Abstract
Abstract We have computed and mapped the absolute migration of global mid-ocean ridges in the past 80 m.y. and found that ridges have migrated substantially during that period. Presently, the faster-migrating ridges are Pacific-Antarctic, Central Indian, Southeast Indian, Juan de Fuca, Pacific-Nazca, Antarctic-Nazca and Australia- Antarctic ridges which migrate between 3.3 and 5.5 cm/yr. The slower-migrating ridges are Mid-Atlantic and Southwest Indian ridges which migrate between 0.3 and 2.0 cm/yr. Comparing these results with mantle tomography and geochemistry suggests that slower-migrating ridges have deeper depth of origin than faster-migrating ridges, implying a correlation between migration velocity and depth of origin of ridges. The reconstructed Southwestern Indian ridge (near 44°E) between 60 Ma and Present, lies atop reconstructed Central Indian ridge between 80 and 50 Ma, and the present-day Antarctic-Nazca or (Chile) ridge lies atop the reconstructed East Pacific Rise at 70 Ma. Furthermore, the South Mid Atlantic Ridge and the East Pacific Rise near 10?S appear to have been stationary relative to the mantle for the last 80 m.y. These observations suggest that different portions of the mantle have undergone different recycling history, and may explain the origin of mantle heterogeneities.
Highlights
Over the past two decades, absolute migration of midocean ridges has been correlated with major observable features of the ridges
The reconstructed Southwestern Indian ridge between 60 Ma and Present, lies atop reconstructed Central Indian ridge between 80 and 50 Ma, and the present-day Antarctic-Nazca or (Chile) ridge lies atop the reconstructed East Pacific Rise at 70 Ma
Rapid migration of mid-ocean ridge has been cited as a possible cause of melting asymmetry (Scheirer et al, 1998; Buck, 1999; Evans et al, 1999)
Summary
Over the past two decades, absolute migration of midocean ridges has been correlated with major observable features of the ridges. For example Stein et al (1977) correlated spreading asymmetry with migration rate, and Davis and Karsten (1986) explained asymmetry in seamount abundance by absolute ridge migration. Ridge migration rate is thought to be an important factor that influences the diversity of ridge-crest lavas and the compositional uniformity of ridge-crest basalts (Davis and Karsten, 1986). In plate tectonics mid-ocean ridges are considered to be passive features the motions of which are governed by the interactions and motions of global plates, a property that makes absolute migration of ridges, a potential recorder of global tectonics. Despite its apparent importance, mapping of historical absolute migration of mid-ocean ridges has not previously been defined and done. We attempt to compute and map the absolute migration of global mid-ocean ridges since 80 Ma
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