Physics
Scientific paper
Apr 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998e%26psl.157..167l&link_type=abstract
Earth and Planetary Science Letters, vol. 157, Issue 3-4, pp.167-181
Physics
13
Mantle, Mid-Ocean Ridges, U-238/Th-230, Mid-Atlantic Ridge, Convection
Scientific paper
Uranium series disequilibria have been used to study the physical melting regime along a section of the southern Mid-Atlantic Ridge where the largest mantle Bouguer anomaly yet observed on ridges exists. Zero age excesses for and are age constrained by the presence of measured disequilibria. By this criterion, 7 out of 15 samples are younger than 8000 years. Zero age range between 1.06 and 1.25 while zero age range between 1.77 and 3.57. Concentrations of Th range from 100 to 866 ppb and strongly correlate with . The U-series data differentiate the segment with the large gravity anomaly from the surrounding segments. Specifically, this segment shows combined 231 Pa and 230 Th systematics unlike any observed in MORB thus far, having exceptionally low zero-age 231 Pa excesses. The U-series data can be modeled using upwelling rates similar to the half-spreading rate of this area of ridge. The disequilibria systematics for the anomalous segment 4 possibly suggest a solid upwelling rate that is a factor of two higher than the adjacent segments. The similarity between melting at segment 4 and at ocean islands is noted.
Gill John J.
Hanan Barry B.
Lundstrom Craig
Williams Quentin
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