Geodynamic evolution of Central Asia in the Paleozoic and Mesozoic

Abstract

Central Asia is an ideal laboratory to study geodynamics and continental growth in the Phanerozoic (Şengor et al. 1993; Şengor and Natal’in 1996; Jahn et al. 2004; Xiao et al. 2004a, b; Kroner et al. 2007; Windley et al. 2007; Jian et al. 2008). Three important orogenic collages are exposed in Central Asia, i.e. the Altaids or Central Asian Orogenic Belt in the north, Tethysides in the south, and Western Pacific orogenic collages in the east. The architecture of Central Asia was mainly constructed from the interactions between these collages (Isozaki et al. 1990; Şengor et al. 1993; Yin and Nie 1996; Maruyama 1997; Xiao et al. 2008a, b). The interaction among these collages was the major topic of a 5-day thematic workshop on ‘‘Geodynamic Evolution of Central Asia in the Paleozoic and Mesozoic’’, held in Beijing, China, in December 2006 and funded by the SinoGerman Centre for Research Promotion (Chinesisch-Deutsches Zentrum fur Wissenschaftsforderung) (Xiao and Kroner 2007). The workshop was attended by more than 50 participants representing eight countries (Germany, UK, France, Russia, Australia, Italy, Cuba, and China) and was co-sponsored jointly by Task Force I (Earth Accretionary Systems) of the International Lithosphere Program (ILP), IGCP Project 480, and the State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences (CAS). The current thematic volume arises from this workshop and also includes several invited contributions. The 18 papers in this volume reflect a relatively broad spectrum of current research and cover regions in the southern Altaids as well as the northern Tethysides and the Japan Islands where the Altaids and Tethysides possibly join (Fig. 1). Wenjiao Xiao and co-authors (this volume) synthesize accretionary processes during final terrane amalgamation in the Altai and Tien Shan Mountain Range of NW China and Inner Mongolia in the late Permian to mid-Triassic. They use structural, geochemical, geochronological and palaeomagnetic data to show that there was continuous southward accretion in the late Paleozoic to middle Triassic of volcanic arcs, accretionary wedges and HPto UHPmetamorphic rocks. Final closure of the Paleoasian Ocean led to docking of the Tarim and North China Cratons with the amalgamated CAOB terrranes and terminal orogenesis. This complex geodynamic evolution led to formation of major metal deposits and substantial crustal growth. Jun Gao and co-authors (this volume) provide geochemical data and zircon ages for metaluminous to weakly peraluminous granitoids in the southern Chinese Tianshan and relate these to continental arc settings between ca. 480 and 275 Ma ago. These authors favor Silurian to Carboniferous northward subduction of the South Tianshan oceanic plate beneath the southern margin of the Central Tianshan-Kazakhstan-Yili continental plate and argue for W. Xiao (&) State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China e-mail: wj-xiao@mail.igcas.ac.cn