Abstract

From the Late Paleozoic to the Early Mesozoic, Mongolia and Northeast China have been influenced by the subduction of numerous oceans¹ which have likely modified the lithospheric mantle. The Mesozoic was a time of anomalous widespread extension² across southern and eastern Mongolia, which produced Basin-and-Range type topography in Mongolia and China³. This extension occurred after a major collisional event associated with the closure of the Mongol-Okhotsk Ocean. Accompanying this phase of extension are large abundances of basin-infilling basalts which have had a number of models proposed to explain their genesis.

Examining Mongolian Mesozoic volcanism is crucial for understanding magmatic processes across the Central Asian Orogenic Belt. Yet there has been comparatively little study done on the Mongolian volcanism⁴ compared to neighbouring China, despite the likelihood that the magmatism is linked to shared geological processes. This talk will initially introduce new whole-rock geochemical data for basaltic to intermediate volcanism, including new low-Si and high-Si adakitic lavas, across eastern and southern Mongolia. Some parallels between the volcanism in China and Mongolia will be emphasised.

Focus on how the geochemistry changes with time will be used to assess lithospheric controls. A fascinating story of how a preconditioned subduction-modified lithospheric mantle has been stripped away during the Mesozoic will unfold.

[1] Windley et al., 2010. American Journal of Science. 310 (10), 1250-1293. [2] Meng Q. R. 2003. Tectnophysics. 369(3), 155-174. [3] Graham et al., 2012. Phanerozoic Rift Basins and Sedimentary Basins. 17, 443-461. [4] Dash, Batulzii, et al., 2015. Gondwana Research 27.1 (2015): 281-299.