The evolution of Kerguelen mantle plume and breakup of eastern Gondwana: New insights from multistage Cretaceous magmatism in the Tethyan Himalaya

Abstract

The relationship between the breakup of eastern Gondwana and Kerguelen mantle plume remains extremely controversial. The crucial conundrum is that when and where the Kerguelen mantle plume initially formed and its evolutionary history are unclear. In this paper, we report the oldest Cretaceous bimodal magmatism (144–140 Ma) associated with the Kerguelen mantle plume from the Comei large igneous province in the Tethyan Himalaya. The mafic rocks are dominated by oceanic island basalt (OIB)-like dykes with occasional normal mid-ocean ridge basalt (N-MORB)-like intrusions, while the felsic rocks show A-type granites affinities. Our results suggest that the > 140 Ma bimodal magmatism was clearly a response to early Kerguelen plume activity, and the Kerguelen plume initially formed underneath the Tethyan Himalaya but not the triple junction between Australia, Antarctica, and Greater India. We argue that the Cretaceous magmatism associated with the Kerguelen plume in the Tethyan Himalaya can be divided into three pulses of ca.141 Ma, ca.132 Ma, and ca.117 Ma, which correspond to vertical underplating, continuous ascent, and a southward migration process, respectively. Moreover, we propose that the multistage OIB-like magmas in the Tethyan Himalaya are mainly the products of interactions between the lower crust and mantle plume, while the contribution of the lithospheric mantle is negligible. This proposal implies that the lithosphere was significantly thinned before ca.141 Ma, and the Kerguelen plume had been incubating underneath the Tethyan Himalaya prior to this. Our findings suggest that the Kerguelen plume may not have been the trigger for the initial breakup of eastern Gondwana, but was complementary to the later complete breakup process. We also innovatively consider that the northward dragging and slab-pull forces caused by the Cretaceous intra-oceanic subduction of the Neo-Tethys Ocean may have played an active role in the evolution of the Kerguelen plume and the breakup of eastern Gondwana.