Early Miocene uplift of the eastern Himalayan syntaxis: Constraints from U-Pb ages of zircon and rutile

Zircon and rutile U-Pb chronology of rocks from the eastern Himalayan syntaxis (EHS) were carried out to reveal the early uplift history of the EHS. The zircon U-Pb ages of two hornblendite samples are (34.0±0.2) Ma and (31.4±0.4) Ma, respectively. The rutile U-Pb ages are (23.8±0.9) Ma and (21.8±0.5) Ma, respectively. The rutile inclusions in the skarn garnet marble (with garnet as the host mineral) yield a U-Pb age of (19.5±0.7) Ma. Both zircon and rutile in the hornblendite are of magmatic origin, while the rutile inclusions are of metamorphic origin. We interpret the zircon age to represent the time of magma crystallization. While the ages of magmatic and metamorphic rutile represent the time of uplift and cooling after intrusion and crystallization. Comprehensive analyses show that the core of the EHS, surrounded by the Yarlung Tsangpo River, underwent significant uplift in the Early Miocene from 23 Ma to 19 Ma, and the uplift has accelerated since the Pliocene, from 5 Ma to 3 Ma. In addition, it is inferred that the EHS and the central Himalaya share a concurrent uplift history during the closure of Neotethys Ocean and the Early Miocene.