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1910 Goldschmidt2013 Conference Abstracts
Synthesis and characterization of Environmental diversity of
K-zeolites by the use of a diatomite denitrification
C. PACE1, D. NOVEMBRE1*AND D. GIMENO2 LAURA A. PACE1, JAMES HEMP 2 , RANJANI MURALI3,
1
Dipartimento di Ingegneria e Geologia, Università degli Studi
ROBERT B.GENNIS3 AND WOODWARD W. FISCHER2
G. D’Annunzio, Chieti Scalo 66100, ITALY 1
University of Utah (laura.a.pace@gmail.com)
(*correspondence: dnovembre@unich.it) 2
California Institute of Technology (jim.hemp@gmail.com)
2
Depart. de Geoquímica, Petrología i Prospecció Geològica, 3
University of Illinois at Urbana-Champaign
Facultat de Geologia, Universitat de Barcelona, 08028,
SPAIN (domingo.gimeno@ub.edu) The modern nitrogen cycle is a complex web of
microbially mediated redox reactions found in both oxic and
Hydrothermal crystallization of K-zeolites (K-F and W- anoxic environments. Recently, the breadth of microbial roles
Merlinoite type) from gels obtained by the use of k-aluminate in the nitrogen cycle has expanded substantially, with the
and naturally derived k-silicate is here achieved. The use of discovery of both new metabolisms (ANAMMOX; anaerobic
an inexpensive natural rock (“Tripoli” siliceous rock from oxidation of methane coupled to denitrification), and novel
Crotone, Italy) reduces the high costs of the usual industrial organisms performing known reactions (ammonia oxidation in
synthesis protocols and favours the exploiting of the same Archaea). Here we use metagenomics, coupled with
natural material. Chemical treatments were performed on the biochemical and physiological experiments, to identify new
opaline siliceous rock, whose composition resulted in quartz,
enzyme families able to catalyze nitric oxide reduction. These
amorphous opaline silica, clay minerals and a minor amount
results greatly expand the known diversity of organisms
of calcite [1], in order to obtain K-silicate. A first attack with
nitric acid to eliminate the calcitic and carbonatic fraction and capable of performing denitrification, suggesting also that this
Fe and Mn oxides, was followed by a treatment in an alkaline metabolism is more widespread than previously recognized.
bath (KOH 10%) to induce the solubilization of the siliceous Nitric oxide reduction is catalyzed by enzymes from the
fossil fraction and the production of the K2SiO3 solution. The heme-copper oxidoreductase (HCO) superfamily. The
second reagent, potassium aluminate, was achieved by the superfamily is extremely diverse, with members playing
mixing of potash crucial roles in both aerobic and anaerobic respiration. It is
currently divided into two reaction classes; oxygen reductases
and nitric oxide reductases. The oxygen reductases are
terminal enzymes in aerobic respiratory chains, and are able to
conserve energy in a proton electrochemical gradient. The
nitric oxide reductases (NOR) catalyze the reduction of nitric
oxide to nitrous oxide (2NO + 2H+ + 2e- ! N2O + H2O) in
microbes capable of denitrification, and are not known to
conserve energy.
The HCO superfamily currently consists of three oxygen
Figure 1: Left: W-Merlinoite type zeolite; right: K-F zeolite. reductase families (A, B and C) and two NOR families (cNOR
and qNOR). We used metagenomics and comparative
(20%) with Al(OH)3 (65%). Five series of synthesis were genomics to discover at least seven new families capable of
performed inside autoclaves at a temperature of 150°C and nitrogen cycle reactions. Five of these families (eNOR, bNOR,
ambient pressure by varying the ratio of the silicatic and sNOR, gNOR, nNOR) catalyze nitric oxide reduction. The
aluminatic solutions. Infrared and X-ray spectroscopy, thermo two other families are predicted to perform reactions new to
diffraction, nuclear magnetic resonance 29Si, structural the superfamily; nitric oxide dismutation (2NO ! O2 + N2)
refinement together with high temperature diffraction textural, and nitrous oxide reduction (N2O + 2H+ + 2e- ! N2 + H2O).
chemical, and physical characterization give values All sequenced ammonia-oxidizing bacteria have the sNOR
comparable to those proposed by literature. family, whereas the gNOR family is specifically found in
environments where sulfide oxidation is coupled to
[1] Novembre et al (2004) Microp. and Mesop. Mat. 75, 1-11.
denitrification. The eNOR and bNOR families have proton
channels, which allow them to conserve energy, enabling
these microbes to extract more energy from denitrification.
Significantly, according to metagenomic data, the eNOR
family appears to be the most common NOR found in Nature.
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by guest
Goldschmidt2013 Conference Abstracts 1911
Hydrogen diffusion in Fluorine, Cl, Br & I in serpentinites
Ti-bearing forsterite LILIANNE PAGE* AND KEIKO HATTORI1
PADRON-NAVARTA J.A.1,2, HERMANN J. 3, 1
Dept. Earth Sci., Univ. Ottawa, Ottawa, Canada, K1N 6N5
AND O’NEILL H.S.C (*correspondance: lpage097@uottawa.ca)
1
Géosciences Montpellier, CNRS-UM2, Montpellier, France.
The abundance of F, Cl, Br and I in serpentinites were
3
Research School of Earth Sciences, ANU, Australia.
examined to evaluate their behaviour in subduction zones.
Samples include (1) unmetamorphosed, obducted hydrated
Migration of point defect in ferromagnesian silicates
abyssal peridotites, (2) subducted abyssal peridotites to depth
controls the transport properties of the Earth’s mantle. The
of ~30 km, (3) forearc mantle serpentinites from shallow
geodynamic and chemical evolution is dictated by the
depth (
1912 Goldschmidt2013 Conference Abstracts
Primary and secondary biomass Loss of Volatile Elements After the
burning aerosols determined by Moon-Forming Giant Impact
factor analysis of H-NMR spectra K. PAHLEVAN1, S. KARATO1AND B. FEGLEY2
M. PAGLIONE1*, S. DECESARI1, L. GIULIANELLI1, 1
Dept. of Geology and Geophysics, Yale University, USA
E. TAGLIAVINI2, R. HILLAMO3, S. CARBONE3, 2
Dept. of Earth & Planetary Sciences and McDonnell Center
S. SAARIKOSKI3, E. SWIETLICKI5, S. FUZZI1 for Space Sciences, Washington U. St. Louis, USA
AND M.C. FACCHINI
1
Among the most striking observations made of the Apollo
1
CNR-Institute of Atmospheric Sciences and Climate(ISAC),
samples is the relative dearth of volatile elements observed in
Bologna, Italy (*correspondence: m.paglione@isac.cnr.it)
the lunar material [1], including moderately volatile elements
2
Dept. of Chemistry, University of Bologna, Bologna, Italy
that condense from the solar nebula at relatively high (T >
(emilio.tagliavini@unibo.it)
1,000 K) temperatures. Although such an observation is
3
Finnish Meteorological Institute, Air Quality Research,
generally thought to be consistent with the energetic events
Helsinki, Finland (risto.hillamo@fmi.fi)
associated with a giant impact, no quantitative chemical and
4
Div. of Nuclear Physics-Dept. of Physics, Lund University,
dynamical scenario has been put forward to explain it.
Sweden (erik.swietlicki@pixe.lth.se).
The energy released in the Moon-forming giant impact is
sufficient to melt and partially vaporize both the Earth and the
Discovery of Secondary Organic Aerosol (SOA)
impactor. The timescale to eliminate this heat by radiation is
formation in biomass burning plumes leads to the question
~103 years [2]. Hence, the Earth-Moon system is expected to
whether oxidized fraction of biomass burning aerosol is rather
be in a molten, partially vaporized state for the first thousand
of secondary instead of primary origin and what are chemical
years after the giant impact. This stage of the evolution may
compositions of oxidized biomass burning POA and SOA.
permit the loss of volatile elements via selective partitioning
In the frame of EUCAARI project proton-nuclear
of elements into a vapor phase followed by phase separation
magnetic resonance (H-NMR) spectroscopy was applied to
of the lunar material. It has been known for decades that H –
investigate the functional group composition of fresh and aged
in molecular form – is gravitationally unbound in the
biomass burning aerosols during an intensive field campaign
circumterrestrial lunar disk [2]. However, no process is
carried out in spring 2008 at a Po Valley rural station, Italy.
known that can separate the light, unbound vapor species from
Factor analysis applied to set of NMR spectra was used to
the heavier molecules of the silicate vapor atmosphere on the
apportion wood burning and other OC source contributions,
relevant timescales.
including aliphatic amines. Comparison between NMR results
Here, we investigate a new possibility: redistribution of
and those from parallel high resolution aerosol mass
elements in the proto-lunar disk. Because the Moon accretes
spectrometry (HR-Tof-AMS) measurements shows only a
from the outermost regions of the proto-lunar disk, it may
partial overlap between NMR and AMS factors relating to
inherit a composition distinct from that of the inner disk which
fresh biomass burning. The comparison between the two
accretes back onto the Earth. We will present model
techniques substantially improves when adding factors tracing
calculations that explore physical and chemical conditions
possible contributions from biomass burning SOA. The
necessary for the Earth-ward transport of volatile elements in
chemical composition of such secondary combustion aerosols
the proto-lunar disk and present the consequences of such a
was shown to be markedly different from that of the
redistribution process. Such an approach has the potential not
corresponding POA and, at the same time, was not represented
only to explain the abundances and isotopic composition [3] of
by most common organic tracers used to apportion biomass
lunar volatiles but also to permit the observed abundances to
burning POA. NMR results, in fact, show that fresh wood
be used to yield insight into the largely unknown processes
burning is composed of polyols and aromatic compounds, with
accompanying lunar origin.
a sharp resemblance with wood burning POA obtained from
smoke chambers, while aged samples are depleted of alcohols
[1]. Ringwood, A.E. (1979), Origin of the Earth and Moon.
and are enriched in aliphatic acids with a smaller contribution
Springer-Verlag, New York. [2]. Stevenson, D.J. (1987),
of aromatics. Factor analysis applied to NMR proven to be
Annu. Rev. Earth Planet. Sci. 15 271-315. [3]. Humayun, M.,
able to overcome the main drawbacks of methodologies
Clayton, R.N. (1995), Geochim. Cosmochim. Acta 59 2131-
relying on molecular tracer analysis and could be profitably
2148.
used for the identification of SOA fractions.
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by guestGoldschmidt2013 Conference Abstracts 1913
Distribution of dissolved neodymium High Precision measurements of sub
isotopes across the southern South nanogram levels of neodymium
Pacific measured as NdO+ using Phoenix X62
KATHARINA PAHNKE*AND CHANDRANATH BASAK Thermal Ionization Mass
Max Planck Research Group for Marine Isotope Spectrometer
Geochemistry, Institute for Chemistry and Biology of the
ZENON PALACZ1, DAVID BURGESS AND JEREMY INGLIS1
Marine Environment (ICBM), University of Oldenburg,
Oldenburg, Germany (*correspondence: kpahnke@mpi-
1
Isotopx, Unit 1A Milbrook Court, Middlewich, Cheshire,
bremen.de) CW10 0GE.
The South Pacific is an important area of bottom and We have analysed sub nanogram amounts of the JNd-I
intermediate water formation, and a key location for the Neodymium standard as NdO+ using the Phoenix X62 TIMS.
communication of the Pacific with the Indian and Atlantic Samples were loaded on single Re filaments with a TaF5
Ocean basins. Despite its importance for the global ocean, the activator. Ion/Atom detection efficiency increases with
South Pacific is largely understudied with respect to the decreasing sample size, with efficiencies of up to 30% attained
distribution of trace elements and their isotopes, and in for sample sizes between 500 and 50pg. For sample sizes of 1-
particular neodymium isotopes (143Nd/144Nd, expressed in !Nd), 10ng efficiencies are about 10%. Similar efficiencies are also
for which only a limited database exists in the southeast observed for Sr. The maximum detection efficiency is close to
Pacific [1]. the transmission of the spectrometer, and that the TaF5
Here we present dissolved Nd isotopes from 11 stations activator is producing nearly 100% ionization off the filament
across the South Pacific between South America and New for small samples of Sr and Nd, which have similar ionization
Zealand and between 46°S and 69°S. The transect samples potentials of 5.2 and 5.5eV respectively. This is much higher
South Pacific water masses east and west of the Pacific- (by more than an order of magnitude) than Sr and Nd+ without
Antarctic Ridge and north and south of the circum-Antarctic the TaF5 and probably indicates an increase due to close
frontal system, affording insight into the spatial variation of coupling with the very high work function fluorine atom.
the Nd isotopic composition of different water masses. We Using static multicollection and 1e11 ohm resistors, the
observe a clear difference in !Nd between bottom waters in the reproducibility of 143Nd/144Nd remains better than 20ppm
western basin within the Deep Western Boundary Current (!Nd 1RSD for sample sizes down to 100pg. It is possible that using
= -9) and the eastern basin just north of the Ross Sea (!Nd = - a higher gain resistor will improve this since ion intensities for
7), suggesting that Antarctic Bottom Water from different 143
Nd16O are only 50mv.
source regions carries different isotopic signatures. Notably,
bottom water formed in the Ross Sea (RSBW) can also be
distinguished from overlying Circumpolar Deep Water,
making !Nd a useful tracer for past changes in RSBW export
into the southeast Pacific. Most profiles further show a shift
towards less radiogenic !Nd at the depth of Upper Circumpolar
Deep Water (UCDW) that is associated with a salinity
maximum in the Southern Ocean. This negative shift is
consistent with a higher component of unradiogenic North
Atlantic Deep Water (!Nd " -13) in UCDW. The results
provide a good basis for an improved understanding of the
distribution of Nd isotopes in the Pacific Ocean, and for the
use of !Nd as a tracer of past circulation changes.
[1] Carter et al (2012), Geochim. Cosmochim. Acta 79, 41-59.
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by guest1914 Goldschmidt2013 Conference Abstracts
Soil aggregate-scale chemical Formation of chondritic meteorites
gradients resulting from coupled H. PALME
biogeochemical and transport Sektion Meteoritenforschung, Forschungsinstitut und
processes Naturmuseum Senckenberg, Senckenberganlage 25 D-
60325 Frankfurt, Germany
CÉLINE PALLUD1* AND MATTEO KAUSCH1 (palmeherbert@googlemail.com)
1
Environmental Science, Policy and Management
(ESPM),University of California, Berkeley, More than 99% of the mass of the solar system is in the
USA(*correspondence: cpallud@berkeley.edu) Sun. The chemical composition of the Sun and similar stars is
well known from absorption line spectroscopy. The Sun has
A continuing challenge in environmental science is to about equal numbers of Mg, Si and Fe atoms. Planetesimals
understand and predict how concentrations of nutrients and with these characteristics are parental to primitive,
contaminants vary over space and time in natural systems. undifferentiated or chondritic meteorites. Bulk Earth, Venus
Within soils, biogeochemical processes controlling elemental and Mars also have approximately solar ratios of Mg, Si and
cycling are heterogeneously distributed owing partly to the Fe. CI-chondrites match solar abundances to within a few
physical complexity of the media. Structured soils are percent. Small deviations from solar abundances in other
composed of individual aggregates that form a network of groups of chondritic meteorites reflect nebular processes prior
interconnected microenvironments. The aggregate scale (mm- to accretion to larger objects: (a) Loss or gain of refractory
cm) is of particular interest due to the sharp transition in pore phases (Ca, Al, Ti), (b) variable accumulations of forsteritic
size between the aggregates themselves and the macropores olivine and (c) of metallic FeNi and (d) incomplete sampling
surrounding them. The objective of this study is to investigate of volatile elements. In addition, large variations in oxygen
the coupling of physical (transport) and biogeochemical contents are observed. Each chondrite group is formed from a
processes that affect small-scale iron transformations and that comparatively small isolated nebular reservoir [1].
control selenium sequestration within soils.
On a cm scale chondritic meteorites are chemically
We present a combined experimental and modelling
uniform [2]; on a mm scale and below they are extremely
study on single artificial soil aggregates assessing the
variable. Chondrules, mm sized once molten silicate droplets,
biogeochemical processes governing transformations of redox
sensitive elements (iron and selenium) in a complex but and fine grained matrix are two major components of
controlled setting representative of natural systems. chondrites. They are chemically complementary: The low
Circumventing byproduct accumulation and substrate average Fe/Mg and Si/Mg of chondrules is balanced by higher
exhaustion common in batch systems and avoiding the poor atomic ratios in matrix yielding the chondritic bulk
physical analogy to aggregated soils of homogenously packed composition. Both components must have formed from a
columns, our novel experiments mimic soils using constructed single solar-like reservoir [3]. This is an important often
cm-scale aggregates in flow-through reactors, which results in neglected constraint for chondrule formation models. The
diffusively and advectively controlled regions. A newly reason for the enormous chemical variability of chondrules is
developed reactive transport model is used to delineate unclear. Yet, the bulk composition of primitive chondrites
transport regimes, identify reaction zones, and estimate kinetic requires that it must have been established in a closed
parameters and reaction rates at the aggregate scale. reservoir of chondritic composition.
Overall, our findings demonstrate significant aggregate- Each chondrite group has its own stable isotope signature
scale variations in biogeochemical processes and consequent [4]. The Earth and the other planets were built of a series of
distribution patterns of solid phases within soils. We show that chondritic planetesimals. But stable isotopes indicate that the
those chemical gradients are mainly controlled by diffusive
presently known population of chondrite parent bodies did not
mass-transfer limitations of both solute delivery to the
significantly contribute to the Earth [5].
aggregates and metabolite removal from the aggregates. This
Lit.:
highlights the importance of appreciating the spatial
connection between reaction and transport fronts and of
[1] Palme H. and O’Neill H.St.C. (2003) in: Treatise on
obtaining information on transport-limited, intra-aggregate
Geochemis-try, Volume 2-The Mantle and Core, ed: Carlson,
biogeochemical dynamics to better understand reactive
R.W., Elsevier-Pergamon, Oxford, pp. 1-38. [2] Stracke A. et
transport of redox-sensitive species in structured soils.
al (2012) Geochim.Cosmochim. Acta 85, 114-141. [3] Hezel
D.C. and Palme H. (2010) Earth Planet Sci. Lett. 280, 85-93
[4] Warren P. (2011) Earth Planet. Sci. Lett. 311, 93-100.
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by guestGoldschmidt2013 Conference Abstracts 1915
The chemical composition of the The role of tephra diagenesis in the
Earth carbon cycle
H. PALME1 AND H.ST.C. O’NEILL2 M.R. PALMER1*, T.M. GERNON1 AND SHIPBOARD
SCIENTISTS OF IODP LEG 340
2
1
Sektion Meteoritenforschung, Forschungsinstitut und
Naturmuseum Senckenberg, Senckenberganlage 25, 60325 1
School of Ocean & Earth Science, University of
Frankfurt /Main, Germany, Southampton, European Way, Southampton SO14
(palmeherbert@googlemail.com), 3ZH,UK (*correspondance: pmrp@noc.soton.ac.uk)
2
Research School of Earth Sciences, Australian National 2
(http://iodp.tamu.edu/scienceops/expeditions/antilles_volcani
University, Canberra ACT, 0200 Australia sm_landslides.html)
The composition of the Earth is derived from ultramafic Most volcanoes are located close to the oceans. Hence a
rocks, samples from the Earth’s mantle in a variety of geologic high proportion of the 1015 g/yr of tephra that is created by
settings [1]. The high Mg, Ni and PGE contents, chondritic subaerial volcanism ends up in marine sediments, such that
Ni/Co ratios, unfractionated compatible refractory elements tephra comprises ~25% of Pacific Ocean sediments. In
(Yb/SC), chondritic Na/Mn ratios etc. support a primitive addition, individual massive explosive eruptions have covered
mantle origin, affected only by core formation and loss of a large areas of the globe during Earth history. Given that fresh
small fraction of partial melt, which may have occurred before tephra is highly reactive when exposed to seawater it is
final accretion of the Earth [2,3]. From a detailed comparison important to consider the implications of this flux of material
with chondritic meteorites it is concluded that the bulk Earth to the oceans.
composition is not CI chondritic (i.e. precisely solar) but has We hypothesise that tephra deposition in the oceans may
similarities to the chemical composition of the CV group of influence the ocean-atmosphere carbon cycle through the
carbonaceous chondrites: (a) Enrichment of refractory following mechanisms: (1) Leaching of tephra deposited in
elements, (b) bulk Earth Mg/Si ratio, assuming 7 % Si in the surface waters may cause increased productivity (and
core, (c) similar patterns of moderately volatile elements as drawdown of atmospheric CO2) via addition of nutrients to Fe-
CV (d) depletion of Mn and other moderately volatile limited areas. (2) Deposition of tephra in sediments leads to
elements shortly after the first solids had formed in the solar rapid depletion of dissolved O2 in pore waters, thus enhancing
organic carbon preservation in underlying sediments. (3) After
nebula (based on 53Cr). Despite chemical similarities Earth
tephra deposition, bioturbation mixes the upper tephra surface
does not mach CV precisely: (a) Earth has excess Fe, (b) Earth
with background sediments. Tephra contains reactive Fe
is more depleted in volatiles than CV chondrites (d) the stable phases that are known to complex organic carbon in non-
isotopic composition of several elements in the Earth is similar volcanic sediments and enhance organic carbon preservation.
to ordinary chondrites and even closer to enstatite chondrites (4) As the tephra layer is buried deeper, it moves into zones of
but different from carbonaceous chondrites [4]. However, CH4 and alkalinity production. Alkalinity (and oxidised CH4)
enstatite chondrites have very different chemistry and are not diffuses into the overlying tephra where it encounters high
good candidates for the Earth. It seems impossible to make the dissolved Ca levels from Ca-Mg exchange during tephra
primitive upper mantle from a high Si, low Al source. As diagene-sis, leading to precipitation of calcite cements that
chemistry and stable isotopes are decoupled similarities of in effectively sequester CO2 produced from organic carbon and
stable isotopes have limited significance: Isotopically main form a further barrier to downwards diffusion of oxidising
group pallasites fit with the non-carbonaceous chondrites species.
while Eagle Station pallasites are close to carbonaceous We review here the evidence supporting each of these
chondrites [4]. Considering chemistry and stable isotopes one processes and indicate times and places in Earth history when
has to conclude that Earth is made of a variety of chondritic they have played a particularly important role.
meteorites, different from known groups of chondrites.
Lit.: [1] Palme H. and O’Neill H.St.C. (2003) in: Treatise on
Geochemis-try, Volume 2-The Mantle and Core, ed: Carlson,
R.W., Elsevier-Pergamon, Oxford, pp. 1-38. [2] O'Neill
H.St.C. and Palme H. (2008) Phil. Trans. R. Soc. A 366, 4205-
4238.[3] Campbell I.H. and O’Neill H.St.C. Nature 483, 533-
558. [4] Warren P. (2011) Earth Planet. Sci. Lett. 311, 93-100.
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by guest1916 Goldschmidt2013 Conference Abstracts
Coherent pyroxene-akimotoite phase Single crystal elasticity of the
transformation in NWA 5011 Na1.07Mg1.58Al4.91Si1.26O12 NAL phase
shocked chondrite and seismic heterogeneity in the deep
E. PÁL-MOLNÁR1*, SZ. NAGY1, K. FINTOR1, I. GYOLLAI2 mantle
AND ZS. BEND!
3
M. G. PAMATO 1*, A. KURNOSOV 1, T. BOFFA
1
University of Szeged Department of Mineralogy, BALLARAN1, D. M. TROTS 1, R. CARACAS 2
AND D. J. FROST
1
Geochemistry and Petrology, Szeged, Hungary
(*correspondence: palmolnare@gmail.com) 1
Bayerisches Geoinstitut, Universität Bayreuth, Germany
2
University of Vienna, Vienna, Austria
(*correspondence: martha.pamato@uni-bayreuth.de)
3
Eötvös Loránd University, Budapest, Hungary 2
Laboratoire de Sciences de la Terre, Ecole Normale
Supérieure de Lyon, France
Introduction
Akimotoite is a major constituent phase through Earth’s
Subducted mid-oceanic ridge basalts (MORB) are likely to
transition zone [1]. Up to now this phase transition has been
be important components of the lower mantle. As a
observed as incoherent nucleation and growth in and around
consequence of plate tectonics, basaltic oceanic crust is
opaque shock melt veins [2]. In this abstract we are reporting
subducted into the mantle introducing chemical heterogeneity.
the possible first coherent pyroxene-akimotoite transformation
Compared to average peridotitic mantle, MORB are enriched
along the cleveages of pyroxene.
in silicon, aluminium, calcium and alkalis. At lower mantle
Results and Discussion
conditions, experimental studies have shown that subducted
The NWA 5011 shocked chondrite consists of shock veins
MORB comprises more than 20 % of an aluminium rich
in various thickness and chondrules. A mixed-type pyroxene
phase, the so called NAL (new aluminium phase) phase.
chondrule (approx. 1 mm in diameter) contains numerous
Evidence for the existence of the NAL phase has been
subchondrules observed in the sample. One of the
observed in sublithospheric diamonds, where composite
subchondrules exhibits dense cleavage network in which the
multiphase inclusions have been found with similar bulk
angle between two cleavage plains is nearly right (87°).
compositions to NAL. If present, NAL will be a contributor to
Therefore this orientation of crystal face is {110}. The BSE-
the bulk elastic properties of the lower mantle and knowledge
images revealed that plain of cleveages enriched in Fe and it
of its elasticity is crucial for investigating the consequences of
shows microgranular texture. However, the microgranular
subducted crust for the seismology of the mantle.
character is slightly overhanging from the original boundary
NAL crystallising in MORB form complex solid solutions
of cleavages to the host grain area. The thickness of
and have the general formula XY2Z6O12 where X is a large
“overhanged” transition area is observed up to 0.5µm, and
monovalent or divalent cation (Ca2+, K+, Na+), Y a middle-
parallel to the direction of cleavages. In some areas between
sized cation (Mg2+, Fe2+ or Fe3+), and Z a small sized cation
the cleavages incoherent pyroxene-akimotoite phase
(Al3+ and Si4+). Here we report the crystal structure refinement
transformation occurs. Raman spectra have been collected
of NAL synthesized at lower mantle conditions with a
along the cleavage, which confirmed the pyroxene-akimotoite
composition close to that expected to crystallise in a
phase transition. The Fe-enrichment in cleavage is possible
subducting slab. We also report for the first time its full elastic
due to weathering processes, or melting and subsequent metal-
tensor experimentally determined by Brillouin scattering
sulfide formation. The most characteristic feature of the
spectroscopy at room and high pressure. We complement
Raman spectra is the presence of main vibrations of
these experimental results with first-principles calculations,
ringwoodite and stishovite besides akimotoite peaks. This
performed using density-functional theory and density-
feature confirms that inside the fragments far from boundary
functional perturbation theory.
of shock melt veins lower P-T regime transformation products
in the Mg4Si4O12-Mg3Al2Si3O12 system can survive due to the
fast temperature drop. This suggests subsequent evidence for
high P-T regime change in shock melt veins within a small
affected area.
[1] Tomioka & Fujino (1999) Am. Min. 84, 267-271. [2] Hu et
al (2012) 43rd LPSC, abs#2728.
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by guestGoldschmidt2013 Conference Abstracts 1917
Impact of suspended inorganic Nd-Sr Isotopic Constraints on the
particles on phosphorus cycling in the Source of the Hexi Corridor Loess
Yellow (Huanghe) River PAN YAODONG1 RAO WENBO1 AND WU WEIHUA2
GANG PAN1*, MICHAEL D. KROM2,3, MEIYI ZHANG1, 1
Institue of Isotope Hydrology, Hohai University, Nanjing, 210098,
XIANWEI ZHANG1 AND ROBERT J.G. MORTIMER2 China.( Panyaodong612@163.com)
2
Institute of surficial geochemistry, Nanjing University, Nanjing,
1
Research Center for Eco-Environmental Sciences, Chinese
210093, China
Academy of Sciences, Beijing 100085, China,
(*correspondence: gpan@rcees.ac.cn)
Analysis and Comparison
2
Earth and Biosphere Institute, School of Earth and
The loessial soil is very important for habitants in the Hexi
Environment, University of Leeds, Leeds LS2 9JT, UK
Corridor, North China. However, knowledge on the loess
3
Charney school of Marine Scinces, Haifa University, Haifa,
source of this region is uncertain till now. In order to answer
Israel
this question, Sr-Nd isotopic comparisons between the loess of
the Hexi Corridor and surface sediments of surrounding areas
While the importance of phosphorus (P) as a limiting
nutrient is well established, the understanding of global scale are conducted in this study.
control on P cycling in continents and how these affect River sediments from the Qilian mountian are collected for
riverine P fluxes is still incomplete. P in water and sediment in isotopic analysis of their fine-grained fractions in this study. The
the Huanghe was measured for 21 stations from the source to measured !Nd(0) values vary from -11.84 to -11.95 with 87Sr/86Sr ratios
the Bohai Sea. The average total particulate matter (TPM) from 0.7196 to 0.7388 �As listed in Table 1�.
increased from 40 mg/L (upper reaches) to 520 mg/L (middle According to topographical and meteorologic data, the
reaches) and 950 mg/L in lower reaches of the river. Badain Jaran desert, the Qaidam desert, the Taklimakan
Although there was considerable nutrient pollution, the desert, the Gurbantunggut desert and Rivers of the Qilian
dissolved PO4 concentration remained low (0.32-0.58 mountains might be potential sources to supply fine-grained
µmol/L) due to adsorption on particles. The P removed was fractions for the loess formation in the Hexi Corridor. !Nd(0)
mainly due to the high TPM rather than the surface activity of values and 87Sr/86Sr ratios of fine-grained fractions vary from -
the particles since they had low labile Fe and low affinity for 7.4 to -10.2 and from 0.7132 to 0.7174 for the Badain Jaran
P. The sediment was a major sink for P in the middle to lower Desert, from -10.0 to -10.5 and from 0.7166 to 0.7187 for the
reaches but not in the initial upper to middle reaches. TPM has Qaidam Desert, from -9.5 to -11.7 and from 0.7136 to 0.7171
been reduced by more than 10-fold due to artificial dams over for the Taklimakan Desert, from -1.2 to -3.3 and from 0.7113
the last decades. Experimental modeling revealed that TPM of
to 0.7136 in the Gurbantunggut Desert, respectively [2].
1 g/L was a critical threshold for Huanghe below which most
of the P input to the river can no longer be removed by the
particles where eutrophication may occur. These findings Results and Conclusion
provide realistic representations of particle control on riverine Isotopic compositions of the Hexi Corridor loess are
P fluxes which can be used in coupled land-ocean modeling in distinctly different from those of the Badain Jaran Desert, the
global biogeochemical P cycling. Qaidam Desert and the Gurbantunggut Desert, but are roughly
similar to the Taklimakan Desert and river sediments of the
Qilian mountian. Due to the stability of Sr-Nd isotopes in the
surficial process [3], the geochemical similarity of the loess in
the Hexi Corridor with the fine-grained fractions of the
Taklimakan Desert and river sediments of the Qilian mountian
indicates the two areas might be main sources of the Hexi
Corrdior loess.
Region Type Grain size !Nd(0) 87
Sr/86Sr
-11.84 0.7335
River -12.95 0.7338
Qilian Mts.1918 Goldschmidt2013 Conference Abstracts
Molecular level characterization of Multiple pools of reduced carbon can
methyl sugars and other be released during hyperthermals
carbohydrate compounds in marine R.D. PANCOST1*, M.P.S. BADGER1, B. D. A. NAAFS1,
high molecular weight dissolved S. FROEHNER1, J.M. CASTRO2, G.A. DE GEA2,
M.L. QUIJANO3, R. AGUADO3, C. LOWSON1
organic matter (HMWDOM) AND A. RIDGWELL
4
C. PANAGIOTOPOULOS12*, D.J. REPETA3, L. MATHIEU12, 1
Organic Geochemistry Unit, Chemistry, University of
J-F. RONTANI12 AND R. SEMPERE12 Bristol, UK (*corr author: r.d.pancost@bristol.ac.uk)
1
Aix-Marseille Université, Mediterranean Institute of
2
Depto. Geologia, Univ. Jaén, E-23071, Spain
Oceanography (MIO), 13288, Marseille, Cedex 9, France;
3
Depto. Química Inorgánica y Orgánica, Univ. Jaén, E-23071,
2
Université du Toulon, CNRS/INSU, IRD, MIO UM 110, Spain
83957 La Garde, France
4
BRIDGE, Geographical Sciences, University of Bristol, UK
(*correspondance: christos.panagiotopoulos@univ-amu.fr)
3
Department of Marine Chemistry and Geochemistry, Woods Numerous transient hyperthermals have been identified in
Hole Oceanographic Institution, Woods Hole, MA 02543, Earth history, and most are associated with a sharp negative
USA (drepeta@whoi.edu) carbon isotope excursion (CIE). The CIEs indicate that rapid
global warming was at least partly caused by the release of
Dissolved organic matter (DOM) is an active component reduced carbon, with methane hydrates, peat deposits and
of the carbon cycle however its chemical composition, fate, permafrost all being proposed as sources. Much work on
and sources are poorly understood. Approximately 30% of hyperthermals, and especially the Paleocene-Eocene Thermal
surface DOM can be sampled by ultrafiltration, and thereby Maximum (PETM), illustrates that rapid global warming
concentrates the high molecular weight DOM fraction caused dramatic changes in the hydrological, erosional and
(HMWDOM > 1kDa)[1]. Previous studies have shown that weathering regime. These changes were associated with a
most HMWDOM is comprised of carbohydrates (acylated marked increase in the mobilisation and transport of soil and
carbohydrates or APS), but only a minor fraction of the terrestrial vegetation, and it is likely that under a warmer
carbohydrate has been identified at the “molecular level” (as climate state at least some of this OM was oxidised, providing
monosaccharides after hydrolysis, i.e. fucose, rhamnose, a positive feedback on global warming. Here, we present
arabinose, galactose, glucose, mannose, and xylose). The evidence that even reduced carbon reservoirs that are
discrepancy between NMR derived estimates of HMWDOM generally perceived as recalcitrant (i.e. kerogen) are also
carbohydrate (50-70% C) and molecular level analyses (10- mobilised during such events.
20% C) has not been explained, and no new sugars have been Kerogen inputs to marginal marine sediments increased
identified in HMWDOM in about 10-15 years[2]. dramatically during both OAE1a and the PETM. This is
Here using ultrafiltration, silver cation preparative documented by a shift in biomarker (sterane and hopane)
chromatography, and GC-MS we identified 50 novel sugar assemblages from thermally immature to mature signatures
compounds after hydrolysis of the HMWDOM. Sugars were over short stratigraphic scales. This is indicative of mixing of
identified using chemically synthetized sugar standards and two distinct organic matter sources, most likely a source
mass spectra data available in literature. Our results showed contemporaneous with sediment deposition and another older,
that mono- and di- methylated hexoses; mono- and di- reworked source. These observations confirm that an increase
methylated pentoses; mono- and di- methylated 6- in hydrological energy during hyperthermals was sufficient to
deoxysugars, as well as heptoses, methylated heptoses, 3,6- markedly and widely increase sedimentary rock erosion. We
dideoxysugars and 1,6 anhydrosugars (i.e. levoglucosan, suggest that this strong response was particularly due to rapid
galactosan, and mannosan) are components of HMWDOM, deviation from steady state conditions. Moreover, erosion and
which may explain in part the low apparent yields of sugars chemical weathering are generally coupled and even ancient
recovered by molecular level (HPLC) analyses compared to kerogens have been shown to be highly oxidisable during
NMR estimates. shale weathering; thus, these events were likely associated
Our results also indicated that the above compounds with kerogen oxidation. Although unlikely to have been a
accounted 2-3% of the APS in surface/deep waters and their major source of additional reduced carbon (Goldschmidt2013 Conference Abstracts 1919
Anomalous lithospheric and Atmospheric Evolution and Chemical
geodynamical evolution of the Aging of Combustion Organic
southern part of Vindhyan basin, Particulate Matter
central India SPYROS N. PANDIS1, NEIL M. DONAHUE2
AND ALLEN L. ROBINSON
3
O.P. PANDEY, NIMISHA VEDANTI*
AND RAVI PRAKASH SRIVASTAVA 1
Department of Chemical Engineering, University of Patras,
Greece (spyros@chemeng.upatras.gr)
CSIR-National Geophysical Research Institute, Hyderabad, 2
Department of Chemical Engineering, Carnegie Mellon
India (*correspondence: nim.ved@gmail.com)
University, USA (neil.donahue@andrew.cmu.edu)
3
Department of Mechanical Engineering, Carnegie Mellon
Introduction
University, USA (allen.robinson@andrew.cmu.edu)
Tectonically active sickle shaped Vindhyan basin is
considered the largest intra-cratonic Proterozoic sedimentary
Organic particulate material has been traditional classified
basin in peninsular India that covers an area of about 200,000
as either primary or secondary with the primary component
sq.km. It is well known for diamond occurrences. Possibility
being treated as nonvolatile and inert. Laboratory and field
of hydrocarbon potential has led to a surge in various kinds of
studies during the last decade, demonstrate that primary
geological and geophysical investigations during recent times.
combustion aerosol is highly dynamic, consisting of mostly
An attempt has been made here to synthesize seismic, gravity
semi-volatile material that moves between the gas and
[1,2] magnetotelluric, geothermal and borehole geological
particulate phases in the atmosphere and at the same time is
data, which throws a new light into the crustal and upper
oxidized forming a variety of oxygenated products. This
mantle evolution of this basin.
oxidation can lead to both lower volatility material through
functionalisation but also to smaller lower volatility molecules
Significant Results
through fragmentation. A unifying framework for the
The southern part of this basin appears to have undergone
description of all organic components based on their volatility
episodic thermal interactions between crust and hot underlying
distribution and oxygen content (the two-dimensional
mantle, which induced magmatism, upwarping and erosion
volatility basis set) can be used for the treatment of a wide
followed by crustal rifting and sedimentation. Seismic data
range of processes affecting organic aerosol loadings and
reveals that as much as 10-15 km crustal exhumation may
composition in the atmosphere. This modeling framework is
have taken place beneath this region. Almost 5 to 6 km thick
combined with emission characterization studies, laboratory
Proterozoic sediments have deposited over exhumed high
smog chamber studies, and field measurements to simulate the
velocity middle crust in the Jabera basin. A high heat flow of
atmospheric evolution of these organic emissions.
almost 80 mW/m2 has also been estimated for this region,
Applications of this modeling framework to major urban areas
which indicates presence of extremely high Moho temperature
(Paris and Mexico City) and continental Europe, where major
and mantle heat flow. Lithosphere has been found to be
field campaigns have recently taken place are used to provide
extremely thin at about 50 Km below Jabera basin. In some
insights about our understanding (or lack thereof) of the
geo-tectonic segments, granitic-gneissic upper crust has been
corresponding physical and chemical processes.
totally eroded due to sustained exhumation of deep seated
mafic rocks. A 5-10 km thick retrogressed metasomatically
altered layer with significantly reduced velocities consequent
to interaction with hydrothermal and other mantle fluids, has
also been delineated at around mid to lower crustal transition.
There is a possibility that this region may have been under the
influence of a super mantle plume around 1.1 Ga.
[1] Srivastava et al (2007), Pure and Applied Geophys 164,1-
14. [2] Srivastava et al (2009), J.Geol.Soc.India 73,715-723.
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by guest1920 Goldschmidt2013 Conference Abstracts
Ore genesis of the Longshan Sb-Au Mafic potassic volcanics from the
deposit, Hunan, China: Evidence Altiplano, South America: Indication
from fluid inclusions of a dynamic A-type magma source
M. ZHANG1, B. PANG1*, D. YANG2, X. LIU1 under construction?
AND B. WANG
1
M. J. PANKHURST1,2*, B. F. SCHAEFER2
AND S. P. TURNER
2
1
Guilin University of Technology, Guilin, 541004, China
(*correspondence: pbc@glut.edu.cn) 1
School of Earth and Environment, University of Leeds,
2
Guangzhou Institute of Geochemistry, Guangzhou, 510640,
Leeds,UK (*correspondence: m.j.pankhurst@leeds.ac.uk)
China ( yds1019@gig.ac.cn) 2
GEMOC, Macquarie University, Sydney, Australia
The Longshan gold-antimony deposit is one of the typical Sb-Au
Small volume monogenetic mafic volcanoes, erupted onto
associatioins in Hunan province, China. The mineralization is related to
the Altiplano (active orogenic platuea) during the Neogene to
NWW and NNE trending fault systems and hosted within gravel sandy
Quaternary, display high K, F, Ga/Al and low Ca relative to
slate in Jiangkou Formation of Sinian System. Gold occurs mainly in
typical basalts. These characteristics match key chemical
cracks in stibnite, pyrite and arsenopyrite, or in the contact area of these
affinities of post-orogenic A-type granite magmas.
three minerals and gangue minerals, or enclosed by stibnite. From a limited
number of hydrogen and oxygen isotope data, some previous workers
proposed that the ore-forming fluid was predominantly meteoric in origin.
In contrast, we argued that metamorphic fluid is an alternatively likely
source of the ore-forming fluid based on a preliminary study of fluid
inclusion microthermometry and Raman spectrum.
Mineralization and paragenesis of the Longshan deposit can be
divided into three stages as follows based on geology and petrography of
the deposit: Qz + Py +Asp +Au (stage#); Qz + Py +Asp + Sb + Au
(stage!) ; Qz + Sb + Cal (stage"). Stage! is the mainest ore-forming
stage accounting for approximately 82% of ore reserves. Primary
inclusions in quartz from stage! ores are mainly mixed aqueous-gaseous
fluid inclusions (H2O–NaCl–CO2-other gases). Pure liquid and pure
gaseous can be occasionally observed. For mixed aqueous-gaseous fluid
inclusions, two or three phases can be observed at room temperature: a
bubble of carbonic vapor suspended in aqueous liquid, or a double
bubble in which a bubble of carbonic vapor is enclosed by a bubble of Figure 1. Geochemical affinites between orogenic mafic volcanics and
carbonic liquid suspended in aqueous liquid. The size of inclusions A-type granites. Arrow indicates liquid evolution involving
ranges from 2.31$m to 12.89$m, mainly 3$m to 7$m. These plagioclase and clinopyroxene from a deep crustal reservoir stacked
inclusions exhibit relatively variable vapor to liquid ratios (5-25%, with mantle-derived, low degree partial melts into the A-type field.
mostly 10-15 percent vapor by volume), and have homogenization
temperatures ranging from 235! to 320!. Two-phase inclusions show New geochemical data and Sr, Nd and Hf isotopic ratios
a wide salinity range of 0.18-9.85wt% NaCl equiv, with most data of these Altiplano volcanics are consistent with a petrogenetic
clustering around 3-8 wt% NaCl equiv. By contrast, three-phase model that involves iterative low-degree partial melting
inclusions have a lower range in salinity (1.42-2.2 wt% NaCl equiv). regimes within underlying metasomatised aesthenospheric and
Trapping pressure estimated from three-phase inclusions is up to lithospheric mantle. We consider generation of such melts to
135MPa, suggesting that antimony-gold mineralization occurred at the be widespread and significant, since the same signatures are
depth of approximately 7.7km. Laser Raman Spectrum analysis for observed across ~1750 km of strike length and are not
two-phase of CO2-H2O inclusions indicate the existence of minor N2 restricted to a specific time period. Their small individual
and C2H6 besides CO2. Physical and chemical characteristics of fluid erupted volumes suggest ascending batches are subject to
inclusions suggest that the Longshan Sb-Au deposits may have efficient cooling and stalling at deeper levels. Therefore it is
resulted from metamorphic fluids. plausible they may be vastly underrepresented at the surface,
and difficult to directly detect by geophysical methods.
Acknowledgments This project is supported by NSFC( Second order convections within the mantle during
no.40772056) and the Foundation of Guangxi Key Lab of HMODE( downwelling/delamination of lithosphere may account for the
no.11-031-20) production and emplacement of these magmas. We propose
that the generation of these melts during orogenesis
contributes chemical and isotopic signatures to subsequent
post-orogenic magmas, via their iterative pooling and
crystallisation within the lithosphere.
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by guestGoldschmidt2013 Conference Abstracts 1921
LREE-rich beach sands from Organic matter oxidation and
Sithonia Peninsula (Chalkidiki, authigenic rhenium in late Eocene
Greece) pelagic sediments
A. PAPADOPOULOS1*, G. CHRISTOFIDES1, FRANCOIS PAQUAY*1 AND GREG RAVIZZA1
G. PE-PIPER AND A. KORONEOS
2 1
1
Geology & Geophysics, SOEST, University of Hawaii,
1
Department of Mineralogy, Petrology, Economic Geology, Manoa, Honolulu HI 96822 USA. ravizza@hawaii.edu,
Aristotle University of Thessaloniki, 54124, Thessaloniki, (correspondance: paquay@hawaii.edu)
Greece (*correspondence: argpapad@geo.auth.gr,
christof@geo.auth.gr, koroneos@geo.auth.gr) Poor organic carbon preservation in the deep sea during
2
Department of Geology, Saint Mary's University, Halifax, Eocene warmth suggests an important change in the carbon
Nova Scotia, B3H 3C3, Canada (gpiper@smu.ca) cycle during greenhouse episodes [1]. An expected
consequence of this phenomenon is that Eocene pelagic
Beach sands, being the weathering products of the sediments should be more reducing than similar modern
adjacent Sithonia Plutonic Complex [1], have been studied for sediments. Measured Re concentrations demonstrate
their heavy mineral and LREE content. For the mineral significant authigenic Re-enrichment, up to 30X average
separation, the 125-500 $m grain-size fraction, accounting for crustal concentrations, associated with very low total organic
90.6-95.4 wt % of the whole sample, was used. Among the carbon (TOC;1922 Goldschmidt2013 Conference Abstracts
Major and trace elements Early Solar System 87Rb-87Sr
composition of basalts from Chronology
ultramafic and volcanic seafloor. R. PARAI1*, S. HUANG1 AND S. B. JACOBSEN1
Southwest Indian Ridge (61 to 67°E) 1
Dept. of Earth and Planetary Sciences, Harvard University,
20 Oxford St., Cambridge, MA 02138, USA. (*email:
MARINE PAQUET* , MATHILDE CANNAT , CÉDRIC
1 1
parai@fas.harvard.edu)
HAMELIN2, MANUEL MOREIRA1AND DANIEL SAUTER3
1
Institut de Physique du Globe de Paris, France The long-lived 87Rb-87Sr system provides a useful
(*paquet@ipgp.fr) chronometer for early Solar System events. Due to differences
2
Centre for Geobiology, University of Bergen, Norway in the volatility of Rb and Sr, 87Sr/86Sr ratios record
3
Institut de Physique du Globe de Strasbourg, France information about condensation and volatile depletion in the
early Solar System. Thus, high-precision analysis of Rb-Sr
Our study area is located on the ultra-slow Southwest systematics in Solar System materials such as calcium-
Indian Ridge, east of the Melville Fracture Zone, between 61 aluminum inclusions (CAIs), meteorites and lunar rocks
and 67°E. This part of the SWIR has a very low magmatic provide insight into processes that shaped the early Solar
supply, and the axial lithosphere is thick. The melt distribution System, including the formation of Earth’s Moon.
is very heterogeneous with volcanic areas and areas of Recent studies have argued for a late formation of the
ultramafic seafloor where plate separation is accomodated by Moon based on Sm-Nd and U-Pb systematics [e.g., 1-2], but
large offset normal faults [1]. The ultramafic rocks are locally have avoided use of Rb-Sr chronometry due to possible
overlain by a thin veneer of basalt. Basalts samples have been disturbance of the Rb-Sr system. However, a chronology may
dredged on these two types of seafloor during the EDUL be constructed based on relative variations in initial 87Sr/86Sr in
(1997) and SMS (2010) cruises. We use the major and trace Solar System materials, rather than absolute ages derived by
elements composition of these basalts to discuss the magmatic the Rb-Sr isochron method. For Rb-poor samples such as
plumbing system of this very low melt supply ridge. Moore Co. plagioclase, Angra dos Reis, Juvinas and the lunar
Most basalts from ultramafic seafloor areas have higher anorthosite 60025, corrections for radiogenic ingrowth are
Na2O and TiO2 contents at a given MgO, and higher Zr/Y and small, and variations in resulting initial 87Sr/86Sr may be
Sr than those from volcanic seafloor. These differences could interpreted to reflect differences in the timing of separation
be explained [2] by a lower degree of partial melting of the from an evolving solar nebula [e.g., 3-5]. Based on a
mantle source for ultramafic seafloor basalts. However, the compilation of literature Rb-Sr data measured in various
lower CaO content of most ultramafic seafloor basalts laboratories over the course of decades, Halliday and Porcelli
suggests larger amounts of early fractionation of [6] computed a young Sr model age for lunar formation of
clinopyroxene [3] from the melts feeding ultramafic areas. 90±20 Myr after the formation of CAIs. However, from the
This early clinopyroxene fractionation could also partly fact that 60025 has an initial 87Sr/86Sr between the basaltic
explain the Na2O and TiO2 trends, but not the Zr/Y trend. Our achondrite best initial and Angra dos Reis [3-4], it appears that
data therefore suggest that both the melting regime and the 60025 must be essentially as old as these meteorites, requiring
magma plumbing system producing the two groups of basalts a very old age for the Moon (Goldschmidt2013 Conference Abstracts 1923
Pore scale heterogeneity in the Termination and hydration of
reactive surface area of rocks Forsterite (010) and Diopside (010)
ALICIA PARBHOO1*, PETER LAI1,2 surfaces
AND SAMUEL KREVOR
1,2
CHANGYONG PARK AND HONGPING YAN1
1
Department of Earth Science & Engineering, Imperial 1
HPCAT, Geophysical Laboratory, Carnegine Institution of
College London, London UK (*correspondence:
Washington, Argonne, IL 60439, USA, (cpark@ciw.edu)
ap3409@ic.ac.uk)
2
The Qatar Carbonates and Carbon Storage Research Centre at
The hydrous alteration of ultramafic rocks has been paid
Imperial College London, London UK
much attention for its attribution to the abiogenic hydrocarbon
There are major knowledge gaps in the ability to generation from crystalline rocks. The molecular processes at
characterize reactive transport in porous media at scales larger the interface of water and those mineral surfaces, however,
than individual pores. This precludes prediction of the field- have not been described. We use in-situ high-resolution X-ray
scale impact of geochemical processes on fluid flow [1]. This reflectivity to examine the forsterite (010) and diopside (010)
is a source of uncertainty for CO2 injection, which results in a surfaces in water. By modelling the electron density profile in
reactive fluid-rock system, particularly in carbonate rock the surface normal direction and fitting the measured data with
least-square method, the atomic structures of hydrated single
crystal surfaces could be depicted. We found, for the forsterite
surface polished with alumina colloidal suspension under
acidic environment (pH 3.5), a homogeneous termination with
about half of the surface magnesium depleted and replaced
with possibly a water species. In contrast, the forsterite surface
polished with silica colloids under basic condition (pH 9-10)
does not show such homogenous surface, but substantial
morphological difference from the alumina-polished surface is
observed by Atomic Force Microscopy measurement. The
difference indicates the importance of solution chemistry to
constrain the surface reactivity and dissolution mechanism. On
Figure 1: Ratio of surface area to pore volume [m2/m3] in an
the other hand, the diopside (010) surface is a naturally grown
Indiana limestone at various length scales.
surface, which shows qualitatively identical features in its
reservoirs. A potential cause is the inability of the continuum termination plane and the first adsorbed water electron density
approach to incorporate the impact of heterogeneity in pore- profile compared to those of the forsterite (010) surface. This
scale reaction rates. This results in part from pore-scale similarity indicates common features in the hydration structure
heterogeneities in surface area of reactive minerals [2,3]. of these mineral surfaces, although the silicate compositions
In this study we have created µm resolution 3D images of and structures are quite different.
3 sandstone and 4 carbonate rocks using x-ray
microtomography. Using in-house image processing
techniques we quantified the surface area from the images.
This quantification was validated against N2 BET surface area
and He porosity measurements of the imaged samples.
Distributions in reactive surface area were constructed by
calculating surface areas in thousands of randomly selected
subvolume images of the total sample (Fig. 1), each
normalized to the pore volume in that image. Berea sandstone
was far less heterogeneous and has a characteristic pore size at
which a surface area distribution may be used to quantify
heterogeneity. In carbonates, heterogeneity is more complex
and surface area must be characterized at multiple length
scales for an accurate description of reactive transport.
[1] Maher et al (2006) Geochimica et Cosmochimica Acta,
70, 337-363. [2] Landrot et al (2012) Chemical Geology 318-
319, 113-125. [3] Li et al (2007) American Journal of Science
307, 1146-1166.
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