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Evidence for primordial water in Earth's deep mantle

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The hydrogen-isotope [deuterium/hydrogen (D/H)] ratio of Earth can be used to constrain the origin of its water. However, the most accessible reservoir, Earth’s oceans, may no longer represent the original (primordial) D/H ratio, owing to changes caused by water cycling between the surface and the interior. Thus, a reservoir completely isolated from surface processes is required to define Earth’s original D/H signature. Here we present data for Baffin Island and Icelandic lavas, which suggest that the deep mantle has a low D/H ratio (δD more negative than –218 per mil). Such strongly negative values indicate the existence of a component within Earth’s interior that inherited its D/H ratio directly from the protosolar nebula.
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ACKNOW LEDGM ENTS
We thank M. Lein for valuable discussions and F. Lépine, V. Despré,
P. Lopez, and U. Röthlisberger for performing supporting calculations.
Supported by ERC starting grant (project no. 307270-ATTOSCOPE)
and the Swiss National Science Foundation via the National Centre
of Competence in Research Molecular Ultrafast Science and
Technology (P.M.K. and H.J.W.), the Fonds National de la
Recherche Scientifique of Belgium and Fonds de la Recherche
Fondamentale Collective grant 2.4545.12 (B.M. and F.R.), the
Belgian American Education Foundation and Wallonie-Bruxelles
International (B.M.), Compute Canada through access to
high-performance computers (E.F.P. and A.D.B.), the Ministry
of Education and Science of Russia state assignment
no. 3.679.2014/K (O.I.T.), VKR Centre of Excellence QUSCOPE
and ERC starting grant (project no. 277767-TDMET) (L.B.M.).
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/350/6262/790/suppl/DC1
Materials and Methods
Supplementary Text
Figs. S1 to S14
Tables S1 to S9
Movies S1 to S4
References (35101)
29 June 2015; accepted 25 September 2015
Published online 22 October 2015
10.1126/science.aab2160
GEOCHEMISTRY
Evidence for primordial water
in Earths deep mantle
Lydia J. Hallis,
1,2
*Gary R. Huss,
1,2
Kazuhide Nagashima,
2
G. Jeffrey Taylor,
1,2
Sæmundur A. Halldórsson,
3
David R. Hilton,
3
Michael J. Mottl,
4
Karen J. Meech
1,5
The hydrogen-isotope [deuterium/hydrogen (D/H)] ratio of Earth can be used to constrain the
origin of its water. However, the most accessible reservoir, Earths oceans, may no longer
represent the original (primordial) D/H ratio, owing to changes caused by water cycling between
the surface and the interior.Thus, a reservoir completely isolated from surface processes is
required to define Earths original D/H signature. Here we present data for Baffin Island and
Icelandic lavas, which suggest that the deep mantle has a low D/H ratio (dD more negative than
218 per mil). Such strongly negative values indicate the existence of a component within
Earths interior that inherited its D/H ratio directly from the protosolar nebula.
Establishing Earths initial D/H ratio is im-
portant for understanding the origin of our
planetswater,aswellasthedynamicalpro-
cesses that operated during planet forma-
tion in the solar system. However, evolution
of this ratio occurs over time as a result of surface
and mantle processing. Collisions with hydrogen-
bearing planetesimals or cometary material after
Earths accretion should have altered the D/H ra-
tio of the planets surface and upper mantle (1).
In addition, experimentally based chemical mod-
els suggest an increase in the atmospheric D/H
valuebyafactorof2 to9sinceEarthsformation
(2). Preferential loss of the lighter hydrogen iso-
tope from the upper atmosphere causes this in-
crease, driven by thermal atmospheric escape or
plasma interactions with the atmosphere. As at-
mospheric D/H is linked with that of ocean wa-
ter and sediments, the D/H ratio of the mantle
also increases with time via subduction and con-
vective mixing. Only areas of the deep Earth that
have not participated in this mixing process are
likely to preserve EarthsinitialD/Hratio.
Studies of the trace-element, radiogenic-isotope,
and noble gas isotope characteristics of mid-
ocean ridge basalts (MORBs) and ocean-island
basalts (OIBs) reveal the existence of domains
within Earths mantle that have experienced dis-
tinct evolutionary histories (3,4). Although alterna-
tive theories exist [e.g., (5)], most studies suggest
that high
3
He/
4
He ratios in some OIBs indicate
the existence of relatively undegassed regions in
the deep mantle compared to the upper mantle,
which retain a greater proportion of their pri-
mordial He (6,7). Helium-isotope (
3
He/
4
He) ra-
tios more than 30 times the present-day ratio of
Earthsatmosphere(R
A
=1.38×10
6
)(8)canbe
found in volcanic rocks from oceanic islands, in-
cluding Iceland and Hawaii (912). Early Tertiary
(60-million-year-old) lavas from Baffin Island and
west Greenland, which represent volcanic rocks
from the proto/early Iceland mantle plume, con-
tain the highest recorded terrestrial
3
He/
4
He ra-
tios of up to 50 R
A
(6,7). These lavas also have Pb
and Nd isotopic ratios consistent with primordial
mantle ages [4.45 to 4.55 billion years (Ga)] (13),
indicating the persistence of an ancient, isolated
reservoir in the mantle. The undegassed and
primitive nature (14) of this reservoir means that
it could preserve Earths initial D/H ratio. This study
targets mineral-hosted melt inclusions in these
rocks in search of this primordial signal.
A range of D/H ratios are found on Earth. We
compare the ratio of deuterium (
2
HorD)tohy-
drogen (
1
H) relative to Vienna Standard Mean
Ocean Water (VSMOW, D/H = 1. 5576 × 10
4
)
using dD={[(D/H)
unknown
/(D/H)
VSMOW
]1} ×
1000, in units of parts per thousand [per mil ()].
The hydrological cycle fractionates hydrogen,
creating glacial ice [standard Greenland Ice Sheet
Precipitation dD=190(15)], ocean water
(VSMOW dD=0), and fresh water [dD=0 to
300(16)] reservoirs. Subduction provides a
meanstomixwaterbackintothemantle,produ-
cing a variation in dDfrom126 to +46from
slab dehydration and sediment recycling (17,18).
TheMORBsourceappearstobebettermixed,
with a uniform dDof60 ± 5(19).
We measured the D/H ratios of olivine-hosted
glassy melt inclusions in two depleted picrite sam-
ples (basaltic rocks with abundant Mg-rich olivine)
from Padloping Island, northwest Baffin Island
(20), and in three picrite samples from Icelands
western and northern rift zones (911). The high
forsterite (Fo) contents of these olivines (Fo
87-91
)
suggest crystallization from primitive melts (21).
We monitored possible contamination from crust-
al materials, or meteoric water due to weathering,
by measuring the oxygen-isotope ratios of the
samples (21). One Icelandic sample shows slight-
ly raised d
18
O, indicative of crustal contamination.
All other samples fall within the range expected
for uncontaminated mantle-derived samples.
Baffin Island melt inclusions are characterized
by extremely low D/H ratios, from dD97 to 218
SCIENCE sciencemag.org 13 NOVEMBER 2015 VOL 350 ISSUE 6262 795
1
NASA Astrobiology Institute, Institute for Astronomy,
University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI
96822-1839, USA.
2
Hawaii Institute of Geophysics and
Planetology, Pacific Ocean Science and Technology (POST)
Building, University of Hawaii, 1680 East-West Road,
Honolulu, HI 96822, USA.
3
Scripps Institution of
Oceanography, University California San Diego, 9500 Gilman
Drive, La Jolla, CA 92093-0244, USA.
4
Department of
Oceanography, University of Hawaii, Marine Sciences
Building 304, 1000 Pope Road, Honolulu, HI 96822, USA.
5
Institute for Astronomy, University of Hawaii, 2680
Woodlawn Drive, Honolulu, HI 96822, USA.
*Present address: School of Geographical and Earth Sciences,
University of Glasgow, Gregory Building, Lillybank Gardens,
Glasgow G12 8QQ, UK. Corresponding author. E-mail: lydia.
hallis@glasgow.ac.uk Present address: Nordic Volcanological
Center, Institute of Earth Sciences, University of Iceland, Askja,
Sturlugata 7, 101 Reykjavík, Iceland.
RESEARCH |REPORTS
on November 12, 2015www.sciencemag.orgDownloaded from on November 12, 2015www.sciencemag.orgDownloaded from on November 12, 2015www.sciencemag.orgDownloaded from
(Table 1). Melt-inclusion dehydration, where H
2
O
preferentially diffuses faster than HDO through
encapsulating olivine, accounts for the inverse
correlation between dD and water content (Fig. 1A).
The longer olivine grains are resident in hot melt
before eruption, the stronger the effect of dehy-
dration (22). In addition to dehydration, melt-
inclusion degassing can also raise D/H ratios and
lower water contents. Melt inclusions may under-
go degassing due to depressurization during erup-
tion. We selected rapidly quenched subglacially
(Iceland) and subaqueously (Baffin Island) erupted
samples to mitigate the effects of degassing. How-
ever, two of the three Icelandic samples exhibit
the high dD and low water contents indicative of
this process. Revealingly, sample MID-1 is known
to be one of the least degassed Icelandic basalts
(10) and contains melt inclusions with the lowest
dD(88 to 90) and highest H
2
O contents
[946 to 964 parts per million (ppm)] of the three
Icelandic samples.
Thewidespreadind
18
O values between sam-
ples (Table 1 and Fig. 1B) supports a heteroge-
neous Baffin Island and Iceland plume with respect
to d
18
O(11,23,24). The Baffin Island melt in-
clusion d
18
O values (4.73 to 5.18) are similar
to those of Baffin Island picrite matrix glasses
(4.84 to 5.22)(25). These values are lower than
typical MORB d
18
O[5.5±0.2(26)], indicating
a possible correlation between low D/H, low
18
O/
16
O, and high
3
He/
4
He as an intrinsic pro-
perty of the undegassed mantle.
Lithospheric slab dehydration during sub-
duction and deep recycling can produce low D/H
ratios in glasses from plume-related localities
(17,27). Basaltic glasses from the Hawaiian Koolau
volcano contain low dDvaluesandwatercon-
tents similar to those of the Baffin Island picrites
(27) (Fig. 1A). However, the Koolau mantle source
is thought to contain a substantial fraction of re-
cycled upper oceanic crust and sediment (27), and
its distinct d
18
O (Fig. 1B) is attributed to an EM2
signature (sedimentary recycling). The Baffin Is-
land samples do not contain any evidence of a
recycled slab component (21); hence, their low dD
values must be attributed to a different origin.
The correlation between low D/H and high
3
He/
4
He ratios in the Baffin Island and Icelan d
samplessuggeststhattheyoriginatefroma
region isolated from mixing. Thus, our data sup-
port a heterogeneous mantle, which contains
deep, primitive, undegassed regions that have
never been involved in subduction-related mix-
ing or recycling (13).
Magma-ocean crystallization models (28), and
Nd isotopic evidence from some of Earthsoldest
rocks (29), indicate a small volume of late-solidifying
dense cumulates developed during the first 30 to
75 million years of Earth history. High pressures
near the base of Earths magma ocean would
cause magma to become denser than coexisting
minerals; thus, crystallization would proceed from
the top downward (30).Top-down crystallization
would trap volatile elements in cumulates at the
deepest section of the mantle. Nd-isotope data
suggest that such cumulates still exist, represent-
ing a hidden incompatible-elementenriched res-
ervoir complementary to the depleted nature of
most of Earthsmantle(29,31). The depth of this
enriched reservoir explains its absence in modern-
day upper-mantle melts. However, deep plume
melting can transfer melt from the core-mantle
boundary to the surface (32).The olivine compo-
sitions of Baffin Island picrites, as well as other
samples with high
3
He/
4
He (e.g., basalts from
western Greenland and the Galapagos), suggest
that these lavas originated from a peridotite source
~20% higher in Ni content than the modern de-
pleted mantle source, apparently as a result of
interaction with the Ni-rich core (5). The noble
gas composition of many OIBs, including high
proportions of solar Ne, suggests that these plumes
sample a volatile-rich reservoir (33,34).
The lowest measured D/H value (dD=218)
provides an upper limit on the D/H of early Earth
if the Baffin Island picrite melt inclusions sample
a deep mantle reservoir with preserved primitive
volatiles. One possibility is that this strongly neg-
ative dD was added to the Earth during initial
accretion, via dust grains with adsorbed H
2
Oin-
herited directly from the protosolar nebula (870)
(35). The temperature was high at Earthsorbital
distance during the early solar system, but 1000
to 500 K would still allow adsorption of 25 to
300% of Earths ocean water onto fractal grains
during Earthsaccretion(36).Solar wind hydro-
gen and additional accreting objects from the outer
796 13 NOVEMBER 2015 VOL 350 ISSUE 6262 sciencemag.org SCIENCE
Table 1. Water content, D/H ratio (dD), and
18
O/
16
Oratio(d
18
O) of Baffin Island and Icelandic
samples. Owing to the small size of melt inclusions in the samples, it was mostly not possible to
collect hydrogen- and oxygen-isotope data from the same inclusions. Therefore, oxygen-isotope data
are calculated on the basis of the average value of melt inclusions (n= 2 to 4) within the same olivine
grain as that measured for D/H. Olivine oxygen data are also presented as an average (n= 2 to 6).
Scanning electron microscope images showing the location of each data point on the sample surfaces
are available (21).
Sample and phase H
2
O (ppm) dD()2s()d
18
O()2s()
Baffin Island picrites
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 4_melt inclusion 1 709 115 38 5.18 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 6_melt inclusion 1 926 107 39 5.18 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 7_melt inclusion 1 1189 108 35 5.18 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 8_melt inclusion 1 1039 122 36 5.18 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 9_melt inclusion 1 1175 158 51 5.18 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 9_melt inclusion 2 576 114 40 5.18 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 4_olivine 1 194 4.53 0.34
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 6_olivine 1 413 4.53 0.34
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 7_olivine 1 153 4.53 0.34
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 8_olivine 1 200 4.53 0.34
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-16_area 9_olivine 1 187 4.53 0.34
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 1_melt inclusion 1 1337 137 35 4.73 0.16
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 1_melt inclusion 2 1465 177 37 4.73 0.16
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 2_melt inclusion 1 1719 173 34 4.73 0.16
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 2_melt inclusion 2 1964 218 34 4.73 0.16
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 3_melt inclusion 1 1779 197 34 4.73 0.16
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 6_melt inclusion 1 997 137 32
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 7_melt inclusion 1 868 97 34
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 8_melt inclusion 1 901 126 32
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 1_olivine 1 557 4.38 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 2_olivine 1 641 4.38 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 2_olivine 2 712 4.38 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 3_olivine 1 781 4.38 0.25
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 8_olivine 1 187
.................................... ....................................... ........................................ ....................................... ........................................ ...................
PI-19_area 8_olivine 2 190
.................................... ....................................... ........................................ ....................................... ........................................ ...................
Icelandic picrites
.................................... ....................................... ........................................ ....................................... ........................................ ...................
MID-1_bullet 2_melt inclusion 1 946 88 51 4.83 0.40
.................................... ....................................... ........................................ ....................................... ........................................ ...................
MID-1_bullet 2_melt inclusion 2 964 90 50 4.83 0.40
.................................... ....................................... ........................................ ....................................... ........................................ ...................
MID-1_bullet 3_melt inclusion 1 474 34 53 4.83 0.40
.................................... ....................................... ........................................ ....................................... ........................................ ...................
MID-1_bullet 2_olivine 1 157 2.43 0.46
.................................... ....................................... ........................................ ....................................... ........................................ ...................
MID-1_bullet 3_olivine 1 85 2.43 0.46
.................................... ....................................... ........................................ ....................................... ........................................ ...................
NAL828_bullet 5_melt inclusion 1 600 34 53 6.54 0.48
.................................... ....................................... ........................................ ....................................... ........................................ ...................
NAL828_bullet 5_melt inclusion 2 510 29 53 6.54 0.48
.................................... ....................................... ........................................ ....................................... ........................................ ...................
NAL828_bullet 5_olivine 1 100 5.36 0.46
.................................... ....................................... ........................................ ....................................... ........................................ ...................
NAL 688_bullet 13_melt inclusion 1 587 25 28 5.89 0.35
.................................... ....................................... ........................................ ....................................... ........................................ ...................
NAL 688_bullet 13_olivine 1 36 5.72 0.56
.................................... ....................................... ........................................ ....................................... ........................................ ...................
RESEARCH |REPORTS
part of the inner solar system may also have mixed
into the accreting planet (34).Experimentally
based atmospheric chemical models support proto-
solar nebula adsorption, as they suggest an ini-
tial dD between 500 and 889for Earth (2).
The dD versus H
2
O [weight percent (wt %)]
correlation for Baffin Island sample PI-19 (Fig.
1A) suggests that a deep mantle source with a
protosolar dDvalueof870would have a wa-
ter content of 0.94 wt %. This value is higher than
that calculated for typical bridgmanite (<220 ppm
H
2
O) (37), although post-bridgmanite can con-
tain more hydrogen (38). In addition, isotopic ra-
tios show that plume material is not typical of
ambient mantle (47), and primary Hawaiian mag-
mas have been shown to contain 0.36 to 0.6 wt %
water (27). A 20/80% mixture of a protosolar-like
deep mantle source (dD=870,H
2
O=0.94wt%)
(35)andMORB(19,37)reproducesthelowest
measured Baffin Island dD values. This proportion
is consistent with mantle Xe-isotope anomalies,
also estimated to reflect admixture with about
20% of a solar Xe component (33).
Thesimilaritybetweenthebulkchemicalcom-
position of Earth and carbonaceous chondrites
indicates that Earth accreted from building blocks
similar to these meteorites (39). An initial Earth
dDvaluemorenegativethan218is at the very
lower end of the dD range for bulk-rock CM and
CI chondrites (+338 to 227)(40), whereas other
carbonaceous chondrite groups have more positive
bulk-rock dD(48 to +763)(40).However, the
dD range for water in CI and CM chondrites is
low (383 to 587)(40), hinting that their parent
bodies may have gained water via protosolar neb-
ula adsorption. Recent reports of Earth-like dDin
the martian interior (41) also suggest protosolar
nebula adsorption as a source for martian water.
Therefore, the adsorption mechanism could pro-
vide an important source of water in inner solar
system terrestrial bodies.
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39.B.Marty,Earth Planet. Sci. Lett. 313-314,5666
(2012).
40. C. M. Alexander et al., Science 337, 721723 (2012).
41. L. J. Hallis, G. J. Taylor, K. Nagashima, G. R. Huss, Earth Planet.
Sci. Lett. 359-360,8492 (2012).
ACKNO WLED GME NTS
This material is based on work supported by the National
Aeronautics and Space Administration through the NASA
Astrobiology Institute under Cooperative Agreement
no. NNA09-DA77A, issued through the Office of Space Science.
We thank D. Francis for allocation of the Baffin Island picrite
samples and K. Grönvold for invaluable help in the field in
Iceland. The data reported in this paper are tabulated in the
supplementary materials. L.J.H. prepared samples, collected and
processed data, and was the primary author of this manuscript.
G.R.H. and K.N. managed the ion-microprobe, perfected
hydrogen- and oxygen-isotope analytical methods, and assisted
with data processing. S.A.H. and D.R.H. collected the Icelandic
samples and provided Icelandic geological background. G.J.T.
assisted with the development of hydrogen-isotope analytical
methods and provided solar system disk model chemistry
information. K.J.M. initiated this study and provided solar system
disk model chemistry information. All authors discussed
the results and commented on the manuscript. Correspondence
and requests for materials should be addressed to L. J. Hallis
(lydia.hallis@glasgow.ac.uk).
SUPPLEMENTARY MATERIALS
www.sciencemag.org/content/350/6262/795/suppl/DC1
Materials and Methods
Supplementary Text
Figs. S1 to S9
Tables S1 to S3
References (4272)
3 May 2015; accepted 9 October 2015
10.1126/science.aac4834
SCIENCE sciencemag.org 13 NOVEMBER 2015 VOL 350 ISSUE 6262 797
-300
-250
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-150
-100
-50
0
50
100
150
00.1 0.2 0.3
MID-1
NAL 688
NAL 828
PI-16
PI-19
y = -892x -35
R² = 0.89
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Fig. 1. Hydrogen- and oxygen-isotope ratios. The hydrogen-isotope ratios
(dD) of Baffin Island and Icelandic basaltic melt inclusions versus water
content (A) and oxygen-isotope ratios (B). Uncertainties are 2s,exceptfor
(B) dD, where error bars represent the full range of the data set. The dD
versus H
2
O (A) data trendline gradient for sample PI-19 is shown by the red
dashed line. Mixing lines between a protosolar-like deep mantle source [dD=
870,H
2
O = 0.94 wt %] (35) and MORB (19,37) are shown by the black
and gray dashed lines, which assume minimum and maximum MORB source
region H
2
O contents of 0.008 and 0.095 wt %, respectively (37). Melt in-
clusion data from the Hawaiian Koolau volcano, which contains the lowest dD
values of the Hawaiian plume (27),are represented by the green crosses and
envelope in (A) and green cross in (B). Average melt inclusion dDvaluesare
shown on the dD versus d
18
O plot (B). The colored envelopes (B) indicate
regions of crustal contamination, based on the d
18
O variation of possible
contaminants from the Icelandic crust (7.5to+1.65, green envelope) (24),
and hydrothermally altered oceanic crust (+7 to +15, yellow envelope) (26).
The dD variation of the envelopes is as reported for hydrothermally altered
oceanic crust (34 to 46)(17,18).
RESEARCH |REPORTS
DOI: 10.1126/science.aac4834
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... Cependant, la Terre contient une grande quantité d'eau à sa surface, et l'équivalent de dix océans terrestres d'hydrogène sous forme de OH et H2O pouvant être piégés dans le manteau (Marty, 2012;Marty et al., 2016;Peslier et al., 2017, Hirschmann, 2018 Une contribution nébulaire est mise en évidence par la présence de néon ayant une signature solaire dans le manteau terrestre (Honda et al., 1993;Marty, 1989). Cependant, cette contribution solaire est considérée comme mineure pour les éléments volatils tels que l'hydrogène et l'azote (Marty, 2012;Hallis et al., 2015). ...
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Les éléments volatils comme l’hydrogène et l’azote contrôlent l'évolution des corps planétaires et de leurs atmosphères, et sont des éléments essentiels au développement de la vie sur Terre. Néanmoins, l'origine des éléments volatils et la chronologie de leur accrétion par les planètes telluriques formées au sein du système solaire interne restent un sujet de débat et de controverse en sciences planétaires. Pour répondre à ces questions, les rapports isotopiques de l'hydrogène (D/H) et de l'azote (15N/14N) sont des outils puissants pour tracer l'origine (solaire, chondritique ou cométaire) des éléments volatils piégés par les planètes telluriques. Pour contraindre l’origine(s) des éléments volatils piégés par les planètes rocheuses, nous avons donc mesuré les teneurs et les compositions isotopiques de l’hydrogène et de l’azote par microsonde ionique (LGSIMS) dans des achondrites (angrites, météorites maritennes et aubrites) qui proviennent d’astéroïdes différenciés ou de planètes qui sont considérés s’être formés dans le système solaire interne. Ces météorites conservent un enregistrement des étapes initiales de la formation de leurs corps parents et peuvent imposer des contraintes quant à l’évolution précoce des éléments volatils planétaires. L'analyse in-situ par SIMS est une technique quasi-non-destructive, qui permet de mesurer la teneur et la composition isotopique des éléments volatils de différentes phases dans des échantillons terrestres, extraterrestres et synthétiques. Le développement récent du protocole d'analyse de l'azote dans les échantillons silicatés par sonde ionique nous permet de caractériser des objets de la taille d’une dizaine de microns, tels que des inclusions vitreuses. Au cours de cette thèse, les éléments volatils ont été mesurés dans des inclusions magmatiques piégées dans des minéraux et dans les verres interstitiels. Bien que l’analyse de l’azote dans des aubrites n’a pas pu aboutir, les analyses réalisées sur des météorites martiennes et des angrites ont permis de mettre en évidence la présence de quantité importante d’eau et d’azote au sein de ces météorites et de leurs corps parent. En particulier, l’étude des angrites et plus précisément de la météorite d’Orbigny nous a permis de mettre en évidence la présence d’eau et d’azote ayant des compositions isotopiques similaires à celles des météorites primitives formées dans le système solaire externe (i.e., chondrites carbonées de type CM). Ces résultats impliquent que ces éléments volatils étaient présents ~4 millions d’années après la formation des CAIs (i.e., premiers solides à se former dans le système solaire) dans le système solaire interne et ont pu être piégés par les planètes telluriques lors de leur formation. De plus, l’analyses des météorites martiennes et plus particulièrement de Chassigny a révélé la présence d’azote ayant une composition isotopique enrichie en 15N comparée aux chondrites à enstatite et aux diamants terr estres qui sont supposés représenter la valeur la plus primitive de l’azote sur Terre.
... To produce a similar amount of Fe 3+ at a similar redox state, the amount of molecular hydrogen is less than that of both carbon and iron. Interestingly, the measurements of D/H ratios in depth-derived lavas have led Hallis et al. (2015) to infer that the deep mantle may have preserved primordial water inherited from the protosolar nebula. Probably, such water could be accounted for by the storage of molecular hydrogen in the deep mantle, that was delivered from molecular hydrogen in the Solar nebula during the early formation of the Earth (Yang et al., 2016). ...
... Probably, such water could be accounted for by the storage of molecular hydrogen in the deep mantle, that was delivered from molecular hydrogen in the Solar nebula during the early formation of the Earth (Yang et al., 2016). As such, the proposed origin of Earth's water from nebular H 2 by Yang et al. (2016) is consistent with the isotopic evidence of Hallis et al. (2015) for the storage of primordial water in the deep mantle. ...
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Redox state is an important parameter in describing the thermodynamic state of the Earth’s interior. In contrast to the considerable efforts in early studies that have been expended on the redox state of Earth’s different spheres, much attention in the recent about 10 years has been paid to the effects of redox state on the various geodynamical aspects of Earth’s interior, or more commonly the redox geodynamics. Redox geodynamics plays a critical role in driving many processes that are involved in the accretion, differentiation, and re-shaping of the Earth from its early birth to modern periods and from its surface to the deep interior, including the structure, composition, nature, and evolution of the Earth and the significant effects on many important issues such as the climate change and habitability of the planet. This field has blossomed in these years around the chemical and physical properties of the Earth. In this review, a brief summary is provided for the basic concepts, general background and applications relevant to redox geodynamics. The redox state of the crust and mantle and its evolution have received particular attention in the past years, however, there are still fundamental issues remaining ambiguous, poorly quantified and/or even controversial. At the same time, significant progress has been made, mostly through experimental studies, on the redox geodynamics of the Earth’s interior, including (but are not limited to) the early oxidation of the shallow mantle, the rapid growth of the early continental crust, the redox freezing and melting associated with carbon or hydrogen, the transfer of metal elements and formation of ore deposits, the low seismic velocity and high attenuation of the asthenosphere, the aerobic processes around the core-mantle boundary, and the magma degassing and released gases. Redox geodynamics is becoming increasingly important in renewing the understanding of the chemical evolution, physical properties, and dynamical processes of the Earth.
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... Recently, increasing evidence supported the first hypothesis [1][2][3]. The deuterium/hydrogen (D=H) ratio, considered as the fingerprint of the origin of water, offers a persuasive argument: the Earth's deep mantle has a low D=H ratio quite close to that of enstatite chondrite meteorites [4], which are the fundamental building blocks of the young Earth, indicating that water within the Earth's interior may have come directly from the protosolar nebula [1]. ...
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The origin of water on the Earth is a long-standing mystery, requiring a comprehensive search for hydrous compounds, stable at conditions of the deep Earth and made of Earth-abundant elements. Previous studies usually focused on the current range of pressure-temperature conditions in the Earth's mantle and ignored a possible difference in the past, such as the stage of the core-mantle separation. Here, using ab initio evolutionary structure prediction, we find that only two magnesium hydrosilicate phases are stable at megabar pressures, α-Mg_{2}SiO_{5}H_{2} and β-Mg_{2}SiO_{5}H_{2}, stable at 262-338 GPa and >338 GPa, respectively (all these pressures now lie within the Earth's iron core). Both are superionic conductors with quasi-one-dimensional proton diffusion at relevant conditions. In the first 30 million years of Earth's history, before the Earth's core was formed, these must have existed in the Earth, hosting much of Earth's water. As dense iron alloys segregated to form the Earth's core, Mg_{2}SiO_{5}H_{2} phases decomposed and released water. Thus, now-extinct Mg_{2}SiO_{5}H_{2} phases have likely contributed in a major way to the evolution of our planet.
... The lowest values are closer to the protosolar D value of −865 ± 32‰ [e.g., (49)] than to the D range of +390 to +1100‰ observed in mare basalts [references in (48)]. The upper-limit D value of the proto-Earth mantle has been estimated to be −218‰ (50), which is below the range of D values in the mare basalts but coincides with the D range in KREEP. ...
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The origin of volatiles in the Moon's interior is debated. Scenarios range from inheritance through a Moon-forming disk or "synestia" to late accretion by meteorites or comets. Noble gases are excellent tracers of volatile origins. We report analyses of all noble gases in paired, unbrecciated lunar mare basalts and show that magmatic glasses therein contain indigenous noble gases including solar-type He and Ne. Assimilation of solar wind (SW)-bearing regolith by the basaltic melt or SW implantation into the basalts is excluded on the basis of the petrological context of the samples, as well as the lack of SW and "excess 40Ar" in the magmatic minerals. The absence of chondritic primordial He and Ne signatures excludes exogenous contamination. We thus conclude that the Moon inherited indigenous noble gases from Earth's mantle by the Moon-forming impact and propose storage in the incompatible element-enriched ("KREEP") reservoir.
... This proves that the Earth's mantle is, at least locally, hydrated. H 2 O can be introduced into the deep Earth by subducted slabs via hydrous minerals (Schmidt and Ulmer 2004;Ohtani 2005) or originally stored in the deep Earth from the protosolar nebula material (Hallis et al. 2015;Peslier 2020). H 2 O could be incorporated in some nominally anhydrous minerals such as olivine, wadsleyite, and ringwoodite. ...
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Dense hydrous magnesium silicates (DHMSs) with large water contents and wide stability fields are a potential H 2 O reservoir in the deep Earth. Al-bearing superhydrous phase B (shy-B) with a wider stability field than the Al-free counterpart can play an important role in understanding H 2 O transport in the Earth's transition zone and topmost lower mantle. In this study, a nominally Al-free and two different Al-bearing shy-B samples with 0.47(2) and 1.35(4) Al atoms per formula unit (pfu), were synthesized using a rotating multi-anvil press. Their single-crystal structures were investigated by X-ray diffraction (XRD) complemented by Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR). Single-crystal XRD shows that the cell parameters decrease with increasing Al-content. By combining X-ray diffraction and spectroscopy results, we conclude that the Al-poor shy-B crystallizes in the Pnn2 space group with hydrogen in two different general positions. Based on the results of the single-crystal X-ray diffraction refinements combined with FTIR spectroscopy, three substitutions mechanisms are proposed: 2Al 3+ = Mg 2+ + Si 4+ ; Mg 2+ =  Mg2+ + 2H + ( Mg2+ means vacancy in Mg site); Si 4+ = Al 3+ + H +. Thus, in addition to the two general H positions, hydrogen is incorporated into the hydrous mineral via point defects. The elastic stiffness coefficients were measured for the Al-shy-B with 1.35 pfu Al by Brillouin scattering (BS). Al-bearing shy-B shows lower C 11 , higher C 22 , and similar C 33 when compared to Al-free shy-B. The elastic anisotropy of Al-bearing shy-B is also higher than that of the Al-free composition. Such different elastic properties are due to the effect of lattice contraction as a whole and the specific chemical substitution mechanism that affect bonds strength. Al-bearing shy-B with lower velocity, higher anisotropy, and wider thermodynamic stability can help understand the low-velocity zone and the high-anisotropy region in the subducted slab located in Tonga.
... Previous data obtained in volcanic gas plumes and fumaroles at persistently active volcanoes along the EARS are compiled from Gerlach (1982), Oppenheimer et al. (2002), Pik et al. (2006), Sawyer et al. (2008aSawyer et al. ( , 2008b, Fischer et al. (2009), Tedesco et al. (2010, Bobrowski et al. (2017a,b), Boucher et al. (2018) and Mollex et al. (2018). The composition of the end-members used to define the mixing curves are defined from the following literature: DMM (Sheppard and Epstein, 1970;Gautheron and Moreira, 2002;Zelenski and Taran, 2011;Clog et al., 2013;Barry et al., 2013;Hallis et al., 2015;Rizzo et al., 2018), African Superplume (Pik et al., 2006;Darrah et al., 2013), SCLM (Gautheron and Moreira, 2002;Rizzo et al., 2018), Continental Crust (Zelenski and Taran, 2011;Taran and Zelenski, 2015), Oceanic Crust (Zelenski and Taran, 2011;Barry et al., 2013;Taran and Zelenski, 2015), Limestone , Sediments (Zelenski and Taran, 2011;Barry et al., 2013), Mantle carbonates (Harmer, 1999;Casola et al., 2020;Carnevale et al., 2021), Air and ASW (Zelenski and Taran, 2011). ...
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Thesis
A Combined Study on Earth's Deep Water Cycle using Numerical Modelling and Laboratory Experiments. The distinctive feature of Earth’s surface compared to other known planets is the abundance of liquid water. This water was delivered during the accretion stage of the planet by rocky asteroids, with minor contributions from comets and protosolar nebular gas. Experimental evidence shows that water can be incorporated into many of the minerals that make up Earth’s interior. When water is hosted in the crystalline structures, it alters the physical properties of minerals, thereby enhancing deformation processes. Therefore, water-bearing rocks are less dense and weaker compared to their dry counterparts. Geophysical observations and natural samples reveal that water is indeed present in Earth’s mantle, mostly concentrated in the mantle transition zone. 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The feedback loop between mineral physics constraints, numerical modelling and geophysical observations represents the best strategy to unravel Earth’s interior. However, despite the efforts of geoscientists, many questions regarding the deep Earth water cycle remain so far unanswered. This thesis focuses on the hydration state of the MTZ, with three aims addressing different aspects of the topic: (1) provide mineral physics measurements on the effect of water on ringwoodite thermal conductivity; (2) produce a model featuring an Earth-like mobile lid while minimizing the effects of numerical parameters; and (3) analyse the parameters that allow for the stagnation of a slab in the MTZ, which may lead to the water enrichment in this region In project (1), hydrous ringwoodite crystals were synthesized with multi-anvil experiments and characterized by X-ray diffraction, electron-microprobe analysis, and infrared spectroscopy. The samples were loaded into a diamond anvil cell to perform measurements at the high-pressure conditions of the MTZ. The thermal conductivity of ringwoodite, Λ(Rw) was measured with the time-domain thermo-reflectance method. It was found that the presence of 1.73 wt% water reduces Λ(Rw) by 40%. From this analysis, it was possible to derive a parameterized equation to extrapolate Λ(Rw) as a function of pressure and water content. With this tool, the large-scale thermal evolution of a slab was studied. The calculations were performed by assuming a slab stagnating in the MTZ, then being progressively heated by the warm ambient mantle. A 1D FD numerical code was designed to solve the heat diffusion equation, and the derived equation for Λ(Rw) was included into the physical model of the slab. The results reveal that hydrous ringwoodite hinders the heating of the slab, thus promoting the survival of water-bearing minerals. 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This second, revised and updated edition of a book first published in 1973 aims to provide a basic introduction to the subject. It comprises 3 main chapters. The first (22pp) provides a brief introduction to the theoretical and experimental principles by dealing with composition, isotopic fractionation, exchange, diffusion, and with mass spectrometry. Chapter 2 (46pp) describes in detail the isotopic properties of hydrogen, carbon, oxygen and sulphur, and briefly those of selenium, nitrogen, silicon, boron and alkaline and alkaline earth metals. Topics dealt with for each element include preparation techniques and measurement, standards, fractionation mechanisms and various interactions. The third and main chapter in the book (105pp) deals with variations of stable isotope ratios in a variety of natural situations. These include extraterrestrial materials, igneous rocks, volcanic gases and hot springs, ore deposits, the hydrosphere, atmosphere and biosphere, and sedimentary and metamorphic rocks. - I. McTaggart
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Stable Isotope Geochemistry is an introduction to the use of stable isotopes in the geosciences. It is subdivided into three parts: theoretical and experimental principles; fractionation processes of light and heavy elements; the natural variations of geologically important reservoirs. Since the application of stable isotopes to earth sciences has grown in the last few years, a new edition appears necessary. Recent progress in analysing the rare isotopes of certain elements for instance allow the distinction between mass-dependent and mass-independent fractionations. Special emphasis has been given to the growing field of "heavy" elements. Many new references have been added, which will enable quick access to recent literature. For students and scientists alike the book will be a primary source of information with regard to how and where stable isotopes can be used to solve geological problems. © 2009 Springer-Verlag Berlin Heidelberg. All rights are reserved.
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Primitive melt inclusions trapped during the earliest stages of fractional crystallisation are able to preserve oxygen isotope ratios inherited from mantle-derived melts. However, assimilation of low-δO hydrothermally altered crustal material and mixing with magmas held in shallow reservoirs may exert a strong control on the δO of melt inclusions trapped during later stages of crystallisation. Oxygen isotope ratios in olivine- and plagioclase-hosted melt inclusions and glasses from tephra samples collected from the Askja central volcano and Askja volcanic system indicate significant differences in the mechanisms of magma supply and storage between the northern and southern segments of the Askja volcanic system. Melt inclusions from the Holuhraun fissure eruption, ˜20 km south of Askja, mostly preserve δO signatures of +4.1‰ to +5.4‰, suggesting that this magma underwent minimal modification by magma mixing or crustal assimilation prior to its eruption. By contrast, melt inclusions and glasses from the Nýjahraun fissure eruption, ˜60 km north of Askja, have δO between +3.1‰ and +4.0‰. These relatively evolved melt inclusions (˜3.9–4.3 wt.% MgO) were probably trapped during late-stage fractional crystallisation in a shallow magma storage zone. Melt inclusions from two phreatomagmatic tuff sequences within the Askja caldera have δO between +2.1‰ and +5.2‰, and this variability cannot be explained by mixing with low-δO rhyolitic or andesitic contaminants in the upper crust. Instead, mixing of the ascending magmas with hydrated, low-δO basaltic magmas is invoked, thus acquiring a low δO signature with minimal modification to the magma's bulk composition. Such magma bodies are likely to be found throughout the upper 11 km of the crust beneath Askja. Assimilation of low-δO meta-basalt in the upper crust is also likely to affect the δO of ascending magmas.