Petrogenesis of basanite-phonolite series of an oceanic intraplate volcano: combining experimental data and field observations

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Phonolites are differentiated end-members of alkalic, silica-undersaturated magmas that commonly occur at oceanic and continental intraplate volcanoes. Despite their global occurrence, little is known as to where, how, and why alkalic magmas differentiate to phonolitic melts at some places but not at others. Only few experimental investigations of thermodynamic conditions and mechanisms of phonolite formation have been carried out, but their general applicability is limited due to the large compositional range of phonolites. To better understand the differentiation of alkalic melts, we propose a combination of phase equilibria experiments and detailed field investigations of the Ti-rich basanite-phonolite series of La Palma, Canary Islands. La Palma is well suited for such a study because the geological background is well known and because lavas and xenoliths cover a wide compositional spectrum and are already well investigated. The major goal of the study is to constrain the range of conditions (pressure, temperature, melt and fluid composition) under which evolved rocks from La Palma have formed and can form. Because the proposed project deals with fundamental petrogenetic processes, the expected results would be relevant not only for La Palma but also for other alkalic provinces and magmas from other geotectonic settings.