Mathematics – Logic
Scientific paper
Aug 1979
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1979e%26psl..44..239d&link_type=abstract
Earth and Planetary Science Letters, Volume 44, Issue 2, p. 239-246.
Mathematics
Logic
24
Scientific paper
The temperature structure of a subduction zone during subduction of an oceanic spreading ridge has been calculated by a finite-difference procedure. The plates preceding and following the ridge crest into the trench had convergence rates of 90 and 20 mm/yr, respectively, corresponding to a spreading half-rate for the ridge of 35 mm/yr and to the velocity balance for a simple three-plate model of ridge subduction. Abrupt temperature increases in the range 50-500°C occur at shallow locations (<=35 km) in the outer 40 km of the arc-trench gap within a few million years of the time that the ridge crest enters the trench. Geological manifestations of these changes could include anomalous near-trench magmatism (gabbroic or granitic), termination of high-pressure metamorphism, enhancement of low-pressure metamorphism, and generation of hydrocarbons. Along the slab-wedge interface the depth of dehydration of hydrous phases in the subducted oceanic crust rapidly migrates upward as the ridge approaches. Consequently, substantial volumes of water may be released at depths of 50-75 km just before the ridge crest is subducted, and relatively shallow dehydration (<100 km) may continue for 20-30 m.y., in contrast to the depth range of 95-135 km during the preceding interval of steady-state subduction. If water release at these greater depths is a requisite for normal arc magmatism, the shallowing of the dehydration front could produce a decrease or hiatus in this magmatism.
Anderson Roger N.
Delong Stephen E.
Schwarz W. M.
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