A new relationship between subsidence rate and zero‐age depth

Abstract

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 mande temperature variations of ∼20°C to ∼170°C, respectively.