Quantitative
polarized infrared analysis of
trace OH in populations of randomly oriented mineral grains
Paul D.
Asimow1,
Leo C. Stein, Jed
L. Mosenfelder, George R. Rossman
Division
of Geological and Planetary Sciences
California Institute of Technology, M/C 170-25, Pasadena, CA
91125-2500, USA.
1Corresponding
author, E-mail: asimow @
gps.caltech.edu
ABSTRACT
Use of infrared spectroscopy as an
accurate, quantitative method to measure concentrations of hydrous species in
minerals requires consideration of the interactions of anisotropic crystals
with infrared light. Ensuring that contributions are identified from species at
all orientations in the crystal requires combining three measurements, taken
with the electric field polarized along three mutually perpendicular
directions. This is typically accomplished by determining the orientation of a
crystal in advance and then sectioning it perpendicular to its principal axes.
In many instances, however, natural or experimental samples are not suitable
for such handling. Here we demonstrate a method that instead uses at least
three randomly sectioned grains, considered to be multiple samples of a homogeneous
population. We explain the theory whereby (1) the orientations of the
polarization vectors of measurements taken on these grains are determined by
comparison to oriented standards of the same mineral, and (2) the
principal-axis spectra of the sample are synthesized from the randomly oriented
spectra. By comparison to complementary electron backscatter diffraction (EBSD)
data, we demonstrate that determination of orientations using the silicate
overtone bands in Fourier-Transform infrared (FTIR) spectra is accurate and
precise, with typical angular errors of 6°. We show that this precision is
sufficient for the synthetic principal-axis spectra to be essentially
indistinguishable from X-ray oriented standard spectra. We demonstrate the
application of this technique to determining the OH concentrations in a
population of hydrated olivine grains recovered from a high-pressure,
high-temperature multi-anvil experiment.
Software
Click on
the blue ball to download the
software. Get documentation and examples below.
| Files
for PC's |
File |
Version
/ date |
|
C Source Code |
|
|
| dpythag.c
|
 |
v1.0 /
18-January-2005 |
| dsvbksb.c
|
|
v1.0 /
18-January-2005 |
| dsvdcmp.c
|
|
v1.0 /
18-January-2005 |
| nrutil.c
|
|
v1.0 /
4-January-2005 |
| nrutil.h
|
|
v1.0 /
18-January-2005 |
| pbg.c
|
|
v1.0 /
8-March-2005 |
| pdc.c
|
|
v1.0 /
25-January-2005 |
| recipes.h
|
|
v1.0 /
4-January-2005 |
| sva.c
|
|
v1.0 /
18-January-2005 |
| |
|
|
|
Windows Executable Files |
|
|
| pbg.exe
|
|
v1.0
/ 3-March-2005 |
| pdc.exe
|
|
v1.0
/ 3-March-2005 |
| |
|
|
|
Linux Executable File |
|
|
| pbg
|
|
v1.0 /
8-March-2005 |
| pdc
|
|
v1.0 /
8-March-2005 |
| |
|
|
|
Mac OS |
|
|
| pbg
|
|
v1.0 /
3-March-2005 |
| pdc
|
|
v1.0 /
3-March-2005 |
| |
|
|
|
All
Files Combined (in a zip file) |
|
v1.0 / 16-July-2005 (right click to 'save as') |
|
All Files Combined (in the sitx Stuffed Format) |
|
v1.0 / 15-July-2005 (right click to 'save as') |
| Unix
Files |
File |
Version / Date |
| All
Files Combined (in the tgz zipped format) |
|
v1.0 /
16-July-2005 (right click to 'save as') |
| Documentation,
Examples, and Data Files |
File |
Version
/ Date |
| FTIR_Readme.txt
|
|
v1.0
/ 16-July-2005 |
| grr997.csv
|
|
v1.0
/ 4-February-2005 |
| examplepdcinput.csv
|
|
v1.0 / 7-January-2005 |
| examplepdcinput.decon.csv
|
|
v1.0
/ 9-March-2005 |
| examplespectrumraw.bgs.csv
|
|
v1.0
/ 8-March-2005 |
| examplespectrumraw.csv
|
|
v1.0
/ 8-March-2005 |
| examplesynth.csv
|
|
v1.0
/ 9-March-2005 |
Olivine Spectra
San Carlos, AZ, GRR997, Forsterite
|
Infrared
Transmission (polarized)
|
Data File
|
|
- E||a = 4.76
Å = gamma
|
|
normalized to 1.0 mm
|
|
E||b
= 10.23 Å = alpha
|
|
normalized to 1.0 mm
|
|
E||c
= 5.98 Å = beta
|
|
normalized to 1.0 mm
|
|
Composite data file for program
|
|
all 3 directions in one file
|
|
Raman
(depolarized)
|
|
|
|
(100
face)
|
|
not
ready at this time
|
|
(010) face
|
|
not ready at
this time
|
|
(001)
face
|
|
not
ready at this time
|
Synthetic Mg2SiO4 (forsterite structure) GRR 1017
| Infrared
Transmission (polarized) |
|
|
| E||a = 4.75
Å = gamma |
|
normalized to 1.0 mm |
| E||b
= 10.19 Å = alpha |
|
normalized to 1.0 mm |
| E||c
= 5.98 Å = beta |
|
normalized to 1.0 mm |
| Composite data file for program |
|
all 3 directions in one file |
| Raman
(depolarized) |
|
|
| (100
face) |
|
not
ready at this time |
| (010) face |
|
not ready at
this time |
| (001)
face |
|
not
ready at this time |
Test
of FTIR orientation determinations. (MS Word document)
Partial
Contents
| Grain
# |
Polarization |
EBSD q |
EBSD j |
FTIR
q |
FTIR j |
Error
(°) |
| 1 |
1 |
14.1 |
85.8 |
14.2 |
82.2 |
3.6 |
|
|
2 |
5.9 |
5.9 |
56.5 |
14.5 |
12.2 |
| 2 |
1 |
2.6 |
2.6 |
0.0 |
90.0 |
3.4 |
| |
2 |
87.2 |
87.2 |
90.0 |
80.2 |
5.8 |
last revision: 30-Dec-2006