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Table 1 Summary of the basalt samples analyzed during this study

From: Alteration and dehydration of subducting oceanic crust within subduction zones: implications for décollement step-down and plate-boundary seismogenesis

Sample name

MGLB

KRB

MGUB

OKB

MKB

56R-1wa

54R-1wa

Sampling site

Mugi

Kure

Mugi

Okitsu

Makimine

Off the Kii

Off the Kii

V.R. (Ro)b

1.0

2.1

2.5

3.1

4.5

  

1 (°C)

148

225

243

266

304

  

2 (°C)

158

225

240

260

293

  

3 (°C)

174

243

259

279

314

  

4 (°C)

160 ± 30

230 ± 30

247 ± 30

268 ± 30

304 ± 30

  

Quantitative rock composition

Quartz

0.0

0.0

0.1

0.0

4.6

0.0

0.0

Plagioclase

45.1

37.1

44.0

47.0

42.4

38.0

39.3

Calcite

1.5

1.0

2.7

0.3

7.7

0.4

0.1

Pyroxene

24.1

27.5

20.2

19.1

0.0

24.4

22.9

Epidote

0.0

0.0

0.0

0.0

12.1

0.0

0.0

Fe oxide

2.1

5.9

5.7

1.9

2.4

3.7

1.5

Titanite

3.3

5.3

4.2

6.4

3.9

2.8

4.0

Total non-clays

76.1

76.8

76.8

74.8

73.1

69.2

67.9

Glass

0.0

0.0

0.0

0.0

0.0

7.1

8.1

Saponite

0.0

0.0

0.0

0.0

0.0

23.7

24.0

C/S

23.9

23.2

23.2

25.2

26.9

0.0

0.0

%Sc in C/S

14.4

9.3

8.6

6.7

0.0

Total clay + glass

23.9

23.2

23.2

25.2

26.9

30.8

32.1

Totald

100 (93.1)

100 (102.8)

100 (100.3)

100 (102.2)

100 (103.3)

100 (97.3)

100 (90.0)

Chemical composition of C/S (based on O10(OH)8)

 Ne

16

15

15

17

15

  

 Si

3.08 (0.23)

2.91 (0.12)

3.02 (0.12)

2.93 (0.10)

2.80 (0.14)

  

 ΣAl

2.14 (0.16)

2.45 (0.16)

2.14 (0.15)

2.44 (0.12)

2.50 (0.12)

  

 IVAl

0.92

1.09

0.98

1.07

1.20

  

 VIAl

1.22

1.36

1.16

1.37

1.30

  

 Fef

1.60 (0.26)

2.31 (0.21)

2.47 (0.24)

2.32 (0.29)

1.44 (0.28)

  

 Mg

2.73 (0.29)

2.11 (0.13)

2.05 (0.26)

2.12 (0.25)

3.11 (0.44)

  

 Ti

0.10 (0.12)

0.04 (0.05)

0.11 (0.06)

0.010 (0.23)

0.05 (0.04)

  

 Ca

0.12 (0.18)

0.01 (0.02)

0.02 (0.04)

0.00

0.00

  
  1. Temperatures for onland samples (1–4) were determined using (1) the equation of Barker (1988), (2) the equation of Sweeney and Burnham (1990) with a heating duration of 10 Myr, (3) the equation of Sweeney and Burnham (1990) with a heating duration of 1 Myr, and (4) averaged temperatures with an uncertainty of ±30 °C. a Samples 54R-1w and 56R-1w were taken from intervals C0012-54R-1w (11–14 cm) and C0012-56R-1w (9–14 cm), respectively. b Vitrinite reflectance (V.R.) values for each sample are from Ikesawa et al. (2005) for samples MGLB and MGUB, from Mukoyoshi et al. (2006) for sample KRB, from Sakaguchi (1999) for sample OKB, and from Ohmori (1998) for sample MKB. c %S values were determined by clay-fraction XRD analysis. d Relative mineral abundances were determined using RockJock software and are normalized to 100% abundances. The total weight percentage values originally derived from the program are shown in parentheses. e N = number of analyzed grains with two standard deviations (2σ) shown in parentheses. f All Fe calculated as Fe2+