Year: 2000
Type: article
Abstract: The sources of arc-related lavas are commonly modified by \nmetasomatic fluids and/or melts believed to be extracted from \nparts of the subducting slab (e.g., the basaltic crust and/or overlying \nsediments). Evidence from phase equilibria, trace-element \ngeochemistry, and volatile contents arc-related lavas and melt \ninclusions strongly suggest that aqueous fluid derived from \nsubducted basalt is one of these phases. In contrast, the \nproperties and even presence of slab-derived melts in the sub-arc \nmantle are relatively uncertain. Commonly, a role for slab-derived \nmelt is implicated where arc lavas are enriched in \nsediment-born and fluid-insoluble trace elements such as Th \n(e.g., Elliott et al., 1997). However, this evidence is contradicted \nby or fails to address other constraints; for instance: Solvi \nbetween water-rich silicate melts and solute-rich aqueous fluids \n'close' at T-P conditions within the range of those in the slab and \nmantle wedge, suggesting that the dichotomy between 'slab \nfluid' and 'slab melt' may be poorly posed (e.g., Bureau and \nKeppler, 1999); furthermore, thermal models of subduction \nzones suggest that no section of the slab should melt except \nunder special circumstances or through generally unexpected \nphysical effects (Peacock, 1991); finally, experimental and \nempirical constraints on the expected geochemical properties of \nslab fluids and melts are inconsistent with one another in several \nrespects, adding ambiguity to trace-element arguments for or \nagainst the role of slab melt (e.g., Keppler, 1996; Johnson and \nPlank, 1999).
Authors: Eiler, John, Schiano, Pierre
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W195000914