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6898046 
Journal Article 
Prolonged Partial Melting of Garnet Amphibolite from the Eastern Himalayan Syntaxis: Implications for the Tectonic Evolution of Large Hot Orogens 
Kang, D; Zhang, Z; Palin, RM; Tian, Z; Dong, Xin; , 
2020 
Yes 
Journal of Geophysical Research: Solid Earth
ISSN: 2169-9313
EISSN: 2169-9356 
AMER GEOPHYSICAL UNION 
WASHINGTON 
125 
6 
19119-19119 
English 
WOS:000565927000025 
The Himalayan orogen, which formed due to collision of the Indian and Asian continents during the Early Tertiary, is a prime example of a large, hot collisional orogen. Despite decades of study, the duration of partial melting of migmatitic rocks exposed in the Himalayan orogenic core remains highly controversial. As such, we have performed detailed petrological and geochronological analyses of garnet amphibolite from the eastern Himalayan syntaxis in order to reveal the thermal conditions, tectonometamorphic mechanisms, and timing and duration of anatexis in metabasic rocks that form a major component of the thickened lower crust of the eastern Himalayan orogen. Phase equilibrium modeling and geothermobarometry show that the studied sample underwent high-pressure granulite-facies metamorphism and partial melting at 15-17 kbar and 805-840 degrees C. Dehydration melting of amphibole during prograde metamorphism generated up to 20 vol. % partial melt with a granitic composition, which thus represents a potential source for Himalayan syn- to post-orogenic crustal-derived granites. Zircon U-Pb geochronology shows that the garnet amphibolite witnessed a long-lived anatectic and melt crystallization process lasting more than 30 Myr. Prolonged anatexis from ca. 40 to ca. 20 Ma predates initiation of the extrusion of Himalayan metamorphic core by up to 15 Myr, indicating that the thick and weak crust of the Himalayan-Tibetan orogen must have remained stationary for this length of time, despite the ongoing continental collision. This study thus provides new insight into the tectonic evolution of hot orogens.Plain Language Summary We have conducted petrological and geochronological studies of garnet amphibolite from the eastern segment of Himalayan-Tibetan orogen. Our results show that the rock experienced a prolonged high-pressure and high-temperature metamorphic and partial melting process from ca. 40 to ca. 20 Ma, indicating that the thickened, molten lower crust of the large hot orogen remained stationary for 15 Myr and then extruded toward the surface during ongoing continental collisional orogeny. 
Physical Sciences - Other Topics; p-t path, granulite-facies metamorphism, contrasting eclogite types,; high-pressure metamorphism, namche barwa complex, phase-equilibria,; southern tibet, tethyan himalaya, channel flow, lower crust