Granitoids from St. Martin/Maarten Island, Caribbean

Author(s): Petros Koutsovitis, Michiel J. van der Meulen, Tirza van Daalen, Pavlos Tyrologou, Nikolaos Koukouzas, Alkiviadis Sideridis, Christos Karkalis, Michel Grégoire, Petros Petrounias, Theodoros Ntaflos, Konstantinos Lentas
Abstract: The granitoids in St. Martin Island, Lesser Antilles – Caribbean, consist of granodiorites (Type-I low REE; Type-II high REE), leucotonalites, melatonalites and Qz-monzodiorites. These are I-type calc-alkaline granitoids, although classification of the newly identified melatonalites remains enigmatic, likely reflecting magma mixing between different sources for their formation. Geothermometry applications yield high formation temperatures for the melatonalites and the Type-II granodiorites exceeding by ∼100 °C those calculated for the other granitoids. Pressure conditions were relatively high for the melatonalites and granodiorites (∼4.2 and ∼ 4.0 kbar respectively), with the lowest assigned to the leucotonalites (∼1.8 kbar). Magnesiohornblende crystallized at the final crystallization stages (∼740 °C; ∼2.5 km depth), under hydrous (H₂O = ∼3.5 wt%) and highly oxidizing conditions (ΔNNO up to +2.7). Fractional crystallization significantly contributed to the compositional variability of the evolved granitoid lithotypes, with plagioclase being preferably fractionated in the Type-I granodiorites, relative to the Type-II granodiorites that mostly involved K-feldspar removal. Additionally, fluctuation of the hydrous and slab-derived fluid fluxes further promoted granitoid differentiation. Geochemical and Sr-Nd isotopic data reveal restricted sediment contamination of the mantle wedge. Melatonalites and Type-II granodiorites appear to have been formed during the early evolution stages of subduction initiation, whereas leucotonalites represent the late-stage shallow crystallization granitoid phase.
Organisation(s): Department of Geology, Department of Lithospheric Research
External organisation(s): University of Patras, Netherlands Organisation for Applied Scientific Research, Centre for Research and Technology-Hellas, Géosciences Environnement Toulouse, Institute of Geodynamics
Journal: Lithos
Volume: 494-495
ISSN: 0024-4937
DOI: https://doi.org/10.1016/j.lithos.2024.107926
Publication date: 02-2025
Peer reviewed: Yes
Austrian Fields of Science 2012: 105120 Petrology, 105105 Geochemistry
Keywords
ASJC Scopus subject areas: Geology, Geochemistry and Petrology
Portal url: https://ucrisportal.univie.ac.at/en/publications/7cf01f4c-07d5-44e6-a361-092106ad0b5a

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