Ｌｕｍｉｎｅｓｃｅｎｃｅ　ｄａｔｉｎｇ　ｏｆ　ＱＬｕｍｉｎｅｓｃｅｎｃｅ　ｄａｔｉｎｇ　ｏｆ　Ｑｕａｔｅｒｎａｒｙｕａｔｅｒｎａｒｙ

ｖｏｌｃａｎｉｃ　ｒｏｃｋｓ　ｕｓｉｎｇ　ｏｌｉｖｏｌｃａｎｉｃ　ｒｏｃｋｓ　ｕｓｉｎｇ　ｏｌｉｖｉｎｅｖｉｎｅ

TAKADA MasashiTAKADA Masashi (Nara Women’s University, Japan : (Nara Women’s University, Japan : takada@cc.nara-wu.ac.jptakada@cc.nara-wu.ac.jp ））

　　1. INTRODUCTION1. INTRODUCTION In Luminescence dating, the principal minerals In Luminescence dating, the principal minerals mostly used are quartz and feldspar. However, tephra and lava origimostly used are quartz and feldspar. However, tephra and lava originated from mafic magma seldom contain quartz and volcanic feldspar onated from mafic magma seldom contain quartz and volcanic feldspar often shows anomalous fading (Aitken, 1985). It practically inhibits ften shows anomalous fading (Aitken, 1985). It practically inhibits luminescence dating. luminescence dating. Olivine ([Mg,Fe]Olivine ([Mg,Fe]22SiOSiO44) is one of the common minerals included in ) is one of the common minerals included in igneous rocks such as basalt, diabase and gabbro which seldom contaiigneous rocks such as basalt, diabase and gabbro which seldom contain quartz. Olivines vary in chemical composition from forsterite (Fon quartz. Olivines vary in chemical composition from forsterite (Fo100; Mg100; Mg22SiOSiO44) to fayalite (Fo0; Fe) to fayalite (Fo0; Fe22SiOSiO44), there being complete diadoc), there being complete diadochy between Mghy between Mg2+2+ and Fe and Fe2+2+ in the structure (Deer et. al., 1966). Thou in the structure (Deer et. al., 1966). Though Koike et al. (2002) clarified some luminescence properties of forgh Koike et al. (2002) clarified some luminescence properties of forsterite as interstellar matter within the low temperature environmensterite as interstellar matter within the low temperature environment, little had been known about ones of natural olivine from geologict, little had been known about ones of natural olivine from geological sites. Therefore Takada et al. (2006) preliminarily studied on Tal sites. Therefore Takada et al. (2006) preliminarily studied on TL and OSL behavior of olivine relative to dosimetry and Cenozoic datL and OSL behavior of olivine relative to dosimetry and Cenozoic dating.ing. In this presentation, the author reports the practical applicatIn this presentation, the author reports the practical application of luminescence from natural olivine to Quaternary dating of volion of luminescence from natural olivine to Quaternary dating of volcanic rocks.canic rocks.

3. SAMPLE PREPARATION3. SAMPLE PREPARATION Firstly I used specimens of pure olivine Firstly I used specimens of pure olivine crystals from Arizona, U.S.A. to check etching condition (crystals from Arizona, U.S.A. to check etching condition (Figures 1 Figures 1 and Table 1and Table 1 ) and internal dose.and internal dose. Secondly I tried to extract olivine crystal Secondly I tried to extract olivine crystals from volcanic rocks s from volcanic rocks in the Hakkoda-san district, northern Japan in the Hakkoda-san district, northern Japan ((Figures Figures ２２ , 4 and Tables 2, 3, 4 and Tables 2, 3). The procedures of the sample ). The procedures of the sample preparation and TL measurements are shown in preparation and TL measurements are shown in Figures Figures ３ ３ and 5and 5. .

Fig. ２ . Location of volcanic　 samples

5. REFERENCES5. REFERENCES・ ・ Aitken, M.J., 1985. Thermoluminescence dating. Academic Press, 359pp.Aitken, M.J., 1985. Thermoluminescence dating. Academic Press, 359pp.・　・　 Deer, W.A., Howie, R.A. and Zussman, T., 1966. An introduction to the rock forming minerals. Longman, 528pp.Deer, W.A., Howie, R.A. and Zussman, T., 1966. An introduction to the rock forming minerals. Longman, 528pp.・　・　 Koike, K., Nakagawa, M., Koike, C., Okada, M. and Chihara, H., 2002. Thermoluminescence of Simulated Interstellar Matter after Gamma-ray Irradiation. Astronomy & Astrophysics, 390, 1133-1139.Koike, K., Nakagawa, M., Koike, C., Okada, M. and Chihara, H., 2002. Thermoluminescence of Simulated Interstellar Matter after Gamma-ray Irradiation. Astronomy & Astrophysics, 390, 1133-1139.・　・　 Takada, M., Tani, A. and Shimada, A., 2006. Preliminary study of the application of natural olivine in Cenozoic dating. Radiation Measurements, 41, 982-986.Takada, M., Tani, A. and Shimada, A., 2006. Preliminary study of the application of natural olivine in Cenozoic dating. Radiation Measurements, 41, 982-986.

P-H4

2. TL MEASUREMENT2. TL MEASUREMENT TL measurements were made on an automated RITL measurements were made on an automated RISO TL/OSL-DA15 reader mounted with an integral SO TL/OSL-DA15 reader mounted with an integral 9090Sr-Sr-9090Y beta source. PhotoY beta source. Photon counting used a Thorn-EMI 9235 QA photomultiplier tube coupled to HA-30 n counting used a Thorn-EMI 9235 QA photomultiplier tube coupled to HA-30 and BG7-59 detection filters (290-480 nm transmission) for TL. Optical stimuand BG7-59 detection filters (290-480 nm transmission) for TL. Optical stimulation were performed using blue LEDs (475±45 nm, power of 15 mW/cm to lation were performed using blue LEDs (475±45 nm, power of 15 mW/cm to the sample). the sample).

Figure 1. Relationship between etching time (mimutes) and residual weight (%) of olivinespecimens f rom Arizona)

92%

94%

96%

98%

100%

0 20 40 60 80 100 120 140

(minutes)Ｔｉｍｅ １）

Resid

ual r

atio (

%)

Y = - 0.000497exp (X)

R = 0.97

Fig. 1 Relationship between etching time (minutes) and residual weight (%) of olivine specimens from Arizona, U. S. A.1) Immersion in 10% hydrofluoric acid

4. RESULTS AND DISCISSIONS 4. RESULTS AND DISCISSIONS Figure 1Figure 1 and Table 1and Table 1 suggest suggest immersion in 10% hydrofluoric acid for about 30 minutes allows immersion in 10% hydrofluoric acid for about 30 minutes allows etching of the outer layer of the olivine grains to a depth sufficient etching of the outer layer of the olivine grains to a depth sufficient for the cores remaining to have a negligible component of alpha for the cores remaining to have a negligible component of alpha particle dosage. Alpha counting of the olivine specimen suggests particle dosage. Alpha counting of the olivine specimen suggests the internal dose from olivine is negligible. Modified SAR protocol the internal dose from olivine is negligible. Modified SAR protocol for TL measurements of olivine extracted from Ohsegawa for TL measurements of olivine extracted from Ohsegawa pyroclastic flow deposits give TL ages but they are disperse and pyroclastic flow deposits give TL ages but they are disperse and underestimated (underestimated (Figs. 5, 6, 7 and Table 4Figs. 5, 6, 7 and Table 4). The reasons are ). The reasons are unknown at present but further studies on sensitivity change and unknown at present but further studies on sensitivity change and fading behaviour of olivine are needed.fading behaviour of olivine are needed.

TL glow curves of olivine grains extracted f rom OhsegawaPyroclastic Flow Deposits (disc No.33)

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

200 250 300 350 400 450

Temperature (Celsius degree)

TL

inte

nsi

ties

(co

unts

) Natural

94 Gy

329 Gy

564 Gy

0 Gy

94 Gy(second)

Table 1a.Assumed crystalline form : Octahedron

Depth of a

removed outer layer

a-axis b-axis c-axis VolumeResidual

ratio

（ μｍ） （ｍｍ） （ｍｍ） （ｍｍ） (mm3) (％ )

0 4.00000 4.00000 4.00000 21.3333

33 100.00

%

1 3.99717 3.99717 3.99717 21.2881

10 99.79%

2 3.99434 3.99434 3.99434 21.2429

52 99.58%

3 3.99151 3.99151 3.99151 21.1978

57 99.36%

4 3.98869 3.98869 3.98869 21.1528

26 99.15%

5 3.98586 3.98586 3.98586 21.1078

58 98.94%

6 3.98303 3.98303 3.98303 21.0629

55 98.73%

7 3.98020 3.98020 3.98020 21.0181

15 98.52%

8 3.97737 3.97737 3.97737 20.9733

39 98.31%

9 3.97454 3.97454 3.97454 20.9286

26 98.10%

10 3.97172 3.97172 3.97172 20.8839

77 97.89%

11 3.96889 3.96889 3.96889 20.8393

92 97.68%

12 3.96606 3.96606 3.96606 20.7948

70 97.48%

13 3.96323 3.96323 3.96323 20.7504

12 97.27%

14 3.96040 3.96040 3.96040 20.7060

17 97.06%

15 3.95757 3.95757 3.95757 20.6616

85 96.85%

16 3.95475 3.95475 3.95475 20.6174

17 96.64%

17 3.95192 3.95192 3.95192 20.5732

12 96.44%

18 3.94909 3.94909 3.94909 20.5290

70 96.23%

19 3.94626 3.94626 3.94626 20.4849

92 96.02%

20 3.94343 3.94343 3.94343 20.4409

76 95.82%

Table 1b.Assumed crystalline form : Globe

Depth of a

removed outer layer

a-axis b-axis c-axis VolumeResidual

ratio

（ μｍ） （ｍｍ） （ｍｍ） （ｍｍ） (mm3) (％ )

0 4.00000 4.00000 4.00000 33.5093

33 100.00

%

1 3.99800 3.99800 3.99800 33.4590

94 99.85%

2 3.99600 3.99600 3.99600 33.4089

06 99.70%

3 3.99400 3.99400 3.99400 33.3587

67 99.55%

4 3.99200 3.99200 3.99200 33.3086

79 99.40%

5 3.99000 3.99000 3.99000 33.2586

41 99.25%

6 3.98800 3.98800 3.98800 33.2086

53 99.10%

7 3.98600 3.98600 3.98600 33.1587

15 98.95%

8 3.98400 3.98400 3.98400 33.1088

28 98.80%

9 3.98200 3.98200 3.98200 33.0589

90 98.66%

10 3.98000 3.98000 3.98000 33.0092

02 98.51%

11 3.97800 3.97800 3.97800 32.9594

65 98.36%

12 3.97600 3.97600 3.97600 32.9097

77 98.21%

13 3.97400 3.97400 3.97400 32.8601

39 98.06%

14 3.97200 3.97200 3.97200 32.8105

52 97.91%

15 3.97000 3.97000 3.97000 32.7610

14 97.77%

16 3.96800 3.96800 3.96800 32.7115

26 97.62%

17 3.96600 3.96600 3.96600 32.6620

88 97.47%

18 3.96400 3.96400 3.96400 32.6127

00 97.32%

19 3.96200 3.96200 3.96200 32.5633

61 97.18%

20 3.96000 3.96000 3.96000 32.5140

73 97.03%

Table 1. Relationship between depth (μｍ） of removed outer layer and residual volume/weight (%) of an olivine

crystal

Fig. 3. Sample preparation

Table 4. TL ages of Ohsegawa pyroclastic flow deposits.

Fig. 6.

Fig. 4. Extracted olivine grains from Ohsegawa pyroclastic deposits

Fig. 5. Modified SAR protocol for TL measurement

No.

Sample nameSample

code

　 Location 　 Depth Cosmic Ray

Reference Age (ka)Latitude Longitude a.s.l. (m) (m) (Gy/ka)

1 Arizona olivine - - - - - 　 - 　 -

2 Ohdake lava Ho1 N40.63 E140.83 740 >5 0.115 ± 0.006 K-Ar

150-300

3Ohsegawa pyroclastic

flow depositHto N40.57 E140.95 300 >150 0.001 ± 0.000

Stratigraphy and paleomagnetism

800-1,000

Table ２ . Samples in this study

Fig. 7. Regenerated growth curve of olivine extracted from Ohsegawa pyroclastic rocks.