T283 From Oceanic Subduction to Inter-Continental Collision: Examples of Convergent Margin Processes in Non-Collisional and Collisional Settings (Posters)

Wednesday, 25 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

THERMOCHRONOLOGIC CONSTRAINTS ON THE PERMO-TRIASSIC PALEO-TETHYS TECTONICS IN EASTERN TIBETAN PLATEAU

Paper number: T283-5
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Structural and thermochronologic studies of the Batang-Deqin area in eastern Tibetan Plateau provide constraints on the Paleo-Tethys orogeny. The NS-trending Paleo-Tethys orogen at Batang-Deqin includes ophiolitic mélange zone, magmatic belt, and fold-thrust belt. Two Paleo-Tethys deformation stages, i.e., the dextral oblique top-to-the-west thrusting (D1) and a top-down-to-the-southeast shearing (D2), and associated metamorphism, are identified in this area. The P-T estimates of the garnet schist of the Barrovian metamorphism suggest the formation condition of ~500-600 °C and ~5-6 kbars. The 40Ar/39Ar analyses on synkinematic and metamorphic micas of the garnet schist yield Late Permian to Early Triassic and Late Triassic ages throughout the Batang-Deqin area. The biotite 40Ar/39Ar and zircon (U-Th)/He analyses on the migmatite yield ages of ~190 Ma and Cenozoic ages, respectively. Integrated with previous 40Ar/39Ar and U-Pb ages, the reconstruction of cooling path for the garnet schist, plutons, and migmatites reveals a rapid cooling from crystallization of igneous zircons through closure temperature of mica (~700 ºC to ~300 ºC), between ~230 Ma to ~210 Ma. Therefore, we propose that the post-orogenic extension and ductile thinning (D2) cooled and exhumed the thickened Paleo-Tethys orogenic crust through the biotite 40Ar/39Ar temperature during the late Late Triassic.

Keywords: Paleo-Tethys tectonics; eastern Tibetan Plateau; Jinsha suture zone; thermochronology; structural analysis

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-341225

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