Planet evolution revealed by fossil gases “entrapped” in the Earth mantle
Some fossil gases of magmatic origin which have remained entrapped in the Earth’s mantle of the volcanic region of Eifel, Germany, seem to carry traces of the evolution of Earth as well as to provide an important contribution to the explanation of the origins of water and other substances that support life. This has been shown in a recent study published in Nature, and carried out by the National Institute of Geophysics and Volcanology (INGV).
The origin of volatile elements found on the Earth – such as hydrogen, water, carbon, nitrogen and noble gases – has always been an important topic for discussion in planetary science, since their current composition does not represent the original composition of the Earth and their origin is still mysterious. However, a considerable step forward in understanding their origin comes from the investigation on some fossil gases which have remained “entrapped” in the Earth’s mantle in the volcanic region of Eifel, Germany, and could explain some important evolutionary processes on our planet. This has been revealed in a study published in Nature, carried out by the National Institute of Geophysics and Volcanology (INGV), Centre National de la Recherche Scientifique (CNRS) and Université de Lorraine.
By analysing the quality of the isotopes of the noble gas xenon in the magmatic gas samples emitted in the volcanic region of Eifel, researchers showed that the light isotopes of this gas were taken to the Earth by asteroidal bodies, while atmospheric xenon seems to have a different origin, which has not been completely identified yet. Hence the idea that at least two distinct sources have contributed to the origin of volatile elements on the Earth, one for the mantle, and one for the atmosphere.
“This study has also shown that the Eifel region volcanism origins from its deep mantle that has remained isolated for most of the Earth’s history, despite the convective processes occurring in the Earth’s mantle. The discovery of the origin of these volatiles, which can be also defined as fossils, helps to better understand the origin of water and other substances which support life on Earth”, explained Antonio Caracausi, the INGV researcher who coordinated the study.
Moreover, the heavy isotopes of the xenon gas taken from the samples of gas of this region show that this gas is very “old” and that its source remained isolated from the rest of the mantle about 4.45 billion years ago. Consequently, in this region, the mantle has been able to preserve the original isotope signal, despite the convective processes.