Rapid continental breakup and microcontinent formation in the western Indian Ocean

Abstract

Two of the main factors that determine the nature of a rifted continental margin are rheology and magmatism during extension. Numerical models of lithospheric extension suggest that both factors vary with extension rate; yet until now extension rates of studied margins, as indicated by the rate of initial seafloor spreading, are mostly less than ‐30 mm/yr on each margin. This article presents the first geophysical results from the Seychelles‐Laxmi Ridge conjugate pair of rifted margins which separated at ‐65 mm/yr. The Seychelles, with its spectacular exposures of Precambrian granite, was the earliest scientifically recognized microcontinent and arguably remains the classic example of one [ Wegener, 1924; Matthews and Davies, 1966]. However, it is still unknown whether microcontinents result from plumes, changes in plate‐boundary forces, lithospheric heterogeneity, or a combination of these factors.