A petrogenetic approach on the St. Martin/Maarten granitoids (Lesser Antilles Arc) and associated mantle processes
- 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, https://doi.org/10.5194/egusphere-egu24-11601, 2024.
