Hotspot-related oceanic islands, associated tracks and large igneous provinces: reconstructing the lifetime of the Galápagos mantle plume
Hotspot oceanic islands are the surface expressions of mantle plumes, and provide reference frames for absolute plate reconstructions. In this project I plan to investigate the geochronological and geochemical link between mantle plumes (plume tail) and their associated oceanic products (plume head) with a focus on the Galapagos mantle plume.
Given the increasing recognition of limitations in Ar-Ar age dating of low K - low temperature altered rocks, the U-Pb dating of zircons (due to their resilience to alteration and enrichment in U but not in Pb) currently emerges as the most reliable geochronometer for dating mafic sequences to reconstruct the evolution of mantle plumes and their products. Here I plan to constrain the temporal evolution of the Galápagos plume using the U-Th-Pb in zircon from the Colombian, Caribbean Large Igneous Province (CCLIP) in Central America and the Caribbean (plume head) and from the present submarine hotspot track (plume tail). The objective will be achieved through the use of novel mineral separation techniques and isotopic compositional studies in zircon (U-Pb/Hf/O/REE by SIMS and LA-ICP-MS). Furthermore, I plan to establish a geochemical connectivity of the Galápagos hotspot and submerged seamount chains with accreted oceanic terranes in central America and the Caribbean.
Figure caption: Mantle plume-lithosphere interactions. Simplified sketch showing a rising mantle plume (not to scale), volcanic islands formed over the plume and associated seamounts and Large Igneous Province (LIP) accreted to the continent. The potential location of zircon grains found in these locations is also shown (1, 2 and 3). Zircon 1 crystallizes from basaltic liquids during the life time of an island volcano dating its volcanism. Zircon 2 crystallizes in asthenosphere dating the time of impingement of the plume head at the base of the lithosphere and subsequent magmatic events. Zircon 2 can be dragged in the convective cell resting below the hotspot until it is captured by rising plume magmas in subsequent stages and brought to the surface in volcanic products forming ocean-island volcanoes. Zircons with similar age also occur in associated LIP (Large Igneous Province) and seamount (eroded ocean-island volcanoes) latter accreted to continents. The dynamics of the plume is cyclic, with periods of slow and steady activity interrupted by more active phases. This results in discontinuous magmatic activity and sub-lithospheric circulation patterns that are mostly confined to the uppermost asthenospheric mantle, allowing the preservation of early plume zircons below the drifting lithosphere (Rojas-Agramonte et al., 2022). Zircon 3 represents relic old/inherited zircon grains stored in the Subcontinental Lithospheric Mantle (SCLM) and eventually eroded into the asthenosphere or introduced into the mantle from subducted detrital sediments.
Project partners: Kaj Hoernle (GEOMAR Helmholtz Centre for Ocean Research Kiel), Antonio García-Casco (Granada University), Axel Gerdes (Frankfurt University, Germany), Elis Hoffmann (Freie Universität Berlin, Germany)