Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377343
Title: The transition from calc-alkaline to potassic volcanism in the Aeolian Islands, southern Italy
Author: Ellam, Robert Mark
ISNI:       0000 0001 3444 3019
Awarding Body: Open University
Current Institution: Open University
Date of Award: 1987
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Abstract:
The geochemical and petrological variations of a range of lavas from the Aeolian Islands volcanic arc, southern Italy are investigated and compared with potassic and ultra-potassic volcanism in the Roman region, and with subduction related basalts from throughout the world. Aeolian Islands lavas range from calc-alkaline basalts and andesites, typified by lavas from the island of Salina, to potassium rich shoshonites and tephrites found at Stromboli and Vulcano. Variations within individual lava series may be largely explained by fractional crystallisation, however the differences between the series are not due to this process and the various series are thought to originate from a range of parental magmas with quite different K2O content. Potassic lavas from Vulcano are characterised by incompatible element ratios typical of subduction related volcanism, and by relatively low 87Sr/86Sr ratios (0.70432-0.70494) similar to those of calc-alkaline lavas from Salina (0.70411-0.70466). In contrast at Stromboli, potassic lavas have relatively high Nb and Ta contents and elevated 87Sr/86Sr (0.7050-0.7075) A three component mixing model is proposed to explain the geochemistry of the Aeolian Islands lavas, this involves mantle wedge, a subduction related component thought to originate by dehydration of the subducting lithosphere, and a component derived from subducted sedimentary material. In addition some heterogeneity of the mantle wedge is indicated by within-plate style trace element enrichment in Stromboli lavas. A similar mixing model is applicable to Roman province lavas and also to subduction related basalts throughout the world. Evidence is presented to suggest that variations in certain incompatible element ratios may result from the involvement of small degree partial melting in the genesis of island arc basalts. However it is clear that such a process is not solely responsible for the anomalous trace element geochemistry of subduction related magmatism.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.377343  DOI:
Keywords: Lava geochemical composition
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