Analytical geochemistry has long depended on the availability of robust suites of rock standards with well-characterized compositions. Standard rock powders for wet chemistry and x-ray fluorescence were initially characterized and supplied to the community by the U.S. Geological Survey, which continues to distribute a few dozen standards. Many other rock standards have subsequently been developed by organizations such as the Centre de Recherches Ptrographiques et Gochimiques (CRPG) and Brammer Standard Company, Inc

Dyar, M. Darby

Fassett, Caleb I.

Hanlon, Avery

Lepore, Kate

Mackie, Jason

Treiman, Allan

Wagoner, Carlie

Ytsma, Caroline

NASA Technical Reports Server

STANDARDS FOR ANALYSIS OF Ce, La, Pb, Rb, Se, Sr, Y, AND Zr IN ROCK SAMPLES USING LA-
SER-INDUCED BREAKDOWN SPECTROSCOPY AND X-RAY FLUORESCENCE. Jason Mackie1, M. 
Darby Dyar2, Caroline Ytsma3, Kate Lepore2, Caleb I. Fassett4, Avery Hanlon2, Carlie Wagoner2, and Allan 
Treiman5, 1Dept. of Geology, Amherst College, 220 South Pleasant St., Amherst MA 01003, USA, jmack-
ie17@amherst.edu, 2Dept. of Astronomy, Mount Holyoke College, 50 College St., South Hadley, MA 01075, 3Dept. 
of Chemistry, Smith College, Ford Hall, 100 Green Street, Northampton, MA 01063, 4NASA Marshall Space Flight 
Center, Huntsville, AL 35805, 5Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 77058. 
 
Introduction: Analytical geochemistry has long 
depended on the availability of robust suites of rock 
standards with well-characterized compositions. 
Standard rock powders for wet chemistry and x-ray 
fluorescence were initially characterized and supplied 
to the community by the U.S. Geological Survey, 
which continues to distribute a few dozen standards. 
Many other rock standards have subsequently been 
developed by organizations such as the Centre de Re-
cherches Pétrographiques et Géochimiques (CRPG) 
and Brammer Standard Company, Inc.  
Because these standards are nearly all naturally-
occurring, they represent a range of concentrations in 
terrestrial rocks that may not cover what is present on 
other bodies. For example, Ni is a primary constituent 
of meteorites, and thus may be abundant in ancient 
surface materials of planetary bodies with impact cra-
ters [1-3]. Yet no terrestrial standards come close to 
covering the possible extremes of Ni concentration that 
would result under those conditions. Moreover, chemi-
cal analysis techniques that depend on specific peaks 
for individual elements may have their accuracies re-
duced by the presence of overlapping peaks from other 
elements. To mitigate these issues, standards with var-
ying concentrations of the same dopant are desirable 
for development of calibration curves. Such standards 
are labor-intensive to prepare and expensive to charac-
terize accurately. However, the need for such materials 
will continue to expand as landers and rovers with ge-
ochemical analysis instruments explore new and di-
verse targets in the solar system. 
The current study is part of an ongoing project fo-
cusing on the creation of laboratory calibration stand-
ards for analytical techniques used in the exploration 
of planetary surfaces. Previously, we studied five rock 
matrices doped with Ni, Mn, Zn, Cr, Co and S using 
LIBS spectroscopy [4,5]; these standards are now be-
ing shared with XRF users, x-ray absorption spectros-
copy facilities at Argonne National Laboratory, and the 
Planetary Instrument for X-Ray Lithochemistry (PIXL) 
science team on Mars 2020 for potential use in calibra-
tion. This study adds four matrices and eight additional 
dopants to the suite of existing standards, which now 
numbers over 290 samples. Here, we describe the 
newest additions to our standard suite. 
Geochemical Rationales for Dopant Selection: 
Eight different dopants (Ce, La, Pb, Rb, Se, Sr, Y, and 
Zr) were chosen to complement our previous standards 
discussed above. Elements were chosen to be useful 
indicators of processes in igneous rocks on planetary 
surfaces, in order to maximize their usefulness on mul-
tiple planets (Mars, Venus) as well as some asteroids. 
Their occurrences are well-summarized in [6] and the 
classic references by Mielke [7] and Wedepohl [8]. 
Rationales for choosing them as dopants useful for 
planetary science problems listed below. 
Ce3+,4+ is the most abundant rare earth element 
(REE), and can be used (in igneous rocks) as a general 
proxy for REE abundances and more specifically the 
light REE. Ce is concentrated in minerals such as al-
lanite, apatite, zircon, and sphene [6]. Felsic igneous 
rocks are commonly far richer in Ce (and) REE than 
are basalts (although there are exceptions). 
La3+ is the second-most abundant REE, and can 
serve (like Ce) as a proxy for light REE abundances. 
La (and Ce) is refractory during planetary accretion, so 
that ratios like K/La and Rb/La can indicate planetary 
depletions in volatile elements. La can also serve as a 
monitor of Ce oxidation (3+  4+); because Ce4+ can 
be fractionated away from La3+ during aqueous and 
oxidizing processes. 
Pb2+ is incompatible in igneous processes, and so 
becomes enriched in fractionated (felsic) igneous 
rocks. It can substitute for K in alkali feldspar, also be 
enriched in zircons. On Venus, Pb may be mobile in 
the atmosphere and could be concentrated in so-called 
“heavy metal frost” [9]. 
Rb1+ is a “large ion lithophile” incompatible ele-
ment in igneous systems, like K1+, and is enriched in 
late-stage differentiated magmas. The Rb/K ratio in 
basalts can constrain planetary composition, because 
Rb is more volatile during accretion than K but be-
haves otherwise identically. Rb1+ is strongly adsorbed 
onto clay minerals, which then commonly have higher 
Rb/K ratios than their source igneous rocks. 
Se2- is important on planetary surfaces because it 
substitutes for S in sulfide minerals like pyrite and 
sphalerite. Thus the ratio of Se/S could be valuable in 
assessing surface/atmosphere reactions on Venus. 
Sr2+ substitutes readily for Ca2+ in feldspar but not 
in pyroxene and thus is a good tracer of the presence of 
plagioclase, both in the source magma, and as a frac-
tionating phase. For instance, rocks enriched in plagio-
clase, like anorthosites, have high Sr abundances.  
Y3+ is a useful as a proxy for heavy REEs, with 
https://ntrs.nasa.gov/search.jsp?R=20170002462 2019-08-31T17:18:12+00:00Z
which it shares charge and ion size. Alone, it is an in-
dicator of the degree of igneous fractionation. La/Y is 
a proxy for light REE enrichment, as occurs during 
fractionation & mantle metasomatic processes.  
Zr4+ is incompatible (a high-field-strength element) 
in igneous processes, and so is generally enriched in 
fractionated (felsic) magmas. Zr is refractory in plane-
tary accretion, so that the Na/Zr can indicate planetary 
depletions in the volatile element Na. 
Table 1. Major element concentrations in matrices 
Element Holyoke Mexico Hawaii Sea sand 
SiO2 52.01 75.68 51.56 97.69 
TiO2 1.04 0.14 2.50 0.49 
Al2O3 13.74 11.18 13.98 0.35 
Fe2O3* 13.44 2.80 12.49 1.34 
MgO 5.46 0.02 6.68 0.01 
CaO 9.34 0.17 10.93 0.01 
Na2O 2.82 5.04 2.49 0.01 
K2O 0.71 4.39 0.44 0.12 
P2O5 0.13 0.01 0.24 0.01 
*Fe reported as total Fe in terms of Fe2O3. 
Samples and Methods: This project used four ma- 
trices with very different bulk compositions (Table 1). 
They include: 
1. Weathered basalt from Holyoke, MA that is 
part of the Lower Jurassic basalt in the Newark 
Supergroup, Massachusetts; 
2. Rhyolitic volcanic glass from Mexico; locality 
unknown, but likely from Tequila Volcano; 
3. Hawaiian basalt collected from Kīlauea by Tim 
Orr (USGS, HVO); and  
4. Sea sand purchased from Fisher Scientific.  
For dopants, we used reagent-grade chemicals in the 
form of CeO2, La2O3, PbO, RbCl, SeO2, SrO, Y2O3, 
and ZrO2. Rock powders were shatterboxed to grain 
sizes <25 m prior to weighing into mixtures. 
Preparation of doped samples used a protocol es-
tablished for creation of x-ray fluorescence standards. 
Exactly 10.000 g of each dopant oxide or chloride (in-
dividually) were shatterboxed with 90.000 g of each 
powdered matrix, each with 10 wt.% dopant (Figure 
1). Those powders were then diluted with additional 
aliquots of matrix to create mixtures of approximately 
10, 1, 0.5, and 0.1 wt.% and 500, 250, 100, 50, and 10 
ppm of dopant, depending on the molecular weight of 
the dopant. At higher concentrations of 10%, 1% and 
0.5%, only a single dopant was used in each matrix to 
minimize interactions between the dopant and the ma-
trix (3 concentrations × 8 elements × 4 matrices = 96 
samples total). At lower concentrations, all dopants 
were mixed into the same matrix, yielding an addition-
al (6 concentrations × 4 matrices) 24 samples. Each 
mixture was then shatterboxed for one minute to ho-
mogenize it and reduce the grain size <<25 µm.  
Powders of each mixture were sent to Bureau Veri-
tas Mineral Laboratories, (Vancouver BC, Canada) for 
analysis by x-ray fluorescence (XRF) for major ele-
ments and ICP-MS for trace elements using their 
LF600 package. Fused glass disks were prepared for 
XRF. Replicate analyses (up to 7 for each matrix) were 
averaged to create the penultimate reference data. All 
samples were subsequently pressed into pellets using 
1.5 cm diameter aluminum cups for LIBS analysis; 
their initial results are given in [10].  
Conclusions: These and our previously-created 
standards will form the basis for useful cross-
comparisons of analytical techniques to be flown on 
future missions to planetary surfaces. Integration of 
data on these standards for use in bulk rock analysis 
techniques will increase our understanding of quantita-
tive analyses and produce improvements in accuracy of 
predicting these elements. Limited amounts of pow-
dered samples and XRF glass disks are available for 
loan from the second author, along with complete 
chemical analyses for all samples. 
Acknowledgments: Research supported by NASA 
grants NNX14AG56G and NNX15AC82G and NSF 
grants CHE-1306133 and CHE-1307179. 
References: [1] Yen A.S. et al. (2005) Nature, 436, 
49-54. [2] Yen A.S. et al. (2006) JGR, 111, E12S11. 
[3] Fassett C.I. and Dyar M.D. (2015) LPSC XLVI, 
Abstract #1875. [4] Lepore K. et al. (in press) Appl. 
Spectrosc. [5] Dyar M.D. et al. (2016) Spectroch. Acta 
B, 123, 93-104. [6] De Vos W. and Tarvainen T., eds. 
(2010) Geochemical Atlas of Europe, Part 2, ISBN 
951-690-960-4 [7] Mielke J.E. (1979) Composition of 
the Earth’s crust and distribution of the elements. In 
F.R. Siegel (ed.) Intl. Assoc. Geochem. Cosmochem., 
Earth Sci. Ser., 16, UNESCO Rep. SC/GEO/544/3, 13-
37. [8] Wedepohl K.H. (1995) GCA 59, 1217-1232. [9] 
Schaefer L. and Fegley B.Jr. (2004) Icarus, 168, 215-
219. [10] Lepore K. et al. (2017) LPSC XLVIII Ab-
stract #1122.  
Figure 1. JM weighing out 9:1 mixtures of matrices to do-
pants. 


Standards for Analysis of Ce, La, Pb, Rb, Se, Sr, Y, AND Zr in Rock Samples Using Laser-induced Breakdown Spectroscopy and X-ray Fluorescence

Standards for Analysis of Ce, La, Pb, Rb, Se, Sr, Y, AND Zr in Rock Samples Using Laser-induced Breakdown Spectroscopy and X-ray Fluorescence

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server