Evolution of Magma Differentiation at Piton de la Fournaise Volcano

1. The Geochemical Regimes of Piton de la Fournaise Volcano (Réunion) During the Last 530 000 Years By: F.Albarède, B. Luais, G. Fitton, M.Semet, E. Kaminski, B.G.J. Upton, P.Bachèlery and J.-L. Cheminée Louise von Allemann 14612682 Figure 1:

2. Geological Overview Figure 2: World Map Figure 3: Réunion

3. Figure 4: Piton de la Fournaise I will only focus on the following aspects: • Magma Differentiation • The fractionation of the differentiated magma Figure 5: Piton de la Fournaise

4. Magma Differentiation What we know: • Mean composition of lavas becomes less alkalic with time. • Massive removal of clinopyroxene leads to alkalic lavas • Dominant control of alkalinity is not the source composition • Alkalic and Tholeiitic basalts have same parent magma but fractionation is different Lavas evolve from mildly alkaline to slightly tholeiitic So we know that the differentiation process is driven by the fractionation Figure 6: Total alkali vs silica plot

5. Fractionation FRACTIONATION drives DIFFERENCIATION Low Pressure: Olivine replaces Clinopyroxene driving lavas from alkalic to tholeiitic High Pressure: Removal of Clinopyroxene by Olivine drives lavas from tholeiitic to alkalic Figure 7: Tentative saturation boundary of olivine, clinopyroxene and plagioclase

6. Conclusion • The character of differentiation at Piton de la Fournaise changes form mildly alkalic to mildly tholeiitic over the known lifetime of the volcano = 530 000 years • Mineral fractionation becomes shallower with time as olivine replaces clinopyroxene as the liquidus phase.

7. Recent Eruptions Eruption of the Piton of the Furnace (in top on the right) on April 5, 2007, seen by satellite MODIS of NASA. Appropriations NASA. Figure 10: ABOVE Eruption in 2007 Figure 8: ABOVE Satellite image of Réunion Figure 9: RIGHT Eruption in 2007

8. References • Rapid change of lava composition from 1998 to 2002 at Piton de la Fournaise (Reunion) inferred from Pb isotopes and trace elements: Evidence for variable crustal contamination, Vlastelic I, Staudacher T, Semet M, JOURNAL OF PETROLOGY 46 (1): 79-107 JAN 2005 • How deep do common basaltic magmas form and differentiate, ALBAREDE F, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 97 (B7): 10997-11009 JUL 10 1992 • Photos: Wikipedia (Figure 8) Google Earth (Figure 4) www.fournaise.info/-67k–2May2007 (Figure 9+10) www.volcano.si.edu/world/volcano.cfm?vnum=0303-02= (Figure 2+3+5) From the Paper itself (Figure 6+7)

9. Thank you