A NEW RELATIONSHIP BETWEEN SUBSIDENCE RATE AND ZERO-AGE DEPTH

The relationship between subsidence rates and axial depths for zero-age crust has been documented along the mid-ocean ridge systems of three separate oceans. A systematic, linear relationship exists between these two parameters. Shallow zero-age depths are associated with high subsidence rates, and deep zero-age depths are associated with low subsidence rates. The linear subsidence rate versus zero-age depth trends have similar slopes for all three oceans, but their zero-age depth intercepts are offset by a few hundred meters. The scatter of individual subsidence rate and zero-age depth values about each linear trend varies from ocean to ocean and is related to the presence and extent of long-lived, large-scale segmentation of each mid-ocean ridge system. One-dimensional thermal conduction models typically used to quantify subsidence rates cannot account for the observed relationships. A qualitative model that was used previously to explain long-lived tectonic segmentation can also explain the subsidence rate versus zero-age depth relationships and associated variance by assuming the existence of average regional and local mantle temperature variations of approximate to 20 degrees C to approximate to 170 degrees C, respectively.