This study presents a comprehensive geochemical dataset for the most recent volcanics from the Mariana Islands, providing new insights into the timing and nature of fluxes from the subducting slab. The lavas exhibit typical features of island arc volcanics, including large negative niobium (Nb) anomalies and enrichments in alkaline earth elements and lead (e.g., high Ba/La and Pb/Ce ratios). These ratios correlate with a wide range of 238U excesses (0.97-1.56). Geochemical variations between islands indicate two distinct slab additions to the subarc mantle. Agrigan lavas are consistent with a dominant subducted sediment contribution, while Guguan lavas are attributed to a slab-derived aqueous fluid phase. The sedimentary component shows a marked Th enrichment relative to Nb, likely due to melt fractionation and transfer of sedimentary material as a melt phase. The sedimentary contribution dominates the elemental budgets of most lavas, while the aqueous fluid phase contributes to the Guguan lavas. High field strength element ratios (Ta/Nb and Zr/Nb) in Guguan lavas suggest a highly depleted subarc mantle prior to slab additions. The 238U-230Th systematics indicate a time gap of over 350,000 years between sediment and mantle melting, and less than 30,000 years between slab dehydration and eruption. This suggests rapid magma migration and the potential role of aqueous fluid in triggering mantle melting. The study highlights the importance of distinguishing between subducted sediment and crustal contamination in arc volcanics, emphasizing the role of slab-derived fluids and sediments in shaping the geochemical characteristics of Mariana lavas.This study presents a comprehensive geochemical dataset for the most recent volcanics from the Mariana Islands, providing new insights into the timing and nature of fluxes from the subducting slab. The lavas exhibit typical features of island arc volcanics, including large negative niobium (Nb) anomalies and enrichments in alkaline earth elements and lead (e.g., high Ba/La and Pb/Ce ratios). These ratios correlate with a wide range of 238U excesses (0.97-1.56). Geochemical variations between islands indicate two distinct slab additions to the subarc mantle. Agrigan lavas are consistent with a dominant subducted sediment contribution, while Guguan lavas are attributed to a slab-derived aqueous fluid phase. The sedimentary component shows a marked Th enrichment relative to Nb, likely due to melt fractionation and transfer of sedimentary material as a melt phase. The sedimentary contribution dominates the elemental budgets of most lavas, while the aqueous fluid phase contributes to the Guguan lavas. High field strength element ratios (Ta/Nb and Zr/Nb) in Guguan lavas suggest a highly depleted subarc mantle prior to slab additions. The 238U-230Th systematics indicate a time gap of over 350,000 years between sediment and mantle melting, and less than 30,000 years between slab dehydration and eruption. This suggests rapid magma migration and the potential role of aqueous fluid in triggering mantle melting. The study highlights the importance of distinguishing between subducted sediment and crustal contamination in arc volcanics, emphasizing the role of slab-derived fluids and sediments in shaping the geochemical characteristics of Mariana lavas.