Origin of the DUPAL anomaly in the Tethyan mantle domain and its geodynamic significance.

Mantle heterogeneity has revealed systematic differences in Pb isotopic compositions between the Indian Ocean-South Atlantic mantle in the Southern Hemisphere and the Pacific Ocean-North Atlantic mantle in the Northern Hemisphere. This large-scale difference in mantle isotopes in the Southern Hemisphere is known as the DUPAL anomaly, but its origin remains controversial. Based on a systematic review of the Nd-Pb isotopic evolution of the Tethyan mantle domain, this study identified the long-term presence of the DUPAL anomaly in this domain since the early Paleozoic, characterized by long-term and high mantle thorium/uranium (Th/U) ratios. By comparing the Nd-Pb isotopic compositions of the Tethyan mantle domain with the Panthalassic-Pacific mantle domain (the Paleo-Asian, Paleo-Pacific, and modern Pacific oceans), it is shown that the mantle initially had low Th/U features due to early Earth crust-mantle differentiation, with the crust having high Th/U ratios. As such, the mantle initially had uniformly low Th/U ratios that were inherited throughout the Panthalassic-Pacific mantle domain. However, the plate tectonics and continental collisions in the Tethyan domain affected its characteristics, leading to the long-term and large-scale DUPAL anomaly. During the opening of and subduction in the Tethys Ocean, Gondwanaland fragmentation and frequent continent-continent collisions led to long-term and extensive crust-mantle interactions and the continuous input of high-Th/U mantle sources, which thus modified the mantle. This process formed not only the unique DUPAL anomaly in the Tethyan mantle domain, but also the Tethyan tectonic domain dominated by continental collisions. Moreover, the high DUPAL anomaly in the Proto- and Paleo-Tethyan mantle domains records the effects of mantle plumes, which might have occurred primarily during the formation of the Proto- and Paleo-Tethys oceans during the early evolution of the Tethyan domain. Therefore, the inherent coupling of mantle domain properties and plate tectonic mechanisms provides important insights for understanding plate tectonics and geodynamic processes in the Tethyan domain. [ABSTRACT FROM AUTHOR]