Zircon U-Pb ages and geochemical characteristics of diabase in Nie'erco area, central Tibet: Implication for Neo-Tethyan slab breakoff

This paper is the result of geological survey engineering.

Objective Mantle-derived magmatism generally provided an ideal research object to reveal the geodynamic evolution in the depth. The mafic dikes, which shown intensive distribution in Nie'erco area of central Tibet, are regarded as a key aspect to understanding the regional tectono-magmatic evolution.

Methods In this paper, we report geochronological and geochemical data of the diabases in the Nie'erco area.

Results The zircon U-Pb dating yielded magmatic crystallization ages of (50.8 ±0.6) Ma, indicating the Nie'erco diabases emplacement in the early Eocene. The diabase samples have low SiO₂, high MgO, Al₂O₃, TiO₂ and total alkali (Na₂O+K₂O) contents, similar to alkaline ocean island basalt (OIB). These geochemical features suggest that the studied diabases were generated by partial melting of asthenosphere, with the involvement of continental crustal components.

Conclusions Combined with the post-collisional Linzizong volcanic rocks and OIB-like mafic rocks in southern Tibet, we prefer that the Cenozoic magmatism in Tibet is mainly controlled by the northward subduction of the Neo-Tethyan ocean and the following continent collision between India and Eurasia plates. Our research favor that the Nie'erco diabases were generated in response to the slab breakoff and related upwelling and decompressional melting of sub-slab asthenosphere.