Provenance study of the Lubok Antu Melange from the Lupar valley, West Sarawak, Borneo: Implications for the closure of eastern Meso-Tethys?

The Lubok Antu Melange is exposed along one of the most important tectonic lineaments, the Lupar Line in Sarawak, Borneo. However, the depositional age of the Lubok Antu Melange is poorly known, and no provenance studies have been conducted so far. Here, we use geochemical, Nd isotopic and detrital zircon U-Pb analyses of samples from the Lubok Antu Melange to constrain provenance and routing in order to better understand Borneo's evolution history. Bulk rock geochemistry reveals that the Lubok Antu Melange was deposited in a continental arc setting related to the Paleo-Pacific subduction margin. New U-Pb detrital zircon data suggest that the maximum depositional age for the Lubok Antu Melange is ca. 115 to 105 Ma. The Lubok Antu Melange with a strongest Jurassic peak is interpreted to be sourced from the Mesozoic continental arc related to the Paleo-Pacific subduction, with contributions from West Borneo, the Malay Peninsula and possibly Sumatra. Compared with the detrital zircon data of the uppermost Cretaceous sedimentary rocks in Sarawak, our study records a change in source in the latest Cretaceous from erosion of basement magmatic rocks of the Paleo-Pacific subduction-related arc that was probably located offshore of what is now South Vietnam and West Borneo, to the Schwaner Mountains arc of SW Borneo. This indicates that the rapid uplift and exhumation of the Schwaner Mountains could have initiated in the latest Cretaceous, which may imply the arrival of SW Borneo and the closure of the eastern Meso-Tethys at that time.

Automated summary

The study of the Lubok Antu Melange reveals that its maximum depositional age is approximately 115 to 105 million years ago, sourced from a Mesozoic continental arc related to the Paleo-Pacific subduction, with possible contributions from West Borneo, the Malay Peninsula, and Sumatra. A change in source is recorded in the late Cretaceous, shifting from erosion of basement magmatic rocks of the Paleo-Pacific subduction-related arc to the Schwaner Mountains arc of SW Borneo. This suggests rapid uplift and exhumation of the Schwaner Mountains in the late Cretaceous, indicating potential geological changes in SW Borneo and the closure of the eastern Meso-Tethys during that time.