K. Nagao1, H. Kagi1, I. Kaneoka2, V.S. Kamenetsky3, M.B. Kamenetsky3 and A. V. Sobolev4, 1Laboratory for
Earthquake Chemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan, (su-, 2Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan,
  ARC Centre of Excellence in Ore Deposits and School of Earth Sciences, University of Tasmania, Hobart, Tasma-
nia 7001, Australia, 4Max Planck Institute for Chemistry, Geochemistry Division, Mainz 55020, Germany.

    Introduction: In order to identify the parental             First, major element composition of the polished
magma or source mantle, noble gases in mafic miner-         olivine slabs were analyzed by SEM-EDX in order to
als such as olivine and pyroxene have been widely           distinguish their phenocrystic/xenocryst-like origin in
used to investigate the isotopic signature of volcanic or   terms of Fo zoning [6], and then distributions of car-
mantle-derived rocks. Generally magmatic noble gases        bonate and water were investigated using micro FT-IR
are considered to concentrate in fluid/melt inclusions      spectrometer with an aperture of 60×60 μm2. Compos-
in the minerals, whereas in situ radiogenic/cosmogenic
noble gas isotopes may relatively homogeneously dis-
tribute in the solid phase of mineral lattices and/or          (A)                         0.4 ± 0.1
melt/mineral inclusions [1]. Recently, a combination of
low-blank and high-sensitivity noble gas mass spec-                                                1.0 ± 0.3
trometry and laser gas extraction has greatly improved
spatial resolution of noble gas isotope analysis. How-
ever, the low concentration of the noble gases in ter-
restrial samples has hindered the practical application
of laser-microprobe analysis to such samples except in
the case of 40Ar-39Ar and (U-Th)/He dating methods.
For this reason, there have been few attempts to inves-
tigate the distribution of mantle-derived noble gases in
minerals in terrestrial volcanic or mantle-derived rocks
using laser-microprobe analysis [2, 3], and the inclu-                                                 0.9 ± 0.4
sion-hosted component is often extracted by crushing        1.2 ± 0.5
several hundred to thousands of grains together in vac-                                                        500
uum [1]. Here we present an attempt to reveal the no-
ble gas trapping sites in single olivine crystals sepa-
rated from the Udachnaya kimberlite from Siberia with
non-destructive analytical methods such as SEM-EDX,
micro FT-IR and Raman spectroscopy.
    Samples and experiments:              Fresh olivine
phenocrysts in kimberlite collected from the deep
levels (~500 m) of the Udachnaya-East kimberlite pipe
in Yakutia, Russia, have been revealed to preserve
magmatic noble gases possibly in low density CO2
fluid inclusions associated with carbonate-chloride
inclusions [4]. Since a preliminary noble gas laser-
microprobe analysis on a 400-μm thick doubly-
polished section of bulk kimberlite revealed that re-
lease of abundant radiogenic 4He which had accumu-                                            200 μm
lated in matrix after the kimberlite emplacement (ca.
                                                            Figure 1. (A) An optical microscope image of a thin
350 Ma [5]) considerably increased blank level even at
                                                            olivine slab analyzed in this study. Boxes indicate
room temperature, olivines separated from the kimber-
                                                            laser-ablated areas for noble gas extraction. Numbers
lite were doubly polished into thin slabs (approxi-
                                                            are 4He/3He (in unit of 106 with 1σ errors) observed
mately 200-300 μm thick) and resin used to mount
                                                            for each laser pit. (B) A color map of CO32- content
them on glass slides during the polishing was com-          (ppm) of the same slab obtained by micro FT-IR
pletely removed.                                            spectrometer.
ite inclusions of carbonate, chloride, sulfate and fluid     mantle-derived rocks, especially when it is combined
[6, 7] were investigated in detail using micro Raman         with other non-destructive microscopic analytical
spectroscopy with several microns resolution. After          methods.
these non-destructive analyses, the samples were                 References: [1] Kurz M.D. (1986) Nature 320,
loaded into a vacuum chamber equipped with a sap-            435-439. [2] Burnard P.G. et al. (1994) Earth Planet.
phire glass window and connected to a noble gas puri-        Sci. Lett., 128, 243-258. [3] Sumino H. et al. (2008) J.
fication and separation line. Noble gases were ex-           Volcanol. Geotherm. Res., 175, 189-207. [4] Sumino H.
tracted by drilling and carving out a sample area ap-        et al. (2006) Geophys. Res. Lett., 33, L16318. [5] Maas
proximately several hundreds of microns in size by an        R. et al. (2005) Geology, 33, 549-552. [6] Kamenetsky
ultraviolet laser beam (213 nm wavelength). Ablated          V.S. et al. (2007) J. Petrol, 49, 823-839. [7] Golovin
volumes of each laser pit were about 10-5 cm3, corre-        A.V. et al. (2003) Dokl. Earth Sci., 388, 369-372. [8]
sponding to several tens of micrograms of olivine.           Thomas J.B. et al. (2008) Chem. Geol., 253, 1-22.
Average procedural blank values of 4He and 40Ar were
5 × 10-11 cm3 STP and 3× 10-11 cm3 STP, respectively.
    Results: Amounts of 4He and 40Ar extracted from
each laser pit vary by more than an order of magnitude
(0.6-16 × 10-10 cm3 STP for 4He and 0.5-9 × 10-10 cm3
STP for 40Ar) and are heterogeneous even in a single
crystal. From their homogeneous Fo content [6] the
xenocryst-like olivines systematically show low noble
gas concentrations. 4He/3He ranging from 1.1 × 105 to
2.6 × 106 are also heterogeneous in a single crystal.
Based on He-Ar isotope systematics, three components
can be recognized. The first one bears similar 4He/3He
and 4He/40Ar*, where 40Ar* is non-atmospheric 40Ar,
to those obtained by bulk in-vacuo crushing of
phenocrystic olivines [4], suggesting its residence in
the fluid phase of inclusions. Another component has
higher 4He/40Ar* and 4He/3He than the fluid inclusion-
hosted component, implying a significant part of 4He
in the second component is in situ radiogenic origin. A
rough correlation between CO32- content determined
by micro FT-IR analysis and 4He/3He in a single crys-
tal (Fig. 1) suggests the radiogenic component is en-
riched in the carbonate phase in inclusions. This is
consistent with a relatively high concentration of U in
carbonates. The last component shows atmospheric
  Ar/36Ar and was predominantly observed when ca. 5
μm depth of the whole area of the sample surface was
planed away by laser beam scanning or a laser pit
penetrated to the bottom surface of the sample thin
slab. These features suggest that this atmospheric
component is absorbed on the sample surface or at-
mospheric noble gases are incorporated into the up-
permost several hundred nm of surface layers of the
olivine crystal [8].
    Although the spatial resolution of this work, which
is mainly limited by noble gas detection limits, is too
low to analyze noble gases in each single inclusion
(from 2 to 80 μm in size [7]), the preliminary results
show the potential of noble gas laser-microprobe
analysis in distinguishing several noble gas compo-
nents trapped in distinct sites of minerals in volcanic or

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