Relation between alkalic volcanism and slab-window formation

• Main Authors: Hole, M.J., Rogers, G., Saunders, A.D., Storey, M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Geological Society of America 1991
• Subjects: Antarctic; The Antarctic; Antarctic Peninsula; Pacific; Antarc*; Ocean Island
• Online Access: http://nora.nerc.ac.uk/id/eprint/520001/; https://doi.org/10.1130/0091-7613(1991)019<0657:RBAVAS>2.3.CO;2

Ridge crest-trench interactions along continental destructive plate margins may result in the development of slab-free windows beneath the continental margin. Slab windows were generated at various locations along the Pacific margin of the Americas and the Antarctic Peninsula during the past 70 m.y. Slab-window formation is temporally and spatially associated with mafic, alkalic volcanism. Lavas erupted above the loci of slab windows are geochemically indistinguishable from some ocean-island, plume-related basalts. However, generation of slab-window basalts from deep-seated mantle plumes requires the fortuitous initiation of plume activity following cessation of subduction. Asthenospheric upwelling and associated decompressional melting following slab-window formation are probably promoted by removal of subducted oceanic lithosphere from beneath the continental margin following the cessation of subduction. Major lithospheric extension is not a prerequisite for alkalic volcanism in this case. The close association of subduction-related volcanism and within-plate alkalic volcanism within the geologic record may also be explained by this mechanism.