Understanding the recent history of active volcanoes is crucial to assessing the volcanic hazard for the surrounding areas. In this perspective, a detailed petrochemical characterization of the emplaced products can give useful insights on the ongoing magma processes driving the volcanic system to its current state. This is particularly true for the La Soufrière Volcano of St. Vincent, the most active subaerial volcano in the Lesser Antilles in historical times, with the last eruption of 1979 reaching a VEI of 3 and leading to the evacuation of ~20000 people. However, most of the current knowledges on magma processes at La Soufrière relies on petrological studies performed on the products of the oldest prehistorical activity, covering the ~600-1.3 ka age interval. We here present a petrological characterization (whole-rock, mineral and glass phases geochemistry) for the juvenile products of explosive events occurred during the last 1000 years at La Soufrière: the historical eruptions of 1902/03 and 1718/1812 and the prehistorical eruptions of 1580, 1440 and an older undated event. The products of the prehistorical eruptions are represented by basaltic andesite scoria clasts displaying a quite homogeneous composition in terms of both petrography (with labradorite-bytownite plagioclase, Mg- and Al-poor augite clinopyroxene, Mg-poor orthopyroxene and Ti- magnetite) and whole-rock geochemistry (e.g. SiO 2 = 55.1-56.7 wt.%, MgO = 3.13-3.73 wt.%, wt.%, Cr = 20-30 ppm, Zr = 82-96 ppm). Products of the historical eruptions are generally similar but also include less evolved lithotypes, with 1902/03 scoria clasts reaching basaltic compositions with labradorite-anorthite plagioclase, Mg- and Al-rich diopside clinopyroxene and Mg-olivine, SiO 2 = 50.6-51.2 wt.%, MgO = 7.64-7.91 wt.%, wt.%, Cr = 270-300 ppm, Zr = 60-65 ppm. This speaks in favour of a recent magma renewal which possibly triggered a phase of relatively intense volcanic activity (~80-100 year periodicity), culminating with destructive events causing ~1500 deaths.

A petrological insight on the juvenile products of the last 1000 years of explosive activity at La Soufrière Volcano, St. Vincent (Lesser Antilles)

Lorenzo Fedele
;
Claudio Scarpati;
2018

Abstract

Understanding the recent history of active volcanoes is crucial to assessing the volcanic hazard for the surrounding areas. In this perspective, a detailed petrochemical characterization of the emplaced products can give useful insights on the ongoing magma processes driving the volcanic system to its current state. This is particularly true for the La Soufrière Volcano of St. Vincent, the most active subaerial volcano in the Lesser Antilles in historical times, with the last eruption of 1979 reaching a VEI of 3 and leading to the evacuation of ~20000 people. However, most of the current knowledges on magma processes at La Soufrière relies on petrological studies performed on the products of the oldest prehistorical activity, covering the ~600-1.3 ka age interval. We here present a petrological characterization (whole-rock, mineral and glass phases geochemistry) for the juvenile products of explosive events occurred during the last 1000 years at La Soufrière: the historical eruptions of 1902/03 and 1718/1812 and the prehistorical eruptions of 1580, 1440 and an older undated event. The products of the prehistorical eruptions are represented by basaltic andesite scoria clasts displaying a quite homogeneous composition in terms of both petrography (with labradorite-bytownite plagioclase, Mg- and Al-poor augite clinopyroxene, Mg-poor orthopyroxene and Ti- magnetite) and whole-rock geochemistry (e.g. SiO 2 = 55.1-56.7 wt.%, MgO = 3.13-3.73 wt.%, wt.%, Cr = 20-30 ppm, Zr = 82-96 ppm). Products of the historical eruptions are generally similar but also include less evolved lithotypes, with 1902/03 scoria clasts reaching basaltic compositions with labradorite-anorthite plagioclase, Mg- and Al-rich diopside clinopyroxene and Mg-olivine, SiO 2 = 50.6-51.2 wt.%, MgO = 7.64-7.91 wt.%, wt.%, Cr = 270-300 ppm, Zr = 60-65 ppm. This speaks in favour of a recent magma renewal which possibly triggered a phase of relatively intense volcanic activity (~80-100 year periodicity), culminating with destructive events causing ~1500 deaths.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/723232
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