Variations in Subsidence Rates Along Intermediate and Fast Spreading Mid-Ocean Ridges.

摘要

Subsidence near the ridge crest of the intermediate and fast spreading mid-ocean ridges of the Indian and Pacific Oceans is investigated using surface-ship bathymetry and magnetics profiles. The ridge can be divided into discrete sections, apparently bounded by distinct structural features such as major fracture zones, in which bathymetry plotted against crustal age forms a well-defined envelope with a width roughly the amplitude of the local bathymetry. The averaged bathymetry in all of the regions studied follows closely a square root of age subsidence curve which in most regions has a subsidence coefficient in the range of 340-390 m/sq root (M yr). The best fitting subsidence curve, however, never reproduces the amplitude of the axial topographic high. The most notable region displaying unusual behavior is the East Pacific Rise between 9 deg S. Other anomalous areas include the region between the Easter Island hot spot and the Chile Rise triple junction in which the ridge crest is shallow and which is subsiding at rates of about 290 m 1 sq root (M yr), and the region east of the Australia-Antarctic Discordance in which the northern flank is subsiding at 440 m 1 sq root (Myr). This area may also bu subsiding asymmetrically. (Reprints)