Widespread prehistoric volcanic activity across Mongolia and China linked to a common cause

Research by a Leicester-led team of geologists has uncovered new evidence for the causes of widespread volcanic activity in eastern Asia 100 million years ago. Geochemical analysis of igneous rock samples suggests that volcanic activity over a field more than 2,000km wide, from eastern China to central Mongolia, had a common origin.

The team, led by Dr Thomas Sheldrick and Dr Tiffany Barry from our School of Geography, Geology and the Environment, spent several weeks in the Mongolian wilderness collecting and analysing rocks formed from lava that erupted from volcanoes between 133 and 171 million years ago. They were looking in particular at residual isotopes of Argon which provided an accurate dating system.

The results indicate that two ancient oceans, the Mongol-Okhotsk Ocean and the Paleo-Asian Ocean, closed up during the period studied and a tectonic slab below the Pacific Ocean may have broken up, creating a ‘slab graveyard’ underneath eastern Asia. This could explain the mysterious disappearance of a massive reservoir of magma – molten rock that becomes lava when it reaches the surface – which had vanished completely by 107 million years ago.

Dr Sheldrick said: “This is exciting research which suggests that Mesozoic and Cenozoic volcanic activity across East Asia is linked to shared geological processes. This largescale, simultaneous magmatism contradicts existing localised explanations for the volcanism, and instead indicates that magmatism is linked to a widespread event. This is a key finding has not been reported before.

“It is amazing to think that these widespread events, despite being sometimes more than 2,000 km away from each other, are all linked. This is comparable to the distance between London and Gibraltar.”

Drs Sheldrick and Barry collaborated with colleagues from Natural Environment Research Council (NERC) facilities in Nottinghamshire and East Kilbride as well as colleagues from the Open University, Sun Yat-sen University in Guangzhou, China and the Mongolian University of Science and Technology in Ulaan Baatar.

The team’s results, published in the journal Scientific Reports, challenge previous theories about tectonic and magmatic activity in the region, and raise the possibility that the affected area may also extend into eastern Russia.

• ‘Simultaneous and extensive removal of the East Asian lithospheric root’ doi:10.1038/s41598-020-60925-3