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THE AQUEOUS ALTERATION OF CR CHONDRITES: EXPERIMENTS AND GEOCHEMICAL
MODELING. M. Perronnet1, G. Berger
2, M. E. Zolensky
1, M. J. Toplis
3, V. M. Kolb
4, M. Bajagic
4,
1NASA JSC
(2101 Nasa road one, Mail code KT, Houston, TX 77058-3696, USA, [email protected],
[email protected] ), 2LMTG
3DTP (14 avenue E. Belin, 31400 Toulouse, France, [email protected]
mip.fr, [email protected] ), 4 University of Wisconsin-Parkside (Kenosha, WI 53141, USA, [email protected] ).
Introduction: CR carbonaceous chondrites are of
major interest since they contain some of the most
primitive organic matter known (e.g. [1], [2]).
However, aqueous alteration has more or less
overprinted their original features in a way that needs
to be assessed. This study was initiated by comparing
the mineralogy and modal abundances of the most
altered CR1 chondrite, GRO 95577, to a less altered
CR2, Renazzo [3, 4]. Calculated element distributions
imply that GRO 95577 may result from aqueous
alteration of Renazzo by an isochemical process on
their parent asteroid, whose mineralogical composition
was estimated (‘Unaltered CR’ inTable 1).
Table 1. Modal abundances in Renazzo, GRO 95577, CRs
and unaltered CR parent-body.
In the present study, laboratory alteration
experiments were performed on mineralogical
assemblages whose composition was as close as
possible to that of the unaltered CR parent-body. The
mineralogy of reaction products was compared to that
of Renazzo and GRO 95577 in order to estimate the
conditions under which alteration occurred.
Experimental results were also compared to predictions
of geochemical modeling.
Methods:
Images and chemical analyses. The composition
of silicate minerals and opaque phases were determined
before and after experiments using a JEOL JSM-
5910LV Secondary Electron Microscope (SEM) and
Cameca SX-100 electron microprobe in WDS mode.
Appropriate silicate and metal standards were used and
analyses were performed at 15 keV accelerating
voltage, 20 nA beam current and 1 µm spot diameter.
Experiments of aqueous alteration. From oxygen
isotopic data and the presence of serpentine/smectite in
CRs, the temperature of aqueous alteration on the CR
parent-body has been estimated to be between 0 and
300°C [5-8]. The abundance of FeNi metal and sulfides
indicates a low fugacity in O2 and a high fugacity in S2.
Preliminary experiments were performed at 250°C for a
duration of 1 month using pure distilled water in anoxic
Paar bombs (log fO2=-6). The system was closed such
that the chemical conditions were buffered by the
mineralogical assemblage. In order to identify the
elementary reactions, six sub-assemblages were used
(Table 2). The objectives were to understand the
reactivity of silicates within chondrules (SA1); the
influence of FeNi metal within chondrules (by
comparing SA1 and SA2); the influence of FeNi metal-
sulfides on the reaction within chondrules (by
comparing SA2, SA3 and SA4); the reactivity of
silicates and metals in the matrix (SA5); the influence
of organic matter in the matrix (by comparing SA5 and
SA6). Moreover the influence of water/rock ratio
(W/R=1 or 40) was tested for whole “synthetic
unaltered CR chondrites” (A7-3 and A7-4).
Table 2. Mineralogical assemblages.
We used pure minerals (forsterite Fo, fayalite Fa,
clinopyroxene CPX, anorthite An, FeNi metal from
Chinga, pyrrhotite Po), whose compositions were
checked by EMPA. Maillard products were used as an
analogue of CR Organic Matter (O.M.) because they
share similar functional groups [10].
Geochemical modeling. The Geochemist
Workbench software was used to model the reactivity
of unaltered CR parent-body and sub-assemblages
(Table 2) after 1 month at 250°C for the same
conditions as the laboratory experiments.
Thermodynamic data from thermo.dat database were
computed. Using the EQ 3/6 software, the data on
kamacite 83 and pentlandite were calculated. O.M. was
tentatively described by benzeneaq, phenolaq, tolueneaq
and CH3COOHaq. The kinetic laws for non-oxidative
dissolution of minerals were defined.
Results:
Experiments of aqueous alteration. The silicates
within the chondrule assemblage (SA1) are altered to
https://ntrs.nasa.gov/search.jsp?R=20070011758 2020-06-29T19:27:15+00:00Z
clinochlore, An being completely eliminated (Figure 1).
The alteration of FeNi metal or Po liberates Fe which
is incorporated into clinochlore (SA2 and SA3). Po
favors the alteration of Fo but this is no longer true
when FeNi metal and Po are both present (SA4). On
the contrary, for the matrix assemblage, formation of
clays is very limited (SA5). This may be due to the
absence of An in the matrix assemblage, such that no
Al is available. When O.M. is present in the matrix, no
clay formation is observed (SA6). On the contrary,
when the constituents of matrix and chondrule are in
contact, clays are formed and their formation is favored
by an increase in the W/R ratio (A7-3 and A7-4).
Figure 1. SEM observation of the SA1 polished section.
The reaction products in chondrule (SA1 to SA4)
are TOT O’ clays whose composition is characterized
by Si>Al>Mg>Fe. These products are quite similar to
the alteration products found in GRO 95577
chondrules, which are vermiculite in the core
(Si>Mg>Fe>Al) and clinochlore in the mesostasis
(Si>Mg>Fe‰Al). It was not possible to get good
chemical analyses of the experimental phyllosilicates
formed in the matrix assemblages, and therefore not
possible to compare them to the phyllosilicates in the
matrix of GRO 95577.
The slight difference in composition between the
experimental alteration products of the chondrule
assemblage and those in chondrules of GRO 95577
may result from the short duration of the experiments.
During the initial stages of the experiment, alteration of
An dominates that of Fo or CPX, explaining why
experimental clays are richer in Al than natural
samples, which experienced longer term alteration. The
low level of clay formation in the presence of O.M.
indicates that organics may inhibit silicate alteration.
However, despite the slower alteration of silicates in
the presence of O.M., for the longer durations and
smaller grain sizes typical of the alteration of natural
matrix, transformations of the silicate phases may take
place.
Geochemical modeling. Only the results for the
chondrule assemblage are presented since it is the
system for which there is the best match between the
natural sample and the reaction products. GWB
predicts the consumption of An and Fo, the alteration
of CPX and the neoformation of clinochlore in
chondrule.
This is in good agreement with the SA1 reaction
products and chondrule mineralogy of GRO 95577.
Nevertheless the modeling predicts complete
elimination of Fo, whereas this mineral remains in the
experiments. The poor agreement in terms of reaction
kinetics (despite good agreement in terms of
mineralogy) may be due to the formation of a
protective nanometric layer at the surface of Fo.
Moreover GWB uses the Transition State Theory law,
which does not take into account the influence of
surface properties of minerals (defects, energetic
heterogeneities) on kinetic laws [11].
Conclusions:
This work shows that the aqueous alteration of CR
parent asteroid may have occurred at 250°C in an
anoxic medium without any S2 flow and in the presence
of pure water. It also illustrates the great influence of
Al, produced by breakdown of the feldspathic
mesostasis, of Po and of O.M. on the crystallization of
clinochlore. Al seems to be necessary while Po favors
the formation of these clays on Fo unlike O.M. This
latter point may be due to the kind of O.M. used.
Maillard products seem to have been decomposed into
oil which wet the surfaces of silicates and thus
inhibited their alteration. New alteration tests with
other organics will start in March 2007. Moreover, the
geochemical modeling gives good prediction of the
evolution of the system from a thermodynamic point of
view whereas the kinetic aspect needs to be refined. As
future work, other experiments will be conducted at
different temperatures, longer term and under CO2 and
H2S fluxes. Modeling work will be refined to constrain
long-term predictions.
References:
[1] Ash R. D. et al. (1993) Meteoritics & Planet.
Sci., 28, 318 [2] Abreu N. M. et Brearley A. J. (2006)
69th Metsoc, Abstract #5372 [3] Perronnet M. et
Zolensky M. E. (2006) LPS XXXVI, Abstract #2402 [4]
Perronnet M. et al. Submitted to Meteoritics & Planet.
Sci. [5] Clayton et al. (1977) Meteoritics, 12, 199 [6]
Zolensky M. E. (1991) Meteoritics, 21, 414 [7]
Weisberg et al. (1993) Geochim. Cosmochim. Acta.,
57, 1567-1586 [8] Kallemeyn et al. (1994) Geochim.
Cosmochim. Acta., 58, 2873-2888 [9] Smith C. et al.
(2004) Meteoritics & Planet. Sci., 39, 2009-2032 [10]
Kolb V. M. et al. (2005) Proceedings of SPIE 5906,
5906OT [11] Perronnet M. et al. (2006) Geochim.
Cosmochim. Acta, doi: 10.1016/j.gca.2006.12.011
Fo
Clinochlore
CPX
1
Th
e a
qu
eo
us
alt
era
tio
n o
f C
R c
ho
nd
rite
s:
ex
pe
rim
en
ts a
nd
ge
oc
he
mic
al
mo
de
lin
g.
Mu
rielle P
err
on
net
& M
ich
ael Z
ole
nsk
yN
AS
A J
oh
nson S
pace C
ente
r, H
ousto
n
Gille
s B
erg
er
& M
ike T
op
lis
Observ
ato
ire
Mid
i-P
yré
né
es,
Toulo
use
Vera
Ko
lb&
Milic
aB
aja
gic
Un
ivers
ity o
f W
isconsin
-Park
sid
e,
Kenosh
a
2
1 m
m
Re
na
zzo
GR
O 9
55
77
CR
2C
R 1
Aq
ue
ou
sa
lte
rati
on
Ob
jec
tive
s
Th
e a
qu
eo
us a
lte
ratio
n o
f C
Rs
�m
inera
log
icaltr
ansfo
rma
tio
ns ?
�o
rig
ina
l co
mp
ositio
n o
fC
Rs ?
�in
flu
en
tia
lm
ine
ralp
hases ?
�p
hysic
o-c
hem
ica
lco
nd
itio
ns ?
3
�Im
age
s, co
mp
ositio
n, a
bun
da
nce
of each
ph
ase
�E
stim
atio
n o
f th
e c
om
positio
n o
f th
e u
nalte
red C
R b
od
y
SE
M im
ag
es
EM
PA
ch
em
ica
l a
naly
se
s
Mo
da
l a
naly
sis
usin
g X
-Ra
y e
lem
en
tal m
ap
pin
ga
nd
ID
L im
age
tre
atm
en
t so
ftw
are
on
Ren
azzo
(CR
2)
an
dG
RO
95
57
7 (
CR
1)
Step 1
1. C
ha
racte
rizati
on
of
CR
ch
on
dri
tes
4
1. N
ew
da
ta o
n the
min
era
log
yo
f R
ena
zzo
an
d G
RO
95
57
7.
2. P
he
nom
eno
log
ica
l in
form
atio
n o
n the a
qu
eo
us a
ltera
tio
n p
rocess
•u
nusu
al p
etr
olo
gic
typ
e 1
: lim
its o
f ch
ond
rule
are
still
vis
ible
in
GR
O 9
55
77
→che
mic
al a
lte
ration
with
ou
t m
ajo
r m
ech
an
ica
l p
rocess
•o
livin
e +
pyro
xe
ne
verm
icu
lite
Fe
oliv
ine
-ric
h m
atr
ix ch
am
osite
3. M
od
al a
na
lysis
Fd
mesosta
sis
Aq
ue
ous a
ltera
tio
nA
l
Al
1. C
ha
racte
rizati
on
of
CR
ch
on
dri
tes
5
Ma
gne
tite
S in
ter.
ph
ase
s
Pyrr
hotite
Lo
w-N
i kam
acite
Ka
ma
cite
Op
aq
ue
ph
as
es
Ma
trix
Ch
on
dru
les
Matr
ix
19
.2
23 0 2.8
1.4
0 0
25
.2 0
13
.2
RG
Ch
am
osite
me
so
.
Fe
ldsp
atic
me
so
.
Ve
rmic
ulit
e
Pyro
xe
ne
Oliv
ine
0.7
3.3 0 0.9 0
0.2
2.3
1.1
5.0
1.1
RG
47
.94
5.6
RG
vo
l% =
are
a%
for
pri
sm
atic c
rysta
ls
46
.43
8.4
4.9
9.7
Com
puta
tion o
f chem
ical com
positio
n
►is
och
em
icala
lte
ratio
n
►com
positio
n o
f th
e u
na
lte
red
CR
19
.5
23 3
.5
4
50CR
CR
CR
1. C
ha
racte
rizati
on
of
CR
ch
on
dri
tes
6
�T
est th
e r
ele
va
ncy o
fo
ne
se
t o
fph
ysic
o-c
hem
ica
l con
ditio
ns
�S
ho
w th
e in
flu
en
tia
l m
inera
l p
hase
s
�U
nd
ers
tand
th
ea
ltera
tio
n m
ech
an
ism
s
Step 2
Ex
pe
rim
en
ts o
f a
qu
eo
us
alt
era
tio
n
•o
n a
syn
the
tic u
na
lte
red
CR
com
positio
n•
on
6 s
ub
-asse
mb
lag
es (
cho
ndru
le, m
atr
ix…
)
Co
mpa
riso
n w
ith
GR
O 9
55
77
2. E
xp
eri
men
tal s
tud
y
7
Exp
eri
me
nta
l co
nd
itio
ns
•T
em
pera
ture
: 2
50°C
(s
ee
Cla
yto
n e
t a
l. 1
97
7, W
eis
berg
et a
l. 1
99
3)
•D
ura
tio
n : 1
mo
nth
•S
olu
tio
n :
pure
dis
tille
d w
ate
r (f
usio
n o
f accre
ted
ice
s)
•G
az
fug
acity
:th
e m
ine
ralo
gic
al a
ssem
bla
ges s
et th
e p
hysic
o-c
hem
ica
l
cond
itio
ns
= C
LO
SE
D S
YS
TE
M
•R
/so
lutio
n : 1
or
1/4
0
•S
yste
m: -
pre
para
tio
n in
an
an
oxic
glo
ve
bo
x-
hydro
therm
al P
arr
bo
mb
-in
itia
l in
jectio
n o
f N
2→
an
oxic
2. E
xp
eri
men
tal s
tud
y
8
Exp
eri
me
nta
l co
nd
itio
ns
•D
iffe
ren
t syste
ms
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
+ F
a+
O.M
.
«U
na
ltere
d C
R»
, R
/so
l°=
1A
7-3
«U
na
ltere
d C
R»
, R
/so
l°=
1/4
0
Ma
trix
with
org
an
ic m
atte
r
Ma
trix
Sili
ca
tes c
hon
dru
le+
Fe
Ni+
su
lfid
es
Sili
ca
tes c
hon
dru
le+
su
lfid
es
Sili
ca
tes c
hon
dru
le +
Fe
Ni
Sili
ca
tes c
hon
dru
le
Syste
m
A7
-4
Fo
+ F
a+
FeN
i+
Po
+ O
.M.
SA
-6
Fo
+ F
a+
FeN
i+
Po
SA
-5
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
SA
-4
Fo
+ C
PX
+ A
n +
Po
SA
-3
Fo
+ C
PX
+ A
n +
Fe
Ni
SA
-2
Fo
+ C
PX
+ A
nS
A-1
Re
ag
en
ts
2. E
xp
eri
men
tal s
tud
y
= M
aill
ard
pro
du
ct, K
olb
et a
l. 2
005
9
(1)
Alte
ratio
n w
ith
in c
hon
dru
le
•S
A1
: F
o+
CP
X +
An
Fo
CP
X
Cru
sts
Ph
yllo
sili
ca
te c
rusts
2. E
xp
eri
men
tal s
tud
y
10
(1)
Alte
ratio
n w
ith
in c
hon
dru
le
•F
orm
atio
n o
f a
cru
st o
f p
hyllo
sili
ca
tes
Fo
+ C
PX
+ A
n
2. E
xp
eri
men
tal s
tud
y
11
(1)
Alte
ratio
n w
ith
in c
hon
dru
le
•F
orm
atio
n o
f a
cru
st o
f p
hyllo
sili
ca
tes
Fo
+ C
PX
+ A
n +
Fe
Ni
≈
Fo
+ C
PX
+ A
n
2. E
xp
eri
men
tal s
tud
y
12
(1)
Alte
ratio
n w
ith
in c
hon
dru
le
•F
orm
atio
n o
f a
cru
st o
f p
hyllo
sili
ca
tes
Fo
+ C
PX
+ A
n +
Po
↑
↑
Fo
+ C
PX
+ A
n
2. E
xp
eri
men
tal s
tud
y
13
(1)
Alte
ratio
n w
ith
in c
hon
dru
le
•F
orm
atio
n o
f a
cru
st o
f p
hyllo
sili
ca
tes
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
≈
Fo
+ C
PX
+ A
n
2. E
xp
eri
men
tal s
tud
y
14
ch
on
dru
leF
o
CP
X
An
Si, M
g
Si, M
g, C
a
Si, A
l, C
a
clin
och
lore
2. E
xp
eri
men
tal s
tud
y
15
ch
on
dru
leF
o
CP
X
An
Si, M
g
Si, M
g, C
a
Si, A
l, C
a
clin
och
lore
Fe
Ni
Fe
2. E
xp
eri
men
tal s
tud
y
16
ch
on
dru
leF
o
CP
X
An
Si, M
g
Si, M
g, C
a
Si, A
l, C
a
clin
och
lore
Fe
Ni
Fe
Po
Fe
Po+ -2
. E
xp
eri
men
tal s
tud
y
e.g
.T
aka
tori
et a
l. 1
99
3
e.g
.O
hn
ish
ia
nd
Tom
eoka
20
07
17
ch
on
dru
leF
o
CP
X
An
Si, M
g
Si, M
g, C
a
Si, A
l, C
a
clin
och
lore
Fe
Ni
Fe
Po
Fe
Po+ -
Fe
Ni
2. E
xp
eri
men
tal s
tud
y
18
(2)
Alte
ratio
n w
ith
in m
atr
ix
•S
A-5
: F
o+
Fa
+ F
eN
i+
Po
Few
cru
sts
!
Fo
Fa
50µ
m
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
2. E
xp
eri
men
tal s
tud
y
19
(2)
Alte
ratio
n w
ith
in m
atr
ix
•F
orm
atio
n o
f a
cru
st o
f p
hyllo
sili
ca
tes
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
Fo
+ F
a+
FeN
i+
Po
↓
↑
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
2. E
xp
eri
men
tal s
tud
y
20
(2)
Alte
ratio
n w
ith
in m
atr
ix
•F
orm
atio
n o
f a
cru
st o
f p
hyllo
sili
ca
tes
Fo
+ F
a+
FeN
i+
Po
+ M
.O.
↑
↑F
o+
Fa
+ F
eN
i+
Po
2. E
xp
eri
men
tal s
tud
y
21
ma
trix
Fo
Fa
Fe
Ni
Po
Si, M
g
Si, F
eL
imite
d c
lay
form
atio
n
2. E
xp
eri
men
tal s
tud
y
22
ma
trix
Lim
ite
d c
lay
form
atio
n
Al is
mis
sin
gF
o
Fa
Fe
Ni
Po
Si, M
g
Si, F
e
2. E
xp
eri
men
tal s
tud
y
23
ma
trix
Lim
ite
d c
lay
form
atio
n
Al is
mis
sin
g
O.M
.-
Fo
Fa
Fe
Ni
Po
Si, M
g
Si, F
e
2. E
xp
eri
men
tal s
tud
y
acid
pH
with
ou
t A
l →
dis
so
lutio
n o
nly
24
(3)
Altera
tio
n w
ith
in th
e s
yn
the
tic c
ho
ndri
te
•A
7-3
: F
o+
CP
X +
An
+ F
a+
Fe
Ni+
Po
+ O
.M., R
/so
l°=
1
Few
cru
sts
!
50µ
m
Fa
Fo
CP
X
2. E
xp
eri
men
tal s
tud
y
25
Fo
+ C
PX
+ A
n +
Fa
+ F
eN
i+
Po
+ O
.M.
↑↑
R/s
ol°
=1
(3)
Alte
ratio
n w
ith
in th
e s
ynth
etic c
ho
ndri
te
•F
ew
cru
sts
Fo
+ F
a+
FeN
i+
Po
+ O
.M.
2. E
xp
eri
men
tal s
tud
y
26
(3)
Alte
ratio
n w
ith
in th
e s
ynth
etic c
ho
ndri
te
•A
7-4
: F
o+
CP
X +
An
+ F
a+
Fe
Ni+
Po
+ O
.M., R
/so
l°=
1/4
0
Diffu
se
asp
ect o
f th
e
bo
rders
Fa
Fo
R/s
ol°
=1
/40
R/s
ol°
=1
2. E
xp
eri
men
tal s
tud
y
27
(3)
Alte
ratio
n w
ith
in th
e s
ynth
etic c
ho
ndri
te
Fo
rma
tio
n o
f a
cru
st o
f pseu
do
ph
yllo
sili
ca
tes
Fo
+ C
PX
+ A
n +
Fa
+ F
eN
i+
Po
+ O
.M.
R/s
ol°
=1
/40
↑
↑
R/s
ol°
=1
2. E
xp
eri
men
tal s
tud
y
28
ch
on
dru
leF
o
CP
X
An
Si, M
g
Si, M
g, C
a
Si, A
l, C
a
clin
och
lore
Fe
Ni
Fe
Po
Fe
Po+ -
Fe
Ni
ma
trix
Lim
ite
d c
lay
form
atio
n
O.M
.-
Fo
Fa
Fe
Ni
Po
Si, M
g
Si, F
e
Syn
the
tic c
hon
dri
teL
ow
R/S
ol°
ratio
fa
vo
rs th
e c
lay form
ation
+
2. E
xp
eri
men
tal s
tud
y
29
ch
on
dru
leC
lino
ch
lore
TO
T O
’S
i-A
l-M
g-F
e
ma
trix
Lim
ite
d c
lay
form
atio
n
Al is
mis
sin
g
Exp
eri
me
nts
GR
O 9
55
77
Ve
rmic
ulit
e
TO
T S
i-M
g-F
e-A
l
Ch
am
osite
TO
T O
’S
i-M
g-F
e-A
l
O.M
. --≈ ≠
2. E
xp
eri
men
tal s
tud
y
30
Wh
y is th
ere
an
y d
iffe
rence
s b
etw
ee
n e
xp
eri
men
ts a
nd
GR
O 9
557
7 ?
•L
imite
d d
ura
tio
no
f te
sts
→lim
ite
d a
lte
ratio
n o
f M
g-b
ea
rin
g
min
era
ls (
Fo
, C
PX
) e
t F
e-b
ea
rin
g o
ne
s (
Fa
) com
pare
d to
Al-
be
ari
ng
on
es (
An
)
•O
.M.
•P
oro
sity o
f th
e m
atr
ix n
ot w
ell
repro
du
ce
d
•L
on
g-d
ura
tion
tests
on
syn
the
tic c
ho
ndri
tes
•A
na
lysis
of th
e O
.M. -
be
fore
an
d a
fte
r e
xp
eri
me
nts
-vs.O
.M. in
Ren
azzo
an
d G
RO
95
57
7
•A
na
lysis
of th
e m
atr
ix o
f R
en
azzo
and o
ther
CR
s
Ho
w to
de
al w
ith
th
is …
2. E
xp
eri
men
tal s
tud
y
31
�D
oes the
mod
el p
red
ict w
ha
t ha
pp
en
ed in
th
e e
xpe
rim
en
ts ?
Step 3
Lo
ng
-te
rm p
red
icti
on
s ?
Ap
plic
ati
on
to
oth
er
carb
on
ac
eo
us
ch
on
dri
te g
rou
ps
?
Ge
oc
he
mic
al m
od
elin
g
us
ing
Ge
oc
he
mis
t W
ork
be
nc
h (
GW
B)
•o
n a
n u
na
lte
red
CR
com
positio
n•
on
the
6 s
ub
-asse
mb
lag
es (
ch
on
dru
le, m
atr
ix…
)
Co
mpa
riso
n w
ith
reactio
n p
rodu
cts
(S
tep
2)
3. G
eo
ch
em
ica
l m
od
elin
g
32
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
+ F
a+
O.M
.
«U
na
ltere
d C
R»
, S
/so
l°=
1A
7-3
«U
na
ltere
d C
R»
, S
/so
l°=
1/4
0
Ma
trix
with
org
an
ic m
atte
r
Ma
trix
Sili
ca
tes c
hon
dru
le+
Fe
Ni+
su
lfid
es
Sili
ca
tes c
hon
dru
le+
su
lfid
es
Sili
ca
tes c
hon
dru
le+
Fe
Ni
Sili
ca
tes c
hon
dru
le
Syste
m
A7
-4
Fo
+ F
a+
FeN
i+
Po
+ O
.M.
SA
-6
Fo
+ F
a+
FeN
i+
Po
SA
-5
Fo
+ C
PX
+ A
n +
Fe
Ni+
Po
SA
-4
Fo
+ C
PX
+ A
n +
Po
SA
-3
Fo
+ C
PX
+ A
n +
Fe
Ni
SA
-2
Fo
+ C
PX
+ A
nS
A-1
Ph
ases
Syste
ms
Syste
ms o
f th
e e
xp
eri
me
nts
(S
tep
2)
3. G
eo
ch
em
ica
l m
od
elin
g
33
•T
em
pera
ture
: 2
50°C
•S
olu
tio
n: p
ure
de
ion
ize
d w
ate
r
1e
-9m
ol C
a 2
+, F
e 2
+, M
g 2
+, S
iO2a
q , A
l 3+
, N
i 2
+, S
O 4
2-
•F
ug
acity in
ga
s: th
e m
inera
log
ica
l a
ssem
bla
ges s
et th
e p
hysic
o-
ch
em
ica
l co
nd
itio
ns
= c
lose
d s
yste
m
log
fO
2g=
-6
•R
ock/s
olu
tio
n : 1
or
1/4
0
•1
mon
th
Ph
ysic
o-c
hem
ica
l co
nd
itio
ns
Co
nd
itio
ns o
f th
e e
xp
eri
men
ts (
Ste
p 2
)
3. G
eo
ch
em
ica
l m
od
elin
g
34
Work
on
th
erm
od
yn
am
ic d
ata
Use
da
ta fro
m th
erm
o.d
at=
th
erm
od
yna
mic
da
taba
se
of G
WB
Co
mpu
te lo
g K
for
•K
am
acite8
3: F
e0.8
3N
i 0.1
7
co
nsid
eri
ng
it a
s a
so
lid s
olu
tio
n b
etw
een
Fe
0a
nd
Ni0
Use
EQ
3/6
so
ftw
are
•P
en
tla
nd
ite
: F
e0.5N
i 0.5
S
co
nsid
eri
ng
it a
s a
so
lid s
olu
tio
n b
etw
een
Fe
Sa
nd
NiS
•O
rgan
ic m
atte
r: -
be
nzene
(a
q)
-p
he
no
l (a
q)
-to
lue
ne (
aq
)
-C
H3C
OO
H (
aq
) b
ut m
ostly IO
M in
ch
on
dri
tes !
3. G
eo
ch
em
ica
l m
od
elin
g
35
No
n o
xid
ative k
ine
tic la
ws fo
r d
isso
lutio
n
63
00
0*
63
00
0
62
76
0
62
76
0*
62
76
0
62
76
0
Ea
(J/m
ol)
10
-15*
41
ka
ma
cite
83
10
-14
31
pyrr
ho
tite
10
-12.5
59
8a
nort
hite
10
-14*
66
faya
lite
10
-13.5
87
fors
teri
te
10
-14.1
58
7d
iop
sid
e
k (
mo
l/cm
2.s
)S
(cm
2/g
)
La
w =
S *
k *
(1-Q
/K)
So
urc
es : L
asa
ga
et a
l. (
199
4),
Ja
nze
net a
l. (
20
00)
*Ap
pro
xim
ate
d
3. G
eo
ch
em
ica
l m
od
elin
g
36
(1)
Alte
ratio
n w
ith
inch
on
dru
le
SA
-1: F
o+
CP
X +
An
YE
SExp
eri
me
nt
An
alte
red
Mo
de
ling
Kin
etic
ove
r-estim
atio
n
for
Fo
3. G
eo
ch
em
ica
l m
od
elin
g
37
Ag
reem
en
t be
twe
en
mod
elin
g a
nd
exp
eri
me
nts
•cry
sta
lliza
tion
of clin
och
lore
•a
lte
ratio
n o
f a
nort
hite
•Dis
cre
pa
ncy b
etw
ee
n m
ode
ling
an
d e
xpe
rim
en
ts
•o
ve
r-estim
atio
n o
f th
e k
inetic la
w o
f d
isso
lutio
n for
Fo
(nan
om
etr
icpro
tective
la
ye
r)
•T
ransitio
n S
tate
Th
eory
use
d b
y G
WB
►surf
ace
pro
pe
rtie
s n
o take
n in
to
acco
un
t Work
on
kin
etic la
ws +
ad
d in
fo o
n s
urf
ace
s +
ad
d in
fo o
n I.O
.M.
Ag
reem
en
t m
od
elin
g v
s. e
xp
eri
me
nts
for
the
oth
er
syste
ms
3. G
eo
ch
em
ica
l m
od
elin
g
Lo
ng
-te
rm p
red
icti
on
s
Ap
plic
ati
on
to
oth
er
carb
on
ac
eo
us
ch
on
dri
te g
rou
ps
38
Co
nc
lus
ion
sa
nd
pe
rsp
ec
tive
stu
die
s
•M
ostly iso
che
mic
al pro
cess d
uri
ng
altera
tio
n fro
m R
en
azzo→
GR
O 9
55
77
he
at g
ive
n b
y r
ad
iog
en
ic d
eca
y o
f 26A
l (n
ot accre
tio
n)
•C
om
po
sitio
n o
f th
e u
na
ltere
d C
R b
od
y e
stim
ate
d
•T
=2
50
°C a
nd
an
oxic
cond
itio
ns a
re lik
ely
•Im
port
ance
of th
efe
ldspa
thic
mesosta
sis
(A
l)
•Im
port
ance
of th
eO
.M. (w
et sili
ca
te s
urf
aces)
•Im
port
ance
ofsu
lfid
es (
acid
med
ium
whic
h fa
vors
Fo
dis
so
lutio
n)
•Im
port
ance
of th
e in
tera
ctio
n b
etw
een
ka
macite
-su
lfid
es (
hig
h a
ffin
ity)
SO
ON
, te
sts
at 1
00°C
and
at w
ith
vario
us I.O
.M.
•G
WB
mo
de
ling
is n
earl
y c
on
sis
ten
tw
ith
na
tura
l a
lte
ratio
n
SO
ON
, lo
ng
-te
rm m
od
elin
ga
nd
app
lica
tio
n to
oth
er
CC
s
39
Thanks
to
Loa
n,
Cra
ig, G
eorg
Ann a
tJS
C
Thie
rry a
nd
Phili
pp
e a
tLM
TG
Brig
itte
and
Matthie
u a
tM
NH
N P
aris
MW
G for
GR
O 9
5577
’lo
an
&
Oak
Rid
ge
Associa
ted
Univ
ers
itie
sfo
r th
efu
nd
ing
ofth
isre
searc
h.
