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 Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (11) Citing Articles via Google Scholar Google Scholar Articles by Rossman, G. R. Search for Related Content GeoRef GeoRef Citation

Analytical Methods for Measuring Water in Nominally Anhydrous Minerals

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, 91125-2500, U.S.A., e-mail: grr@gps.caltech.edu

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
Decades of work have shown that trace- to minor-amounts of hydrous components commonly occur in minerals whose chemical formula would be normally written without any hydrogen, namely, the nominally anhydrous minerals (NAMs). When the concentrations of the hydrous components are several tenths of a percent by weight or higher, a variety of analytical methods such as weight loss on heating, X-ray cell parameters, X-ray structure refinement, Karl-Fischer titrations, or even careful electron microprobe analyses can be used to establish their concentrations (e.g., Aines and Rossman 1991). However, for most NAMs, accurate determinations with these common analytical methods prove difficult if not impossible. For this reason, infrared (IR) spectroscopy has become, and remains, the most widely used method to detect and analyze hydrous components (OH or H₂O) in minerals and glasses because it is both highly sensitive and can be done rapidly with a commonly available, modestly priced instrument and at dimensions of just a few tens of micrometers. A change in the electric dipole occurs when the OH bond in either water and hydroxyl ions vibrate. This motion has a resonance coupling with electromagnetic radiation generally in the 3500 cm^–1 region of the infrared spectrum. In addition, bending motions of the water molecule, and overtones and combination of these motions produce absorption in the infrared.

Under favorable conditions, namely a sharp band in a single orientation, just a few nanometers equivalent thickness of a hydroxyl species such as an amphibole can be detected in an otherwise anhydrous mineral such a pyroxene (Skogby et al. 1990). Routinely, detection limits of a few to tens of ppm wt of H₂O in a mineral can be detected and often quantitatively determined. The overtone and combination modes of OH and H₂O behave in predictable fashion in minerals (Rossman . . . [Full Text of this Article]

This article has been cited by other articles:

				E. Libowitzky and A. Beran The Structure of Hydrous Species in Nominally Anhydrous Minerals: Information from Polarized IR Spectroscopy Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 29 - 52. [Full Text] [PDF]

				K. Wright Atomistic Models of OH Defects in Nominally Anhydrous Minerals Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 67 - 83. [Full Text] [PDF]

				E. A. Johnson Water in Nominally Anhydrous Crustal Minerals: Speciation, Concentration, and Geologic Significance Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 117 - 154. [Full Text] [PDF]

				H. Skogby Water in Natural Mantle Minerals I: Pyroxenes Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 155 - 167. [Full Text] [PDF]

				A. Beran and E. Libowitzky Water in Natural Mantle Minerals II: Olivine, Garnet and Accessory Minerals Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 169 - 191. [Full Text] [PDF]

				J. Ingrin and M. Blanchard Diffusion of Hydrogen in Minerals Reviews in Mineralogy and Geochemistry, January 1, 2006; 62(1): 291 - 320. [Full Text] [PDF]