The Sino-Korean–Yangtze suture, the Huwan detachment, and the Paleozoic–Tertiary exhumation of (ultra)high-pressure rocks along the Tongbai-Xinxian-Dabie Mountains

Abstract

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 melange 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 melange is a subduction-accretion complex containing elements of the Qinling microcontinent and its arc, the Paleotethyan ocean floor, and possibly the Yangtze craton.