Fingerprinting glass compositions of Fogo Volcano (Cabo Verde): a tool for tephra correlation

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Abstract
Situated in the Cabo Verde Archipelago, Fogo is among the most active oceanic volcanoes in the Atlantic, hosting frequent eruptions some of which were highly explosive and at least one gravitational flank collapse in the last 100 kyr. This study presents new volcanic glass shard geochemical data with high spatial distribution from 54 sites comprising samples from both pre- and post-collapse times. The analyzed glasses comprise basanites, tephrites, and foidites with a subset extending into the phonolite field. The glass compositions complement bulk rock data particularly in the range between 6 and 1 wt.% MgO, thus enabling more detailed inter-dataset comparison. Major and trace element data reveal five geochemical Groups characterized by incompatible element contents partly delineating rock series. Compositional diversity is primarily controlled by fractional crystallization, and to lesser extents by mantle-source heterogeneity and degrees of partial melting. A geochemical framework is established for investigating provenance of ash and volcaniclastics in the Cabo Verde region and beyond by integrating new glass data with published bulk rock and tephra records. We validate the classification scheme through comparison with primary marine tephra deposits, demonstrating robust sample assignment to the observed compositional Groups. The new provenance data go beyond simple attribution to Fogo by resolving distinct compositional Groups, enabling improved discrimination within Fogo-derived material. Group assignment and characterization of differentiation trends provide a useful first-order indication of pre- versus post-collapse affinity. The glass dataset serves as a reference for future provenance and source correlation studies across the Cabo Verde Archipelago.
Funding Information
  • GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel

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