurian–Early Devonian (ca. 400 Ma) arc magmatism with concomitant regional contact metamorphism up to granulite-facies conditions (peak: 680–740 °C at 0.9–1.1 GPa). A common Proterozoic history links the Qinling microcontinent to the Yangtze craton. Its 400 Ma arc, forearc basin, and its separation from the Yangtze craton by the partly oceanic Huwan mélange make the Qinling microcontinent distinct. The forearc basin sits on the southern part of the 400 Ma arc and underlying Proterozoic continental basement, and detrital geochronology ties it to the Qinling microcontinent basement and its arc. The Huwan mélange is a subduction-accretion complex containing elements of the Qinling micro-continent and its arc, the Paleotethyan ocean floor, and possibly the Yangtze craton. Quartz eclogites (540–590 °C, 2.1 GPa) signify ca. 315 Ma subduction. Devonian to Permian eclogite zircon ages, 40 Ar/ 39 Ar and Rb/Sr mineral ages in the forearc and its basement, and static, Permian blueschist metamorphism in the upper-plate basement testify to subduction throughout the late Paleozoic. The ∼10-km-wide Huwan detachment bounds the high- and ultrahigh-pressure rocks of the Xinxian–Hong'an block (pressure peak at older than 240 Ma) along their northern margin. It is partly responsible for exhumation of the high- and ultrahigh-pressure rocks, but the entire basement core of Hong'an–Dabie orogen is also strongly deformed. The Huwan shear-zone high-strain deformation indicates passage of rocks through the lithosphere by subhorizontal N-S extension and vertical contraction, showcased by condensed Triassic isograds (420 °C and ∼0.4 GPa in the hanging wall and ∼530 °C and 2.2 GPa in the footwall). The Huwan detachment produced Triassic crustal exhumation rates of 1.9–1.4 mm/yr; synkinematic phengite grew as early as ca. 235 Ma, and the main retrograde deformation occurred at 224–195 Ma. The Tongbai-Xinxian area shows a massive 130–115 Ma cluster of cooling ages, reflecting regional cooling after granitoid injection and regional Cretaceous heating. Apatite fission-track ages cluster at 80–55 Ma and signify cooling related to transtension that coincided with rifting marked by Late Cretaceous–Eocene red bed deposition throughout eastern China. Exhumation rates of for the last 70 m.y. have been slow: ∼0.06 mm/yr. The India-Asia collision reactivated the orogen in the Eocene, particularly along the Tanlu fault zone and locally along fault zones in Tongbai-Xinxian.

New sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages from eclogite and associated peridotite near Rongcheng, Sulu terrane, eastern China, indicate that eclogite within peridotite experienced Triassic metamorphism at the same time as the surrounding host gneiss. Cathodoluminescence (CL) images reveal that most of the zircons from two eclogites and one dunite have unzoned, homogeneous or slightly mottled patterns, typical of metamorphic zircons. Some zircons from eclogite sample CJ4C have distinct nonluminescent U-rich cores and luminescent U-poor rims, but similar ages were obtained from both domains. SHRIMP U-Pb zircon analyses of one dunite (MC5A) and two eclogites (CJ4A, 4C) yielded ages of 242 ± 8 Ma, 238 ± 3 Ma, and 232 ± 7 Ma, respectively, which are considered to be the peak metamorphic ages. A much younger age (218 ± 5 Ma) was obtained from eclogite CJ4D, but no petrological evidence for a retrograde event was found in this sample, and therefore this age is also considered to reflect eclogite-facies growth. Thus, new geochronological data confirm that these mantle-derived mafic-ultramafic bodies were emplaced into the subducting slab in the Triassic and experienced the ultrahigh-pressure metamorphism together with the adjacent supracrustal rocks.