@misc{10481/108563,
year = {2025},
month = {7},
url = {https://hdl.handle.net/10481/108563},
abstract = {Isolated ocean islands pose challenges for managing volcanic hazards because of their remote locations. Some, such as Ascension Island in the South Atlantic, have diverse hazards associated with variable magmatic compositions and eruptive styles,
as evidenced by past volcanic deposits. In this context, zircon ages and compositions provide insights into the timing and
nature of magma generation, storage, and eruption. Specifically, zircon crystallisation ages record magmatic cyclicity. This
study examines zircon growth in a small ocean island context, focusing on juvenile volcanic pumice-scoria and plutonic clasts
from the only known explosive deposit on island showing evidence of mingling between mafic and felsic magmas. Dating
reveals a U-Th-Pb crystallisation age for the “Mingled Fall” juvenile components of 0.60+0.11/−0.17 Ma (MSWD=0.92).
However, recycling of rocks and crystals from older magmatic events, at~0.9 Ma and~1.3 Ma, is recorded in both volcanic
deposits and plutonic clasts within these. Hafnium (εHf 2.75–13.77) and oxygen (δ18O 4.3–6.54‰) isotopic analyses point,
respectively, to melting of a moderately enriched mantle source and pre-mingling assimilation of hydrothermally altered
crustal rocks. These data support explosive eruption triggered by mingling of mantle-derived mafic magma with rhyolitic
magma from partially melted gabbroic lower crust. Furthermore, varying zircon Ce and Eu anomalies indicate a transition
in the magmatic system redox state from reducing to oxidising as crystallisation progressed. We also highlight the underexploited potential of U-Th-Pb SHRIMP analysis to date zircon in young Quaternary volcanic rocks, providing a valuable tool
for hazard assessment and monitoring.},
organization = {European Union’s Horizon 2020 - Marie Skłodowska-Curie (grant agreement No. 749611)},
organization = {Spanish Ministerio de Ciencia (CGL 2017-84469-P)},
organization = {Japan Society for the Promotion of Science (Postdoctoral fellowship #PE16724)},
organization = {Universidad de Granada / CBUA (Open Access funding)},
publisher = {Springer},
keywords = {Pleistocene},
keywords = {U-Th-Pb dating},
keywords = {Ocean island volcanism},
title = {Zircon ages and compositions record Quaternary magma mingling and plutonic‑volcanic links on Ascension Island, South Atlantic},
doi = {10.1007/s00445-025-01848-7},
author = {Scarrow, Jane Hannah and Chamberlain, Katy J. and Montero, Pilar and Horstwood, Matthew S. A. and Barclay, Jenni},
}