Earth's atmosphere originated from degassing of the planet's interior over time and release of these gases, some of which are greenhouse intensive (CO2, H2O, and S), continues to this day via igneous processes. Because we have no way to quantify now much of the magmatic volatile load is lost during the eruptive process and how much remains trapped in volcanic rocks. This prevents adequate estimates of gas contributions to greenhouse and other atmospheric gases by submarine volcanism. This research is a pilot study to examine the utility of a novel new experimental and analytical approach for determining magma degassing using noble gases (He, Ne, Ar) and their isotopes and CO2. This research develops new bubble growth/gas fractionation experiments in which synthetic seafloor volcanic glasses will be synthesized at high temperatures and pressures from oxide powders in internally heated pressure vessels. The composition of the glasses will be modified so they are clear so bubbles and bubble size distributions can be measured optically. Glasses will then be remelted and infused with volatiles at high pressure and then exposed to a constant rate of decompression allowing bubbles to form. Glasses and the volatile compositions of the bubbles will be analyzed for He, Ne, Ar, and CO2. Bubble compositions will be analyzed using an excimer laser and FTIR. Results of the work should dramatically improve out understanding of the magma degassing process and rate of volatile input from the mantle to the oceans and atmosphere. Broader impacts of the work include developing new experimental methodology that will increase the infrastructure for science. The project also involved international collaboration with a French scientist and will train a graduate student who will cross-train in the French collaborator's laboratory. The work supports an early career faculty member at an institution in an EPSCoR state.
The interior of the Earth contains a large amount of volatiles, including important greenhouse gases such as carbon dioxide. The transfer of volatiles from the interior into the oceans and atmosphere mostly occurs via volcanism. Constraining the rate of transfer of gases from the mantle to the ocean/atmosphere system is important for understanding both current and past climate change. In addition, understanding the volatile content of the interior the Earth has important implications for the geochemical and geophysical evolution of the Earth's mantle. However, constraining the amount of carbon dioxide released by volcanos is difficult. One approach is to use tracer gases, such as the noble gases. However, measurements of noble gases in volcanic samples have produced unexpected results, and there is disagreements as to how to interpret the data. A major problem is that our knowledge of the mechanisms and rates of noble gas degasing are very limited. The funded project was aimed at developing experimental methods for measuring mechanisms and rates of noble gases degasing. This was done by recreating the high pressure and temperature conditions within volcanic systems, in particular, conditions that produce degassing in magmas. The synthetically degassed samples were then measured for their noble gas compositions. Both the glass and the bubbles within the glass can be analyzed. The results show that the experiments are feasible and that a comprehensive experimental study is possible.
