PENELOPE Computer Simulations of Secondary Fluorescence in EPMA

Jacque L. Kelly, J Gosses, C. Webber, K. Staffier, J. Fournelle

Research output: Contribution to conferencePresentation

Abstract

Researchers are aware that primary electron interaction volumes in EPMA span a few microns in geologic materials. X-rays can travel farther and result in secondary fluorscence (SF) across phase boundaries. In the past, this SF was rarely corrected. Excess x-rays result in inaccurate measurements, particularly at trace element levels. PENELOPE is a new computer modeling program designed to simulate SF across phase boundaries [1]. PENELOPE modeled several situations in which SF was a probable source of error; in particular the goal was to reproduce experimental SF where possible. Fe in Cu grains (Meteorites): PENELOPE showed that at 10µm away from a pure iron phase there was 1 wt.% apparent Fe due to SF, which decreased to 0.2 wt.% at 30µm. Our data was in excellent agreement with recent experimental work [1], but did not coincide with older experimental work. Al (Trace element) in Quartz: PENELOPE generated Al values are similar (100-200ppm) to data collected by Müller et al. [2] and do not represent a significant SF effect. Ti (Trace element) in Quartz: PENELOPE data suggested 10ppm Ti at 100µm from the phase boundary. No SF was experienced at distances greater than 200µm away from the boundary. The Ti ppm data could reflect SF in quartz and not necessarily Ti ppm levels present in the quartz [2]. Ca from CPX in OPX: The SF error in the 2 pyroxene geothermometry method of Taylor [3] and Brey and Kohler [4] was estimated with PENELOPE for Red Hills samples (New Zealand). The effect was found to be minimal. In 5µm opx exsolution lamella, 0.11 wt% Ca was due to SF. Ca in olivine Fo90, Fe in plagioclase An60: PENELOPE shows that Fo90 at 10µm from An80 will have 0.03 wt.% Ca from SF, and drops to near zero (.001 wt.%) at 100µm. Fe SF in plagioclase from adjacent Fe-rich glass or Fe-bearing phases was studied experimentally [5, 6]. PENELOPE SF data is slightly greater than, but generally matches, previous work.
Original languageAmerican English
StatePublished - 2005
EventGoldschmidt -
Duration: Jan 1 2005 → …

Conference

ConferenceGoldschmidt
Period01/1/05 → …

Keywords

  • PENELOPE
  • Iron and Copper Meteorites
  • Secondary Fluorescence
  • Trace Elements
  • PENELOPE computer simulations
  • EPMA

DC Disciplines

  • Geology

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