The K–Ar Cassignol–Gillot technique applied to western Martinique lavas: A record of Lesser Antilles arc activity from 2 Ma to Mount Pelée volcanism

We present 23 new ages from three volcanic complexes of the Lesser Antilles arc in Martinique Island (French West Indies). These ages obtained with the K–Ar Cassignol–Gillot technique are distributed within the whole Quaternary. They allowed us to reconstruct a detailed history of successive volcanic growth and flank collapse stages. Trois Ilets Volcanism has been active during at least 2 Ma, between 2.35 ± 0.03 Ma and 346 ± 27 ka, with monogenetic volcanoes of basaltic-andesite to andesitic compositions. We here propose that magma mixing, which characterizes this volcanism, could have been initiated between 617 and 346 ka by the activation of arc-parallel and arc-transverse fault systems. Meanwhile, the Carbet complex was active 25 km to the north from 998 ± 14 to 322 ± 6 ka, and was partially destroyed by a flank collapse after 602 ± 10 ka. Together with geochemical data, our ages show that Mount Conil and Mount Pelée volcanoes are parts of the same edifice sharing a single magmatic reservoir. Mount Conil started to emerge before 543 ± 8 ka, and andesites erupted until 127 ± 2 ka, when a flank collapse destroyed the western flank of the edifice, probably triggering the emplacement of Piton Marcel, the last eruption of this first stage. We note that this collapse occurred during the transition from oxygen stages 6 to 5, i.e. during glacial to interglacial change, when eustatic level rapidly increased. After that, and until present, Mount Pelée volcano was built with periods of cone growth intercalated by flank collapse events. We here show that a peak of activity occurred between 550 and 330 ka in western Martinique within the three complexes, which are spaced of 15–25 km. Since 330 ka volcanic activity is limited to the northernmost Mount Conil–Mount Pelée complex. Our data are in agreement with the regional scale observations that the whole recent Lesser Antilles arc was subject to a high volcanic activity since 600 ka, probably linked to an increase in magma production. This permanent establishment of rising magma in regularly spaced batches and tectonically controlled, could explain the individual chemical evolution of each edifice and the different eruptive dynamisms occurring at the same time along the recent arc.

► Mt. Conil was built from 543 to 127 ka while Mt. Pelée is active since 126 kyr.
► The main collapse is dated at 126 ± 2 ka during the δ18O stages 6 to 5 transition.
► Carbet complex was built from 998 ± 14 to 322 ± 6 ka.
► Monogenetic volcanoes of Trois Ilets were active from 2.35 ± 0.03 Ma to 346 ± 27 ka.
► An increase of volcanic activity occurred in Martinique between 600 and 300 ka.