Geologists uncover new clues about largest mass extinction ever

A new study could help explain the driving force behind the largest mass extinction in the history of earth, known as the End-Permian Extinction.

Here’s an artist’s idea of what the intense volcanic activity in ancient Siberia might have looked like. Many scientists suggest that effects of this volcanism, which lasted some 60,000 years, may have triggered the extinction of most living species. Image: JOSÉ-LUIS OLIVARES/MIT

The event, also known as the Great Dying, occurred around 250 million years ago when a massive volcanic eruption in what is today the Russian province of Siberia sent nearly 90 percent of all life right into extinction. Geologists call this eruption the Siberian Flood Basalts, and it ran for almost a million years.

“The scale of this extinction was so incredible that scientists have often wondered what made the Siberian Flood Basalts so much more deadly than other similar eruptions,” said Michael Broadley, a postdoctoral researcher at the Centre for Petrographic and Geochemical Research in Vandœuvre-lès-Nancy, France, and lead author of the paper.

The work, which was published in Nature Geoscience, was co-authored by Lawrence (Larry) Taylor, the former director of the Planetary Geosciences Institute at the University of Tennessee, Knoxville. Taylor, whose prolific career at UT spanned 46 years, passed away in September 2017 at age 79.

According to Broadley, “Taylor was instrumental in supplying samples of mantle xenoliths, rock sections of the lithosphere [a section of the planet located between the crust and the mantle] that get captured by the passing magma and erupted to the surface during the volcanic explosion. Taylor also provided advice throughout the study.”

Through the analysis of samples, Broadley and his team tried to determine the composition of the lithosphere. They found that before the Siberian Flood Basalts took place, the Siberian lithosphere was heavily loaded with chlorine, bromine, and iodine, all chemical elements from the halogen group. However, these elements seem to have disappeared after the volcanic eruption.

“We concluded that the large reservoir of halogens that was stored in the Siberian lithosphere was sent into the earth’s atmosphere during the volcanic explosion, effectively destroying the ozone layer at the time and contributing to the mass extinction,” Broadley said.

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From the UNIVERSITY OF TENNESSEE AT KNOXVILLE

The study: https://www.nature.com/articles/s41561-018-0215-4

End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles

Abstract
Magmatic volatile release to the atmosphere can lead to climatic changes and substantial environmental degradation including the production of acid rain, ocean acidification and ozone depletion, potentially resulting in the collapse of the biosphere. The largest recorded mass extinction in Earth’s history occurred at the end of the Permian, coinciding with the emplacement of the Siberian large igneous province, suggesting that large-scale magmatism is a key driver of global environmental change. However, the source and nature of volatiles in the Siberian large igneous province remain contentious. Here we present halogen compositions of sub-continental lithospheric mantle xenoliths emplaced before and after the eruption of the Siberian flood basalts. We show that the Siberian lithosphere is massively enriched in halogens from the infiltration of subducted seawater-derived volatiles and that a considerable amount (up to 70%) of lithospheric halogens are assimilated into the plume and released to the atmosphere during emplacement. Plume–lithosphere interaction is therefore a key process controlling the volatile content of large igneous provinces and thus the extent of environmental crises, leading to mass extinctions during their emplacement.