| Abstract: | Soufriere volcano of St Vincent (<0.6 Ma) is composed of basalts and basaltic andesites, the most mafic of which (mg-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 >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. |
| Genre: | Article |
| ProdID: | 70020077 |
| Citation Author: | Heath, E.; Macdonald, R.; Belkin, H.; Hawkesworth, C.; Sigurdsson, H. |
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| Citation End Page: | 1764 |
| Citation Issue: | 10 |
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| Citation Language: | English |
| Citation Larger Work Title: | Journal of Petrology |
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| Citation Number Of Pages: | 44 |
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| Citation Search Results Text: | Magmagenesis at Soufriere volcano St Vincent, Lesser Antilles Arc; 1998; Article; Journal; Journal of Petrology; Heath, E.; Macdonald, R.; Belkin, H.; Hawkesworth, C.; Sigurdsson, H. |
| Citation Start Page: | 1721 |
| Citation Volume: | 39 |
| Citation Year: | 1998 |
| Type: | citation/reference |
| Text: | Magmagenesis at Soufriere volcano St Vincent, Lesser Antilles Arc; 1998; Article; Journal; Journal of Petrology; Heath, E.; Macdonald, R.; Belkin, H.; Hawkesworth, C.; Sigurdsson, H. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 1998 00:00 -0600 |
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