1. New Application of Cathodoluminescence to Earth and Planetary Sciences
Conference on Solar System Cosmochemistry and Planetary Science Studies in Hungary (September 4, 2008)
New Application of Cathodoluminescence to Earth and Planetary Sciences
H.Nishido, M.Kayama,
T.Okumura and K.Ninagawa
(collaborated with Dr. Gucsik)
Okayama University of Science
I will be talking about our recent work on new application of cathodoluminescence to earth and planetary science, and
demonstrate the advantage of cathodoluminescence microscopy and spectroscopy in these scientific fields.
Hereafter, I use a term of CL as an abbreviation of cathodoluminescence.
RASC

2. Different types of luminescence
Type of luminescence Excitation source　　Application to geosciences
　 Thermoluminescence (TL) Thermal energy Dosimeter, Dating
Optically Stimulated Luminescence (OSL) Visible light Dosimeter, Dating
　Photoluminescence (PL) Ultraviolet radiation Mining exploration
　Cathodoluminescence (CL) Electrons Fabric and domain analysis
　Roentgenoluminescence (RL) X-rays Dosimeter
　Ionoluminescence Ions Dosimeter
　Chemiluminescence Chemical reactions Water circulation analysis
　Bioluminescence Biochemical reactions Detection of micro biomats
　Triboluminescence Shear stress Bedrock monitoring sensor
Luminescence is the non-thermal emission of visible light by a substance.
There are many types of luminescence used for the investigation of geological materials.
These luminescence can be distinguished by the source of incident radiation, such as thermal energy for TL and electros for CL.

3. Different types of luminescence
Type of luminescence Excitation source　　Application to geosciences
　 Thermoluminescence (TL) Thermal energy Dosimeter, Dating
Optically Stimulated Luminescence (OSL) Visible light Dosimeter, Dating
　Photoluminescence (PL) Ultraviolet radiation Mining exploration
　Cathodoluminescence (CL) Electrons Fabric and domain analysis
　Roentgenoluminescence (RL) X-rays Dosimeter
　Ionoluminescence Ions Dosimeter
　Chemiluminescence Chemical reactions Water circulation analysis
　Bioluminescence Biochemical reactions Detection of micro biomats
　Triboluminescence Shear stress Bedrock monitoring sensor
CL provides us useful information on structural defect and trace impurity elements in the materials,
And visualize characteristic features such as growth sector, domain structure and distribution of defect,

4. Different types of luminescence
Type of luminescence Excitation source　　Application to geosciences
　 Thermoluminescence (TL) Thermal energy Dosimeter, Dating
Optically Stimulated Luminescence (OSL) Visible light Dosimeter, Dating
　Photoluminescence (PL) Ultraviolet radiation Mining exploration
　Cathodoluminescence (CL) Electrons Fabric and domain analysis
　Roentgenoluminescence (RL) X-rays Dosimeter
　Ionoluminescence Ions Dosimeter
　Chemiluminescence Chemical reactions Water circulation analysis
　Bioluminescence Biochemical reactions Detection of micro biomats
　Triboluminescence Shear stress Bedrock monitoring sensor
which can't be detected by any other conventional methods.
Here is the example.
In an optical image, quartz has heterogeneous features,
However, CL imaging can visualize growth sectors in it obviously.
Quartz images by polarizing microscopy (Polmi)
and SEM‐CL microscopy (CL), Götze (2000).

5. Cold-cathode type CL instrument (Luminoscope)
・ Color imaging of CL
・ Comparison with petrological observation
Luminoscope ELM-3R (Nuclide Co.）
Cooled-CCD system： DS-5Mc　(Nikon Co.)
Optical system: Video lens (Edmund Co.)
Most popular CL instrument is here. Luminoscope
It has a clold-cathodo gun with a cooled-CCD recording system.
Using Luminoscope, we can get a color CL image comparable to a petrographic microphotograph.

6. CL image of Antarctic meteorite
Phase II
Phase III
Phase I
This is a color CL image of spherical meteorite from Antarctica.
We can see concentric zoning with different CL colors emitted mainly from enstatite.
It suggests a thermal history during atmospheric entry of this meteorite.
Such features can’t be detected by any other methods.
E-type chondrite (Y-86004) width: 4.5 mm
Courtesy of Prof. Ninagawa

7. Hot-cathode type CL instrument (SEM-CL)
・ CL spectral measurement
・ Comparison with SEM and BSE images, linked to EPMA
SEM： JSM-5410LV （JEOL Co.）
Monochromator： Mono CL2 （Oxford Instruments Co.）
PMT： R2228 （Hamamatsu Photonics Co.）
Wavelength： ～800 nm
Resolution： nm
Temperature： ～400 C
Monochromator
For CL spectral analysis, we use a hot-cathode type instrument, cathodoluminescence scanning electron microscope,
usually called SEM-CL, which comprises a SEM instrument combined with a grating type monochromator
with high sensitivity and high wavelength resolution.
This is our machine.
It has a specially designed temperature controlled stage, which enables CL spectral measurements at various temperatures.

8. CL characterization of zoned zirconB D
This slide shows the procedure of CL characterization.
First, we take a color CL photograph using Luminoscope.
This sample is a zoned zircon, exhibiting blue CL emission.
Second, we collect a panchromatic SEM-CL image, and occasionally a monochromatic image using Mini-CL detector with a band pass filter.
And then, we measure CL spectra at specified positions with a SEM-CL.
In this case, relatively sharp CL peaks, this one and this one, can be assigned to trivalent dysprosium and
this broad band peak in blue region to defect center formed by uranium disintegration.
Zircon from Osayama, Okayama Pref., Japan
A: Luminoscope CL image; B: Mono-CL image; C: CL spectral measurement positions; D: CL spectra

9. Conditions of shock metamorphism (from French, 1998)
shatter cone
Well, I show you an actual example of CL application.
Now we are submitting a paper on a first finding of an impact crater from Japan, collaborated with Dr. Arnold Gucsik.
In this study we have used a CL spectroscopy and imaging to characterize a microdeformation structure caused by shock metamorphism recorded on the impactite.
Especially an existence of Planar Deformation Features, called PDFs, indicates an impact shock evidence.
Conditions of shock metamorphism (from French, 1998)
Barringer impact crater, Arizona

10. Shocked quatrz Meteor Impact → shock meatmorphism
　　　　PF (Planar Fractures)
　　　　PDFs (Planar Deformation Features)
Quartz
・Conventional methods：　Optical observation，TEM etc
・New methods：　 CL imaging and spectroscopy,
　　　　　　　　　　 Micro-Raman spectroscopy PF
PDFs
A sample employed for this investigation is quartz occurred from shocked sedimentary rocks.
As you know, quartz has no cleavage.
Usually we can’t observe any linear features under an optical microscope.
If a quartz grain suffered high pressure generated by impact cratering, it occasionally shows linear parallel microdeformation features, PD and/or PDFs.
Typical example is shown here.
But PF, planar fracture, is just strait crack or split, and sometime similar feature can be found in quartz grains in metamorphic rocks, formed during tectonic movement.
Our target is PDFs, of which formation needs high pressure more than several GPa, which causes a destruction of the structure.
So its existence indicates an undoubted evidence of impact createring.
To confirm the PDFs, TEM, transmitted electron microscopic examination has been employed for detection of amorphousization in PDFs.
But this method is not ease-to-use, and all are not success.
In this study we have applied new method using CL and miro-Raman spectroscopy to characterize the PFDs of shocked quartz.
100 mm
50 mm
PF and PDFs in quartz grains from Ries crater

11. Geological setting Location map Geological map
A possible crater in Japan was discovered at Mt. Oikeyama area, Nagano Prefecture in central Japan by our group.
But, it has been on discussion for a long time due to insuficient scientific evidence for cratering.
This area is geologically situated in the Mesozoic Shirabiso Group, which consists mainly of sedimentary rocks such as sand stone, mud stone and chert.
Since the Cretaceous this region has been affected by a series of tectonic disturbances.
So there are many faults with vigorous uplifting.
Geological map

12. Occurrence a: viewing from NE to SW; b: outcrop; c: chert vein
This slide shows a distance view of Mt. Oikeyama area.
You can see a concentric ridge, here, corresponding to a rim of the crater with a diameter of about 900 m.
This outcrop occurs a quartz grain with a high density of PDFs.
A host rock is chert.
Here is a closeup photograph.
a: viewing from NE to SW; b: outcrop; c: chert vein

13. Sampling location map
This slide shows a distribution of PDFs-bearing quartz in this area.
A broken semicircle indicates a rim of a possible crater.
The quartz with high dense PDFs were found just inside the crater.

14. Polarized microscope imagesb c d
These are microphotographs of the PDFs in quartz grains pictured with a petrographic microscope.
High dense PDFs, linear parallel features with narrow spaces, can be recognized in them.
But, also PL, sub-parallel fractures not so strait, can be observed in some quartz grains.
a, b, d: chert; c: sandstone

15. SEM images of HF etched quartzb
Furthermore, we can find out an internal pillaring structure corresponding to PDFs in a hydro-flouride etched sample.
In these SEM images a white arrow indicates pillaring structure, and a black arrow displays an array texture, just cracks on the surface.
PDFs is a glass-filled narrow band, not a fracture.
So it can be easily attacked by hydro-flouride solution, and makes such characteristic texture after etching.
white arrow: "pillaring" texture; black arrow: "array" texture

16. PDF images Optical image SEM-CL image SEM image BSE image
After many trails of CL imaging, we’ve got a CL image of PDFs in the Oikeyama sample, this figure.
An optical image with high magnification shows a multiple set of PDFs in quartz grains.
But we can’t detect any features in SEM and BSE images, suggesting no fractures and chemical heterogeneity.
In CL image, dark lines on bright CL background corresponds to the PDFs observed in an optical image.
It means dark straight lines might be appeared by an extinction of emission centers due to an amorphousization along PDFs.
Up to now there have been few case of success like this.
Only CL imaging can visualize such characteristic of PDFs.
SEM image
BSE image

17. Raman spectral analysis
We measured Raman spectra at various areas in PDFs-bearing quartz.
Of course all spectra have a pronounced peak at around 464 cm-1, assigned to Si-O-Si stretching vibration.
But their peak intensities vary among measured areas.
Micro-Raman spectra of shocked quartz from Mt. Oikeyama

18. Shocked quartz from Mt. Oikeyama
Optical image
SEM-CL image
So, we pictured two dimensional Raman intensity map using an integrated intensity of the peak at 464 cm-1, here.
The reddish area corresponds to high crystallinity quartz with a high intensity of Raman peak.
On the contrary, the greenish or bluish area agrees with the PDFs in optical and CL images, suggesting low crystallinity quartz, maybe amorphousized in some extent.
Furthermore, a three dimensional Raman image is illustrated here.
Also it indicates parallel linear features can be visualized.
Therefore, these results confirm an existence of PDFs in the Oikeyama quartz, suggesting a meteor impacting at Mt. Oikeyama.
It’s a new finding of impact crater in Japan.
2D Raman mapping
3D Raman mapping
Shocked quartz from Mt. Oikeyama

19. Impact crater structure
Bouguer anomaly map
Impact crater structure
As an additional evidence, Bougue gravity anomaly and orientation of the cracks in the host rock, show a cratering structure in this area.
These results enable an estimation of the crater size.
An estimation diameter is approximately 900 m, not so large.
A falling age might be not so old, probably hundreds of thousand years ago, because of geographical traces of the crater rim survived from sever erosion in this mountain area.

20. Concluding Remarks
・ CL method provide us a useful information on defect
in the lattice and trace elements existed as a impurity,
which are so difficult to characterize using any other
conventional methods.
・ SEM-CL and micro-Raman spectroscopy enable to
characterize crystallochemical properties of micro-size
minerals in planetary science.
・ Further CL application can be expected to a new field
in geosciences.
OK, as presented here, I believe CL method can be expected to develop its new applications for the characterization of planetary materials.
Thank you.