Introduction
Geological setting
Methods
Sample preparation
Sample | Core depth (m) | Mineral | Illite | Gypsum | Chlorite | Quartz | Plagioclase | Anhydrite | Analcime | Halite |
---|---|---|---|---|---|---|---|---|---|---|
d (Å) | 10 | 7.61 | 7.05 | 3.342 | 3.1805 | 3.4988 | 3.4254 | 2.821 | ||
hklr
| 002 | 020 | 002 | 101 | 004 | 020 | 400 | 200 | ||
A
| ||||||||||
Refrigerated samples, freeze dried, ground <10 μm | ||||||||||
B2-2-1 AB | 627.5 | 13,996 | 50,472 | 8688 | 273,582 | 70,723 | 125,697 | |||
B2-2-2 | 627.5 | 19,351 | 20,213 | 13,120 | 375,858 | 114,553 | 15,627 | 11,109 | ||
B2-3-2 U | 628.7 | 16,681 | 13,730 | 10,417 | 265,064 | 73,196 | 13,399 | |||
B3-1-2 | 629.8 | 19,217 | 13,229 | 347,447 | 22,551 | 18,591 | ||||
B3-3a-2 | 631.2 | 13,276 | 12,020 | 388,764 | 84,757 | 20,759 | ||||
B3-3c-3 | 632.0 | 26,725 | 12,064 | 309,912 | 133,640 | 18,759 | 20,924 | |||
B4-2-2 | 633.5 | 35,903 | 18,351 | 216,930 | 55,944 | 12,369 | ||||
Frozen samples, freeze dried, ground <10 μm | ||||||||||
B2-2 | 627.5 | 7835 | 5967 | 182,075 | 80,674 | 46,830 | 10,690 | |||
B2-3 | 628.7 | 19,712 | 11,171 | 284,828 | 110,637 | 18,081 | ||||
B3-1 | 629.8 | 9512 | 8148 | 165,390 | 59,332 | 22,867 | 16,691 | |||
B3-3a | 631.2 | 14,333 | 7703 | 352,110 | 15,765 | 15,182 | 15,765 | |||
B3-3c | 632.0 | 12,327 | 7737 | 180,133 | 43,020 | 10,084 | 29,161 | 17,022 | ||
B6-1 | 638.2 | 10,338 | 9187 | 215,068 | 83,078 | 7993 | 11,659 | |||
Cemented and frozen, freeze dried, ground <10 μm | ||||||||||
B4-2 | 633.5 | 9061 | 7413 | 172,328 | 37,807 | 269,596 |
Sample | Left angle | Right angle | FWHM |
---|---|---|---|
B
| |||
B2-1 | 7.193 | 9.392 | 0.436 |
B2-1 | 8.007 | 9.432 | 0.331 |
B2-2 | 7.010 | 9.392 | 0.387 |
B2-2 | 8.007 | 9.392 | 0.260 |
B3-3a | 7.010 | 9.392 | 0.716 |
B3-3a | 8.007 | 9.392 | 0.339 |
B4-3 | 6.623 | 9.697 | 1.248 |
B4-3 | 7.010 | 9.392 | 1.168 |
Scanning electron microscopy with energy-dispersive spectrometry (SEM–EDS)
X-ray diffraction
Total, organic and inorganic carbon
X-ray fluorescence
Sequential extraction of iron
Acid-volatile sulphide and chromium-reducible sulphur extraction
X-ray absorption near-edge structure (XANES) spectroscopy
Results
Sediment description
X-ray diffraction of the bulk sample
X-ray diffraction of the clay fraction
Total, organic and inorganic carbon
Sample | Core depth (m) | TIC (wt%) | TC (wt%) | TOC (wt%) | TS (wt%) |
---|---|---|---|---|---|
Refrigerated samples, freeze dried, ground <10 μm
| |||||
B2-2-2 | 627.5 | 0.09 | 0.28 | 0.19 | 0.92 |
B2-2-1 AB | 627.5 | 0.07 | 0.28 | 0.21 | 3.33 |
B2-3-2 U | 628.7 | 0.09 | 0.33 | 0.24 | 0.73 |
B3-1-2 | 629.8 | 0.01 | 0.04 | 0.03 | 0.14 |
B3-3-3c-3 | 632.0 | 0.01 | 0.03 | 0.02 | 0.14 |
B4-2-2 | 633.5 | 0.02 | 0.14 | 0.12 | 0.02 |
Frozen Samples, freeze dried, ground <10 μm
| |||||
B2-2 | 627.5 | 0.10 | 0.31 | 0.21 | 2.40 |
B2-3 | 628.7 | 0.11 | 0.38 | 0.27 | 0.12 |
B3-1 | 629.8 | 0.02 | 0.03 | 0.01 | 0.09 |
B3-3a | 631.2 | 0.01 | 0.04 | 0.03 | 0.06 |
B3-3c | 632.0 | 0.02 | 0.03 | 0.01 | 0.30 |
B6-1 | 638.2 | 0.02 | 0.03 | 0.01 | 0.46 |
Cemented and frozen, freeze dried, ground <10 μm
| |||||
B4-2 | 633.5 | 0.05 | 0.09 | 0.04 | 5.07 |
X-ray fluorescence
Sample | Core depth (m) | Mg (wt%) | Al (wt%) | Si (wt%) | K (wt%) | Ca (wt%) | Ti (wt%) | Mn (wt%) | Fe (wt%) | Ni (wt%) | Cu (wt%) | Sr (wt%) | Ba (wt%) | Fe/Al (wt/wt) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Refrigerated samples, freeze dried, ground <10 μm
| ||||||||||||||
B2-2-1 AB | 627.5 | 1.19 | 4.07 | 17.26 | 1.81 | 7.06 | 0.259 | 0.036 | 2.31 | 0.0027 | 0.0007 | 0.1257 | 0.0977 | 0.57 |
B2-2-2 | 627.5 | 1.21 | 5.46 | 23.17 | 2.40 | 2.75 | 0.340 | 0.032 | 3.23 | 0.0030 | 0.0014 | 0.0476 | 0.0511 | 0.59 |
B2-3-2 U | 628.7 | 1.23 | 5.64 | 24.04 | 2.38 | 2.39 | 0.337 | 0.034 | 2.64 | 0.0040 | 0.0028 | 0.0456 | 0.0371 | 0.47 |
B3-1-2 | 629.8 | 0.98 | 5.96 | 25.34 | 2.38 | 0.72 | 0.350 | 0.017 | 3.11 | 0.0037 | 0.0004 | 0.0238 | 0.0391 | 0.52 |
B3-3a-2 | 631.2 | 0.79 | 5.65 | 22.90 | 2.38 | 0.43 | 0.337 | 0.014 | 4.26 | 0.0035 | 0.0006 | 0.0189 | 0.0356 | 0.75 |
B3-3c-3 | 632.0 | 0.94 | 6.09 | 26.13 | 2.42 | 0.69 | 0.290 | 0.016 | 2.18 | 0.0027 | 0.0009 | 0.0380 | 0.0366 | 0.36 |
B4-2-2 | 633.5 | 1.50 | 7.79 | 26.18 | 3.35 | 0.33 | 0.445 | 0.019 | 4.10 | 0.0062 | 0.0013 | 0.0156 | 0.0422 | 0.53 |
Frozen Samples, freeze dried, ground <10 μm
| ||||||||||||||
B2-2 | 627.5 | 1.14 | 4.30 | 18.22 | 1.92 | 5.32 | 0.337 | 0.032 | 2.90 | 0.0027 | 0.0008 | 0.0881 | 0.0258 | 0.67 |
B2-3 | 628.7 | 0.73 | 5.21 | 21.61 | 2.40 | 0.87 | 0.365 | 0.032 | 3.34 | 0.0036 | 0.0010 | 0.0239 | 0.0364 | 0.64 |
B3-1 | 629.8 | 0.68 | 5.51 | 21.45 | 2.19 | 0.44 | 0.313 | 0.017 | 3.99 | 0.0032 | 0.0008 | 0.0202 | 0.0391 | 0.72 |
B3-3a | 631.2 | 1.04 | 6.15 | 28.48 | 2.42 | 0.54 | 0.369 | 0.018 | 2.30 | 0.0047 | 0.0009 | 0.0204 | 0.0412 | 0.37 |
B3-3c | 632.0 | 0.66 | 5.60 | 22.11 | 2.33 | 0.81 | 0.258 | 0.017 | 2.38 | 0.0034 | 0.0006 | 0.0419 | 0.0606 | 0.43 |
B6-1 | 638.2 | 0.99 | 5.96 | 24.02 | 2.38 | 1.10 | 0.338 | 0.017 | 2.47 | 0.0049 | 0.0034 | 0.0286 | 0.0553 | 0.41 |
Cemented and frozen, freeze dried, ground <10 μm
| ||||||||||||||
B4-2 | 633.5 | 1.20 | 3.52 | 15.66 | 1.39 | 10.95 | 0.285 | 0.020 | 1.48 | 0.0026 | 0.0008 | 0.1865 | 0.0301 | 0.42 |
Sequential iron extraction
Sample | Core depth (m) | I | II | III | IV | V | Sum I–V | AVS | CRS | Pyrite-Fe |
---|---|---|---|---|---|---|---|---|---|---|
(% dry weight) | (ppm dry weight) | |||||||||
Refrigerated samples, freeze dried, ground <10 μm
| ||||||||||
B2-2-1 AB | 627.5 | 0.024 | 0.043 |
1.708
| 0.065 |
0.228
| 2.07 | |||
B2-2-2 | 627.5 | 0.031 | 0.064 |
4.043
|
0.110
|
0.352
| 4.60 | |||
B2-3-2 U | 628.7 | 0.038 | 0.063 |
2.507
| 0.057 |
0.230
| 2.89 | |||
B3-1-2 | 629.8 | 0.019 | 0.061 |
2.694
| 0.074 |
0.220
| 3.07 | |||
B3-3a | 631.2 | 0.030 | 0.062 |
1.509
| 0.052 |
0.271
| 1.92 | |||
B3-3c-3 | 632.0 | 0.019 | 0.045 |
1.429
| 0.032 |
0.254
| 1.78 | |||
B4-2-2 | 633.5 | 0.034 | 0.085 |
3.123
| 0.059 |
0.233
| 3.53 | |||
Frozen samples, crushed but not ground
| ||||||||||
B2-2 | 627.5 | 0.007 | 0.028 |
2.755
|
0.129
|
0.765
| 3.68 | – | 8.35 | 7.31 |
B2-3 | 628.7 | 0.012 | 0.025 |
1.831
|
0.109
|
0.219
| 2.20 | – | 7.27 | 6.36 |
B3-1 | 629.8 | 0.004 | 0.049 |
6.400
|
0.276
|
5.133
| 11.86 | – | 9.09 | 7.95 |
B3-3a | 631.2 | 0.002 | 0.039 |
6.668
|
0.464
|
2.677
| 9.85 | – | 6.08 | 5.32 |
B3-3c | 632.0 | 0.000 | 0.002 |
0.179
| 0.006 | 0.013 | 0.20 | – | 6.24 | 5.46 |
B6-1 | 638.2 | 0.001 | 0.003 |
0.212
| 0.006 | 0.016 | 0.24 | – | 14.60 | 12.78 |
Cemented, frozen, ground <10 μm
| ||||||||||
B4-2 | 633.5 | 0.024 | 0.025 |
0.458
| 0.043 |
0.367
| 0.92 | – | 37.22 | 32.57 |
Standard minerals
| ||||||||||
Lepidocrocitec
| 0.02 | 1.37 | 1.62 | 0.00 | 0.00 | |||||
Akaganéitec
| 0.02 | 0.24 | 10.44 | 0.00 | 0.00 | |||||
Haematitea
| 0.00 | 0.13 | 4.68 | 0.56 | 3.17 | |||||
Haematitec
| 0.00 | 0.04 | 10.12 | 0.31 | 0.31 | |||||
Goethitea
| 0.00 | 0.03 | 3.56 | 0.73 | 3.59 | |||||
Goethitec
| 0.01 | 0.04 | 8.78 | 0.53 | 0.20 | |||||
Magnetitea
| 0.02 | 0.13 | 2.17 | 9.78 | 3.53 | |||||
Biotitea
| 0.19 | 0.29 | 0.08 | 0.20 | 2.06 | |||||
Nontronitea
| 0.01 | 0.07 | 0.96 | 0.00 | 0.00 | |||||
Nontroniteb
| 0.00 | 0.01 | 0.61 | 0.39 | 1.14 | |||||
Saponiteb
| 0.00 | 0.01 | 0.02 | 0.00 | 0.00 | |||||
Zinnwalditea
| 0.01 | 0.01 | 0.02 | 0.00 | 0.01 | |||||
Riebeckitea
| 0.01 | 0.01 | 0.35 | 0.02 | 0.05 | |||||
Chamositea
| 0.47 | 0.54 | 0.73 | 1.18 | 3.30 | |||||
Chloriteb
| 0.02 | 0.02 | 0.02 | 0.01 | 0.10 | |||||
Sideritea
| 3.58 | 0.95 | 0.95 | 0.15 | 0.10 | |||||
Pyritea
| 0.40 | 0.05 | 0.10 | 0.08 | 0.09 | |||||
Greigitec
| 3.91 | 0.20 | 0.08 | 0.28 | 0.04 | |||||
Greigite, wetc
| 0.78 | 0.00 | 0.00 | 0.00 | 0.00 | |||||
Green rust, wetc
| 0.18 | 0.02 | 0.01 | 0.00 | 0.00 |
Acid-volatile sulphide and chromium-reducible sulphur
XANES spectroscopy
Sample | Core depth (m) | Total Fe (mg/g) | Illite | Nontronite (CV) | Chlorite | Haematite | Reduced χ2
| Calculated redox state |
---|---|---|---|---|---|---|---|---|
Refrigerated samples, freeze dried, ground <10 μm
| ||||||||
B2-2-1 AB | 627.5 | 20.68 | 0.584 | 0.244 | 0.041 | 0.13 | 0.000943 | 2.7 |
B2-2-2 | 627.5 | 46.01 | 0.564 | 0.372 | 0.064 | 0.064 | 0.000144 | 2.7 |
B2-3-2 U | 628.7 | 0.602 | 0.273 | 0.031 | 0.094 | 0.0000949 | 2.7 | |
B3-1-2 | 629.8 | 30.68 | 0.631 | 0.288 | 0 | 0.081 | 0.0000978 | 2.8 |
B3-3a-2 | 631.2 | 0.556 | 0.642 | 0.102 | 0 | 0.0001016 | 2.8 | |
B3-3c-3 | 632.0 | 0.651 | 0.289 | 0.063 | 0 | 0.000898 | 2.7 | |
B3-3c-3 | 632.0 | 0.659 | 0.271 | 0.07 | 0 | 0.0000947 | 2.6 | |
B4-2-2 | 633.5 | 0.63 | 0.34 | 0 | 0.031 | 0.0000982 | 2.7 | |
Frozen Samples, freeze dried, ground <10 μm
| ||||||||
B2-2 | 627.5 | 36.84 | 0.518 | 0.35 | 0 | 0.131 | 0.0001204 | 2.7 |
B2-3 | 628.7 | 21.96 | 0.617 | 0.258 | 0 | 0.125 | 0.0000874 | 2.7 |
B3-1 | 629.8 | 118.63 | 0.471 | 0.414 | 0 | 0.115 | 0.0001215 | 2.8 |
B3-3a | 631.2 | 0.6 | 0.285 | 0.0066 | 0.049 | 0.0001104 | 2.8 | |
B3-3c | 632.0 | 2.01 | 0.67 | 0.283 | 0.023 | 0.024 | 0.000088 | 2.8 |
B6-1 | 638.2 | 0.617 | 0.0324 | 0 | 0.059 | 0.0001172 | 2.8 | |
Cemented and frozen, freeze dried, ground <10 μm
| ||||||||
B4-2 | 633.5 | 9.17 | 0.524 | 0.309 | 0.167 | 0 | 0.00000875 | 2.7 |