Skip to content

Using petrology to constrain the onset and migration of the Lesser Antilles subduction: Insights from zircon and amphibole from Saint Martin

Clothilde Jost 1, Oliver Higgins2, Luca Caricchi1

  • Affiliations: 1Department of Earth Sciences, University of Geneva, Genève, Switzerland; 2School of Earth and Environmental Sciences, University of Saint Andrews, Scotland 

  • Presentation type: Poster

  • Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 254

  • Programme No: 1.1.40

  • Theme 1 > Session 1

Abstract

The island of St Martin is unique owing to its outcrops of both volcanic and plutonic rocks and a conspicuous sequence of volcano-sedimentary deposits, providing a unique archive of the onset of volcanism in the northern portion of the Lesser Antilles. The island of Saint Martin hosts a significant portion of Eocene and Oligocene volcanism missing from the rest of the volcanic arc.  Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry, we have dated and analysed trace elements in zircons from 6 key samples and obtained ages from ~52 to 23.2 Ma, giving us an unprecedented 30 Ma of magmatic evolution. Using an Electron Probe Microanalyzer, we have collected major element concentrations in amphiboles from the same 6 key samples and in gabbroic cumulates found on Saint Martin. We used the thermobarometer and chemometer of Higgins et al. (2021) to trace the evolution of the architecture of the magmatic plumbing system over its entire duration. We find that the system went through changes in the melt crystallization temperature, with increasing and decreasing trends through time. The system's pressure first increased until the middle Eocene and then decreased in the Oligocene. The amphibole thermobarometry results correlate well with zircon geochemistry from Saint Martin, which also suggests similar temperature trends. We will present an interpretative framework linking the temporal evolution of zircon geochemistry and thermobarometric estimates to the geodynamic evolution of the northern portion of the Lesser Antilles.