Anticlockwise metamorphic paths at ca. 890–790 Ma from the NE Baidrag block, Mongolia, indicate back-arc compression at the Rodinia periphery

The processes leading to the assembly of Rodinia supercontinent through Grenvillian collisional orogeny are relatively well known. In contrast, accretionary orogenic occurring at periphery following poorly understood. To fill this gap, we have identified metamorphic rocks in Mongolia collage Central Asian Orogenic Belt, where numerous data testify for Meso- Neoproterozoic magmatic reworking. tectono-metamorphic evolution peri-Siberian tract Belt is mainly characterized by late Proterozoic–early Cambrian (Baikalian) cycle. However, document here a Tonian age metamorphism northern part Precambrian Baidrag block, previously considered as typical example Baikalian belt. This study incorporates zircon and in-situ monazite geochronology linked P-T modelling Grt-Sil-Ky migmatite gneiss Grt-St micaschist. records initial burial sillimanite stability field ∼720 °C 6.0 kbar followed further kyanite ∼750 ∼9 decompression ∼650 ∼8 kbar. schist staurolite ∼620 6 kbar, ∼590 8.5 yield continuum 207Pb-corrected 238U/206Pb dates ca. 926–768 Ma gneiss, 937–754 schist. Based on textural positon, internal zoning, REE patterns, time prograde under thermal gradient 27–32 °C/km estimated 890–853 Ma. It not clear whether such high-grade conditions prevailed until phase geothermal 18–22 dated 835–815 recrystallization 790 related decompression. Additionally, with 568–515 occur whole grains or rims sharp boundaries suggesting minor overprint. Metamorphic Th/U ratios ∼ 0.01–0.06 877 ± 7 age, together lower intercepts detrital discordia lines both support metamorphism. anticlockwise interpreted result thickening supra-subduction extensional hot edifice – probably back-arc arc type. kind has so far only been described Tarim block was be initiation peri-Rodinian subduction Mirovoi Ocean. geodynamic consequences unique discovery discussed terms tectonic switch oceanic during assembly, strong mechanical coupling potentially onset dispersal.