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Abstract:
In the Katha Range of central Myanmar, lithologic tracers and pressure-temperature-deformation-time data identify Cambro-Ordovician, Indian-affinity Tethyan Himalaya Series, located ∼700 km from their easternmost outcrop in S-Tibet, and ∼450 km from Himalayan rocks in the Eastern Himalayan Syntaxis. Metamorphism began at ∼65 Ma, peaked at ∼45 Ma (∼510°C, 0.93 GPa), and exhumation/cooling (∼25°C/Myr) occurred until ∼30 Ma in a subduction-early collision tectonic setting. When the Burma microplate—part of the intra-Tethyan Incertus arc—accreted to SE-Asia, its eastern boundary, the southern continuation of the Indus-Yarlung suture (IYS), was reactivated as the Sagaing fault (SF), which propagated northward into Indian rocks. In the Katha rocks, this strike-slip stage is marked by ∼4°C/Myr exhumation/cooling. Restoring the SF system defines a continental collision-oceanic subduction transition junction, where the IYS bifurcates into the SF at the eastern edge of the Burma microplate and the Jurassic ophiolite-Jadeite belts that include the Incertus-arc suture.
