Supplementary data
Biogenicity of an Early Quaternary iron formation, Milos
Island, Greece
1
Environmental scanning
mineralogical mapping
electron
microscopy-energy
dispersive
x-ray
(SEM-EDS)
Samples were crushed to help improve the identification of mineralogical phases. Scanning
electron microscopy (FEI, Quanta FEG 650) was used to investigate the homogeneity of
samples. The uncoated crushed samples were analysed at 5 kV and low vacuum at a horizontal
field view (HFW) of 1000 µM and 100 µM. Images were captured at different scanning speed,
depending on the degree samples would charge from the excess of electrons. Samples were
further investigated with ESEM-EDS at 20 kV in low vacuum, without x-ray cone using a XMax 80, Oxford instruments, detector. Mapping was performed in Aztec with an averaging of 5
frames and a dwell time of 5 µs. Mineralogical maps are generated by software. Data are
presented below as groups of maps per sample, denoted as supplementary data 1-9.
2
Supplementary data 1
ESEM-EDS micrographs of nano-size grains showing mineralogical maps of Fe and Si phases in
bulk-crushed sample from the conglomerate hosted iron formation (sample M1-10-06B).
Because the data is obtained from materials crushed to to improve the exposure of possible
mineralogical phases, they do not represent the exact spatial arrangement in the original
materials. This applies to all the figures shown below.
Phase
1 FeO
2 Fe
3 FeSiO
4 SiFeAlO
5 SiFeO
7 FeSiKO
8 FeSiO
9 SiFeO
Fraction (%)
Pixel Count
89.3
6.7
0.4
0.4
0.2
0.1
0.0
0.0
40232
3030
169
191
99
23
14
6
3
4
5
6
Supplementary data 2
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
from the conglomerate hosted iron formation (M1-10-06A).
Phase
1 SiKO
2 BaO
4
MnSiFeO
5 MnO
Fraction (%)
Pixel Count
72.0
1.6
1.7
32459
733
782
0.0
8
7
8
9
Supplementary data 3
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
from the conglomerate hosted iron formation (sample M1-1006B).
Phase
1 SiO
2 FeSiO
3 FeO
4 MnO
Fraction (%)
Pixel Count
68.9
26.8
1.7
0.1
31066
12062
758
58
10
1 SiO
Line Type
O
Na
Mg
Al
Si
Cl
K
Ca
Ti
Mn
Fe
Ba
Total
K series
K series
K series
K series
K series
K series
K series
K series
K series
K series
K series
L series
Apparent
Concentration
48.24
0.46
0.14
9.88
22.44
0.06
9.58
0.67
0.06
1.02
4.22
0.97
Wt%
Sigma
0.16233 49.93 0.09
0.00193 0.49 0.02
0.00095 0.17 0.01
0.07094 10.01 0.04
0.17778 23.66 0.06
0.00050 0.06 0.01
0.08114 8.49 0.03
0.00601 0.62 0.02
0.00055 0.06 0.02
0.01019 1.08 0.03
0.04215 4.36 0.04
0.00912 1.08 0.05
100.0
k Ratio
Wt%
Atomic
%
66.35
0.46
0.15
7.88
17.91
0.04
4.62
0.33
0.03
0.42
1.66
0.17
100.0
Standard
Label
SiO2
Albite
MgO
Al2O3
SiO2
NaCl
KBr
Wollastonite
Ti
Mn
Fe
BaF2
Factory
Standard
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
11
O
Al
Si
Cl
K
Line
Type
K series
K series
K series
K series
K series
Ca
K series 0.11
0.00102
0.79
0.09
0.57
Mn
Fe
Ag
Ba
Total
K series
K series
L series
L series
0.00502
0.04110
0.00434
0.00232
3.96
31.60
3.69
2 .01
100.0
0.20
0.38
0.22
0.25
2.08
16.33
0.99
0.42
100.0
2 FeSiO
Apparent
Concentration
3.51
0.58
1.39
0.23
1.25
0.50
4.11
0.43
0.25
29.16
5.88
12.84
1.79
8.27
Wt%
Sigma
0.43
0.14
0.19
0.08
0.15
Atomic
%
52.58
6.29
13.19
1.46
6.10
k Ratio
Wt%
0.01182
0.00419
0.01103
0.00202
0.01063
Standard
Label
SiO2
Al2O3
SiO2
NaCl
KBr
Wollastoni
te
Mn
Fe
Ag
BaF2
Factory
Standard
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
12
13
Supplementary data 4
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
from the BIF-type iron formation (sample M1-10-21 Jasper).
The data do not represent the quantitative equivalent of the
phases in specific bands or their exact spatial arrangement in the
materials.
Phase
Fraction (%)
1 SiO
2
MnSiPbO
3 FeSiO
4 SiFeO
5 PbO
6 SiFeAsO
7 SiO
8 MnO
Pixel Count
88.8
2.7
39988
1225
2.4
3.0
0.4
0.4
0.0
0.0
1099
1333
159
185
5
4
14
1
Line
Apparent
k Ratio
SiO Type
Concentration
O
K series 82.59
0.27791
55.48
Wt%
Sigma
0.05
Wt%
71.85
Standard
Label
SiO2
Factory
Standard
Yes
Atomic %
Al
K series 3.44
0.02468
2.95
0.01
2.26
Al2O3
Yes
Si
Cl
K
Mn
Fe
Zn
As
Pb
Total
K series
K series
K series
K series
K series
K series
L series
M series
0.27602
0.00087
0.03503
0.01600
0.08741
0.00076
0.00508
0.00961
28.08
0.09
3.02
1.37
7.31
0.07
0.65
1.01
100.0
0.03
0.01
0.01
0.01
0.03
0.02
0.02
0.03
20.71
0.05
1.60
0.52
2.71
0.02
0.18
0.10
100.0
SiO2
NaCl
KBr
Mn
Fe
Zn
InAs
PbTe
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
34.83
0.10
4.14
1.60
8.74
0.08
0.96
1.03
15
16
17
18
Supplementary data 5
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
from the BIF-type iron formation (sample M1-10-21Top). The
data is obtained from crushed materials to improve exposure of
potential mineralogical phases and does not represent the
quantitative equivalent in specific to bands or their exact spatial
arrangement in the materials.
Phase
1 SiO
2 FeSiO
3 SiAl
Fraction (%)
Pixel Count
96.9
0.4
0.0
43661
200
10
19
1
SiO
O
Na
Al
Si
Cl
K
Ti
Mn
Fe
Total
Line
Type
K series
K series
K series
K series
K series
K series
K series
K series
K series
Apparent
Concentration
40.27
0.11
4.18
29.86
1.45
6.24
0.11
0.17
2.63
k Ratio
0.13552
0.00045
0.03002
0.23664
0.01270
0.05289
0.00107
0.00167
0.02632
Wt%
Sigma
50.10 0.09
0.13 0.02
4.69 0.03
33.10 0.07
1.82 0.02
6.64 0.03
0.13 0.02
0.21 0.02
3.19 0.04
100.0
Wt%
Atomic
%
65.59
0.12
3.64
24.69
1.08
3.56
0.06
0.08
1.20
100.0
Standard
Label
SiO2
Albite
Al2O3
SiO2
NaCl
KBr
Ti
Mn
Fe
Factory
Standard
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
20
21
Supplementary data 6
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
from the BIF-type iron formation (sample M1-10-21Top). The
data is obtained from crushed materials to improve exposure of
potential mineralogical phases and does not represent the
quantitative equivalent in specific to bands or their exact spatial
arrangement in the materials.
22
Phase
1 SiO
2 FeSiClO
3 FeO
Fraction (%)
Pixel Count
73.3
17.3
2.8
33030
7782
1260
23
24
Supplementary data 7
ESEM-EDS micrographs of Si quartz crystal bulk-crushed
sample from the BIF-type iron formation (sample M1-1021Top).
Phase
1 SiO
2 Fe
Fraction (%)
Pixel Count
90.9
7.0
40938
3149
25
26
Supplementary data 8
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
bulk-crushed at the transition between BIF-type and CIF iron
formation (sample M1-10-09).
Phase
1 SiO
2 SiMnO
3 SiFeO
4 MnO
Fraction (%)
Pixel Count
71.4
12.0
13.5
0.0
32191
5417
6062
4
27
28
29
Supplementary data 9
ESEM-EDS micrographs of nano-size grains showing
mineralogical maps of Fe and Si phases in bulk-crushed sample
at the transition between BIF-type and CIF iron formation
(sample M1-10-09).
Phase
Fraction (%)
1 MnSiO
2 AgO
3
MnFeAgSiO
4 SiO
Pixel Count
62.3
4.1
29.4
28067
1825
13231
0.0
7
30
31
32
Supplementary Data 10
Redox state for the deposition of the BIF-type units
Figure 1 below shows average Rare Earth Element (REE) distribution reported for the Milos
manganese formation (n=27) and the adjacent Milos iron formation facies analysed in this study
(n=6) normalized to the North American Shale Standard (NASC). The data for the manganese
formation known to be deposited under oxic conditions and data for the iron formation are
adapted from Glasby et al. (2005) and Chi Fru et al. (2013), respectively. True Ce anomalies
were calculated for the BIF deposits as: Ce/Ce*=Ce(SN)/0.5Pr(SN) + 05La(SN) and
Pr/Pr*=Pr(SN)/0.5Ce(SN) + 0.5Nd(SN) (Bau et al., 1996); SN represents shale-normalized values.
True negative Ce anomalies apply when the Ce/Ce* and Pr/Pr* values are less than and
greater than 1, respectively (Bau et al., 1996). The Ce/Ce* anomalies ranged from 0.32 to 1.28,
averaging 0.75±0.38 for the iron formation, except for one out of the six samples that was >1.
The Pr/Pr* values were in the range of 0.78-1.1, averaging 1.02±0.13, with the exception of one
sample that was <1. We infer a general lack of significant negative Ce anomalies, comparable to
those reported for Archaean and early Proterozoic BIFs formed in suboxic to anoxic conditions
(Planavsky et al., 2010), usually associated with Algoma-type BIFs deposited proximal to active
volcanic settings (e.g., Han et al., 2014). The positive Eu trend in the Figure 1, suggests both the
iron and manganese formations are predominantly of hydrothermal origin (Han et al., 2014).
Both observations are consistent with previously suggested redox conditions under which both
deposits formed and their provenance (Glasby et al., 2005; Chi Fru et al., 2013).
6
1.2
4
0.8
2
0.4
0
Fe Formation
(NASC normalized)
Mn Formation
(NASC normalized)
Manganese Formation
Iron Formation
0
La Ce Pr Nd Sm Eu Gd Tb Ho Er Tm Yb Lu
Fig. 1. Average Rare Earth Element (REE) distribution for the Milos manganese formation and
the adjacent Milos iron formation
Reference
33
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