Apologies for multiple postings

Dear colleagues,

we would like to draw your attention to session V42 Geochemical heterogeneities in OIB and MORB sources: implications for melting processes and mantle dynamics at the AGU Fall meeting 2008, and encourage you to submit an abstract before September 10th.

We welcome contributions from the fields of trace element and isotope geochemistry as well as geophysical and numerical modelling incorporating the impact of mantle heterogeneity on mantle melting. 
Invited contributions will be presented by Tim Elliott, Andreas Stracke, John MacIennan and Yaoling Niu. 

Please find more detailed information on the webpage: www.agu.org/meetings/fm08

Best regards,

Christoph Beier
Simon P. Turner
Craig O’Neill
Paul Asimow
Cin-Ty Lee
Vincent Salters

V42 Geochemical heterogeneities in OIB and MORB sources: implications for melting processes and mantle dynamics

It is a given that the mantle sources of mid-ocean ridge and intraplate oceanic volcanoes are heterogeneous on multiple scales, principally as a result of recycling of lithospheric material, though other mechanisms may be significant. Such heterogeneity can be seen rather directly using trace element and volatile species concentrations and in stable and radiogenic isotope ratios. Heterogeneity of sources in major elements is more challenging to describe in detail because of strong modifications by and feedback with melting and fractionation processes. It has been shown that various Ocean Islands and Mid-Ocean Ridges have small scale trace element and radiogenic isotope heterogeneities and also exhibit relatively large variations in their melting dynamics as inferred from U-Th-Ra-Pa disequilibria in young samples; sampling opportunities make ocean island localities best for studying temporal variations, whereas mid-ocean ridges are better suited for studies of spatial variations across a wide range of scales, from individual melt inclusions to interoceanic comparisons. Although geochemical studies have provided clear evidence for such recycled components (including volatiles) in the mantle, the details of how these affect or perhaps even control melting rates and processes remain unclear. How do isotopic heterogeneities at various scales correlate with major element variations and physical parameters such as potential temperature, crustal thickness, seismic velocity, etc.? It is necessary to approach the issue of melting and mantle heterogeneity from both geodynamical and geochemical perspectives. The aim of this session is to explore empirical evidence and conceptual models for the impact of geochemical heterogeneities on mantle melting in both Ocean Island Basalts and Mid-Ocean Ridge Basalts. 

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