Subduction fluid transport

ThirlwalJ M. F., Graham A. M., Arculus R. J., Harmon R. S., and Macpherson C. G. (1996) Resolution of the effects of crustal assimilation, sediment subduction and fluid transport in island arc magmas Pb-Sr—Nd—O isotope geochemistry of Grenada, I-esser Antilles. Geochim. Cosmochim. Acta 60, 4785-4810. 

Ono S., Mibe K., and Yoshino T. (2002) Aqueous fluid connectivity in pyrope aggregates water transport into the deep mantle by a subducted oceanic crust without any hydrous minerals. Earth Planet. Sci. Lett. 203, 895-903. 

Philippot P. and Selverstone J. (1991) Trace-element-rich brines in eclogitic veins implications for fluid composition and transport during subduction. Contrib. Mineral. Petrol. 106, 417-430. 

Be, with its 1.5 Ma half-life, adds a longer-lived subduction tracer to the arsenal, one that will decay away in the mantle on a time frame of several million years. The data for the SVZ of S Chile (Figure 6(a)) illustrate the power of the combined approach. The very well correlated U-Th, Ra-Th, and Be/ Be data indicate that uranium, radium, and Be, but not thorium, were transported from slab to mantle to produce the nearly horizontal arrays on the disequilibria diagrams (right panel) and the strong correlations between Be addition and uranium and radium excesses (left panel). Taken at face value, these results suggest that a slab/sediment-derived fluid was added to the... 

Manning C. E. (1997) Coupled reaction and flow in subduction zones silica metasomatism in the mantle wedge. In Fluid Flow and Transport in Rocks Mechanisms and Effects (eds. B. Jamtveit and W. D. Yardley). Chapman and Hall, London, pp. 139-148. 

The role of subducted sediment is particularly well documented for selected, high quality data on arc basalts in which the high Th/La component has Th/La identical to that in the subducting sediment column (Plank, 2003). Very efficient recycling of subducted thorium, together with subducted °Be (present only in surficial sediments), has also been taken as evidence for transport of sediment-derived thorium and beryllium in a partial melt, rather than an aqueous fluid (e.g., Johnson and Plank (1999), Kelemen et al. (1995a) but apparently in disagreement with Morris (see Chapter 2.11) and Schmidt and Poli (see Chapter 3.17). 

Several recent papers have emphasized the presence of substantial Ra excess (over parent °Th) in arc lavas. In the Marianas and Tonga arcs, Ra excess correlates with Ba/La, Ba/Th, and Sr/Th (George et al, 2003 Sigmarsson et al, 2002 Turner et al, 2003, 2000a,b,c, 2001 Turner and Foden, 2001). As a result, Ra excess is linked in these papers to transport of a fluid component from subducted material to arc volcanoes in less than a few thousand years. 

Schurr, B., Asch, G., Rietbrock, A., Trumbull, R., and Haberland, C., 2003. Complex patterns of fluid and melt transport in the central Andean subduction zone revealed by attenuation tomography. Earth Planet. Sci. Lett., 215, 105-19. 

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