Publications and Research
Document Type
Poster
Publication Date
10-9-2022
Abstract
Preliminary field and geochemical investigations were conducted on ash samples from Barbados to chemically characterize and decipher magma chemistry associated with a recent volcanic event. A thick plume of volcanic ash from the La Soufriere Volcano in St Vincent, which erupted on April 9, 2021, caused lower visibility due to ash clouds which engulfed the region for some time. Three authors from the research team visited Barbados during the summer subsequent and completed a reconnaissance investigation on recent ashfall. St Vincent is a small volcanic island in the Eastern Caribbean and lies in the southern part of the Lesser Antilles volcanic arc. Six volcanoes along the arc have erupted since 1900. Magmas that have erupted from the Soufrière of St Vincent during the geologic past (Holocene) include primitive arc basalts and andesites. Collected ash samples were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), Ultra Trace Aqua Regia and whole rock package – X-ray Fluorescence (XRF). Facilities available through the ALS USA Incorporated (Reno, Nevada), an established geochemistry laboratory known for its research quality output, provided access to retrieve both bulk oxide and trace elements data. To achieve better accuracy, samples were pulverized to 75 microns or less. Analyzed samples fell well within the more evolved andesitic compositions (SiO2 = 53- 56 wt. %). A notable concentration of alumina (18%), CaO (9%), and a general decrease in magnesia and soda (each averaging 3%) seem to suggest differentiation of the investigated samples. LOI recorded between less than 1 to 3%. It seems likely that magma evolution was substantially driven by crystal fractionation over time. The results of trace element investigation including Ba, Cu, Mn, Ce, Cr, Ni, Zn, Rb, Sr, V, Y, and Zr, point to an intermediate volcanism constraining the ash composition in Barbados. Utilization of Harker-type binary variation diagrams involving recent ash deposits in Barbados indicate differentiation trend with an evolving nature of the source volcanism. Composition of ash samples record time-integrated enrichment in light REE over heavy REE, and the volcanism in the source area changed character with time and point to an increase in the degree of partial melting and a decrease in crustal involvement with time.
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Comments
This work was presented at the AGU Fall 2022 Meeting in Chicago, Illinois.