Ueda et al. Progress in Earth and Planetary Science (2016) 3:35
DOI 10.1186/s40645-016-0111-8

Progress in Earth andPlanetary Science

RESEARCH ARTICLE

Open Access

Reactions between komatiite and CO2-richseawater at 250 and 350 °C, 500 bars:
implications for hydrogen generation in the
Hadean seafloor hydrothermal system
Hisahiro Ueda1,2*, Takazo Shibuya2,3,4, Yusuke Sawaki1, Masafumi Saitoh2,3,4, Ken Takai2,3,4,5
and Shigenori Maruyama6

Abstract
To understand the chemical nature of hydrothermal fluids in the komatiite-hosted seafloor hydrothermal systemin the Hadean, we conducted two hydrothermal serpentinization experiments involving synthetic komatiite anda CO2-rich acidic NaCl fluid at 250 and 350 °C, 500 bars. During the experiments, the komatiites were strongly
carbonated to yield iron-rich dolomite (3–9 wt.% FeO) at 250 °C and calcite (<0.8 wt.% FeO) at 350 °C, respectively. The
carbonation of komatiites suppressed H2 generation in the fluids. The steady-state H2 concentrations in the fluid wereapproximately 0.024 and 2.9 mmol/kg at 250 and 350 °C, respectively. This correlation between the Fe content incarbonate mineral and the H2 concentration in the fluid suggests that the incorporation of ferrous iron into thecarbonate mineral probably limited magnetite formation and consequent generation of hydrogen during theserpentinization of komatiites. The H2 concentration of the fluid at 350 °C corresponds to that of modern H2-richseafloor hydrothermal systems, such as the Kairei hydrothermal field, where hydrogenotrophic methanogens
dominate in the prosperous microbial ecosystem. Accordingly, the high-temperature serpentinization of komatiite
would provide the H2-rich hydrothermal environments that were necessary for the emergence and early evolution oflife in the Hadean ocean. In contrast, H2-rich fluids may not have been generated by serpentinization at temperatures
below 250 °C because carbonate minerals become more stable with decreasing temperature in the komatiite-H2O-CO2
system.
Keywords: Komatiite, CO2-rich condition, Early Earth, Hydrothermal alteration, Serpentinization

Introduction
Deep-sea hydrothermal environments have been considered as a favorable environment for the emergence andearly evolution of life on Earth (e.g., Yanagawa and Kojima
1985; Russell and Hall 1997). In particular, H2-rich hydrothermal fluids generated through the serpentinization ofultramafic rocks would have driven prebiotic chemical
evolution and the development of biotic energy metabolisms (Takai et al. 2006; Amend and McCollom 2009;* Correspondence: ueda.h.ai@m.titech.ac.jp
1
Department of Earth and Planetary Sciences, Tokyo Institute of Technology,
2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
2
Laboratory of Ocean-Earth Life Evolution Research (OELE), Japan Agency for
Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho,
Yokosuka 237-0061, Japan
Full list of author information is available at the end of the article

Russell et al. 2014; Nakamura and Takai 2014; Shibuya et
al. 2016). Molecular hydrogen (H2) generation duringserpentinization is caused by the reduction of water in
conjunction with the oxidation of ferrous iron in silicates.
This process is written as the following simplified reaction (e.g., Allen and Seyfried 2003; Seyfried et al. 2007;
McCollom and Bach 2009):
2ðFeOÞrock þ H2 O→ðFe2 O3 Þrock þ H2 ;where the ferric iron-bearing solid phase generally precipitates as magnetite (Fe3O4). Therefore, H2 generationis strongly related to magnetite formation duringserpentinization (McCollom and Bach 2009).
Among the various prospects for the seafloor hydrothermal systems in the early Earth (e.g., Kump and Seyfried© The Author(s). 2016 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

2005; Shibuya et al. 2010), two types of serpentinization
are hypothesized to be dominant in the Hadean ocean:a komatiite-hosted high-temperature type at oceanicislands/plateaus (Takai et al. 2006; Yoshizaki et al. 2009;
Shibuya et al. 2015) and a low-temperature alkaline
type hosted by komatiites or peridotites at off-ridge
ocean floors (e.g., Russell et al. 2010, 2014; Shibuya et
al. 2016). Based on the geological records, Archean
oceanic crust was likely much thicker than modern
equivalents owing to the higher potential mantle
temperature at that time (Ohta et al. 1996; Komiya et
al. 2002; Komiya 2004; Moores 2002; Shibuya et al.
2012). This thick lid of oceanic crust probably limited
the exposure of mantle peridotites on the seafloor, thus
suggesting that komatiite volcanism would have beenmuch more abundant than the exposed mantle peridotites
that are frequently observed near modern slow-spreading
ridges without a sufficient magmatic supply (Takai et al.
2006). Therefore, it has been pointed out that H2-richseafloor hydrothermal environments would have been
predominantly driven by komatiite volcanism in the
Hadean ocean (Takai et al. 2006). On the other hand,
the low-temperature alkaline type could provide distinctive chemical environments such as large pH gradients inthe seawater-hydrothermal fluid mixing zones, which may
also have been advantageous for the possible developmentof proton-motive energy metabolisms (Russell et al. 2014;
Shibuya et al. 2016).
Previously, hydrothermal alteration experiments havebeen conducted to understand the potential of H2 generation during the serpentinization of komatiites underCO2-free conditions (Yoshizaki et al. 2009; Shibuya et al.
2015; Suzuki et al. 2015). However, as suggested by theoretical calculations (Walker 1985; Kasting 1993; Sleep
and Zahnle 2001) and geological records (Lowe and Tice
2004; Ohmoto et al. 2004; Shibuya et al. 2007, 2012,2013a), the atmospheric CO2 levels in the early Earthwere likely much higher than the modern level. Furthermore, it has been experimentally demonstrated that carbonate formation during the serpentinization of olivine
under CO2-rich conditions suppresses H2 generation in
fluids (Jones et al. 2010; Klein and McCollom 2013;
Neubeck et al. 2014). Recently, some experiments havebeen conducted in komatiite-CO2-H2O systems (Lazaret al. 2012; Hao and Li 2015), but H2 generation in
fluids was not the objective in these studies. Therefore, the potential for hydrogen generation throughthe serpentinization of komatiites in the Hadean has
not yet been experimentally evaluated under CO2-richconditions.
In this study, we conducted two experiments thatsimulate the reactions between komatiite and CO2-richseawater at 250 and 350 °C, 500 bars, using a batch-type(closed system) hydrothermal reactor (Yoshizaki et al.

Page 2 of 142009). The experiments revealed the chemical composition of high-temperature hydrothermal fluids and CO2
absorption ability of komatiite through serpentinization
under CO2-rich conditions. The results demonstrate thesignificance of komatiite-hosted hydrothermal systems
for seawater chemistry and provide insight into the H2rich hydrothermal environments in the CO2-rich Hadean
ocean.

Methods/Experimental
Synthesis of komatiite

The komatiite used in the experiments was synthesizedfrom a mixture of 12 reagents (SiO2, TiO2, Al2O3, Fe2O3,
MnO, MgO, CaCO3, Na2CO3, K2CO3, P2O5, NiO, andCr2O3). The chemical composition of the mixed reagentswas adjusted to Al-depleted (Barberton-type) komatiite(Smith et al. 1980; Wei et al. 1990; Yoshizaki et al. 2009)
because the volcanism of Al-depleted komatiite was likely
more predominant than Al-undepleted komatiite in the
Hadean (Shibuya et al. 2015). The mixed powder wasplaced in a Pt-Rh crucible at 1000 °C for 1 h in an electronic furnace to decarbonate the reagents. The mixture
was melted at 1600 °C for 0.5 h at the oxygen fugacity ofquartz-fayalite-magnetite (QFM) buffer regulated by a
H2-CO2 gas mixture (Canil 1997). To create a spinifex
texture of olivine, the temperature was lowered to 1450 °C
over 1.5 h. Next, the crucible was quenched to room
temperature, thus yielding a fresh spinifex-textured
komatiite (Fig. 1). The composition and texture of thesynthetic komatiite and its mineral/glass phases wereanalyzed using X-ray diffraction (XRD), X-ray fluorescence(XRF), and an electron probe microanalyzer (EPMA)(Table 1). In the interstitial glass, dendritic olivine crystals
configurate a spinifex texture. Broadly depending on size,these crystals have Mg# values ranging from 89 to 94.
Small amounts of chromian spinels are disseminated in
the vicinity of the olivine crystals. Owing to such a mineral
assemblage, almost all Ca in the komatiite was partitioned
into the interstitial glass (Fig. 1 and Table 1). The synthesized komatiite was crushed in a tungsten mortar andsieved to obtain a <100 μm powder. To remove any contamination of organic materials during sample preparation, the powdered komatiite was washed with acetone
and distilled water several times and dried for 12 h in anoven at 50 °C.
Experimental system

The Inconel alloy autoclave used for the hydrothermal
alteration experiment is based on the study by Seyfried
et al. (1979). It resists corrosion and withstands hightemperature and high-pressure conditions (up to 600 °C
and 600 bars; Fig. 2). The reaction cell is made of a gold
bag with a titanium head because of the resistance of
these materials to high-temperature fluids. Furthermore,Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Page 3 of 14

Table 1 Compositions of the synthetic komatiite, mineral/glass
phases therein, starting materials used in a previous experiment(wt.%)a

100 µmb
Gl

SampleAl-depleted komatiite

OlivineGlass

SpinelBasaltb

SiO2

46.29

41.02

50.74

0.22

49.84

TiO

0.37

0.00

0.68

0.22

0.73

Al2O3

4.30

0.20

7.74

6.43

15.82

Cr2O3

0.21

0.48

0.52

52.22

–

FeOtotala

12.52

9.70

14.81

22.03

11.00

MnO

0.13

0.09

0.18

0.14

0.22

MgO

27.47

48.80

12.57

15.49

9.44

CaO

7.20

0.30

11.84

0.22

10.84

Na2O

0.06

0.00

0.23

0.00

1.88

K2O

0.02

0.02

0.05

0.02

0.18

NiO

0.11

0.34

0.01

0.22

–

Total

98.68

100.95

99.37

97.23

99.95

#c

79.64

89.96

60.21

55.62

60.47

Ol

Mg
Ol

–, no mentionaTotal iron as FeO
bSynthetic basalt used in Shibuya et al. (2013b)c
Mg# = [Mg / (Mg+Fe)] × 100

Spl

Ol

100 µmFig. 1 a Photomicrograph taken in cross-polarized light and b abackscattered electron (BSE) image of the synthetic komatiite. Ol olivine,
Spl spinel, Gl glass

value (approximately 550 mmol/kg) because of the absence of continents and the associated salt deposits/saline
water (Knauth 2005). The komatiite powder was reactedwith this hypothetical seawater in the reaction cell at 250
and 350 °C, 500 bars for 1530–2760 h (hereafter abbreviated as Exp-250 and Exp-350, respectively). At the
Sampling valve

gold has sufficient flexibility to allow the fluid inside thereaction cell to be pressurized by the surrounding water.
In addition, to avoid possible H2 generation via the reaction of metallic titanium with water, the surface of the titanium was completely oxidized before the experiments.
To eliminate organic contamination, all materials incontact with the reacting fluid were baked in a muffle
furnace at 450 °C for 5 h.
The initial solution used in the experiments wascontrolled at pH 4.9 and 400 mmol/kg of ΣCO2(=CO2 (aq) + HCO3− + CO32−) by the addition of NaHCO3,
NaCl, and HCl to ultrapure water, according to the previous studies suggesting that Hadean seawater was acidic
due to the high partial pressure of CO2 in the atmosphere(e.g., Kasting 1993; Macleod et al. 1994). To avoid the degassing of CO2 by a reaction between NaHCO3 and HCl
prior to the sealing of the reaction cell, these materials
were separately placed in the gold tube and then mixed
after sealing (Shibuya et al. 2013b). The Cl concentrationof the solution was regulated to be approximately
1000 mmol/kg because salinity of seawater in the early
Earth was potentially 1.5–2 times higher than the modern

Thermometer

Manometer
Water
Pump

Titanium headGold bagHeaterMinerals &fluid sample

Pressurized water
Fig. 2 Schematic illustration of the Inconel alloy autoclave used inthis study (modified after Yoshizaki et al. 2009). The synthesizedkomatiite and hypothetical Hadean seawater were sealed in thegold bagUeda et al. Progress in Earth and Planetary Science (2016) 3:35

beginning of the experiments, the water/rock mass ratios
were adjusted to approximately 5 because water/rock ratios are commonly below 5 in the high-temperature regions of natural subseafloor hydrothermal systems(Wetzel and Shock 2000). The water/rock mass ratio decreased to ~3 at the end of the experiments due to themultiple fluid samplings during the experiments.
Sampling and analytical methods

During the experiment, approximately 3–4 g of fluid
samples was collected several times through a gold-lined
sampling tube. For CO2 and H2 analyses, 0.5 mL of fluid
sample was directly introduced to each Ar-purged,
sealed vial at room temperature. Especially, for the CO2
analysis, the sampled fluid was acidified (pH <2) by adding HCl to ensure the complete extraction of the dissolved bicarbonate and carbonate ions. Quantitative
analysis for gas species was conducted by gas chromatography. The overall detection precision for the analyses of ΣCO2 and H2 concentrations in the fluid wereboth better than 5%. For the analysis of other dissolved
species, 0.2 mL of the fluid was collected in two vials, towhich either HNO3 or NaOH was immediately added to
avoid the precipitation of transition metals (Fe and Mn)
and silicic acid species, respectively. The fluid samples
were analyzed using inductively coupled plasma opticalemission spectrometry and ion chromatography. The
analytical precision (2σ) was approximately 2% for Cl
and Na, and 5% for the other elements.
The pH of the fluid samples was determined using a
pH meter at 25 °C under atmospheric conditions. The
significant digits and precision of the pH measurementare 2 digits and ±0.1 units. This measurement was performed 1 h after sampling to allow the stabilization of
the pH against CO2 degassing. The pH25 °C of the fluid
cannot be measured directly because it rapidly changes
due to CO2 degassing after the sampling of fluid fromthe reactor. The amount of degassed CO2 was determined from the ΣCO2 concentrations of the fluid sample
directly introduced into the sealed vial and of the fluid
degassed under atmospheric conditions, then the original pH25 °C was calculated based on the amount ofdegassed CO2. We calculated pHin-situ of the hightemperature fluid in the reaction cell with the Geochemist’s Workbench computer code (Bethke 2008)
based on the pH at room temperature (pH25 °C ) andconcentrations of dissolved elements/species and gases. In
the pHin-situ calculations, charge balance was constrainedby pH25 °C , while Na was used to compensate for imbalanced charges derived from analytical errors. The required thermodynamic database was generated by the
SUPCRT92 computer program (Johnson et al. 1992),
using thermodynamic data of minerals, aqueous species, and complexes reported in Shock and Helgeson

Page 4 of 14(1988), Shock and Koretsky (1995), Shock et al. (1989,
1997), Sverjensky et al. (1997), and McCollom andShock (1997). The B-dot activity model was used in thecalculations (Helgeson 1969; Helgeson and Kirkham
1974). The temperature-dependent activity coefficient
for aqueous CO2 was derived from the empirical relationship established by Drummond (1981), and thetemperature-dependent activity of water in NaCl solution was derived from the formulation of Bethke(2008). Cleverley and Bastrakov (2005) provided usefultemperature-dependent polynomial functions for bothof these last-mentioned parameters.
After the experiments, alteration products were retrieved from the reaction cell and dried at 80 °C for 12 h.
The solid alteration product of each experiment was analyzed with XRD and EPMA to determine the assemblage
and composition of the alteration minerals. Powdery alteration products from the experiments at both temperatures
were embedded in Epofix resin, and thin sections weremade of these. The analytical conditions of the EPMA
were 15 kV of accelerating voltage, 10 nA of specimen
current, and 60–80 s of counting time. The precision of
the elemental concentration was less than 10%, which was
based on duplicate measurements. The detection limit for
the elemental concentration was 0.01 wt.%. Moreover, thestarting solid material (unaltered komatiite) was analyzed
with XRD, XRF, and EPMA.

Results and Discussion
Fluid chemistry

The Cl concentration in the fluid was kept relatively
constant throughout both experiments because Cl-bearing
minerals are generally rare in hydrothermally altered rocks(Fig. 3 and Table 2). In contrast, the concentrations of allother components (Na, K, Mg, Ca, Si, Fe, Mn, and ΣCO2)
changed immediately after the beginning of the experiments and reached a near steady state within 2760 h at
250 °C and 1530 h at 350 °C. The Mg concentration in
Exp-250 (36–40 mmol/kg) was 30–40 times higher thanthat in Exp-350 (<1.2 mmol/kg). The Fe concentration in
Exp-250 (0.49–0.97 mmol/kg) was approximately halfthan that in Exp-350 (1.53–1.80 mmol/kg). No large
difference between Exp-250 and Exp-350 was identified
in the concentrations of other dissolved elements. Na(820–1036 mmol/kg across both experiments) had thesecond highest concentration next to Cl. The concentration of Ca increased and converged at 39–49 mmol/kg in
Exp-250 and 37–42 mmol/kg in Exp-350. The concentrations of Si and K were 1.6–6.1 and 0.78–1.24 mmol/kg,
respectively, across both experiments. The concentrationof Mn was the lowest among all analyzed elements (0.15–
0.73 mmol/kg across both experiments).
The ΣCO2 concentration decreased from ca. 400 mmol/kg at the beginning of the experiments to approximately

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Concentration (mmol/kg)

aPage 5 of 14

10

10

10

10

1

10 1

250 °C
10 2
0

500

1000

1500

2000

2500

3000

Time (hours)

Concentration (mmol/kg)

b

10

10

Cl
Na
K
Mg
Ca
Si
Fe
Mn

10

10

1

10 1

350 °C
10 2
0

500

1000

1500

2000

2500

3000

Time (hours)
Fig. 3 Concentrations of the dissolved species in an aqueous fluid coexisting with komatiite powder and its alteration products as a function ofreaction time in the experiments at a 250 and b 350 °C, 500 bars

33 mmol/kg in Exp-250 and approximately 171 mmol/kg
in Exp-350 (Fig. 4a and Table 2). This trend of the steadystate ΣCO2 concentration in the higher-temperature experiment being higher than that in the lower-temperatureexperiment is consistent with the results of experiments
simulating high-temperature reactions between basalt andCO2-rich seawater (Shibuya et al. 2013b). On the other
hand, the pHin-situ values were higher than the pH25 °C
values at the beginning of the experiments due to thetemperature dependence of the ion product of water andspeciation of CO2 species (e.g., Shibuya et al. 2010). As thereaction proceeded, the pHin-situ values finally decreased
to 4.8 in Exp-250 and 5.7 in Exp-350, which are broadly

consistent with those of high-temperature hydrothermal
fluids in modern oceans (pHin-situ = approximately 5)(Seyfried et al. 1991).
In both experiments, the H2 concentration in the fluid
suddenly increased and temporarily reached a high value
just after the start of the experiments, then slightly decreased in each experiment (Fig. 4b). Subsequently, theH2 concentration remained almost constant in Exp-350,
whereas it gradually increased with time in Exp-250. Finally, it converged to reach a steady state at up to
0.024 mmol/kg in Exp-250 and 2.9 mmol/kg in Exp-350(Table 2). This trend indicates that the H2 concentration
was unstable due to extensive water/rock reactions just

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Page 6 of 14

Table 2 Composition of the sampled fluids in the experiments (mmol/kg)
Experiment
250 °C

350 °C

pH25 °CaΣCO2b

pH25 °Cc

pHin-situd

H2

ΣCO2

Cl

Na

K

Mg

Ca

Si

Fe

Mn

0

n.a.

n.a.

4.9

6.0

0.003

396

1128

1036

0.08

n.d.

0.073

n.d.

n.d.

n.d.

43

6.3

0.9

3.7

4.1

0.010

161

1174

939

0.94

36.2

46.5

6.1

0.49

0.19

119

5.8

1.9

4.1

4.5

0.014

67

1168

951

0.89

40.4

39.7

4.4

0.56

0.15

452

6.6

1.0

4.3

4.7

0.004

35

1186

948

0.85

38.4

39.2

2.4

0.77

0.23

Time (h)

859

6.4

2.3

4.6

5.0

0.007

36

1178

937

1.24

37.2

48.7

2.1

0.85

0.24

1771

7.1

1.0

4.4

4.8

0.021

35

1186

820

0.88

36.4

43.6

1.6

0.93

0.24

2760

6.8

1.2

4.5

4.8

0.024

33

1175

949

0.95

36.4

48.8

3.5

0.97

0.25

0

n.a.

n.a.

4.9

7.2

n.d.

396

966

946

0.10

0.03

0.078

n.d.

n.d.

n.d.

90

6.1

1.9

3.8

5.6

6.0

176

971

902

0.78

1.2

39.4

3.7

1.53

0.71

258

6.4

1.7

3.9

5.6

2.8

163

968

882

0.86

1.2

38.0

3.7

1.80

0.73

594

6.4

1.7

3.9

5.6

2.9

179

963

877

0.98

1.1

42.2

3.6

1.65

0.67

1146

6.5

1.8

3.9

5.7

2.7

174

969

900

1.08

1.0

41.1

3.8

1.61

0.63

1530

6.6

1.7

3.9

5.7

2.2

171

953

884

0.81

1.0

37.3

4.1

1.55

0.60

n.a., not analyzed
n.d., not detectedaMeasured pH after CO2 degassingb
Measured ΣCO2 concentration after CO2 degassingcCalculated pH25 °C at 1 bar before CO2 degassing at room temperatured
Calculated pHin-situ at high-temperatures, 500 bars

after the start of the experiments, and then graduallyreached a steady state. The steady-state H2 concentration in Exp-350 was approximately 100 times higher
than that in Exp-250, thus indicating that differences intemperature significantly affect hydrogen generation
during water-rock reactions.
Alteration products

The XRD analysis revealed that the synthetic komatiites
were extensively altered throughout the experiments(Fig. 5). The results show that the alteration product inExp-250 contains dolomite, serpentine, and a smectite/chlorite mixture (Fig. 5b), whereas calcite, serpentine,
and a smectite/chlorite mixture were present as majoralteration minerals in Exp-350 (Fig. 5c). The existence ofserpentine and carbonate minerals in the run products
indicated komatiite was altered by both serpentinizationand carbonation. The precipitated carbonate mineral differed for the two temperatures.
Secondary electron imaging (SEI) and EPMA spot
analysis provided more detailed information on mineral
assemblage and composition (Fig. 6 and Table 3). In
Exp-250, EPMA analyses of the products revealed that
dolomite crystals contained a relatively high content ofiron (3–9 wt.% FeOtotal), whereas the serpentine andsmectite/chlorite mixture had FeOtotal contents of 13–
15.5 wt.% (Fig. 6a–d; Table 3). Siderite (including approximately 40 wt.% FeOtotal) and olivine were present as minor
minerals in the alteration products in Exp-250 (Fig. 6a, c;Table 3). In Exp-350, the EPMA analyses of the alteration

products revealed that calcite crystals had a relatively low
FeOtotal content (0.1–0.8 wt.%) and that the serpentine
and smectite/chlorite mixture had FeOtotal contents of
14–17 wt.% (Fig. 6e; Table 3). Olivine and magnetite werealso identified as minor minerals; however, according to
the SEI observations in many places over the thin sections,
their abundances were likely greater in Exp-350 than in
Exp-250. Comparing the compositions of serpentine andthe smectite/chlorite mixture between Exp-250 and Exp350, no large difference in FeOtotal content was identified.
On the other hand, on average, the FeOtotal content in Febearing dolomite in Exp-250 was ten times higher thanthat in calcite in Exp-350 (Table 3).
Dissolved CO2 concentration and pH

The ΣCO2 concentrations in fluids decreased from approximately 400 to 33 mmol/kg in Exp-250 and 171 mmol/kg in
Exp-350 (Fig. 4a and Table 2). These differing steady-stateΣCO2 concentrations indicate that carbonate minerals aredestabilized with increasing temperature in the komatiiteCO2-H2O system. This trend is consistent with previous
basalt experiments under CO2-rich conditions at 250 and
350 °C, where the final ΣCO2 concentrations were 1 mmol/kg at 250 °C and 108 mmol/kg at 350 °C (Shibuya et al.
2013b). Comparing results for the same temperature, theΣCO2 concentration in our komatiite experiments is higher
than that in the basalt experiments of Shibuya et al.
(2013b), thus indicating that komatiite has a lesser ability
than basalt to absorb CO2 through water-rock reactions.
This would be derived from the lower CaO content ofUeda et al. Progress in Earth and Planetary Science (2016) 3:35

CO2 concentration (mmol/kg)

aPage 7 of 14

400

250 °C
350 °C

300

200

100

0
0

500

1000

1500

2000

2500

3000

Time (hours)

H2 concentration (mmol/kg)

b10

250 °C
350 °C1

is converted to CO2(aq) and OH−, which elevates thepHin-situ value of the hydrothermal fluid (Shibuya et al.
2010). Although reactions with rocks generally cause
fluid pHin-situ to converge near 5.5 (neutral pH at 250–
350 °C), previous experiments have revealed that the alkalinization effect due to the increase in temperature
under CO2-rich conditions potentially elevates thepHin-situ value beyond a neutral pH value at hightemperature, even if the fluid reacts with rocks (Shibuya et
al. 2013b). In this study, however, the assumed pH25 °C of
the initial solution was 4.9, which was likely too low toform substantial HCO3− in the initial solution at room
temperature. This implies that if seawater pH was lower
than approximately 5 (CO2aq was the main species),
metal-rich black smoker-type hydrothermal fluids would
have been generated in the Hadean komatiite hydrothermal systems in contrast to the metal-poor, alkaline hydrothermal fluids in the Archean basalt-hosted system.
Although the difference in whole rock composition between komatiite and basalt should be experimentally
evaluated, seawater pH was likely an important factor
controlling the composition of hydrothermal fluids inthe early Earth.
Serpentinization of komatiites

10 1

10 2

10 3
0

500

1000

1500

2000

2500

3000

Time (hours)
Fig. 4 Changes in a dissolved CO2 and b H2 concentrations in thesampled fluids as a function of reaction time

komatiite (compared with basalt) because CaO is themain component in the alteration carbonate (mainly
calcite or dolomite) in the basalt and komatiite experiments (Shibuya et al. 2013b and the present study).
The final pHin-situ values of fluids in the present experiments (pHin-situ = 4.8 at 250 °C and 5.7 at 350 °C) areclearly lower than those of the previous basalt-CO2NaCl fluid experiments (pHin-situ = 6.6 at 250 °C and 7.2
at 350 °C) (Shibuya et al. 2013b). This discrepancy isprobably derived from the lower pH25 °C of the initial solution (pH25 °C = 4.9) in our experiments than the valueof 6.5 in the basalt experiments and/or compositional
differences between komatiite and basalt. In general,
under CO2-rich and near-neutral pH conditions at room
temperature, substantial HCO3− is dissolved in the solution. With increasing temperature, the dissolved HCO3−

In this section, we compare our experimental resultswith conditions in natural environments and thermodynamic calculations in order to characterize the reaction occurring in the reaction cell. The EPMA analysisof alteration products revealed the presence of a small
quantity of olivine in both experiments, but the amountof olivine in Exp-350 was greater than that in Exp-250.
Thermodynamic calculations for serpentinization of olivine and harzburgite (80 wt.% of olivine, 15 wt.% oforthopyroxene, and 5 wt.% of clinopyroxene) indicatethat olivine becomes stable and is one of the major minerals at temperatures above approximately 315–350 °C
in the peridotite- or olivine-H2O system (e.g., McCollom
and Bach 2009; Klein et al. 2013). In analogy with thecalculation, the experiments in this study suggest that
olivine stabilizes with increasing temperature, evenduring komatiite serpentinization at 250–350 °C. Nevertheless, olivine was observed as a minor phase even in
Exp-350. This is probably due to the composition of
komatiite that contains a certain level of Al2O3 would
stabilize serpentine and/or chlorite/smectite because
smectite becomes stable as bulk Al2O3 content increases in ultramafic rocks such as komatiite (Shibuya
et al. 2015). However, it was difficult to determine
whether the igneous olivine still remains in the absenceof any reaction with a fluid or if the alteration olivine
was newly created through serpentinization.
Brucite commonly occurs in serpentinized rocks inmodern oceanic plates (e.g., Bach et al. 2006; Klein et al.

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Page 8 of 14

Fig. 5 Representative XRD patterns (CuKα) of a the unaltered synthetic komatiite and the alteration products of b Exp-250 and c Exp-350.
Dol dolomite, Cal calcite, Sme smectite, Chl chlorite, Ol olivine, and Serp serpentine

2014) but was not found in the alteration products inthe present experiments. The absence of brucite in Exp350 is consistent with the thermodynamic calculations
for the serpentinization of olivine and harzburgite underCO2-poor conditions, since brucite is destabilized attemperatures above ~350 °C (McCollom and Bach 2009;
Klein et al. 2013). On the other hand, the instability ofbrucite in Exp-250 is likely due to the CO2-rich condition in the experiment because previous experiments revealed that Mg-bearing carbonate mineral is more stable
than brucite under CO2-rich conditions (Zhao et al.
2010; Hövelmann et al. 2012; Klein and McCollom2013). Alternatively, high dissolved Si content in thefluid (3.7–4.1 mmol/kg) possibly prohibited brucite formation, which is supported by thermodynamic calculations (e.g., Klein and McCollom 2013).

Carbonation of komatiites

The steady-state ΣCO2 concentrations in both experiments
indicate that the amount of carbonate mineral was greaterin Exp-250 than in Exp-350 (Fig. 4a and Table 2). The formation of dolomite in Exp-250 is characteristically different
from the basalt-CO2 experiments that yielded only calcite
as carbonate in previous studies at 250 and 350 °C (Shibuya
et al. 2013b). Comparing the experimental conditions of
this study to those in the previous study, compositional differences between komatiite and basalt and/or the difference
in initial pH (4.9 in this study, and 6.5 in Shibuya et al.
(2013b)) likely caused the difference in precipitated carbonate species in the alteration products at 250 °C. Furthermore, it was revealed that the precipitated carbonate
species strongly affected the Mg concentration in thehydrothermal fluid, i.e., Mg concentration in Exp-250

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Page 9 of 14

a

b

Sd
Dol
Sme/Chl or Serp
SEI

BSE
SEI
20 µm

20 µm

d

c
Dol

Sme/Chl or SerpOl

Sme/Chl or Serp
SEI

SEI
80 µm

60 µm

f

e
Ol

Mag
Sme/Chl or Serp

Cal

SEI

SEI
40 µm

20 µm

Fig. 6 Representative SEI images of alteration products (a–d) in the experiment at 250 °C and (e, f) in the experiment at 350 °C. Sd siderite,
Dol dolomite, Cal calcite, Sme smectite, Chl chlorite, Ol olivine, Serp serpentine, and Mag magnetite(carbonate as dolomite) is 30–40 times higher than that inExp-350 (carbonate as calcite), while fluid Ca concentrations in both experiments are similar.
Previously, carbonate species were reported to correlate with the concentration ratio between Mg and Ca(mMg2+/(mMg2+ + mCa2+)) and the temperature of thefluid (Fig. 7) (Rosenberg and Holland 1964; Rosenberg etal. 1967; Tribble et al. 1995). In Exp-350, carbonate was
precipitated as calcite, whereas the mMg2+/(mMg2+ +mCa2+) value of the fluid was approximately 0.03; thus, it
clearly falls within the stability field of calcite. On theother hand, the mMg2+/(mMg2+ + mCa2+) value of thefluid in Exp-250, where dolomite precipitated, was approximately 0.43, which is near the dolomite/magnesite
stability boundary. Therefore, the extremely high fluid
Mg concentration in Exp-250 is consistent with theprecipitation of dolomite in the alteration product. However, it is difficult to discuss the anteroposterior relation

between dolomite formation and enrichment of Mg influids because the decrease in ΣCO2 concentration and
the Mg enrichment in the fluid were already confirmed at
the first sampling. It is widely accepted that seafloorhydrothermal systems play a significant role as Mg sinksin the modern ocean because basaltic oceanic crusts incorporate seawater Mg into alteration minerals such as
smectite and chlorite through hydrothermal alteration
at near mid-ocean ridges (e.g., Alt 1995). In addition,Charlou et al. (2002) reported that ultramafic rockhosted high-temperature hydrothermal systems provide
fluids with little Mg into seawater and generally act as
Mg sinks in the ocean. On the other hand, weatheringof ultramafic rocks exposed at seafloor below 150 °C
and hydrothermal circulation at high water/rock ratios
provide Mg into seawater (Snow and Dick 1995). Our
results hypothesize that dolomite formation during
the serpentinization of komatiite would be a sourceUeda et al. Progress in Earth and Planetary Science (2016) 3:35

Page 10 of 14

Table 3 Composition of run products (wt.%)
Experiment-250 °C

Experiment-350 °C

SampleSerp or Sme/Chl mixtureb

SiO2

41.37

40.89

33.38

Dolomite
0.00

0.00

Siderite
0.00

3.80

Serp or Sme/Chl mixtureb
38.55

35.52

38.87

Calcite
0.00

0.00

0.00

Olivinec

Magnetite

41.60

2.76

TiO

0.44

0.43

0.64

0.01

0.05

0.15

2.96

0.52

0.47

0.17

0.00

0.00

0.00

0.01

0.18

Al2O3

7.00

6.88

11.56

0.06

0.00

0.01

0.13

6.82

6.84

6.38

0.07

0.00

0.01

0.06

0.02

Cr2O3

0.47

0.43

0.29

0.11

0.06

0.12

1.46

0.37

0.47

0.39

0.04

0.00

0.02

0.14

0.23

FeOtotala

13.32

13.65

15.55

3.22

6.66

9.05

39.55

16.84

16.51

13.77

0.18

0.37

0.77

5.33

85.06

MnO

0.16

0.14

0.18

0.53

0.49

0.49

0.12

0.19

0.34

0.20

0.13

0.36

0.72

0.05

0.40

MgO

24.05

23.48

24.10

17.69

17.39

17.43

1.32

23.13

25.21

25.98

0.17

0.74

0.79

51.46

0.36

CaO

0.83

0.81

0.17

26.01

29.47

23.75

0.26

0.28

0.13

0.46

56.29

54.95

58.68

0.32

0.29

Na2O

0.06

0.08

0.03

0.03

0.11

0.04

0.09

0.16

0.07

0.15

0.01

0.00

0.00

0.00

0.02

K2 O

0.09

0.11

0.02

0.03

0.02

0.02

0.05

0.04

0.01

0.03

0.01

0.01

0.01

0.02

0.03

NiO

0.17

0.20

0.12

0.00

0.00

0.08

0.10

0.10

0.00

0.16

0.01

0.00

0.05

0.45

0.10

Total

87.96

87.10

86.05

47.67

54.25

51.13

49.84

86.98

85.59

86.56

56.91

56.43

61.04

99.43

89.45

Mg# d

76.30

75.40

73.43

90.73

82.31

77.43

5.63

71.00

73.13

77.08

61.52

78.23

64.50

94.51

0.74

a

Total iron as FeO
Serpentine or smectite/chlorite mixture
Alterlation or relict olivinedMg# = [Mg / (Mg+Fe)] × 100
b
c

400

1M
2M

250 °C
350 °C

350

Temperature (°C)

300

magnesite + solution

250

200
dolomite+ solution

150

100
calcite + solutlon

50

0
0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

mMg2+/ (mMg2+ + mCa2+) in solution
Fig. 7 The mMg2+/(mMg2+ + mCa2+) values of hydrothermal fluidsin Exp-250 and Exp-350 plotted on the calcite-dolomite-magnesite
stability fields estimated from experiments at 275–420 °C and their
extrapolation to 0 °C (modified after Tribble et al. 1995). The dottedand solid curves are for the solutions with 2 and 1 M of Ca-Mg chloride,
respectively. The blue circle and pink diamond indicate the values in
Exp-250 and Exp-350, respectivelyof Mg for the Hadean ocean, even when thetemperature range of hydrothermal reaction zones
was near 250 °C. Further experiments will be necessary to justify this hypothesis.
The dolomite crystals formed in this study containup to 9 wt.% FeOtotal in Exp-250 because Fe substitutes Mg in dolomite during its precipitation owing
to the similarity in ion radius between Fe and Mg(Mg2+: 0.72 Å; Fe2+: 0.61 Å) (Jia 1991). A similar Febearing carbonate mineral was also reported in a hydrothermal alteration experiment for komatiite conductedunder CO2-rich conditions (water 50.1 mg + CO2 7.3 mg:
about 3300 mmol/kg at the starting condition) at 300 °C
and 500 bars (Hao and Li 2015). Furthermore, Klein and
McCollom (2013) reported the precipitation of Fe-bearing
magnesite (FeO = 6.78 wt.%) through the serpentinizationof olivine under CO2-rich conditions at 230 °C. Althoughdifferences in the composition of the starting materials
between the previous studies and our experiments would
have caused the difference in carbonate species, it seems
likely that carbonate minerals formed duringserpentinization under CO2-rich conditions contain
substantial FeO, probably at temperatures below approximately 300–350 °C.
Effect of seawater CO2 on H2 concentration in fluid

The maximum steady-state fluid H2 concentrations
were 0.024 mmol/kg in Exp-250 and 2.9 mmol/kg in
Exp-350 (Fig. 4b), and the results are consistent withthe analysis of solid alteration products. Magnetite,whose formation is related to H2 generation (McCollom

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

and Bach 2009), was observed in Exp-350 but not in Exp250. Nevertheless, the H2 concentrations in both experiments were clearly lower than the steady-state H2 concentration (~20 mmol/kg) in fluid generated by the reactions
between komatiite and a CO2-free NaCl fluid at 300 °C
and 500 bars (Shibuya et al. 2015). Although direct comparison is difficult owing to the difference in temperature
conditions, two possible factors explain the differences between the previous and present experiments in terms of
the steady-state H2 concentrations from the hydrothermal
reaction of komatiite.
The first factor is the temperature dependence of thestability of magnetite in ultramafic systems. At temperatures below 315–350 °C, the amount of magnetite formation increases with increasing temperature, but it drasticallydecreases at temperatures above 315–350 °C because olivine becomes stable (McCollom and Bach 2009; Klein et al.
2013). Moreover, Klein et al. (2013) reported that within
the temperature range of 25–400 °C, the amount of hydrogen generation caused by the reaction with olivine (Fo 90)
reaches a maximum at 322 °C. Thus, the temperature dependence of the stability of olivine and magnetite would bea primary cause of the difference in fluid H2 concentrations
between the previous CO2-free komatiite experiment at
300 °C and our experiments.
The other factor is the presence of CO2 in the experimental system. Based on thermodynamic calculations
simulating the relative amount of magnetite formation at
50–400 °C under 500 bars, Klein et al. (2013) expectedthat the amount of hydrogen generation caused by thereaction with olivine under CO2-free conditions isgreater at 250 °C than at 350 °C. In our experiments,
however, the steady-state fluid H2 concentration was
higher in Exp-350 than in Exp-250. In previous experiments that simulated the reactions between olivine anda CO2-rich fluid at 230 °C and 35 MPa, ferrous ironbearing talc and magnesite were generated, while magnetite formation and H2 generation were limited (Klein
and McCollom 2013). Under CO2-free conditions, theiron is only partitioned into magnetite and ferrous ironbearing silicate in alteration products,aðFeOÞrock þ bH2 O→dðFe2 O3 Þrock þ dH2
þ ða‐2d ÞðFeOÞrock: :In contrast, the interaction between CO2-rich fluid
and rock leads to carbonate mineral precipitation andferrous iron incorporation therein. The reaction occurring under a CO2-rich condition is the following:aðFeOÞrock þ bH2 O þ cCO2 →dðFe2 O3 Þrock þ dH2
þ eðFeOÞrock þ ða‐2d‐eÞðFeCO3 Þrock
þ ðc‐a þ 2d þ eÞCO2 :In both equations, the value of “d” is the amount ofH2 generation and depends on temperature. Therefore,

Page 11 of 14

it was suggested that the lack of H2 generation is due tothe direct incorporation of ferrous iron into carbonate
minerals without its oxidation during the hydrothermal
alteration. In our experiments, although a large difference in the composition of serpentine and smectite/chlorite mixture was not identified between Exp-250 andExp-350, the Fe content of dolomite in Exp-250 (3–9 wt.% FeOtotal) was clearly higher than that of calcite inExp-350 (Table 3). The amount of generated magnetite
in Exp-350 was greater than that in Exp-250. These datasuggest that the amount of ferrous iron incorporated
into the carbonate mineral strongly affected the extent
of magnetite formation and resulting hydrogen generation in the fluid. Although such a trend in the effect of
CO2 on H2 generation has been reported in some previous experiments at temperatures below 230 °C (Jones etal. 2010; Klein and McCollom 2013; Neubeck et al.
2014), our experiments show that the suppression of H2generation by the presence of CO2 in the system occurs
even at higher temperatures (250 °C) and in the CO2H2O-komatiite system. In addition, a small amount offerrous iron incorporated into calcite (up to 0.8 wt.%)
may have also slightly suppressed magnetite formationin Exp-350.
Implications for the Hadean H2-rich hydrothermal
environments

It has been considered that the serpentinization of komatiite would have served as the most ubiquitous
geological process for hosting H2-rich hydrothermal environments in the Hadean ocean (e.g., Takai et al. 2006).
The present experiments constrained the potential forH2 generation during the serpentinization of komatiite
under CO2-rich conditions. This work provides further
important insights into our interpretation of hatcheries
for the emergence and early evolution of life in the
Hadean Earth. Exp-350 showed that the fluid H2 concentration increased up to 2.9 mmol/kg during theserpentinization and carbonation of komatiite. This value
is lower than the maximum H2 concentration of the ventfluids in modern peridotite-hosted hydrothermal systems;
the H2 and ΣCO2 concentrations in modern peridotitehosted hydrothermal systems are 12 and 10.1 mM at
Logatchev field, 16 and 16 mM at Rainbow field (Charlou
et al. 2002), and <1–15 mmol/kg and <0.8 mmol/kg at
Lost City field (Kelley et al. 2005), respectively. However,the H2 concentration in Exp-350 broadly falls within therange of the fluid H2 concentrations in the Kairei field
hosted by both basalt and troctolite (H2 = 2.5–8.5 mmol/
kg and ΣCO2 < 10.1 mmol/kg; Takai et al. 2004; Gallant
and Von Damm 2006; Kumagai et al. 2008; Nakamura
et al. 2009). This suggests that in the Hadean, the komatiite still had great potential to generate H2-rich hydrothermal fluids at high-temperature, even under CO2-richUeda et al. Progress in Earth and Planetary Science (2016) 3:35

conditions. Furthermore, considering that hydrogenotrophic methanogens—long believed to be one of the mostprobable candidates for the earliest living forms and primary producers on Earth (e.g., Takai et al. 2006; Martin etal. 2008)—indeed dominate in the microbial communities
associated with hydrothermal fluids in the Kairei field(Takai et al. 2004), the komatiite-hosted seafloor hydrothermal systems would have fully prepared the energetic
basis of hatcheries for the emergence and early evolutionof hydrogenotrophic living forms in the Hadean ocean.
In contrast, the fluid H2 concentration in Exp-250(0.024 mmol/kg) was much lower than that in Exp-350
and is comparable to the H2 concentration level in the
typical fluids of modern basalt-hosted hydrothermal
fields (Charlou et al. 1996, 2000; Gallant and Von Damm
2006). Given that the H2 generation potential of ultramafic
rocks decreases with decreasing temperature within theunstable region of olivine (McCollom and Bach 2009;
Klein et al. 2013), the serpentinization of komatiite underCO2-rich conditions might not have afforded the H2-richhydrothermal fluids at temperatures lower than 250 °C.
More importantly, carbonate minerals become stable withdecreasing temperature in H2O-CO2-rock systems (e.g.,
Shibuya et al. 2013b), which indicates that the carbonate
formation and resulting limitation of H2 generation would
occur more significantly at lower temperatures (e.g.,<100 °C). Therefore, the possible H2-rich hydrothermal
environments may have been created only in the deep
ocean floor because high hydrostatic pressure can elevate
the temperature of hydrothermal reaction zones (fluidrock reaction zones). In other words, other potential
candidates, such as the hydrothermal systems in on-landand shallow submarine environments, may not have fully
prepared the energetic basis (abundant H2 availability) of
hatcheries for the emergence and early evolution of life in
the Hadean Earth due to low-temperature hydrothermal
reactions.

Conclusions
High-temperature and high-pressure experiments using
komatiite and a CO2-rich NaCl solution revealed thatdifferent hydrothermal reaction temperatures caused differences in the carbonate species in alteration products(iron-rich dolomite at 250 °C and calcite at 350 °C) during the serpentinization of komatiites. The hydrothermal
fluid coexisting with dolomite at 250 °C showed highMg concentrations (up to ca. 40 mmol/kg), which ismarkedly higher than those in typical modern hightemperature hydrothermal fluids (generally less than
1 mmol/kg). This suggests that, in contrast to modern
seafloor hydrothermal systems, the dolomite-bearing
komatiite-hosted hydrothermal systems may have served
as a source of Mg in the Hadean ocean. The steady-state
H2 concentration in Exp-350 (up to 2.9 mmol/kg) was

Page 12 of 14

approximately 100 times higher than that in Exp-250(up to 0.024 mmol/kg) because the amount of ferrous
iron incorporated into carbonate was greater in Exp-250
than in Exp-350. These results perhaps suggest that only
high-temperature komatiite-hosted hydrothermal systems
have the potential to generate H2-rich hydrothermal environments, even in the CO2-abundant Hadean ocean. Further experiments based on a more precise estimation of
the ancient atmospheric/oceanic CO2 levels from geological records will clarify the geochemical nature ofkomatiite-hosted hydrothermal environments and otherpotential hatcheries for the emergence and early evolutionof life in the Hadean Earth because the ΣCO2 concentration in the fluid may significantly affect the mineral assemblage of serpentinized komatiites and hydrothermal
reactions taking place under various conditions.
Abbreviations
BSE: Backscattered electron; EPMA: Electron probe microanalyzer;
Exp-250: Experiment at 250 °C; Exp-350: Experiment at 350 °C;
QFM: Quartz-fayalite-magnetite; SEI: Secondary electron imaging;
XRD: X-ray diffraction; XRF: X-ray fluorescenceAcknowledgements
We thank two anonymous reviewers for many helpful comments that
greatly improved our manuscript. We appreciate Prof. Hodaka Kawahata for
editorial handling. We are grateful to Y. Ueno for discussions.
Funding
This work was supported by Grants-in-Aid for Scientific Research from the Japan
Society for Promotion of Science (JSPS) (No. 15K13583) and the Ministryof Education, Culture, Sports, Science and Technology (MEXT), Japan.
Authors’ contributions
HU, TS, KT, and SM proposed and designed the study. HU and TS carried out
the experiments. HU, TS, and MS prepared the starting materials. HU, TS, MS,
and YS analyzed the fluid samples and solid materials. All authors interpreted
the data, read, and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Earth and Planetary Sciences, Tokyo Institute of Technology,
2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan. 2Laboratory of
Ocean-Earth Life Evolution Research (OELE), Japan Agency for Marine-Earth
Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka
237-0061, Japan. 3Research and Development Center for Submarine
Resources, Japan Agency for Marine-Earth Science and Technology(JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. 4Project Teamfor Development of New-generation Research Protocol for Submarine
Resources, Japan Agency for Marine-Earth Science and Technology(JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. 5Department of
Subsurface Geobiological Analysis and Research (SUGAR), Japan Agency for
Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho,
Yokosuka 237-0061, Japan. 6Earth-Life Science Institute (ELSI), Tokyo Instituteof Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan.
Received: 22 March 2016 Accepted: 21 October 2016

References
Allen DE, Seyfried WE (2003) Compositional controls on vent fluids from ultramafichosted hydrothermal systems at mid-ocean ridges: an experimental study at
400 °C, 500 bars. Geochim Cosmochim Acta 67:1531–1542

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Alt JC (1995) Subseafloor processes in mid-oceanic ridge hydrothermal systems.
In: Humphris SE, Zierenberg RA, Mullineaux LS, Thomson RE (eds) Seafloorhydrothermal systems: physical, chemical, biological, and geologicalinteractions. Geophysical monograph. American Geophysical Union,
Washington, DC, pp 85–114
Amend JP, McCollom TM (2009) Energetics of biomolecule synthesis on early
Earth. In: Zaikowski L, Friedrich JM, Seidel SR (eds) Chemical evolution II: fromthe origins of life to modern society. American Chemical Society,
Washington, DC, pp 63–94
Bach W, Paulick H, Garrido CJ, Ildefonse B, Meurer WP, Humphris SE (2006)
Unraveling the sequence of serpentinization reactions: petrography, mineralchemistry, and petrophysics of serpentinites from MAR 15°N (ODP Leg 209,
Site 1274). J Geophys Res 33, L13306. doi:10.1029/12006GL025681
Bethke CM (2008) Geochemical and biogeochemical reaction modeling.
Cambridge Univ. Press, Cambridge, U. K
Canil D (1997) Vanadium partitioning and the oxidation state of Archaean
komatiite magma. Nature 389:842–845
Charlou JL, Donval JP, Douville E, Jean-Baptiste P, Radford-Knoery J, Fouquet Y,
Dapoigny A, Stievenard M (2000) Compared geochemical signatures and theevolution of Menez Gwen (37°50′N) and Lucky Strike (37°17′N) hydrothermal
fluids, south of the Azores Triple Junction on the Mid-Atlantic Ridge. Chem
Geol 171:49–75
Charlou JL, Donval JP, Fouquet Y, Jean-Baptiste P, Holm N (2002) Geochemistryof high H2 and CH4 vent fluids issuing from ultramafic rocks at the Rainbow
Hydrothermal Field (36°14′N, MAR). Chem Geol 191:345–359
Charlou JL, Donval JP, Jean-Baptiste P, Dapoigny A, Rona PA (1996) Gases andhelium isotopes in high temperature solutions sampled before and after
ODP Leg 158 Drilling at TAG Hydrothermal Field (26° N, MAR). Geophys Res
Lett 23:3491–3494
Cleverley JS, Bastrakov EN (2005) K2GWB: utility for generating thermodynamic
data files for The Geochemist’s Workbench® at 0-1000 °C and 1-5000 bar
from UT2K and the UNITHERM database. Comput Geosci 31(6):756–767
Drummond SE (1981) Boiling and mixing of hydrothermal fluids: chemical effects
on mineral precipitation. Dissertation, Pennsylvania State University
Gallant RM, Von Damm KL (2006) Geochemical controls on hydrothermal fluids
from the Kairei and Edmond Vent Fields, 23°–25°S, Central Indian Ridge.
Geochem Geophys Geosyst 7, Q06018. doi:10.1029/2005GC001067
Hao X, Li Y (2015) Hexagonal plate-like magnetite nanocrystals produced in
komatiite-H2O-CO2 reaction system at 450 °C. Int J Astrobiol 14:547–553
Helgeson HC (1969) Thermodynamics of hydrothermal systems at elevatedtemperatures and pressures. Am J Sci 267:729–804
Helgeson HC, Kirkham DH (1974) Theoretical prediction of the thermodynamic
behavior of aqueous electrolytes at high pressures and temperatures: II.
Debye–Huckel parameters for activity coefficients and relative partial molal
properties. Am J Sci 274:1199–1261
Hövelmann J, Putnis CV, Ruiz-Agudo E, Austrheim H (2012) Direct nanoscaleobservations of CO2 sequestration during brucite [Mg(OH)2] dissolution.
Environ Sci Technol 46:5253–5260
Jia YQ (1991) Crystal radii and effective ionic radii of the rare earth ions. Journalof Solid State Chemistry 95:184–187
Johnson JW, Oelkers EH, Helgeson HC (1992) SUPCRT92: a software package forcalculating the standard molal thermodynamic properties of minerals gases,aqueous species, and reactions from 1 to 5000 bar and 0 to 1000 °C.
Comput Geosci 18:899–947
Jones LC, Rosenbauer R, Goldsmith JI, Oze C (2010) Carbonate control of H2 andCH4 production in serpentinization systems at elevated P-Ts. Geophys Res
Lett 37, L14306
Kasting JF (1993) Earth’s early atmosphere. Science 259(5097):920–926
Kelley DS, Karson JA, Fruh-Green GL, Yoerger DR, Shank TM, Butterfield DA, Hayes
JM, Schrenk MO, Oison EJ, Proskurowski G, Jakuba M, Bradley A, Larson B,
Ludwig K, Glickson D, Buckman K, Bradley AS, Brazelton WJ, Roe K, Elend MJ,
Delacour A, Bernasconi SM, Lilley MD, Baross JA, Summons RE, Sylva SP(2005) A serpentinite-hosted ecosystem: the lost city hydrothermal field.
Science 307:1428–1434
Klein F, McCollom TM (2013) From serpentinization to carbonation: new insightsfrom a CO2 injection experiment. Earth Planet Sci Lett 379:137–145
Klein F, Bach W, McCollom TM (2013) Compositional controls on hydrogengeneration during serpentinization of ultramafic rocks. Lithos 178:55–69
Klein F, Bach W, Humphris SE, Kahl W-A, Jöns N, Moskowitz B, Berquó TS(2014) Magnetite in seafloor serpentinite—some like it hot. Geology
42:135–138

Page 13 of 14

Knauth LP (2005) Temperature and salinity history of the Precambrian ocean:
implications for the course of microbial evolution. Palaeogeogr
Palaeoclimatol Palaeoecol 219:53–69
Komiya T, Maruyama S, Hirata T, Yurimoto H (2002) Petrology and geochemistryof MORB and OIB in the Mid-Archean North Pole region, Pilbara Craton,
Western Australia, implications for the composition and temperature of theupper mantle at 3.5 Ga. Int Geol Rev 44:988–1016
Komiya T (2004) Material circulation model including chemical differentiation
within the mantle and secular variation of temperature and composition of
the mantle. Phys Earth Planet Int 146:333–367
Kumagai H, Nakamura K, Toki T, Morishita T, Okino K, Ishibashi JI, Tsunogai U,
Kawagucci S, Gamo T, Shibuya T, Sawaguchi T, Neo N, Joshima M, Sato T,
Takai K (2008) Geological background of the Kairei and Edmond hydrothermal
fields along the Central Indian Ridge: implications of their vent fluids’ distinct
chemistry. Geofluids 8:239–251
Kump LR, Seyfried WE (2005) Hydrothermal Fe fluxes during the Precambrian:effect of low oceanic sulfate concentrations and low hydrostatic pressure on
the composition of black smokers. Earth Planet Sci Lett 235:654–662
Lazar C, McCollom TM, Manning CE (2012) Abiogenic methanogenesis duringexperimental komatiite serpentinization: implications for the evolution of theearly Precambrian atmosphere. Chem Geol 326–327:102–112
Lowe DR, Tice MM (2004) Geologic evidence for Archean atmospheric andclimatic evolution: fluctuating levels of CO2, CH4, and O2 with an overriding
tectonic control. Geology 32:493–496
Martin W, Baross J, Kelley D, Russell MJ (2008) Hydrothermal vents and the originof life. Nat Rev Microbiol 6:805–814
Macleod G, McKeown C, Hall AJ, Russell MJ (1994) Hydrothermal and oceanic pH
conditions of possible relevance to the origin of life. Orig Life Evol Biosph24:19–41
McCollom TM, Bach W (2009) Thermodynamic constraints on hydrogengeneration during serpentinization of ultramafic rocks. Geochim Cosmochim
Acta 73:856–875
McCollom TM, Shock EL (1997) Geochemical constraints on chemolithoautotrophic
metabolism by microorganisms in seafloor hydrothermal systems. Geochim
Cosmochim Acta 61:4375–4391
Moores EM (2002) Pre-1 Ga (pre-Rodinian) ophiolites: their tectonic andenvironmental implications. GSA Bulletin 114:80–95
Nakamura K, Morishita T, Bach W, Klein F, Hara K, Okino K, Takai K, Kumagai H(2009) Serpentinized troctolites exposed near the Kairei hydrothermal field
Central Indian Ridge: insights into the origin of the Kairei hydrothermal fluid
supporting a unique microbial ecosystem. Earth Planet Sci Lett 280:128–136
Nakamura K, Takai K (2014) Theoretical constraints of physical and chemical
properties of hydrothermal fluids on variations in chemolithotrophic microbialcommunities in seafloor hydrothermal systems. Progr Earth Planet Sci 1(1):1–24
Neubeck A, Duc NT, Hellevang H, Oze C, Bastviken D, Bacsik Z, Holm NG (2014)
Olivine alteration and H2 production in carbonate-rich, low temperature
aqueous environments. Planet Space Sci 96:51–61
Ohmoto H, Watanabe Y, Kumazawa K (2004) Evidence from massive siderite beds
for a CO2-rich atmosphere before ~1.8 billion years ago. Nature 429:395–399
Ohta H, Maruyama S, Takahashi E, Watanabe Y, Kato Y (1996) Field occurrence,geochemistry and petrogenesis of the Archean mid-oceanic ridge basalts(AMORBs) of the Cleaverville area, Pilbara Craton, Western Australia.
Lithos 37:199–221
Rosenberg PE, Holland HD (1964) Calcite-dolomite-magnesite stability relations insolutions at elevated temperatures. Science 145:700–701
Rosenberg PE, Burt DM, Holland HD (1967) Calcite-Dolomite-Magnesite stability
relations in solutions: the effect of ionic strength. Geochim Cosmochim
Acta 31:391–396
Russell MJ, Barge LM, Bhartia R, Bocanegra D, Bracher PJ, Branscomb E, Kidd R,
McGlynn S, Meier DH, Nitschke W, Shibuya T, Vance S, White L, Kanik I (2014)
The drive to life on wet and icy worlds. Astrobiology 14:308–343
Russell MJ, Hall AJ (1997) The emergence of life from iron monosulphidebubbles at a submarine hydrothermal redox and pH front. J Geol Soc
Lond 154:377–402
Russell MJ, Hall AJ, Martin W (2010) Serpentinization as a source of energy at theorigin of life. Geobiology 8:355–371
Seyfried WE, Ding K, Berndt ME (1991) Phase equilibria constraints on thechemistry of hot spring fluids at mid-ocean ridges. Geochim Cosmochim
Acta 55:3559–3580
Seyfried WE, Gordon PC, Dickson FW (1979) A new reaction cell for hydrothermal
solution equipment. Am Mineral 64:646–649

Ueda et al. Progress in Earth and Planetary Science (2016) 3:35

Seyfried WE, Foustoukos DI, Fu Q (2007) Redox evolution and mass transfer
during serpentinization: an experimental and theoretical study at 200 °C,
500 bar with implications for ultramafic-hosted hydrothermal systems at
mid-ocean ridges. Geochim Cosmochim Acta 71:3872–3886
Shibuya T, Kitajima K, Komiya T, Terabayashi M, Maruyama S (2007) Middle
Archean ocean ridge hydrothermal metamorphism and alteration recordedin the Cleaverville area, Pilbara Craton, Western Australia. J Metamorph Geol
25:751–767
Shibuya T, Komiya T, Nakamura K, Takai K, Maruyama S (2010) Highly alkaline,
high-temperature hydrothermal fluids in the early Archean ocean.
Precambrian Res 182:230–238
Shibuya T, Russell MJ, Takai K (2016) Free energy distribution and hydrothermal
mineral precipitation in Hadean submarine alkaline vent systems: Importanceof iron redox reactions under anoxic conditions. Geochim Cosmochim Acta
175:1–19
Shibuya T, Tahata M, Kitajima K, Ueno Y, Komiya T, Yamamoto S, Igisu M,
Terabayashi M, Sawaki Y, Takai K, Yoshida N, Maruyama S (2012) Depth
variation of carbon and oxygen isotopes of calcites in Archean altered upper
oceanic crust: implications for the CO2 flux from ocean to oceanic crust in
the Archean. Earth Planet Sci Lett 321–322:64–73
Shibuya T, Tahata M, Ueno Y, Komiya T, Takai K, Yoshida N, Maruyama S,
Russell MJ (2013a) Decrease of seawater CO2 concentration in the Late
Archean: an implication from 2.6 Ga seafloor hydrothermal alteration.
Precambrian Res 236:59–64
Shibuya T, Yoshizaki M, Masaki Y, Suzuki K, Takai K, Russell MJ (2013b) Reactions
between basalt and CO2-rich seawater at 250 and 350 °C, 500 bars:
implications for the CO2 sequestration into the modern oceanic crust andthe composition of hydrothermal vent fluid in the CO2-rich early ocean.
Chem Geol 359:1–9
Shibuya T, Yoshizaki M, Satoh M, Shimizu K, Nakamura K, Omori S, Suzuki K,
Takai K, Hideo T, Maruyama S (2015) Hydrogen-rich hydrothermal
environments in the Hadean ocean inferred from serpentinization of
komatiites at 300 °C and 500 bar. Progr Earth Planet Sci 2:1–11.
doi:10.1186/s40645-015-0076-z
Shock EL, Koretsky CM (1995) Metal-organic complexes in geochemical
processes: estimation of standard partial molal thermodynamic propertiesof aqueous complexes between metal cations and monovalent organicacid ligands at high pressures and temperatures. Geochim Cosmochim
Acta 59:1497–1532
Shock EL, Helgeson HC (1988) Calculation of the thermodynamic and transport
properties of aqueous species at high pressures and temperatures:
correlation algorithms for ionic species and equation of state predictions to
5 kb and 1000 °C. Geochim Cosmochim Acta 52:2009–2036
Shock EL, Helgeson HC, Sverjensky DA (1989) Calculation of the thermodynamic
and transport properties of aqueous species at high pressures andtemperatures: standard partial molal properties of inorganic neutral
species. Geochim Cosmochim Acta 53:2157–2183
Shock EL, Sassani DC, Willis M, Sverjensky DA (1997) Inorganic species ingeologic fluids: correlations among standard molal thermodynamic
properties of aqueous ions and hydroxide complexes. Geochim
Cosmochim Acta 61:907–950
Sleep NH, Zahnle K (2001) Carbon dioxide cycling and implications for climate
on ancient Earth. J Geophys Res 106:1373–1399
Smith HS, Erlank AJ, Duncan AR (1980) Geochemistry of some ultramafic
komatiite lava flows from the Barberton Mountain Land, South Africa.
Precambrian Res 11:399–415
Snow JE, Dick HJB (1995) Pervasive magnesium loss by marine weathering of
peridotite. Geochim Cosmochim Acta 59:4219–4235
Suzuki K, Shibuya T, Yoshizaki M, Hirose T (2015) Experimental hydrogenproduction in hydrothermal and fault systems: significance for habitability ofsubseafloor H2 chemoautotroph microbial ecosystems. In: Ishibashi J, Okino K,
Sunamura M (eds) Subseafloor biosphere linked to hydrothermal systems.
TAIGA concept. Springer, Tokyo, pp 87–94
Sverjensky DA, Shock EL, Helgeson HC (1997) Prediction of the thermodynamic
properties of aqueous metal complexes to 1000 °C and 5 kb. Geochim
Cosmochim Acta 61:1359–1412
Takai K, Gamo T, Tsunogai U, Nakayama N, Hirayama H, Nealson KH, Horikoshi K(2004) Geochemical and microbiological evidence for a hydrogen-based,
hyperthermophilic subsurface lithoautotrophic microbial ecosystem(HyperSLiME) beneath an active deep-sea hydrothermal field. Extremophiles
8:269–282

Page 14 of 14

Takai K, Nakamura K, Suzuki K, Inagaki F, Nealson KH, Kumagai H (2006)
Ultramafics-hydrothermalism-hydrogenesis-hyperslime (ultra H3) linkage: a
key insight into early microbial ecosystem in the Archean deep-sea
hydrothermal systems. Paleontol Res 10:269–282
Tribble JS, Arvidson RS, Lane M, Mackenzie FT (1995) Crystal chemistry, andthermodynamic and kinetic properties of calcite, dolomite, apatite, andbiogenic silica: applications to petrographic problems. Sediment Geol 95:11–51
Walker JCG (1985) Carbon dioxide on the early earth. Orig Life Evol Biosph16:117–127
Wei K, Tronnes RG, Scarfe CM (1990) Phase relations of aluminum-undepleted
and aluminum-depleted komatiites at pressures of 4–12 GPa. J Geophys Res
95:15817–15827
Wetzel LR, Shock EL (2000) Distinguishing ultramafic- from basalt-hosted
submarine hydrothermal systems by comparing calculated vent fluid
compositions. J Geophys Res 105:8319–8340
Yanagawa H, Kojima K (1985) Thermophilic microspheres of peptide-like
polymers and silicates formed at 250 °C. J Biochem 97:1521–1524
Yoshizaki M, Shibuya T, Suzuki K, Shimizu K, Nakamura K, Takai K, Omori S,
Maruyama S (2009) H2 generation by experimental hydrothermal alterationof komatiitic glass at 300 °C and 500 bars: a preliminary result from on-goingexperiment. Geochem J 43:e17–e22
Zhao L, Sang L, Chen J, Ji JF, Teng HH (2010) Aqueous carbonation of natural
brucite: relevance to CO2 sequestration. Environ Sci Technol 44:406–411

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