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Magmatic, metamorphic and metasomatic processes in the root-zone of a long-lasting ocean-island volcano: insight from the Basal Complex of Fuerteventura (Canary Archipelago)

English title Magmatic, metamorphic and metasomatic processes in the root-zone of a long-lasting ocean-island volcano: insight from the Basal Complex of Fuerteventura (Canary Archipelago)
Applicant Bussy François
Number 108033
Funding scheme Project funding (Div. I-III)
Research institution Institut de Minéralogie et Géochimie Université de Lausanne
Institution of higher education University of Lausanne - LA
Main discipline Geochemistry
Start/End 01.05.2005 - 31.07.2007
Approved amount 114'032.00
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Keywords (13)

ocean island; alkali basalt; Fuerteventura; magmatic chamber; gabbro migmatite; contact metamorphism; basalt; migmatite; fluid inclusion; experimental; geochemistry; low; pressure anatexis

Lay Summary (English)

Lead
Lay summary
Direct observation of the hypabyssal root zone of an ocean island volcanois a rare opportunity, which is best illustrated in the uplifted BasalComplex of Fuerteventura island (Canary Archipelago, North AtlanticOcean). This complex records a long-lasting magmatic activity,characterized by the intrusion of numerous magma batches as small plutons,dykes, dyke swarms and ring-dyke complexes of alkali-gabbros, pyroxenites,syenites and carbonatites. The high heat flow generated by the successivemagma pulses feeding the overlying subaerial volcanic centers inducedremarkable metasomatic and contact metamorphic processes, culminating withthe low-pressure partial melting of nepheline normative basalts, anexceptional phenomenon on which this project focuses. We aim to (1)characterize the basalt migmatites within the contact aureoles generatedby pyroxenitic intrusions; (2) specify the mechanisms and P-T conditionsof this low-pressure migmatization, with emphasis on the role and natureof the inferred fluids involved; (3) characterize the incipient meltingprocesses and the topology of segregated melt, (4) undertake experimentalwork on natural rocks to duplicate the observed phenomena.
Low pressure partial melting of undersaturated mafic rocks is a rarelyobserved phenomenon. Fuerteventura offers the opportunity to understandthe mineralogical and geochemical behavior of this type of system and tocharacterize the new melts potentially generated in such environments,allowing their identification in ocean island magmatism in general.
P and T conditions of contact metamorphism and partial melting will berefined by cation exchange mineral geothermobarometry, fluid inclusionsand phase equilibria diagrams based on thermodynamic data. Experimentalwork is planned on natural samples to further constrain partial meltingconditions of the basalts. The nature and source of the fluids involved inthis anatectic process (e.g. meteoritic, metamorphic, magmatic) will becharacterized by oxygen stable isotope chemistry. Special attention willbe given to trace-element partitioning between recrystallized andneoformed minerals and the anatectic melt using laser ablation ICPMS, inorder to evaluate if chemical equilibrium was achieved between leuco- andmelanosomes. Melt topology (i.e. leucosome geometry and connectivity) willbe investigated by X-ray microtomography and related to the local andregional stress-field to decipher melt segregation processes.
Direct link to Lay Summary Last update: 21.02.2013

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Number Title Start Funding scheme
100493 Magmatic, metamorphic and metasomatic processes in the root-zone of a long-lasting ocean-island volcano: insight from the Basal Complex of Fuerteventura (Canary Archipelago) 01.05.2003 Project funding (Div. I-III)

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