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Science 20 September 1974:
Vol. 185. no. 4156, pp. 1007 - 1011
DOI: 10.1126/science.185.4156.1007
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Articles

Thermal Structure of the Lithosphere: A Petrologic Model

Ian D. MacGregor 1 and Asish R. Basu 1

1 Department of Geology at the University of California, Davis 95616

A preliminary evaluation of the thermal history of the upper mantle as determined by petrologic techniques indicates a general correspondence with theoretically derived models. The petrologic data supply direct information which may be used as an independent calibration of calculated models, serve as a base for evaluating the assumptions of the theoretical approach, and allow more careful selection of the variables describing mantle thermal properties and processes.

Like the theoretical counterpart, the petrological approach indicates that the lithosphere is dominated by two thermal regimes: first, there is a continental regime which cools at rates of the order of 109 years and represents the longterm cooling of the earth. Secondly, superimposed on the continental evolution is the thermal event associated with the formation of an oceanic basin, and which may be thought of as a 108 year convective perturbation on the continental cycle. Of special interest is petrologic evidence for a sudden steepening of the thermal gradients across the lithosphere-asthenosphere boundary not seen in the theoretical models. The unexpected change of slope points to the need for a critical reevaluation of the thermal processes and properties extant in the asthenosphere. The potential of the petrologic contribution has yet to be fully realized. For a start, this article points to an important body of independent evidence critical to our understanding of the earth's thermal history.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Eclogites, Pyroxene Geotherm, and Layered Mantle Convection.
A. R. Basu, A. R. BASU, J. S. ONGLEY, and I. D. MACGREGOR (1986)
Science 233, 1303-1305
   Abstract »    PDF »
Samarium-Neodymium Systematics in Kimberlites and in the Minerals of Garnet Lherzolite Inclusions.
A. R. Basu, A. R. BASU, and M. TATSUMOTO (1979)
Science 205, 398-401
   Abstract »    PDF »
Quantitative limits to palaeogravity.
A. D. STEWART (1977)
Journal of the Geological Society 133, 281-291
   Abstract »    PDF »
Mineral Inclusions in Diamond: Temperature and Pressure of Equilibration.
H. O. A. Meyer, H. O. A. MEYER, and H.-M. TSAI (1976)
Science 191, 849-851
   Abstract »    PDF »
The Lower "Petrologic Geotherm%": A Transitory State.
L. Thomsen (1975)
Science 188, 1130-1131
   PDF »


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