A composite trans-Atlantic heat flow profile between 20°S and 35°S |
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| Authors: | Tien-Chang Lee Richard P Von Herzen |
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| Institution: | 1. Department of Earth Sciences, University of California, Riverside, Calif. 92502 USA;2. Institute of Geophysics and Planetary Physics, University of California, Riverside, Calif. 92502 USA |
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| Abstract: | Sixty new measurements together with published heat flow data in the South Atlantic between 20°S and 35°S latitude have been analyzed. Heat flux is greater through the eastern Mid-Atlantic Ridge flank and basin than their counterparts on the west but the standard deviation or spatial variation is greater on the west, contrary to expectation based on sediment thickness. The variance in the data indicates that this asymmetry in mean heat flux is statistically significant at 87% confidence level. A pair of ridge-flank minima appear in a composite trans-Atlantic profile of heat flux versus sea-floor age, suggesting hydrothermal circulation in the young oceanic crust. The Walvis Ridge has a mean excess heat flux of 28 mW m?2 (0.7 μcal cm?2 sec?1) above the surrounding Cape and Angola Basins, and decreases along the ridge towards the northeast. Consistent with the apparent asymmetric distribution in the South Atlantic, it is also significantly higher than that of the Rio Grande Rise. We hypothesize that the trend and larger mean heat flux of the Walvis Ridge is best explained by a hot-spot origin, perhaps combined with higher radioactivity in the crust. However, the morphologic and heat flow differences between the Walvis Ridge and Rio Grande Rise suggest that these features have different geologic histories. |
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