Deciphering the magmatic evolution of the northern lesser antilles Arc: Insights from major-trace element and Pb isotopic analyses of submarine tephra

The Lesser Antilles Arc (LAA), a subduction-driven volcanic system, exhibits pronounced geochemical and isotopic variations. Montserrat and Guadeloupe serve as key locations for elucidating magmatic processes in the northern LAA region. This study integrates marine tephra records from IODP Expedition 340 borehole U1396A with terrestrial volcanic data to reconstruct the magmatic evolution of the northern LAA over an extended timescale (∼4.5 Ma to present). Through grain morphology analysis, Pb isotopes, and major/trace element compositions of whole rocks and melt inclusions, we demonstrate that the Pb isotopic compositions of samples from Montserrat and Guadeloupe are primarily controlled by magmatic source regions rather than crustal contamination. Based on mixing models involving depleted mantle and subducted slab components, Guadeloupe exhibits greater sediment input compared to Montserrat, and such sediment contributions must be added as melt additions to the Guadeloupe magmatic system to account for its elevated Th/Nd ratios (0.36). Although significant differences in sediment contributions exist between Guadeloupe and Montserrat, fluid inputs show no discernible distinction. Furthermore, the contrasting Eu and Sr signatures between Guadeloupe and Montserrat are likely attributable to plagioclase accumulation rather than fundamental differences in magmatic differentiation processes. This study extends the volcanic activity history of the northern Lesser Antilles Arc back to 4.5 million years ago, filling a critical gap in previous studies that were limited to terrestrial volcanic rocks.