<b>Short episodes of rare-metal pegmatite formation during </b><b>ephemeral</b><b> thermal pulses across the Himalaya-Tibet Plateau</b>

The mechanisms driving formation of Lithium-Cesium-Tantal (LCT) pegmatite deposits are enigmatic. The Hindu Kush, in the westernmost part of the Himalayan orogen, hosts one of the world's largest lithium-bearing pegmatite deposits. The formation ages (ca. 32-25 Ma), Hf isotopes, and inherited zircon age patterns all match well with those in the south Pamir and Himalaya. Such similarities substantiate an extensive (~3000 km) Oligocene–Early Miocene (ca. 32-18 Ma) rare-metal pegmatite belt across the Himalaya-Tibet Plateau. The high thermobaric ratio of the metamorphic rocks and Ti-in-zircon temperature of two-mica granite suggest that rare-metal pegmatite formation was driven by thermal pulse from asthenosphere upwelling due to Indian slab break-off, causing crustal melting and facilitating fractional crystallization of leucogranite magmas. Our model provides a broader framework for understanding rare-metal pegmatite formation across the Himalaya-Tibet Plateau and highlights the role of mantle thermal pulses in driving rare-metal pegmatite formation in other collisional orogenic systems.