Volcanic rocks provide an integrated, multi-scale record of the processes that govern how magmas form. Using both theoretical and analytical tools, this work will document the critical processes that led to the formation of magmas in the Aeolian Islands, Italy. The volcanoes of the Aeolians were chosen as the study sites because they are compositionally diverse and geologically young; they thus represent prime places to study to how and why young volcanoes erupt. In addition to augmenting our understanding of how these magmas form and evolve, this work will also help characterize features of this young magmatic system such as the depth at which the magma bodies reside under the surface of Earth and the volatile content of the magmas prior to eruption. Such data can provide information to volcanologists who explore when and how volcanic eruptions initiate, thereby potentially enhancing volcanic hazard assessment and mitigation.
This work utilizes two approaches. One is application of a phase equilibria model, the development of which was funded by the National Science Foundation, to document the thermodynamics of processes that led to formation of magmas in the Aeolian Islands. Results of computer modeling allow predictions to be made about particular characteristics of the volcanic rocks. Using state-of-the-art analytical tools, these predictions will be tested by collecting geochemical, textural and field data on a selected suite of rocks. Comparison of theoretical expectations and these new data will allow the strengths and weaknesses of the phase equilibria model to be assessed and will also lead to well documented hypotheses about how the Aeolian volcanoes formed. If this marriage of state-of-the-art theoretical and analytical tools is successful, it will impact how scientists approach studying complex magmatic systems by providing a methodology by which source to surface compositional diversity can be understood. Because improvements to the phase equilibria model are an on-going goal, this work will also provide input that will inform model improvements.
Approximately 5 cubic kilometers of transitional to continental crust is added to Earth's inventory each year by the process of plate subduction. When a circa 100 km thick lithospheric plate is returned to the deeper mantle, rocks formerly at the surface are thrust downwards and eventually recycle to the great mantle depths. Without this primary planet-scale recycling process, life as we know it would not exist;indeed, the Earth would be a very different place with a different atmosphere, biosphere and hydrosphere. This recycling process is called subduction. When subduction occurs, rocks that contain 2-5 wt % water are thrust back into the deeper part of the Earth's mantle. As these rocks heat up, eventually the water that is bound in minerals is released by dehydration reactions. The water that is released upon dehydration triggers melting of the mantle above the subducting slab. The phenomena is very much the same as the reason why we put salt (NaCl) on icy roadways: the presence of the second component decreases the temperature at which ice melts rendering a solid block of ice into a slush that can be swept away. The molten rock that forms due to the water input 'trigger' in the mantle rises through the mantle and crust and, in many cases, erupts at the surface. This style of volcanism is called island arc magmatism. The Aeolian island arc system has formed due to the subduction of oceanic lithosphere beneath the Tyrrhenian Sea. We are studying the age of the volcanic rocks expopsed on the islands to better understand their origin and to be able to inform local authorities regarding volcanic hazards. We have found that there have been numerous eruptions in the last 200,000 years. We can also demonstrate the non synchronicity of Marine terraces on the leeward islands of Alicudi and Filicudi. Although previous researchers had proposed that certain Marine terraces on the islands were of the same age, our data on the age of lavas that are intercalated with Marine sediments shows that this is not the case. Finally we are studying the nature and composition of the deep crust beneath the islands by examination of the mineralogy and petrology of cognate and accidental inclusions or xenoliths brought to the surface by ascending magmas. The results of our studies are being prepared as technical p[apers that will appear in peer-reviewed journals of international standards available to anyone at no cost.
