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Active Tectonics and Ultrahigh-Pressure Rocks
When Continents Collide: Geodynamics and Geochemistry of Ultrahigh Pressure Rocks (1998)
  • Ann Blythe, Occidental College

This chapter compares modern exhumation and surface uplift rates with the rates needed for the preservation of ultrahigh pressure (UHP) metamorphic rocks. The highest recorded exhumation rates of ~ 5–10 mm/a are inferred from isotopic and fission-track analyses in the Himalaya, Southern Alps of New Zealand, and D’Entrecasteaux Islands. Similar rates (~7 mm/a) of surface uplift are measured from leveling surveys in Nepal and correlations of marine terraces in the Southern Alps. In Nepal, however, this surface uplift rate is occurring despite erosion, and the true rate of surface uplift is probably considerably higher. In restraining bends along the San Andreas and Denali strike-slip faults in North America, contraction has produced localized regions with relatively high exhumation rates of 1–5 mm/a. A similar surface uplift rate (3–5 mm/a) was obtained from marine terrace correlations in the King Range of northern California. Few modern exhumation rates fall within the range thought to be necessary for the preservation of high-pressure minerals during exhumation (10–100 mm/a), even though, because of a long-term shift in global climate, erosion rates appear to have accelerated during the late Cenozoic. Both the Himalaya and the Southern Alps of New Zealand have high erosion rates that are a direct result of modern precipitation and glaciation patterns; these high rates of erosion may act to enhance exhumation rates. Therefore, because the exhumation rates recorded in these two mountain ranges are the highest modern rates yet recorded, researchers studying UHP rocks are urged to consider the possibility that UHP minerals can be preserved at exhumation rates of <10 mm/a.

Publication Date
Bradley R. Hacker; Juhn G. Liou
Springer Netherlands
Citation Information
Ann Blythe. "Active Tectonics and Ultrahigh-Pressure Rocks" When Continents Collide: Geodynamics and Geochemistry of Ultrahigh Pressure Rocks (1998)
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