R. Macdonald H. Belkin C. Hawkesworth Haraldur Sigurdsson E. Heath 1998 <p class="chapter-para">Soufriere volcano of St Vincent (&lt;0.6 Ma) is composed of basalts and basaltic andesites, the most mafic of which (<i>mg</i>-number 75) may be representative of the parental magmas of the calc-alkaline suites of the Lesser Antilles arc. Parental, possibly primary, magmas at Soufriere had MgO ∼12.5 wt % and were probably nepheline-normative. They last equilibrated with mantle at ∼17 kbar pressure, at temperatures of around 1130°C and f(O₂) exceeding FMQ (fayalite–magnetite–quartz) + 1. They fractionated, along several liquid lines of descent, through to basaltic andesites and rarer andesites over a range of crustal pressures (5–10 kbar) and temperatures (1000–1100°C), separating initially olivine + Cr-spinel + clinopyroxene + plagioclase ± titanomagnetite and then clinopyroxene + plagioclase + titanomagnetite + orthopyroxene assemblages. The total amount of crystallization was some 76 wt %. Amphibole was apparently not a fractionating phase. Sr and Nd isotopic and trace element systematics show no evidence for significant crustal assimilation. There is conflicting evidence as to the pre-eruptive water contents of Soufriere magmas; compositions of clinopyroxene phenocrysts and melt inclusions suggest H₂O &gt;3 wt %, whereas various projections onto phase diagrams are more consistent with relatively anhydrous magmas. Primary magmas at Soufriere were generated by around 15% melting of mid-ocean ridge basalt type mantle sources which had been modified by addition of fluids released from the slab containing contributions from subducted sediments and mafic crust.</p> application/pdf 10.1093/petroj/39.10.1721 en Oxford Academic Magmagenesis at Soufriere volcano St Vincent, Lesser Antilles Arc article