Geobarometers clarify crustal doubling



Two University of Chicago geochemists report what they believe is confirming evidence for the crustal-doubling theory. The theory, which could explain the great height of the Himalayas, says that parts of several continents were once buried to a depth of 35 km, the entire thickness of the earth's crust.

Robert C. Newton, professor of geology, and Dexter Perkins III, a postdoctoral research associate, report in an article in the July 15 Nature that they have developed geobarometers, or formulas, that relate the compositions of minerals in rock to the pressure at which the rock crystallized. By determining the pressure, they can calculate the depth at which the rocks were formed. Newton and Perkins base their work on granulite rocks (found in Europe, Asia, North America, and Australia), which contain pyroxenes, plagioclase, garnet, and quartz. Thermodynamic measurements, taken over a period of years by Newton and Ole J. Kleppa, a physical chemist at Chicago, were used to derive the geobarometers.