Tertiary deformation and metamorphism SE of Tibet: The folded Tiger-leap décollement of NW Yunnan, China

摘要: The Yulong-Haba Xue Shan range, in the northwestern part of Yunnan (China), is a large N-S antiform that folds Paleozoic series Yangzi platform. upper River (Jinsha Jiang) has cut 3500 m-deep valley (Hu Tiao gorge) across this antiform, thus exposing folded, bedding-parallel, ductile shear zones (decollements), with transport toward SSW (in present geographical coordinates). finite strain implies tens kilometers transport, pointing to regional significance these decollements. Rb/Sr radiometric dating phlogopites crystallized marbles within foliation planes yields age metamorphic and deformation event (35.9 ± 0.3 (2σ) Ma). derives from an internal Rb-Sr isochron, made on different size fractions same mineral, which provides novel demonstration feasibility such plots. Transport decollement related shortening occurred prior to, or at onset of, extrusion Indochina along Ailao Shan-Red zone, ≈80 km west Yulong Shan. 39Ar/40Ar spectra K-feldspar core suggest uplift by antiformal folding around 17 Ma, as Indochina's came end. We infer other large-scale Cenozoic decollements exhumed underlie some vast, folded areas surround eastern Himalayan syntaxis. decollements, first south then east, above them, might have during two principal phases, whose ages bracket escape SE.