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Figure 1: REEs concentration of danburite
from different deposits
Discrimination of danburite from different deposits by chemical components:
a Femtosecond LA-ICP-MS study
Huong, L.T.T.1, Otter, L.M.2, Macholdt, D.S.2, Foerster, M.W.3, Stoll, B.2, Weis, U.2, Jochum,
K.P.2
1Faculty of Geology, Vietnam National University Hanoi, 334 Nguyen Trai, Hanoi, Vietnam
2Department of Climate Geochemistry, Max-Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128
Mainz, Germany
3Institute for Geosciences, Johannes Gutenberg University Mainz, J.-J.-Becher-Weg 21, D-55128 Mainz,
Germany
__________________________________________________________________________
Femtosecond Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry was used to determine
the concentration of 51 elements, i.e. Li, Be, B, Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga,
As, Se, Rb, Sr, Y, Zr, Nb, Ag, Cd, Sn, Sb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf,
Ta, W, Pt, Au and Tl in 8 danburite samples from 3 deposits in Vietnam (2 samples), Mexico (2
samples) and Tanzania (4 samples, 2 with yellow and 2 with green colour). Ca was determined in a
previous study by Huong et al [1] with Electron Microprobe Analysis and used as internal standard for
the current LA-ICP-MS measurements. A fs laser was used, since it allows a non-matrix-matched
calibration that is necessary since there exists no suitable reference material for danburite [2]. The
objective of this study is to characterize the elemental composition of danburite among the three
deposits.
The obtained results show that the concentrations of REEs in samples from the three deposits differ
strongly (Fig. 1). The yellow Tanzanian danburite samples contain extreme high concentration of
lanthanide impurities. Total lanthanide content of Tanzanian sample are about 1900 ppm, whereby
the concentration of light rare earth elements (LREE:
La, Ce, Pr, Nd, Sm, Eu) exceed those of the heavy rare
earth elements (HREE: Gd, Tb, Dy, Ho, Er, Er, Tm, Yb,
Lu) by a 450-fold enrichment. This result is in good
agreement with the investigations of Chadwick and
Laurs [3}. Analyzation of green samples from Tanzania
will follow in the near future and will be presented
together with the other samples. The Vietnamese
samples are obviously different with a total
lanthanide content of ca. 1100 ppm, whereby the
concentrations of LREE exceed those of HREE again
by a 200-fold enrichment. Two Mexican danburites
appear to be fairly clean from lanthanide with total
contents of approx. 0.9 ppm and 1.2 ppm. Together
with REEs contents, the three danburite origins can
also be separated from each other by the mass
fractions of minor and trace elements i.e Be, Ti, Mn,
Ni, As, Sr and Y. In addition, a very low concentration of 0.1 – 0.6 ppm of the radioactive element Th
is identified in all samples independently from their origin.
References:
[1] Huong LTTet al. (in review) Gems & Gemology
[2] Jochum KP et al. (2014) Geostandards and Geoanalytical Research 38(3): 265–292.
[3] Chadwick KM and Laurs BM (2008) Gems & Gemology 44(2): 169-171
