New constraints on the pre‐Permian continental crust growth of Central Asia (West Junggar, China) by U–Pb and Hf isotopic data from detrital zircon

Abstract

Terra Nova, 24, 189–198, 2012 Abstract In situ U–Pb geochronology of detrital zircons from various Palaeozoic sedimentary rocks of West Junggar accretionary complexes (Central Asia) suggests two distinct episodes of arc magmatism, and an evolution in three steps: (i) Ordovician‐Silurian subduction generating juvenile arc crust; (ii) Late Silurian subduction jamming, erosion and intraplate magmatism; (iii) development of two new opposed Devonian‐Carboniferous subductions recycling the Early Palaeozoic crust. Zircon Hf isotopes document three pre‐Permian episodes of mantle‐derived magmatic input into the crust: (1) Neoproterozoic (850–550 Ma), (2) Early Palaeozoic (530–450 Ma) and (3) Late Palaeozoic (380–320 Ma). Zircons also record the recycling of Neoproterozoic and Early Palaeozoic juvenile crusts during the Early and Late Palaeozoic. These data support a model of episodic continental crust growth in Central Asia.