EGU24-11601, updated on 09 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

A petrogenetic approach on the St. Martin/Maarten granitoids (Lesser Antilles Arc) and associated mantle processes  

Petros Koutsovitis1, Michiel J. van der Meulen2, Tirza van Daalen2, Pavlos Tyrologou3, Nikolaos Koukouzas3, Alkiviadis Sideridis1, Christos Karkalis3, Michel Grégoire4, Petros Petrounias1, Theodoros Ntaflos5, and Konstantinos Lentas6
Petros Koutsovitis et al.
  • 1University of Patras, Department of Geology, Section of Earth Materials, GR-26504 Patras, Greece
  • 2TNO, Geological Survey of the Netherlands, P.O. Box 80015, 2508 TA, Utrecht, the Netherlands
  • 3Centre for Research and Technology, Hellas (CERTH), Egialias 52, Marousi 15125, Attica, Greece
  • 4Géosciences Environnement Toulouse (GET), CNRS, UPS, IRD, CNES, Université de Toulouse, Observatoire Midi Pyrénées (OMP), 14 Av. E. Belin, 31400 Toulouse, France
  • 5University of Vienna, Department of Lithospheric Research, Althanstr. 14, Vienna, Austria
  • 6National Observatory of Athens, Institute of Geodynamics, Lofos Nymfon, Athens 11810, Greece

In St. Martin, the Oligocene granitoids comprise granodiorites, leucotonalites, melatonalites and Qz-monzodiorites. Tonalites are low-K, whereas granodiorites and Qz-monzodiorites are related with calc-alkaline suites. Mineralogical, geochemical and Sr-Nd isotopic data denote that most rocks are I-type calc-alkaline, except for the melatonalites that seemingly resemble peraluminous S-type granitoids. The melatonalites display the lowest Al2O3/TiO2 and highest CaO/Na2O ratios, pointing to high temperature conditions. Various geothermometry applications, which include Ti-in-zircon thermometry reveal high generated temperatures for the melatonalites, exceeding by ~100 °C those calculated for the other granitoids. Regarding the granodiorites (Type-I low REE; Type-II high REE), Type-II are associated with higher temperature conditions by ~70 °C. Zircon saturation thermometry also show higher crystallization temperatures for the melatonalites and Type-II granodiorites. Thermobarometric results elucidated from mineral chemistry and bulk-rock geochemical point to  higher temperature and pressure crystallization conditions for the melatonalites compared to the leucotonalites and granodiorites. The granitoids were affected by extensive differentiation processes; plagioclase preferably fractionated in the Type-I granodiorites; Type-II mainly involved K-feldspar removal. Fluctuation of hydrous and slab-derived fluid fluxes  contributed to magma differentiation as inferred by the Th/Nb and Ba/La ratios, with hydrous-saturated conditions favouring formation of granodiorites rather than leucotonalites.

Melatonalites and Type-II granodiorites likely formed at proto-arc settings, with melting of a fertile mantle during subduction initiation. Melatonalites may have involved magma mixing via interaction of a hotspot plume within the forearc mantle, as denoted by geochemical and geothermometry results. The geochemical features of the Type-II granodiorites likely reflect formation at the early subduction stages, associated with a fertile source.

Reference: Koutsovitis et al. 2024. Granitoids from St. Martin/Maarten Island, Caribbean: Insights on the role of Mantle processes in the Lesser Antilles Arc. Lithos (Under Review).

How to cite: Koutsovitis, P., van der Meulen, M. J., van Daalen, T., Tyrologou, P., Koukouzas, N., Sideridis, A., Karkalis, C., Grégoire, M., Petrounias, P., Ntaflos, T., and Lentas, K.: A petrogenetic approach on the St. Martin/Maarten granitoids (Lesser Antilles Arc) and associated mantle processes  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11601,, 2024.