1. Techniques for Improving Quantitative Analysis of Mineral Glasses
John Donovan
Micro Analytical Facility
CAMCOR
University of Oregon
Eugene, OR
Michael Rowe
Dept. of Geosciences
Oregon State University
Corvallis, OR
(541)
epmalab.uoregon.edu

2. Points of Discussion Volatilization effects Na, K
Si, Al
Instrument drift
Beam drift corrections
Intensity drift corrections
Spectrometer drift
Recipes for Accuracy
Standards
Acquisition Parameters
Re-Peaking
Time vs. intensity
MAN Backgrounds
Standards for Si (silicate vs. glass)
Coordination Peak shifts?
Beam damage?
Charging Effects
Water by difference
Matrix correction effects
Sulfur Peak Shift Mechanisms
Peak Shape Changes?
Peak Position Changes?
Variables (time, current)

3. Standards for Glass Analysis
“Use Glass for Glass”
-but why?

4. Something Is Going On!

5. Standards for Glass Analysis
Satellite Lines? Beta Lines?

7. Standards and Coordination Effects
Subtle peak shift effects for different silicate minerals
Fournelle, 2004, 2005

8. Standards and Beam Damage?

9. Standards and Beam Damage?

10. Or Maybe Charging?
Sub surface Charging Effects
Cazaux, 2004

11. “Volatile” or Migrating Elements
Correct for Na, K loss and Si and Al gain

12. Change in Intensity Over Time
36% loss
0.6% gain

13. Matrix Effects 24H-1-1 No Volatile Correction, No Water By Difference
John Donovan:
Note: SiO2 and Al2O3 values as a function of the corrections
Note: changes in matrix corrections and P/B (MAN)
Matrix Effects
24H-1-1
No Volatile Correction, No Water By Difference
Results in Oxide Weight Percents
ELEM: CaO K2O FeO SiO2 MgO Na2O Al2O3 TiO2 P2O O H2O SUM
AVER:
SDEV:
SERR:
%RSD:
ZCOR:
KRAW:
PKBG:
Gives ~ 4.7% H2O

14. Volatile Correction Matrix Effects
24H-1-1
With Volatile Correction, No Water By Difference
Results in Oxide Weight Percents
ELEM: CaO K2O FeO SiO2 MgO Na2O Al2O3 TiO2 P2O O H2O SUM
AVER:
SDEV:
SERR:
%RSD:
ZCOR:
KRAW:
PKBG:
INT%:
VOL%:
DEV%:
Gives ~ 4% H2O

15. Water By Difference Matrix Effects
24H-1-1
With Volatile Correction, Water By Difference
Results in Oxide Weight Percents
ELEM: CaO K2O FeO SiO2 MgO Na2O Al2O3 TiO2 P2O O H2O SUM
AVER:
SDEV:
SERR:
%RSD:
ZCOR:
KRAW:
PKBG:
INT%:
VOL%:
DEV%:
Gives 3.4% H2O

16. Instrument Effects Beam Drift Corrections Standard Drift Corrections
Sample Tilt (melt inclusions)
Spectrometer Reproducibility

17. Trace Sulfur Accuracy Issues