mineral grains from ivuna (2004.06.16) short summary

Mineral grains from Ivuna (2004.06.16)Short summary

• 4 samples removed from the Ivuna meteorite were imaged at beamline BL47XU of SPring-8 on June 16, 2004.

• All the samples seem to be carbonate. MZ-IV2-3 must be calcite deducing from its CT value (see Table below). The phases of the other samples cannot be estimated due to the effect of harmonics at 8 keV.

• Voids were seen in three samples (MZ-IV2-1, 2 and 3). Many voids in MZ-IV2-3 (calcite) are closed and might be fluid inclusions. Many voids in MZ-IV2-1 and 3 are connected to the outside and should be healed cracks.

sampleimaging

No.energy

exposuretime

projectionmineral

candidatesCT value at

histogram peakremarks

keV sec cm-1

MZ-IV2-2 040616b 8 1 750 183.529412 heald cracks?MZ-IV2-4 040616c 8 1 750 126.406236 very clear crystal, no voidMZ-IV2-1 040616d 8 1 750 97.56186 healed cracksMZ-IV2-3 040616e 10 1 750 calcite 105.07392 many closed voids

mineral/density（g/cc） LAC at 8 keV LAC at 10 keV

cm-1

cm-1

magnesite/MgCO3/2.98 56.557539 29.187255 dolomite/CaMg(CO3)2/2.86 141.6159 75.743928 calcite/CaCO3/2.72 204.654557 110.27765

MZ-IV2-2 (040616b)

Imaging No.: 040616bSample: MZ-IV2-2; a piece of transparent crystalBeamline: BL20XUX-ray photon energy: 8 keVExposure time for each projection: 1 sec.No. of pixels for each projection image: 512× 530 pels

No. of projection images for dark current ： 2 (1 each before and after sample imaging)No. of projection images for incident beam current (I0): 151 (+1; for determining the rotation axis)No. of projection images for transmitted beam current (I): 750 (+1; ditto)Imaging sequence: One I0 imaging after every 5 I imagingPixel size of projection images: 0.23 micron

Voxel size of reconstructed CT images ： 0.23 micronNo. of voxels ： 512 × 512 × 530Location of sample rotation axis:R0(z)= 0.007793×z +233.936012 ±0.828852 （ z=0 ～ 529 ）

Byte images:PV=0: CT value = 0 1/cmPV=180: CT value = 183.529412 1/cm

(peak value)

Cut images: Threshold: PV=74Erosion: 3 layersDilation: 6 layers

Voxel size ： 0.23 micronNumber of voxels ： 371 × 331 × 509

cut/271.tif (width: 85.33 m)

0

5 104

1 105

1.5 105

2 105

2.5 105

3 105

3.5 105

4 105

0 50 100 150 200 250

byte_hst

N

PV

PV=74 (min)

PV=180

MZ-IV2-2 (040616b): browse image

MZ-IV2-2 (040616b): external shape

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MZ-IV2-2 (040616b): frequency diagram and phases

CT value of calcite: 204.65 cm-1

Estimated LAC of calcite: 181.8 cm-1

CT value of dolomite: 141.62 cm-1


CT value = 0.88305(651) * LAC

MineralsWhite (CTv >260 cm-1): ?Gray (CTv = 183.5 cm-1): calcite??Black: void, airIdentification of mineral phases from the CT values is difficult due to contribution of harmonics at this energy (8 keV).

voidcarbonate

?

3

3.5

4

4.5

5

5.5

6

6.5

7

0 50 100 150 200 250

byte_hst

CT value /cm-1

183.5 cm -1


MZ-IV2-4 (040616c)

Imaging No.: 040616cSample: MZ-IV2-4; a piece of transparent crystalBeamline: BL20XUX-ray photon energy: 8 keVExposure time for each projection: 1 sec.No. of pixels for each projection image: 512× 280 pels




(peak value)




0

5 104

1 105

1.5 105

2 105

0 50 100 150 200 250

byte_hst

N

PV

PV=100 (min)

PV=180

MZ-IV2-4 (040616c): browse image

MZ-IV2-4 (040616c): external shape

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MZ-IV2-4 (040616c): frequency diagram and phases





CT value = 0.88305(651) * LAC

MineralsWhite (CTv >179 cm-1): ?Gray (CTv = 126.4 cm-1): dolomite-calcite??Black: void, airIdentification of mineral phases from the CT values is difficult due to contribution of harmonics at this energy (8 keV).

carbonate

?

3

3.5

4

4.5

5

5.5

6

6.5

0 40 80 120 160

byte_hst

CT value /cm-1

126.4 cm -1


MZ-IV2-1 (040616d)

Imaging No.: 040616dSample: MZ-IV2-1; a piece of transparent crystalBeamline: BL20XUX-ray photon energy: 8 keVExposure time for each projection: 1 sec.No. of pixels for each projection image: 512× 420 pels




(peak value)




0

5 104

1 105

1.5 105

2 105

0 50 100 150 200 250

byte_hst

N

PV

PV=116 (min)

PV=180

MZ-IV2-1 (040616d): browse image

MZ-IV2-1 (040616d): external shape

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MZ-IV2-1 (040616d): frequency diagram and phases





CT value = 0.88305(651) * LAC

cut/176.tif (width: 46.23 mm)

MineralsWhite (CTv >138 cm-1): ?Gray (CTv = 97.61 cm-1): magnesite-dolomite??Black: void, airIdentification of mineral phases from the CT values is difficult due to contribution of harmonics at this energy (8 keV).

void

carbonate

?

3.5

4

4.5

5

5.5

6

6.5

0 20 40 60 80 100 120 140

byte_hst

CT value /cm-1

97.6 cm -1

MZ-IV2-1 (040616d): voids(1) Voids along healed cracks? We can see many voids. Some of them seem to be closed. But they are located along

lines and seem to be healed cracks.

255.tif 260.tif250.tif

265.tif 270.tif 275.tif

MZ-IV2-3 (040616e)

Imaging No.: 040616eSample: MZ-IV2-3; a piece of transparent crystalBeamline: BL20XUX-ray photon energy: 10 keVExposure time for each projection: 1 sec.No. of pixels for each projection image: 1024× 820 pels




(peak value)




0

2 105

4 105

6 105

8 105

1 106

0 50 100 150 200 250

byte_hst

N

PV

PV=80(min)

PV=180

MZ-IV2-3 (040616e): browse image

MZ-IV2-3 (040616e): external shape

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MZ-IV2-3 (040616e): frequency diagram and phases



CT value = 0.88305(651) * LAC

cut/492.tif (width: 115.46 mm)

MineralsWhite (CTv >149 cm-1): ?Gray (CTv = 105.1 cm-1): calciteBlack: void, air

void

calcite

?

2

3

4

5

6

7

8

0 50 100 150

byte_hst

CT value /cm-1

105.1 cm -1

MZ-IV2-3 (040616e): voids(1) Closed voids We can recognize many closed voids in slices of 95-104, 111-115, 127-144, 163?, 210-

211, 269?, 314-317, 353, 382?, 411-424, 536-551, etc.

(2) Voids along healed cracks?

100.tif

316.tif

418.tif

572.tif

Glossary Beamline

Three beamlines (BL20B2, BL20XU and BL47XU) are now available at Spring-8 for X-ray microtomography. We can choose the beamline mainly depending on the sample size and the spatial resolution.

Browse imageSome of a successive CT images of a sample can be seen at a glance by this image. Size scale (cm) and gray scale for CT values (cm-1) are shown in the right and left bottoms of the image, respectively.

Byte imageAn monochromatic image where the brightness of each pixel is expressed by 8 bit (0-255 steps). A series of byte images of an sample stored in the directory named “byte” are formed from original CT images by conversion from CT value to PV (usualy the theoretical LAC of a standard mineral is used for this conversion).

CT valueThis is the value of LAC in each pixel of an CT image. In other words, an CT image is expressed as spatial distribution of CT values. CT values are calculated by CT reconstruction. If we use a monochromatic X-ray beam, CT value is ideally equal to the LAC of a material. However, they are not identical with each other in practice. Their empirical relations were determined at BL20B2 and BL47XU of Spring-8 (see np.29 for the relation at BL47XU). From this relation, we can estimate materials from CT values.

Cut imageThis is a CT image, where unnecessary regions without sample are trimmed. A series of cut images of an sample stored in the directory named “cut” are formed from “byte” images by image processing using threshold for a sample and erosion and dilation procedures.

Imaging No.Imaging number shows the date of imaging and its order. For example, 031204c shows the third experiment (in alphabetical order) on 4 December, 2003.

LAC (Linear attenuation coefficient) (of X-ray)A characteristic properties for X-ray attenuation of a material. This is a function of the bulk density, the chemical composition and X-ray photon energy..

PixelOne of many from which a 2-D image is composed. The shape is usually square.

Projection imageCT images are reconstructed from a series of projection images by rotating a sample by180 degrees. The size of a projection image gives the size of a CT image. For example, projection images of 512 × 220 pixels give 220 CT images of 512 × 512 pixels.

Projection image for dark currentA projection image without X-ray beam (dark image). This gives back ground of the projection images. Usually, 1 (or 2) dark image(s) is (are) taken before and after sample imaging experiment and their average is used for CT reconstruction calculation.

Projection images for incident beam current (I0)A projection image of X-ray beam without sample (I0 image). This is taken at regular intervals of sample imaging (ussually 5 or 10 intervals).

Coordination system

Projection images for transmitted beam current (I)A projection image of sample (I image). The projection , p=ln(I0/I), is calculated and used for CT reconstruction.

Sample rotation axisThe location of a sample rotation axis is required for CT reconstruction. This is called “center value”, which is generally described as a function of the height of a projection image (z: see the coordinate system). For example, the center value is expressed as follows: 249.934 -0.003046 × z ±0.320748（ z = 0 - 219） .

PV (Pixel value)This is the value that expresses the brightness of each pixel of a digital image. For example, the pixel is black and white for PV=0 and 255, respectively, in a byte image.

VoxelOne of many from which a 3-D image is composed. The shape is usually cubic.

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mineral grains from ivuna (2004.06.16) short summary

Documents

samples mziv2

187255dolomitecamgco322

healed cracksmziv2

ct value of dolomite

phasesct value of calcite

ct values

byte images

estimated lac of calcite