0000000000280684
AUTHOR
Dondov Tomurhuu
Zircon ages of the Bayankhongor ophiolite mélange and associated rocks: Time constraints on Neoproterozoic to Cambrian accretionary and collisional orogenesis in Central Mongolia
Abstract Central Mongolia is geologically characterized by close juxtaposition of an accreted oceanic terrane with an arc-microcontinent collision zone. We present new U–Pb zircon ages and geochemical data for the Bayankhongor ophiolite melange from the oceanic terrane and for a syenite porphyry pluton from the arc-microcontinent zone, providing critical constraints on the regional evolution in late Neoproterozoic to early Cambrian times. An anorthosite (655 ± 4 Ma) associated with layered gabbro, a rodingite (metasomatized layered gabbro) (647 ± 6 Ma), and a high-level isotropic amphibole gabbro (647 ± 7 Ma) yielded the oldest zircon ages for the plutonic part of the ophiolite. A plagiogra…
Evolution of a Permian intraoceanic arc–trench system in the Solonker suture zone, Central Asian Orogenic Belt, China and Mongolia
Abstract The identification of a fossil arc–trench system from the ophiolite-decorated Solonker suture zone in the southernmost Central Asian Orogenic Belt (CAOB) enables us to constrain the timing of pre-subduction extension (ca. 299–290 Ma), subduction initiation (ca. 294–280 Ma), ridge–trench collision (ca. 281–273 Ma) and slab break-off (ca. 255–248 Ma) in the Permian. A fraction of proto-arc crust (ca. 45 km long, up to 8 km wide) is preserved as a volcanic–plutonic sequence and is juxtaposed against a wide (ca. 30–80 km) forearc melange. This proto-arc crust comprises two distinct magma series, island arc tholeiite (IAT) and mid-ocean ridge basalt (MORB), both of which have strong sup…
Zircon dating of Neoproterozoic and Cambrian ophiolites in West Mongolia and implications for the timing of orogenic processes in the central part of the Central Asian Orogenic Belt
Abstract We present new isotopic and trace element data to review the geochronological/geochemical/geological evolution of the central part of the Central Asian Orogenic Belt (CAOB), and find a fundamental geological problem in West Mongolia, which has traditionally been subdivided into northwestern early Paleozoic (formerly Caledonian) and southerly late Paleozoic (formerly Hercynian) belts by the Main Mongolian Lineament (MML). We resolve this problem with SHRIMP zircon dating of ophiolites and re-evaluation of much published literature. In Northwest Mongolia the Dariv–Khantaishir ophiolite marks the boundary between the Lake arc in the west and the Dzabkhan–Baydrag microcontinent in the …
Zircon ages for a felsic volcanic rock and arc-related early Palaeozoic sediments on the margin of the Baydrag microcontinent, central Asian orogenic belt, Mongolia
Abstract Magmatic zircons from the basal part of an arc terrane in the accretionary complex NE of the Baydrag microcontinental block in central Mongolia were dated at 544 ± 7 Ma and reflect arc magmatism at the Ediacaran/Cambrian boundary. Detrital zircon ages for clastic metasediments of the adjacent Dzag zone suggest a depositional age