Polycyclic Palaeozoic evolution of accretionary orogenic wedge in the southern Chinese Altai: Evidence from structural relationships and U-Pb geochronology

摘要: Abstract Structural analysis and U–Pb geochronological study on zircons from the southern Chinese Altai (the Kalasu area, SE of city) show that Cambro-Ordovician accretionary wedge (ca. 520–492 Ma) underwent four major geological events: 1) emplacement Early Devonian magmas 410–400) associated with formation a volcano-sedimentary cover, 2) Middle 390–374 Ma) tectono-metamorphic event, 3) Late Devonian-Early Carboniferous folding without apparent metamorphism, 4) regional localized Permian high- to ultrahigh-temperature reworking 300–280 Ma). The magmatism is characterized by mafic rocks granitoids in centre NE-SW profile, coevally granitoid rhyolite volcanism southwest northeast, respectively. whole magmatic edifice was transposed sub-horizontal metamorphic fabric variable degrees different areas ranging greenschist facies northeast (mu + bi±g) amphibolite (st + g ± sill) granulite (g + sill+kfs). This architecture, distribution character zircon populations allow correlate these upper, middle lower orogenic crust developed during important vertical shortening horizontal flow Devonian. Subsequently, affected trending upright (possibly Carboniferous) folding. Finally, produced NW-SE folds crustal-scale vertical, tabular deformation zone centre. accompanied (kfs + cd + sill+g) metamorphism anatexis crust, extensive resetting growth new intrusions granites gabbros. suggests event related massive perturbation thermal structure mantle lithosphere due collision Junggar arc terrane.