zircon U-Pb geochronlogical and Ar-Ar thermochronlogical data in Gyaca county, NE Himalaya

The data include zircon U-Pb age of a intermediate dike (Table S1-sample STV01-mendeley), and 39Ar-40Ar thermochronology result of mica quartz phyllite (Table S2-Ar-Ar data-mendeley) from the Gyaca mélange zone in Gyaca county, NE Himalaya. Sample STV01 was collected from the intermediate dikes and parrlleled to the replaced cleavages of folds, while sample DX2085 was collected from the matrix of Gyaca mélanges near the dikes. The intermediate dikes intruded the Gyaca mélange along the foliation S2 (axial plane cleavage) and remoulded each other, indiacating the syntectonic relationship and the deformation timing of folding. Fourteen zircons among twenty two dated grains obtained from sample STV01 (Appendix 2) show concordance of >95% yielded weighted mean 206Pb/238U age of 55.29±0.54 Ma (MSWD=0.85), suggesting that the folding deformation happened nearly simultaneous in the Early Eocene. Steps 2 to 5 of muscovite 39Ar-40Ar data from sample DX2085 yileded a plateau age of 55.78±0.14 Ma (81.73% of the 39Ar gas release, MSWD=2.38) and an inverse isochron age of 55.62±0.15 Ma (MSWD=4.2). The sub-particle rotation recrystallization and bulging recrystallization of quartz particles from sample DX2085 indicate a deformation temperature range of 380°~420°, exceeding the closure temperature of muscovite(~350°), which implies the 39Ar-40Ar age can be used to constrain the timing of the contraction deformation in the Gyaca mélange zone. The positive flower structural style in the upper Triassic tectonostratigraphy in NE Himalaya implies intense contraction deformation and contemporaneous folding between the Gyaca mélange zone and the Langjiexue fold-thrust belt. Combined with the regional geological background, consequently, the dramatical contraction deformation in the NE Tethyan Himalaya should begin after the Early Cretaceous, and it’s most likely to take place in the Early Eocene (55~56 Ma) through the India-Asia collision rather than in the Early Cretaceous by the collision of the “Longzi block” and an intra-oceanic arc.