Deciphering variable mantle sources and hydrous inputs to arc magmas in Kamchatka

The chemistry of primitive arc rocks provides a window into compositional variability in the mantle wedge, as well slab-derived inputs to subduction-related magmatism. However, long-term cycling elements between Earth's internal and external reservoirs, key unknown is importance retaining mobile within subduction system, through metasomatism mantle. To address these questions, we have analysed olivine-hosted melt inclusions corresponding bulk from Kamchatka arc. Suites record evidence for entrapment along mixing arrays during assembly diverse parental magma compositions. Systematic variations B/Zr, Nb/Zr, Ce/B, ?11B are also apparent among different eruptive centres studied. These element ratios constrain nature provide ambient heterogeneity variable degrees melting. High Nb/Zr low B/Zr back-arc indicate smaller degree melts, lower inputs, but relatively enriched Similarly, small monogenetic located away main stratocones tend erupt magmas with slab contribution overall melting degrees. Conversely, arc-front compositions reflect greater contributions larger melts more depleted Across-arc (ranging ca. ?6‰ rear-arc Sredinny Ridge +7‰ Central Depression) generally consistent addition an isotopically heavy component MORB composition. individual volcanic (e.g. Bakening volcano) show correlations inclusion other geochemical indicators Cl/K2O, Ce/B) that require distinct batches undergone extents crustal evolution degassing processes. Our results while volatile inventories largely overprinted shallower storage aggregation, incompatible trace B isotope faithfully initial inputs. Furthermore, suggest signals generated sub-arc by protracted earlier phases can be preserved later crust.