APPLICATIONS OF THE MOLE RAMAN
MICROPROBE TO THE STUDY OF FLUID
INCLUSIONS IN MINERALS
J. Dubessy, C. Beny, N. Guilhaumou, P. Dhamelincourt, B. Poty
To cite this version:
J. Dubessy, C. Beny, N. Guilhaumou, P. Dhamelincourt, B. Poty. APPLICATIONS
OF THE MOLE RAMAN MICROPROBE TO THE STUDY OF FLUID INCLUSIONS IN MINERALS. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-811-C2-814.
<10.1051/jphyscol:19842186>. <jpa-00223861>
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JOURNAL DE PHYSIQUE
Colloque C2, suppl6ment au n02, Tome 45, fgvrier 1984
page C2-8 11
APPLICATIONS OF THE MOLE RAMAN MICROPROBE TO THE STUDY OF FLUID
INCLUSIONS IN MINERALS
J. Dubessy, C. Beny*, N. Guilhaumou**, P.
CREGU, B.P.
r ham el in court*** and
B. Poty
23, 54501 Vandoeuvre-22s-Naney Cedex, France
Za FgroZZerie, 45045 OrZdans Cedex, F r a m e
Lab. GdoZogie, ENS, 46 r u e dlUZm, 75230 P a r i s Cedex 05,
*CRSCM, r u e d e
**
ER-224-CNRS,
France
***
LASIR-LP-2641-CNRS,
USTL, B.P. 36, 59650 V<liZZeneuve d l A s c q , France
RESUME - Dans les inclusions fluides aqueuses, la microspectrometrie Raman permet
d'analyser l'ion SO4 et d'identifier indirectement les ions monoatomiques par les
hydrates de sels nuclGBs au cours du refroidissement. Deux exemples d'identification
de gaz (C02-H2S) et (H2-02) dans les inclusions fluides sont prGsentGs.
-
ABSTRACT
In aqueous fluid inclusions, micro-Raman spectrometry allows to analyse
SO4 ion and to identify indirectly monoatomic ions by the salt hydrates nucleated
during cooling. Two examples of gas identification (C02-H2S) and (Hz-02)in fluid
inclusions are given.
I
-
INTRODUCTION
A rock is the product of chemical reactions between solid phases, the
minerals, and fluids which for the most part have disappeared. Some relics of these
fluids, however, remain in small intracrystalline cavities, 10 to 100 pm in size.
Knowledge of the composition of the fluids in these inclusions is essential to reconstruct the mineral - fluid chemical equilibria. A single mineral may contain
fluid inclusions of various age, origin and consequently composition. Only microscopic analytical techniques, therefore, can give fruitful data. Micro-Raman spectrometry is one of these techniques (1). The machine we used is the MOLE type (JobinYvon) described elsewhere (2).
I1
-
IONS DISSOLVED IN AQUEOUS SOLUTIONS OF FLUID INCLUSIONS
Ionic sulphate is the only polyatomic ion which has been successfully
identified in fluid inclusions ( > 200 ppm concentration) (3). The ratio of the
intensity of the Raman signal of the symmetric stretching vibration of SO4 (vl = 980
cm-l) and of the bending mode of liquid water (1500-1800 cm-')(~i~.
1) has been
calibrated as a function of bulk SO4 concentration in solution saturated in halite.
Using this calibration curve, the SO4 concentration inside primary fluid inclusions
of halite crystals sampled in a present day salt pan has been proved to be the same
as that of the parent brine of these host crystals. The same methodology applied to
Keuper evaporites (-200 millions years) have shown that the parent brine had a composition incompatible with the evaporation of present day sea-water (Fig. 2).
As one cannot detect monoatomic ions by Raman spectra, it is necessary to
use an indirect method for their determination. During cooling an aqueous solution
of the H20-NaC1-CaC12-KC1-MgC12 system, various salt hydrates may nucleate depending
on the composition of the solution. The fundamental internal modes of the water
molecules of the main salt hydrates (NaC1.2H20, CaC12.6H20, MgC12.6H20, MgC12.12H20,
KC1.MgC12.6H20) have different frequencies. Raman spectra of these crystals have
been recorded at -190°C (3). These references spectra were subsequently used to
identify the salt hydrates which have nucleated during cooling the host mineral of
the fluid inclusion with the Chaix-Meca (5) freezing stage. In figure 3, the Raman
spectrum of NaC1.2H20 in a fluid inclusion is compared with that of synthetic NaC1.2H20. The lower resolution of the Raman lines of the hydrate from the inclusion
results from a greater supply of heat relative to the reference due to the objective
being (LEITZ, Plx160) very close to the mineral plate.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842186
JOURNAL DE PHYSIQUE
Fig. 1
-
Raman spectra of sulphate
(vial) and water (v2al)
from A) prepared solutions
and B) the aqueous phase of
a natural inclusion
Fig. 3
-
Fig. 2
- Diagram SO
concentration (molefkg H20) in
brines of modern saltworks.
Keuper brine with Br- estimated from the Br- concentration of halite host crystal.
Raman spectra of hydro-halite (NaC1.2H20) from A)
prepared solutions and B) a natural inclusion
recorded at -190°C.
I11
- MOLECULAR GAS SPECIES
The C-O-H-N-S system is the basic system of many geological fluids. C02CH4-C2H6-N2-H2S-CO-SO2-H2-O2 are the common molecular species identified by microRaman analysis (1,6,7,8,9,10). The measurement of the intensity of the Raman signal
of each gaseous species and the corresponding cross-section of Raman scattering a
(11,12) allows one to determine the mole fraction of each gas. For example, C02-H2S
fluids have been detected in native sulphur bearing fluid inclusions, figure 4 (7).
The (C02/H2S) in gas / (C02/H2S) in water ratio measured is 3.3 and is consistent
with the theoretical ratio. This indicates that (oH2S/uC02) in water is not very
different from (aH2S/uC02) in gas.
solid phase
Fig. 4
- Raman spectra in a
single natural inclusion of
A) native crystalline sulphur,
B) C02 and H2S in gaseous, liquid and aqueous phase.
Free molecular hydrogen and oxygen have been identified inside fluid inclusions from the Rabbit Lake uranium deposit, Fig. 5. At room temperature, the
partial pressure of O2 is around 50 atm. and that of H2 around one atm. This composition is obviously far from equilibrium and must result from radiolysis of pore
water by a particles originating from the natural radioactive decay of uranium minerals. Numerical simulation shows that one mole % of free O2 and H2 can be yielded by
such process in 10 000 years.
Fig.
3
- Raman
spectra of H2, O2
and N2 in a natural
inclusion from the
Rabbit Lake uranium
on deposit.
JOURNAL DE PHYSIQUE
IV
-
CONCLUSION
The Raman microprobe is now for fluid geochemistry what is the electronic microprobe
for mineral geochemistry. The detailed characterization of fluid chemistry through
the continental crust is now possible.
REFERENCES
1. DHAMELINCOURT P., BENY J.M., DUBESSY J. et POTY B. (1979) - Bull. Mineral., 102,
600-610.
2. DELHAYE M. and DHAMELINCOURT P. (1975) J. Raman Spectrosc., 3, 33-43.
3. DUBESSY J., GEISLER D., KOSZTOLANYI C. and VERNET M. (1983) - Geochim. Cosmochim
Acta, 7, 1-10.
4. DUBESSY J., AUDEOUD D., WILKINS R. and KOSZTOLANYI C. (1982) - Chem. Geol., 37,
137-150.
5. POTY B., LEROY J. et JACKIMOWICZ L. (1975) - Bull. Soc. Fr. Mineral. Cristallogr., 2, 182-186.
6. GUILHAUMOU N., DHAMELINCOURT P., TOURAY J.C. and TOURET J. (1981) - Geochim.
Cosmochim. Acta, 65 : 657-673.
7. BENY C., GUILHAUMOU N. and TOURAY J.C. (1982) - Chem. Geol. 37, 113-127.
8. GUILHAUMOU N. and TOURAY J.C. - Bull. Mineral. (in press).
9. BERGMAN S. and DUBESSY J. - Contrib. Miner. Petrol. (in press).
10. CLOCHIATTI R. DHAMELINCOURT P., MASSARE D., TANGUY J.C. et WEISS J.
Bull.
Mineral. (in press).
11. FENNER W.R., HYATT H.A. and PORT0 S.P.S. (1973) - J. Opt. Soc. Am., 63, 73-77.
12. SCHROTTER H.W. and KLOCKNER H.W. (1979) - In "Raman Spectrometry of Gases and
Liquids", chap. 4, 123-166 - Springer Verlag.
13. DUBESSY J., HICKEL B., PAGEL M. (1983) - Terra Cognita, 3, n02-3, 178.
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