SGC51-P01

Room:Convention Hall

Time:May 24 18:15-19:30

Present status for in-situ noble gas analysis by Sputtered Neutral Mass Spectrometry withtunneling ionization
BAJO, Ken-ichi1∗
1

Hokkaido University

LIMAS (Laser Ionization MAss nanoScope) was installed in 2011. In-situ analysis for trace elements in nanometer-scale is aconcept of this apparatus. I have conducted mechanism of solar wind (SW) implantation into extra-terrestrial materials such as
Itokawa particles. Because depth profile of SW-He have not been determined by using conventional noble gas mass spectrometer(NG-MS) in a quantitative way, a depth profiling of the SW noble gas contributes to the great progress for understanding implantation and removing processes of the SW noble gases. The processes imply the space-weathering history of the materials on its
asteroid surface.
LIMAS is mainly composed Ga focused ion beam (FIB) for primary ion, femtosecond (fs) laser for tunnel ionization of sputtered particles, and time-of-flight mass spectrometer. Depth profiling procedure is as follows. The FIB system is carried out highspatial resolution with large primary current. The smallest beam size was 8 nm at 3 pA, and the largest size was 600 nm at 30nA. The fs laser can ionize the all element even He because of high energy density. The energy density is 8E15 W/cm2 because
the pulse energy and width was 6.3 W and 30 fs, respectively, and the laser pulse was focused on a volume of 50 x 50 µm2 . Thislaser pulse induces tunneling ionization (Delone and Krainov, 1998). Helium depth profile method in a few micrometer has beendeveloped with LIMAS and atomic force microscope for crater depth measurement.
LIMAS can detect tens ppma He from sub-micrometer area on solid surface. In presence useful yield of He is 0.02% whichshould be up to 1% by optimize laser focusing and irradiation position. The yield of 0.02% corresponds to 4000 He atoms for
single He ion count. The back ground of He is much less than that of the NG-MS because LIMAS is used by dynamic operation
under the ultra-high vacuum.
LIMAS can measure locally concentrated noble gas because the sputter rate of the pulsed FIB is low, which indicates that thismeasurement is almost non-destructive isotope analysis. This feature can play a role for analysis of tiny and precious samples
such as the Itokawa particles. U,Th-He and K-Ar dating for single grain can be applied by the in-situ noble gas analysis. The
in-situ dating may obtain a new insight of thermal history of igneous rocks by comparing conventional in-situ dating method
such as U-Pb age.
Keywords: noble gas, in-situ analysis, Sputtered Neutral Mass Spectrometry

1/1

SGC51-P02

Room:Convention Hall

Time:May 24 18:15-19:30

New preparation apparatus for noble gas isotope analyses to measure submarine hydrothermal fluids and renewed GVI-5400
SATO, Keiko1∗ ; KUMAGAI, Hidenori1 ; IWATA, Naoyoshi2 ; SUZUKI, Katsuhiko1 ; TAKANO, Susumu3
1

R&D CSR, JAMSTEC, 2 Faculty of Science, Yamagata University, 3 Hiruzen Institute for Geology and Chronology

Hydrothermal activity is an essential phenomenon to drive geochemical differentiation on the Earth’s surface, which should
form polymetallic massive sulfide ores. Noble gas isotopes are regarded to be a powerful tracer even for the geochemical study
on hydrothermal activity; however, there are abundant interference volatiles, e.g. halogens and hydrogen sulfide. Here, we designed a new preparation system to remove such volatiles using non-traditional gettering materials. This new preparation system
consists of following components: the water preparations system, composite gettering system (halogen getter, sulfide getter andTi-Zr getter), cryogenic pump, Saes-getter pump and charcoal trap to analyze the all noble gases. The new preparation system
has compact volume, which needs small amount of seawater sample of 2-5 cc in volume. It is almost 1/20 compared to the typicalrequirement for He isotope measurement.
To design new noble gas measurement system in JAMSTEC, another critical problem is to be solved. One of widely used
noble gas mass spectrometers, GVI-5400, is now not listed in commercial production models. Thus, all successor models ofVG-5400 series have entirely finished their production support since several years ago. However, the VG-5400 series and its
successor models still show satisfactory sensitivity and precision to determine noble gas isotope ratios. If we decide to use themmuch longer, we should maintain their control units, such as power supply, emission control or source control and so on, which
requires replacement of essential electrical parts, including vacuum tube (!), regularly. At present, some of these parts are notsupplied anymore and we are forced to choose between not replacing them with the new/second-hand electrical parts while they
still worked, or renew their electrical circuits with currently manufactured electrical parts. By chance we had started the project
to re-use old model of power supply unit. The first trial was applied to the very original VG5400 that was moved from Univ.
Tokyo to Yamagata Univ. As the second case, we renewed the power supply and the emission control unit equipped for theJAMSTEC-2 noble gas mass spectrometer (GVI-5400He).
Here we report the better performance of new version of the renewed power supply unit, noiselessness and better stability, with
the new noble gas preparation system.

Keywords: noble gas, getter pump, hydorothermal activity, mass spectrometer, extraction system

1/1

SGC51-P03

Room:Convention Hall

Time:May 24 18:15-19:30

High sensitive noble gas mass spectrometer equipped with a Giese-type ion source
SUMINO, Hirochika1∗ ; NAGAO, Keisuke1
1GCRC, Grad. Sch. Sci., Univ. Tokyo

Although noble gas isotopes are powerful tracers in geosciences, their extremely low abundances in mineral and rock samples
make their analysis quite difficult. For example, concentration of 3 He, which is a good indicator of mantle-derived component
because of its primordial origin, is as high as 0.01 parts-per-trillion in volcanic rocks and mantle-derived materials. Such scarcenoble gas isotopes are detected with a special mass spectrometer operated in static mode. We have made it possible to detect
103 to 104 atoms of noble gas isotopes by modifying a commercial sector-type single focusing noble gas mass spectrometer(VG5400), which is equipped with a double collector system to detect 3 He and 4 He simultaneously with a secondary electron
multiplier and Faraday cup, respectively [1]. Here we report an attempt of further improvement of sensitivity of the mass spectrometer by installation of a new ion source (Giese-type source).
The Giese-type electron ionization (EI) ion source is equipped with two electrostatic quadrupole lenses [2]. This source has
been reported to have up to two orders of magnitude higher sensitivity than conventional Nier-type EI source because of theabsence of a beam defining slit to collimate the ion beam and thus high transmission [3]. We designed a Giese-type source tohave an adequate resolution to separate 3 He+ from HD+ and H3 + , to have the source housing volume as small as possible, andto be bankable at up to 300 ℃ to reduce outgas from the source materials. The ion and electron optics were based on a calculation
by Lu and Carr [4] and refined using SIMION-3D software [5]. Prior to the installation on the mass spectrometer, the ion beamprofile emitted from the source was monitored by a microchannel plate and phosphor screen to optimize the configuration of thequadrupole lens.
A sufficient mass resolution over 500 essential for 3 He/4 He analysis has been achieved with an improved sensitivity approximately three times higher than the previous condition. The amount of helium required to obtain a precision with 3 He/4 He ratiois two orders of magnitude smaller than that with the condition installed by the manufacture. However, total ion transmission isestimated to be about 30%, suggesting further refinement of the source condition is required to obtain the maximum sensitivity.
References: [1] H. Sumino et al., J. Mass Spectrom. Soc. Jpn., 49, 61-68 (2001). [2] C.F. Giese, Rev. Sci. Instrum., 30,260-261 (1959). [3] E.T. Kinzer and H. Carr, Rev. Sci. Instrum., 30, 1132 (1959). [4] C.-S. Lu and H.E Carr, Rev. Sci. Instrum.,
33, 823-824 (1962). [5] D.A. Dahl, Int. J. Mass Spectrom., 200, 3-25 (2000).
Keywords: Noble gas, Mass spectrometer, Quadrupole lens, Ion source

1/1

SGC51-P04

Room:Convention Hall

Time:May 24 18:15-19:30

Ar-Ar dating by fluid inclusions in hydrothermal quartz, compared with its field and microscopic observations
SAITO, Takuya1∗ ; QIU, Huaning2 ; SHIBUYA, Takazo3 ; MARUYAMA, Shigenori4
1

Department of Earth and Planetary Science, Tokyo Institute of Technology, 2 Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, 3 Precambrian Ecosystem Laboratory, Japan Agency for Marine-Earth Science and Technology, 4 Earth-Life
Science Institute, Tokyo Institute of Technology
The chemical evolution history of the ocean must have been one of the most critical factors to unravel the evolution of lifeon the Earth. However, this topic has not fully understood yet. Recently, de Ronde et al. (1997) and some studies try to estimate seawater composition during Archean and Proterozoic using fluid inclusions trapped in hydrothermal quartz correlatedwith pillowed basalt, which is expected to erupt in sub-seawater condition. Lowe and Byerly (2003) claims that the hydrothermal
minerals used by de Ronde et al. (1997) were formed at far younger age (Quaternary) than expected age of eruption of the matrix
lavas (3.2 Ga), based on the only field and microscopic observations. This problem must be solved by dating of the fluid inclusions trapped in hydrothermal quartz and comparing the age of pillowed basalt as a matrix in addition to field and microscopic
observations. We carried out Ar-Ar dating of the fluid inclusions with stepwise crushing techniques at Guangzhou Institute ofGeochemistry, Chinese Academy of Sciences.
Analyzed samples in this study are from 2.2 - 2.4 Ga Ongeluk Formation, Transvaal Supergroup, South Africa. Above Ongeluk Formation, two younger volcanic layers exist, one is mafic intrusions of the Malopo Farms complex formed at 2044 ± 24
Ma, the other is porphyritic andesite of the Hartley Formation formed at 1928 ± 4 Ma.
The analyzed samples are hydrothermal quartz with growth zoning texture, filling the primary shaped drainage cavities andinterstitial spaces of lava flows of the Ongeluk Formation without quartz vein crosscut pillow of lava, suggesting the quartz
had precipitated soon after eruption of the lava. We analyzed four of the most primary-rich samples (GU84, GU91, GU103aand GU103b), in terms of microscopic observations. However, secondary fluid inclusions are not excluded completely, in otherwords, argon gas extracted the quartz samples including some secondary fluid inclusions origin in the analysis.
Three samples, GU 84, GU103a and GU103b, yielded Ar-Ar isochron ages of 2688 ± 584 Ma, 1952 ± 279 Ma and 1967 ±64 Ma Ar-Ar isochron ages, respectively. GU91 was also dated in the same manner as well, but failed to obtain a tight line ofisochron with a diffused age (611 ± 517 Ma).
Comparing the age of the Ongeluk lava and younger two volcanisms with the results, the age from GU84 has a wide range oferror, but is consistent with Ongeluk lava, GU103a has also a wide range of error, but is consistent with all three volcanisms, andGU103b has the narrowest range of error and is consistent with Malopo Farms complex and Hartley Formation, especially matchwith Hartley. Based on field and microscopic observations, it is unlikely to precipitate quartz with filling cavities 100-200 Myr
after eruption of Ongeluk lava. Two probable mechanisms to explain the results, one is that fluid inclusions were re-equilibrated
at younger volcanisms in terms of the argon with preserving primary textures. The other is that secondary fluid inclusion formedby younger volcanism driving hydrothermal circulations and that extracted argon gas in the analysis is mainly composed of
the secondary inclusions. The secondary fluid inclusions have argon ratio suggesting younger age than primary fundamentally,suggesting that GU84 obtaining the oldest argon age is the most primary rich samples. Assuming that obtained younger ages
than Ongeluk lava are resulted in argon gas from secondary fluid inclusions, the consistency with Ar-Ar age of GU84, the mostprimary-rich sample, and Ongeluk lava support that our field and microscopic observations are robust and that the primary fluidinclusions formed soon after Ongeluk lava eruption.
Keywords: fluid inclusion, Ar-Ar dating, quartz, seawater

1/1

SGC51-P05

Room:Convention Hall

Time:May 24 18:15-19:30

Possibility of K-Ar age mapping on the moon using cosmogenic 39 Ar
TAKESHIMA, Yuko1 ; HYODO, Hironobu2∗ ; ITAYA, Tetsumaru21NEC Aerospace systems, 2 RINS, Okayama Univ. of Sci.

Rapid and wide range of age survey on the moon surface requires in situ measurement. 39 Ar of cosmogenic origin from 39 K
in meteorite has been noticed since the early stage of noble gas research, and became a cue to the 40 Ar/39 Ar method. If theproduction rate of 39 Ar is considered uniform, the production and decay of 39 Ar reaches to equilibrium after a long time, since39
Ar has a half life of 293 years. This half life is long enough to detect 39 Ar in meteorites and moon rocks, and short enough toreach equilibrium of the isotope. Thus, such rocks or minerals possess a certain amount of 39 Ar proportional to their potassium
content. Using meteorites or rocks on moon surface under the same exposure condition, 40 Ar/39 Ar age can be determined. Fora start, a precise date of one of those samples in a laboratory and 40 Ar/39 Ar ratio measurement of the same sample in the field
are required to obtain J-value in the field. 40 Ar/39 Ar ratios measurement of the rest of unknowns in the field allow us to calculateages. Interfering isotopes from calcium will not affect much as long as Ca/K ratio is low. Samples in a depth or a shadow fromexposure are not suitable for the measurement since the neutron density attenuates with depth. However, no need for atmosphericcontamination, mass measurement and 36 Ar measurement may provide us more mobility and rapid measurement.
Keywords: 39 Ar, Cosmogenic, age distribution, 40 Ar/39 Ar age, moon surface

1/1