Other
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.v54a..04d&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #V54A-04
Other
1012 Reactions And Phase Equilibria (3612, 8412), 1025 Composition Of The Mantle, 1037 Magma Genesis And Partial Melting (3619), 1038 Mantle Processes (3621), 1060 Planetary Geochemistry (5405, 5410, 5704, 5709, 6005, 6008)
Scientific paper
This talk will review estimates of water partitioning during subduction as determined by studies of mantle- derived melts. A major uncertainty in the earth's water cycle is the effect of subduction and recycling of hydrated lithosphere on deep mantle water concentrations. The problem with quantifying the variablility of mantle volatiles is that their concentrations are easily modified by shallow crystallization and degassing processes. Careful examination of volatile data from submarine basalts is required to select only those that have not degassed water. For example, even basalts collected deep on a submarine rift zone are not immune because basaltic volcanoes that have breached the sea surface are like champagne bottles; once the cork is popped, the entire bottle goes flat (e.g., Dixon et al., 1991). Once degassing effects have been eliminated, mantle water concentrations show systematic variations. Mantle sources for mid-ocean ridge basalts contain about 120 ppm water, with the most depleted MORB end-member having about 60 ppm. Source regions for mantle plumes are wetter than MORB sources. The wettest mantle is found in plumes dominated by the "common mantle plume component" (FOZO; 700 to 800 ppm H2O, H2O /Ce=210 to 300). Mantle sources for plumes enriched in recycled lithosphere (EM1, EM2, LOMU, and HIMU) have about half as much water (300 to 400 ppm H2O) and lower ratios of water to similarly incompatible elements (H2O/Ce<=100). High H2O /Ce in FOZO plumes cannot be derived from recycled lithosphere; therefore, a significant amount of water must be juvenile, left over from planetary accretion. Thus, dehydration during subduction effectively partitions water into the exosphere (mantle wedge, crust, ocean, atmosphere) resulting in time-integrated depletion of water relative to other incompatible elements in recycled (deeply subducted) lithosphere and sediments and, ultimately, the majority of the mantle. These results are consistent with a global water cycle model (Ruepke et al., 2006) in which the oceans have formed by efficient outgassing of the mantle. Entrainment of hydrated suprasubduction zone mantle (0.025 to ~2 wt% H2O) may lead to water enrichments in the upper ~400 km, as evidenced by seismic tomography. Mantle below this depth is likely to be quite dry (<0.08 wt%), regardless of the existence of high pressure hydrous phases observed in laboratory studies.
No associations
LandOfFree
Water in Mantle Sources of Oceanic Basalts does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Water in Mantle Sources of Oceanic Basalts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Water in Mantle Sources of Oceanic Basalts will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-963361