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Experimental Evidence of Ca Segregation to Antiphase Boundaries in Pigeonite

Published online by Cambridge University Press:  02 July 2020

KT Moore
Affiliation:
Dept. of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, 21218, U.S.A.
DR Veblen
Affiliation:
Dept. of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, 21218, U.S.A.
JM Howe
Affiliation:
Dept. of Material Science and Engineering, University of Virginia, Charlottesville, VA, 22903, U.S.A.
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Abstract

For over 30 years geologists have been trying to better understand antiphase domains (APD) and boundaries (APB) in pigeonite in hopes of using them as markers for the thermal history of the rocks in which they are found. The ability to know the cooling history of igneous rocks is of great interest to geologists and pigeonite has received special attention on this matter because it has exsolution (precipitation) and antiphase domains (APD), both of which can be used as possible thermal markers. APDs in pigeonite arise because of the C2/c → P21/c transformation that occurs upon cooling. When multiple APDs nucleate, grow, and impinge upon one another, they are either in registry or have a translational discrepancy of ½(a+b). The size of the APDs can be used as a qualitative marker of cooling rates, since slowly cooled pigeonites favor large APDs and rapidly cooled pigeonites favor small APDs.

Type
Quantitative Transmission Electron Microscopy of Interfaces (Organized by M. Rüehle, Y. Zhu and U. Dahmen)
Copyright
Copyright © Microscopy Society of America 2001

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References

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5.The authors are grateful for support from NSF grant EAR-0073955 to David R. Veblen and from NSF grant DMR-9908855 to James M. Howe.Google Scholar