An in Situ Method of Determining the Pressure Dependence of Phase-Transition Temperatures in the Crust

  1. John G. Heacock
  1. Anthony F. Gangi and
  2. Neal E. Lamping

Published Online: 15 MAR 2013

DOI: 10.1029/GM014p0185

The Structure and Physical Properties of the Earth's Crust

The Structure and Physical Properties of the Earth's Crust

How to Cite

Gangi, A. F. and Lamping, N. E. (1971) An in Situ Method of Determining the Pressure Dependence of Phase-Transition Temperatures in the Crust, in The Structure and Physical Properties of the Earth's Crust (ed J. G. Heacock), American Geophysical Union, Washington D. C.. doi: 10.1029/GM014p0185

Author Information

  1. Department of Geophysics, Texas A&m University, College Station, Texas 77843

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1971

ISBN Information

Print ISBN: 9780875900148

Online ISBN: 9781118664049

SEARCH

Keywords:

  • Basalt-eclogite transition;
  • Central United States model;
  • Clausius-Clapeyron equation;
  • Mohorovicic discontinuity;
  • Monte Carlo method;
  • Phase-transition temperatures;
  • Solid-solid phase transition

Summary

A multidisciplinary geophysical and geological approach has been undertaken to determine the temperatures and pressures at various velocity discontinuities (in particular, the Mohorovicic discontinuity, or Moho) in the earth's crust. One purpose of the investigation is to determine whether the Moho is the interface between two isochemical solid phases, such as basalt and eclogite. If this condition holds, the temperatures and pressures at the Moho would be linearly related as expressed by the Clausius-Clapeyron equation. Three different radioactive heat production models are used to calculate the temperatures at the Moho. An empirical relationship betwe.en surface heat flow and radioactive heat production provides a constraint on the calculated temperature values. The pressure is determined by using the thicknesses and densities determined from seismic data. An empirical velocitydensity relationship is used to obtain the density from the measured seismic velocities. These crustal layer densities and thicknesses are constrained by the requirement that they be consistent with the measured gravity values. A modified Monte Carlo method is used to determine the variances in the determined temperatures and pressures caused by the variances in the values of the parameters used in the calculations. The area chosen as the test site for determining the Moho temperatures and pressures is the central United States because it is expected that a one-dimensional, steady-state thermal and kinetic model will be valid in this tectonically stable area. A calculation for an ideal (or representative) model of the central United States yields temperature and pressure values that are consistent with expected Moho values.