A 6000-km-long Neo-Tethyan arc system with coherent magmatic flare-ups and lulls in South Asia

Abstract

Magmatic arcs typically exhibit non-steady-state evolution with episodic flare-ups and lulls, yet the main drivers remain contentious. Situated in the southwest margin of Southeast Asia, Sumatra records a long-lived magmatic arc that is still poorly constrained in age and tempo. Detrital zircon data from Sumatra delineate major arc magmatic pulses at ca. 212, 102-85, 52, and 22-11 Ma. The mid-Cretaceous to early Eocene zircons mostly yield high positive £`Hf(t) values, indicating magma derivation from juvenile sources and matching well with those of the Gangdese batholiths in the southern Lhasa terrane. These similarities substantiate an extended (~6000 km) Neo-Tethyan arc system from southern Tibet to Sumatra that exhibits concurrent magmatic lulls (ca. 150-105 and 85-65 Ma) and flare-ups (ca. 105-85 and 65-40 Ma). The Late Cretaceous magmatic lull coincided with a period of strong regional deformation and increasingly fast northward drift of India, likely attributable to Neo-Tethyan flat slab subduction. Periodic pulses of Neo-Tethyan arc magmatism most likely correlated with repeated steepening and shallowing of slab dip, rather than India-Eurasia convergence rates. ? 2019 Geological Society of America.