Extensional tectonics within a subduction-type orogen. The case study of the Wugongshan dome (Jiangxi Province, southeastern China)

摘要: Abstract In southeastern China, the Wugongshan massif consists of metamorphic rocks and granites generally considered as “basement” formed during an early Paleozoic orogeny. Our structural radiometric reappraisal this shows that it results from a Mesozoic doming. rocks, foliation defines E-W elliptical shape bears N-S stretching lineation. The axial zone dome is occupied by oriented plutons. outer part Devonian quartzite, Carboniferous-Permian limestone Triassic-Jurassic sandstone. Ductile deformation observed in Permian carbonates older units develops contrasting kinematics. northern southern flanks present top-to-the-north top-to-the-south motions, respectively. same divergent pattern motion recorded brittle structures up to Jurassic late Cretaceous red beds are undeformed. zone, coaxial flow indicated symmetric pressure shadows quartz fabrics predominates. Along N S dome, post-folial recumbent folds symmetrically overturned respectively, but at two extremities fold axes parallel 40 Ar 39 ages biotite muscovite mylonite granite suggest Triassic age for ductile final similar core complex extensional tectonic regime. A model which emphasizes plutonism discussed. From Cretaceous, China was subduction-type orogen, crust thickened accretion mantle derived magmas. emplacement large amount granitoids promoted thermal softening gravitational instability allowed extend. formation other complexes appears be direct consequence plutonic activity rheology.