Middle Jurassic collision of an exotic microcontinental fragment: implications for magmatism across the southeast China continental margin

Sewell, R.J. and Carter, Andrew and Rittner, M. (2016) Middle Jurassic collision of an exotic microcontinental fragment: implications for magmatism across the southeast China continental margin. Gondwana Research 38 , pp. 304-312. ISSN 1342-937X.

Abstract

Thrusting, folding and metamorphism of late Paleozoic to middle Mesozoic sedimentary rocks, together with high precision U–Pb zircon ages from Middle to Late Jurassic volcanic and granitic rocks, reveals evidence for a major deformation event in northwestern Hong Kong between 164 and 161 Ma. This episode can be linked with collision of an exotic microcontinental fragment along the southeast China continental margin determined from contrasting detrital zircon provenance histories of late Paleozoic to middle Mesozoic sedimentary rocks either side of a NE-trending suture zone through central Hong Kong. The suture zone is also reflected by isotopic heterogeneities and geophysical anomalies in the crustal basement. Detrital zircon provenance of Early to Middle Jurassic rocks from the accreted terrane have little in common with the pre-Middle Jurassic rocks from southeast China. Instead, the zircon age spectra of the accreted terrane show close affinities to sources along the northern margin of east Gondwana. These data provide indisputable evidence for Mesozoic terrane accretion along the southeast China continental margin. In addition, collision of the exotic terrane, accompanied by subduction roll-back, is considered to have hastened foundering of the postulated flat-slab beneath southeast China leading to a widespread igneous flare-up event at 160 Ma.

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