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Published October 2007 | public
Journal Article

Insights into mantle melting from graphical analysis of one-component systems


Decompression melting can be approximated as an isentropic (that is, reversible adiabatic) process. In such a process, specific entropy (S) and pressure (P) are the independent variables and equilibrium is achieved when the specific enthalpy (H) of the system reaches a minimum. We present a largely graphical analysis of decompression melting in one-component systems based on phase equilibria in H-P-S space. Although mantle sources contain more than one component, use of one-component model systems provides insights into several aspects of mantle melting that can be generalized to more complete and complex systems (for example, batch vs. fractional fusion; the influence of pressure-dependent solid-solid reactions on melting; melting of multilithologic mixtures such as peridotite plus eclogite; advection of heat and melting by rising magmas) and places these insights into the visualizable framework of simple phase diagrams.

Additional Information

© 2007 American Journal of Science. This manuscript is an outgrowth of various lectures and classes given by the authors over several years, including especially the Ingerson lecture of the Geochemical Society (1996), a series of Bateman lectures given at Yale (2005), and the Crosby lectures at MIT (2006) by EMS. We are particularly grateful to Marc Hirschmann for his many contributions to the material presented here over the past decade; to Paula Smith for her more recent help and advice; to Peter Reiners for suggesting that we put it together into a manuscript for publication in this journal; and to reviewers John Longhi and S. A. Morse for their helpful suggestions. Finally, EMS wishes to acknowledge Professor J.B. Thompson's influence on his thinking about many of the issues presented in this paper and particularly, as pointed out by S. A. Morse, Professor Thompson's "emphasis on the felicitous choice of thermodynamic variables in petrology, and in choosing the variable to fit the problem" and his use of P-S diagrams in his two remarkable Harvard courses, "Phase equilibrium in mineral systems" and "Metamorphism".

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August 22, 2023
October 18, 2023