Analysis
of hydrogen and fluorine in pyroxenes by SIMS
and FTIR:
Part
I. Orthopyroxene
Jed L. Mosenfelder, George R.
Rossman
Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA 91125-2500
Abstract
We measured trace concentrations of
hydrogen (~40-400 ppm H2O) and fluorine
(<1 to 17 ppm) in a suite
of nine orthopyroxenes from varying geological environments, using
secondary
ion mass spectrometry (SIMS) and Fourier transform infrared (FTIR)
spectroscopy.
The hydrogen data are considered with reference to both the manometry
based
calibration of Bell et al. (1995) and the frequency dependent
calibration for
the absorption coefficient derived by Libowitzky and Rossman (1997).
Despite
the fact that our samples exhibit a wide range of IR band structures,
with varying
percentages of absorbance split among low (2600-3350 cm-1)
and high
(3350-3700 cm-1) wavenumber bands, our SIMS data
are fit with the same
precision and virtually the same regression slope regardless of which
IR
calibration is used. We also confirm previous suggestions that the
matrix
effect for SIMS analyses between
orthopyroxene
and olivine is small (≤20%). Anomalously high yields of 16O1H
in some analyses can be attributed to the presence of amphibole
lamellae, and
these analyses must be filtered out with
different criteria than for olivine due to differences in the
geometrical
relationship of host to inclusion. For fluorine, our derived values are
highly
dependent on a number of analytical uncertainties related to the use of
silicate glasses as standards. Regardless of the accuracy of our
calibration,
we see systematic differences in fluorine concentrations in
orthopyroxenes and
olivines depending on their geological context. Samples derived from
crustal
environments and from Colorado Plateau minette diatremes have very low
fluorine
(≤3 ppm), while higher contents (up to 17 ppm in orthopyroxene and 47
ppm in
olivine) can be found in megacrysts from South African kimberlites.
Raw Data: orthopyroxene samples:
IR Spectra (Microsoft Excel files with alpha, beta and gamma
spectra):
All FTIR
spectra in one file
DE 2-1
GK opx A
GRR 1650b
GRR 2334a
JLM14
JLM 46
JLM 50
KBH 1
PRM 54
Appendices: SIMS analyses and calibration data (Microsoft
Excel files):
All
SIMS data in one file
Table 1: SIMS glass
analyses
Table 2: SIMS
orthopyroxene analyses
Table 3: SIMS olivine
analyses
Last updated 30-Jan-2014