Apatite incorporates several volatile elements (including S, as SO_4 ^(2-)) and can provide a record of magmatic volatile

evolution. Recent measurements of volatiles in apatite from Apollo sample 14053.241 revealed 300-450 ppm S. Although

many lunar melts have sufficient S for sulfide saturation, the observed S content of lunar apatite is surprising because lunar

samples (especially 14053) are highly reduced (≤ IW) and are thus expected to contain little SO_4 ^(2-). One possibility is that

there are micro-environments in late-stage lunar melts that are more oxidized than one would infer from conditions recorded

by other components of these rocks. Alternatively, it may be that S^(2-) substitutes for F+Cl+OH in lunar apatite: S^(2—)bearing

apatite has been synthesized, but to our knowledge has not been observed in nature

Boyce, J. W.

Eiler, J. M.

Liu, Y.

Ma, C.

Stolper, E.

Taylor, L. A.

Caltech Authors - Main

Goldschmidt Conference Abstracts 
Mineralogical Magazine  www.minersoc.org 
569 
Uranium dynamics in biostimulated 
field-site sediments:  
Spatial distribution and formation of 
non-uraninite U(IV) phases 
MAXIM I. BOYANOV1*, EDWARD J. O’LOUGHLIN1, 
KELLY SKINNER1, BHOOPESH MISHRA1,  
SHELLY D. KELLY2, WEI-MIN WU3, CRAIG CRIDDLE3, 
MARCELLA MUELLER4, TONIA MELHORN4,  
DAVID WATSON4, SCOTT BROOKS4 AND  
KENNETH M. KEMNER1 
1Molecular Environmental Science Group, Biosciences 
Division, Argonne National Laboratory, Argonne, IL 
60439, USA (*email: mboyanov@anl.gov) 
2EXAFS analysis, 719 Crestview Dr., Bolingbrook, IL 60440  
3Department of Civil and Environmental Engineering, 
Stanford University, Stanford, CA 94305-4020  
4Oak Ridge National Laboratory, Oak Ridge, TN 37831 
 
The fate of U released in the environment is determined by 
a complex array of complexation, adsorption, redox, and 
precipitation reactions. Reduction of soluble UVI species to UIV 
by direct or indirect bacterial activity often results in the 
precipitation of UIVO2 (uraninite) and has been explored as an 
immobilization strategy for subsurface U plumes. We will 
present results from a three year experiment in which the 
biogeochemical conditions in U-contaminated groundwater 
and sediments from a field site at Oak Ridge National 
Laboratory (U.S.A.) were allowed to evolve in diffusion 
limited reactors under iron- and sulfate-reducing conditions. 
The reactors were amended with ethanol at the water-sediment 
interface, mimicking the injection of electron donor during in 
situ subsurface remediation by biostimulation. Synchrotron x-
ray absorption spectroscopy (XANES and EXAFS) was used 
to track in situ the spatial distribution, valence state, and 
speciation of U and Fe in the reduction zone propagating into 
the sediment, in parallel with measurements of solution phase 
[SO4], [U], [ethanol], and pH. Results show rapid initial 
reduction of FeIII and UVI in the sediment near the interface, as 
well as redistribution of UVI in the areas ahead of the reduction 
front. Sulfate removal from the solution phase and UVI 
reduction throughout the sediment continued for two years. 
EXAFS spectroscopy demonstrated that UIV in the reduced 
sediment was present as a non-uraninite UIV species, similar to 
the non-uraninite UIV species detected in sediment samples 
collected from the injection wells during field-scale 
biostimulation campaings at Oak Ridge National Laboratory. 
The immobilization of UIV as a non-uraninite species in 
natural settings has important implications for the post-
remediation stability of U plumes. 
 
Sulfur speciation in lunar apatite 
J.W. BOYCE1,2*, C. MA1, J.M. EILER1, Y. LIU3,  
E. STOLPER1 AND L.A. TAYLOR3 
1Division of Geological & Planetary Sciences, Caltech, 
Pasadena, CA 91125 (*jwboyce@alum.mit.edu) 
2Department of Earth & Space Sci., UCLA 
3Department of Earth & Planetary Sci., Univ. of Tennessee 
 
Apatite incorporates several volatile elements (including 
S, as SO42-) and can provide a record of magmatic volatile 
evolution. Recent measurements of volatiles in apatite from 
Apollo sample 14053.241 revealed 300-450 ppm S. Although 
many lunar melts have sufficient S for sulfide saturation, the 
observed S content of lunar apatite is surprising because lunar 
samples (especially 14053) are highly reduced (0 IW) and are 
thus expected to contain little SO42-. One possibility is that 
there are micro-environments in late-stage lunar melts that are 
more oxidized than one would infer from conditions recorded 
by other components of these rocks. Alternatively, it may be 
that S2- substitutes for F+Cl+OH in lunar apatite: S2—bearing 
apatite has been synthesized, but to our knowledge has not 
been observed in nature. 
The K, X-ray wavelength can be used to determine the 
relative amounts of S2- and SO42- in lunar apatite. Analyses 
were conducted at Caltech (JEOL 8200 with a 15 kV, 300nA, 
15µm defocused beam, at 30 s/step, using PET crystals), 
referenced to FeS2, CaSO4, and SO42--rich Durango apatite.  
 
Figure 1: S K, peak position (L-value) for two spectrometers. 
The K, peak of S in 14053 apatite is consistently shifted 
toward sulfide relative to both anhydrite (< = 29-44%) and 
Durango apatite (< = 19-24%; presumably containing all 
sulfur as sulfate) standards. This may indicate the first 
observation of a sulfide component in natural apatite. 
However, large uncertainties and apparent matrix effects 
(offset between anhydrite and Durango apatite) demand more 
data. Nevertheless, taking these data at face value indicates 
that lunar apatite includes both a S2- and SO42- component, in 
sub-equal proportions. The apparent SO42- component in lunar 
apatite may indicate the presence of SO42- in the late-stage 
lunar melt from which this apatite crystallized. 


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Sulfur speciation in lunar apatite

http://authors.library.caltech.edu/39786/1/Eiler_2011p569.pdf

Sulfur speciation in lunar apatite

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