X-Ray Laboratory

The X-ray Laboratory contains two major research instruments. The first is a Malvern PANalytical, Inc. Zetium X-ray fluorescence vacuum spectrometer that was installed and calibrated in mid-January 2019. A major step forward with this generation of XRF spectrometers is the 4kW Rh super sharp X-ray tube that maintains its output x-ray intensity over the life of the tube. The sample deck is capable of holding 68 individual samples when fully loaded. The lab also has a Malvern PANalytical, Inc. X’Pert PRO X-ray diffractometer equipped with a 15-position sample changer and a ceramic Cu X-ray tube. Standard phase identification and Rietveld analysis are our forte.  Both instruments are available for contract work. Please contact Dr. Stan Mertzman for details concerning cost per analysis, turnaround time, etc.

The personnel who handle day-to-day operation of the X-ray instrumentation are Dr. Stan Mertzman, the Earl D. Stage and Mary E. Stage Professor of Geosciences, Karen Mertzman, senior lab technician, and Emily Wilson, Research Lab Manager and Technician.

 

XRD and XRF in Brief - More detailed instructions are available if needed.

X-Ray Diffraction

Students and faculty in the Departments of Earth and Environment, Chemistry and Physics use the Malvern PANalytical X’Pert Pro X-ray diffractometer. Examples of student and faculty XRD research include identification of minerals in rocks, soils and lake sediment, characterizing nanoparticles, and the properties of synthetic double chain salts.

X-Ray Fluorescence

Sample preparation for major element analysis

To start, a total volatile determination (% LOI) is made by weighing out ~1 gram of sample to 4 decimal places, placing in a muffle furnace at 950C for 1.5 hours, removing and cooling to room temperature in a desiccator, and re-weighing and noting the weight change. A portion of this anhydrous sample powder (0.4000 +/- 0.0001 grams) is mixed with lithium tetraborate (3.6000 +/- 0.0002 grams), placed in a platinum crucible and heated with a meeker burner until molten. This molten material is swirled and mixed several time over 10-12 minutes and transferred to a platinum casting dish and quenched. This procedure produces a glass disk that is used for XRF analysis including SiO2, TiO2, Al2O3, Fe2O3 Total, MnO, MgO, CaO, Na2O, K2O, and P2O5,

Working curves for each element are determined by analyzing geochemical rock standards prepared exactly as described in the paragraph above. (See Abbey (1983) and Govindaraju (1994) for chemical analyses of the rock standards). Between 50 and 60 data points are gathered for each working curve; various element interferences are also taken into account. Results are calculated and presented as percent oxide.

Ferrous Iron Titration

The amount of ferrous Fe is determined by the titration using a modified Reichen and Fahey (1962) method. XRF determines total iron as Fe2O3.

Preparation for XRF trace element analysis

Trace element analysis is accomplished by weighing out 7.0000 +/- 0.0004 grams of whole rock powder and adding 1.4000 +/- 0.0002 of high purity copolywax powder, mixing for 10 minutes, and pressing the powder into a briquette at 50,000 psi. Data are reported as parts per million (ppm) for Rb, Sr, Y, Zr, V, Ni, Cr, Nb, Ga, Cu, Zn, Co, Ba, U, Th, La, Ce, Sc, and Pb. Working curves for each element are determined by analyzing geochemical rock standards prepared exactly as outlined above, data for which has been synthesized in Abbey (1983) and Govindaraju (1994). Between 50 and 60 data points are gathered for each working curve; various elemental interferences are also taken into account. The Rh Compton peak is utilized for a mass absorption correction for region one elements.

Important

Always keep in mind that the original rock or mineral powder must be crushed so that ALL of the sample passes through a clean 80-mesh sieve screen. Do NOT use Tungsten Carbide grinding vessels if at all possible. Always use alumina or ceramic crushing implements if available.

References

Abbey, S., 1983, Studies in “Standard Samples” of silicate rocks and minerals 1969-1982: Geological Survey of Canada Paper 83-15, pp. 1-114.

Bennett, H. and Oliver, G. 1992, XRF Analysis of Ceramic, Minerals and Allied Materials, John Wiley &Sons, LTD (ISBN 0 471 93457 7 (cloth)) pp. 298.

Boyd, F.R., and Mertzman, S.A., (1987): Composition of structure of the Kaapvaal lithosphere, southern Africa: In Magmatic Processes- Physiochemical Principles, B.O. Mysen, Ed., The Geochemical Society, Special Publication #1, pp. 13-24. (Contains description of XRF methodology).

Govindaraju, K. 1994: Compilation of Working Values and Sample Description for 383 Geochemical standards: Geostandards Newsletter, Vol. 18, Special Issue, pp. 1-58.

Jenkins, R., 1999, X-Ray Fluorescence Spectrometry, 2nd ed., John Wiley & Sons, Inc. (ISBN 0-471-29942-1 (cloth)) 207 pp.

Mertzman, S.A., 2000, K-Ar results from the Southern Oregon- Northern California Cascade Range. Oregon Geology, V. 62, no. 4, pp.99-122.

Reichen, L.E. and Fahey, J.J, 1962, An Improved Method for the Determination of FeO in Rocks and Minerals Including Garnet. U.S. Geological Survey Bulletin 1144B, pp. 1-5.

Waterton, P., Pearson, D. G., Mertzman, S. A., Mertzman, K. R., Kiarsgaard, B.: Komatiites, basalts and dunites: Plumbing system of a Proterozoic greenstone belt (submitted to Journal of Petrology February 2019)

Last Revised April 2019

  • xray lab

Panalytical PW 3040 X-Ray Diffraction Unit (on left) and Panalytical PW 2404 X-ray Fluorescence spectrometer with the PW2540 sample changer (on right).

 

  • zetium sample changer

Zetium sample changer loaded with major element glass disks.