Out of sequence thrusting in the northern Indo-Burma Ranges: evidence from preliminary zircon (U-Th)/He thermochronology
Abstract
Zircon (U-Th)/He (ZHe) cooling ages are used to quantify the timing of exhumation across the northern Indo-Burma thrust belt, the easternmost segment of the Cenozoic Himalayan collisional system. Single grain ZHe ages were determined for fourteen bedrock samples of major lithologic units, which consist from northeast to southwest: (1) the Mesoproterozoic and latest Jurassic-Cretaceous granitoids of the Lohit Plutonic Complex, (2) Tidding and Mayodia mélange complexes, (3) Mesoproterozoic-Cambrian Mayodia gneiss, (4) Mesoproterozoic-Jurassic Lalpani schist, and (5) Tertiary Sewak unit. Zircons from Cretaceous granitoids of the Lohit Plutonic Complex yield ZHe ages of 10-6 Ma. Garnet schist from the Tidding mélange complex yields an older ZHe age of 18 Ma. Samples of the Lalpani schist in the Hunli duplex and Mayodia mélange complex in the Mayodia klippe yield ZHe ages of 8 Ma and 7 Ma, respectively. In the foreland of the thrust belt, ZHe ages of the Mayodia gneiss, Lalpani schist, and Sewak unit are 9-5 Ma. The spatial distribution of ZHe ages of 18 Ma in the Tidding mélange complex to 5 Ma in the Sewak unit in the foreland suggest a younging trend from northeast to southwest, parallel to the thrust transport direction. However, ZHe ages of 10-6 Ma from the Lohit Plutonic Complex in the hinterland of the thrust belt suggest renewed exhumation via out of sequence thrust motion along the southwest-directed Lohit thrust. This study reveals a complex exhumation history of the northern Indo-Burma Ranges, such that Late Miocene activity along the Lohit thrust was coeval with exhumation of foreland rocks during southwestward propagation of the thrust belt.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T23C0378H
- Keywords:
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- 8104 Continental margins: convergent;
- TECTONOPHYSICSDE: 8169 Sedimentary basin processes;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICSDE: 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS