Evolution of a Shallow Volcanic Arc Pluton During Arc Migration: A Tectono‐Thermal Integrated Study of the St. Martin Granodiorites (Northern Lesser Antilles)

Abstract

Along subduction trenches, strain partitioning, vertical motions (of both rocks and surface), and volcanic activity respond to variations in large-scale slab dynamics while accommodating global geodynamical changes (e.g.,

Evolution of the Northern Part of the Lesser Antilles Arc—Geochemical Constraints From St. Barthélemy Island Lavas

“…The extinct Northern Lesser Antilles arc has an early magmatic activity that started at ∼43 Ma during the Eocene and ended at ∼24 Ma during the Latest Oligocene (Legendre et al., 2018; this study). Only few samples from St. Martin Island, located c. 40 km northwest from St. Barthélemy Island, have been dated (Briden et al., 1979; Cornée et al., 2021; Davidson et al., 1993; Nagle et al., 1976; Noury et al., 2021) and provide ages of 24.5–32 Ma. This age range is similar to that provided by the Oligocene samples from St. Barthélemy Island.…”

“…The Lesser Antilles subduction arc is 750 km long and can be schematically separated into: a southern single segment extending from Grenada to Martinique, which splits into two curved segments north of the Martinique Island forming the northern parts of the arc system with an extinct segment to the east (trenchward) and an active segment to the west (landward) (Figure 1). Outcrops of the extinct arc observed in a limited number of small islands with, from north to south, (a) Late Eocene‐Early Oligocene granodiorites in St Martin (Briden et al., 1979; Cornée et al., 2021; Nagle et al., 1976; Noury et al., 2021); (b) Middle Eocene‐Latest Oligocene volcanic complexes in St. Barthélemy (Andreieff et al., 1987; Legendre et al., 2018); (c) Middle Eocene or Oligocene volcanic complexes in western Antigua (Briden et al., 1979; Nagle et al., 1976); (d) Late Oligocene–Early Miocene volcanic complexes in Martinique (Germa et al., 2011); and v‐a Late Eocene dike in Grenada (White et al., 2017).…”

“…Although the difference is subtle, this observation suggests a more depleted Hf-Nd composition for the Early Oligocene lavas, which may be related to a slight mantle input. Phillipon et al (2020a) demonstrated a switch from a compressive to an extensive tectonic regime in the Lesser Antilles forearc by the end of the Eocene, exemplified by sealed thrusts, change in stress direction (Legendre et al, 2018), intra-arc rifting with the opening of the Kalinago basin (Cornée et al, 2021), opening of V-shaped basins in the forearc (Boucard et al, 2021), and a regional forearc uplift of St. Martin Island plutons and carbonate platforms (Cornée et al, 2021;Noury et al, 2021). We propose that the extensive tectonic regime imposed in the arc-forearc area during the Early Oligocene may have favored a slightly higher mantle input at that time.…”

An Unusually Warm Upper‐Crust in the Late Paleozoic North China Continental Arc: Implications for the Thermal Modification of the Giant Bayan Obo REE Deposit

“…Our previous thermochronometric results for basement rocks and arc plutons exhumed from the mid-to upper-crust (18.7-13.8 km) across the middle part of the NCA indicate that during the late Paleozoic, the mid-to upper-crust of the arc was warm with average paleogeothermal gradients of 37.0-44.5°C/km and the mid-to upper-crust beneath the retroarc foreland to the south of the arc was cold with relatively low paleogeothermal gradients of <21.5°C/km (S. H. Zhang et al, 2019). biotite Ar/Ar: 300 ± 50°C) are compiled from Chew and Spikings (2015), Gehrels et al (2003), Hodges (2014), McDougall andHarrision (1999), Nadin et al (2016), Noury et al (2021), andSaleeby et al (2007).…”

Variable element enrichment sources and contributions to volcanic rocks along the Lesser Antilles Island Arc

“…The Lesser Antilles subduction system has been volcanically active for the past 40-50 Ma, as old Atlantic Ocean crust subducts beneath the Caribbean plate (Westercamp 1988; Figure 1A). The geometry and location of the subduction zone has changed substantially over time, as the Lesser Antilles have been the focus of volcanism over much of the past 40 Ma (Nagle et al, 1976;Brown et al, 1977;Briden et al, 1979;Hawkesworth and Powell 1980;Wadge and Shepard 1984;Legendre et al, 2018;Noury et al, 2021). Volcanism was restricted to the present Limestone Caribbees and the islands south of 15 °N (Nagle et al, 1976) until ~20 Ma, when volcanism stopped in the northern part of the arc.…”