Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Huddlestone-Holmes, C. R. Articles by Ketcham, R. A. Search for Related Content

Getting the inside story: using computed X-ray tomography to study inclusion trails in garnet porphyroblasts

¹ School of Earth Sciences, James Cook University, Townsville, Queensland 4811, Australia
² Department of Geological Sciences, University of Texas, Austin, Texas 78712, U.S.A.

Correspondence: ^* E-mail: cameron.hholmes{at}jcu.edu.au

This study demonstrates how high-resolution X-ray computed tomography can be used to determine the geometry of curved inclusion trails in garnet porphyroblasts. For the first time, the three-dimensional geometry of these features is shown as an animation, a stereo pair, a VRML model, and two-dimensional sections. The spatial resolution of the data in this study, approximately 10 µm, is high enough to resolve inclusions, and finer resolutions are possible. Comparisons of scan imagery with thin section and microprobe data demonstrate that many typical inclusion phases in garnet porphyroblasts can be clearly distinguished, including quartz, ilmenite, and monazite. A sodium metatungstate solution with a density of 1.19 g/cm³ was used for a wedge calibration during scanning, reducing artifacts to a minimum and allowing maximum image contrast. The overall conclusion of this study is that high-resolution X-ray computed tomography is a quick, non-destructive technique that is invaluable in the study of porphyroblast microstructure. The three-dimensional data generated by this technique can be compared with geometries predicted by the varying theoretical models for the formation of curved inclusion trails in garnet porphyroblasts. They can also be analyzed to determine the three-dimensional orientation of curvature axes in individual porphyroblasts, which has not been possible until now.