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updated: 21 Sept. 2014
My past and present research
0. Cu and Mo ores in Ireland
I am supervising three projects hinging on definition of mineralisation across Ireland:
1) Hydrothermal Cu ore in SW Ireland and Irish Midlands;
2) Vein-hosted Cu ore in the volcanic-sedimentary sequence of Waterford Copper Coast;
3) Mo-prorphyry mineralisation in Connemara granites.
1. Origin of pallasite meteorites
are a fairly misterious type of meteorite. They belong to the
stony-irons group and are made essentially of olivine, Fe(Ni) and FeS.
To define the formation conditions of pallasites I have used annealing
experiments of olivine + Fe-S mixtures and image analyses of synthetic
and natural samples.
2. Properties and ordering of water-bearing silicate liquids, and silicate-bearing supercritical fluids
Starting September 2010 I
studied the structure of hydrous granite melts and silicate-rich
fluids using high energy X-Ray Diffraction (XRD) and I will try to
enlighten the local
structure of metals in hydrous melts and silicate-rich fluids by mean
of X-ray Absorption Spectroscopy (XAS).
The main topics related with these investigations are the complexation
of transition metals and High Field Strenght Elements (HFSE) in
water-bearing melts (granites) and in
the closely realted pegmatitic and hydrothermal fluids, often advisable
as "intermediate" fluids, with both characters of a hydrous-melt and a
The tools that I will use are: 1. Hydrothermal Diamond Anvil Cell
(HDAC) 2. Synchrotron XRD, X-Ray Fluorescence (XRF) and XAS
operated in-situ (i.e. at
Synchrotron analyses/experiments will be performed at the Advanced Photon Source
(APS), belonging to the Argonne National Laboratory (Chicago, USA),
whereas standard (well not really!) HDAC runs will be made in the
hydrothermal laboratory of Prof. Alan J. Anderson, at St. F.X. Univesity,
Antigonish, NS, Canada.
Left: snapshot of an experiment, where
hy-melt (droplets) and solute-rich fluid coexist at 720 °C and 160
Right: snapshot of gasketless experiment with the x-ray beam crossing
through the top (fluorescent) diamond anvil (room temperature).
Another topic of my current research is determination of thermal
reduction temperature and dissolution of various metal oxides (e.g.
MoO3, Cr2O3) in water domintaed fluids at sub- and supercritical
conditions. The following video illustrate examples of visual
dissolution of MoO3 (run name: moly-0.25M-GS-4)and thermal reduction of
the same phase into MoO2 (little opaque prisms - run name:
video of dissolution & thermal reduction
3. Core formation in terrestrial bodies
I am involved in the debate
over the feasibility of percolative core
formation in accreting planets and planetesimals. The key points of
this controversy are: the finding of a percolation threshold for Fe-S
melt in a peridotite matrix, which would tell us how much metalis left
in a silicate mantle separated from metal melt through
gravitational percolation, and the measurement of the segregation velocity of the
melt, in order to compute the actual separation time of metal from
silicates and compare it with isotopical ages and modelled times for
core formation in terrestrial bodies. Yoshino et al. (2004) and Roberts
et al. (2007) measured interconnectivity threshold of 4-6 vol% for a
solid peridotitic aggregate, however, Walte et al. (2008), assert that,
for any fraction of metal melt, the system will equilibrate forming
isolated melt pockets surrounded by silicates, with enough time to
reach textural maturation. Our data (Bagdassarov et al., 2009 a) seem
confirm the existence of a fairly higher threshold.
Nevertheless, in my personal opinion, it would be necessary to run long
duration experiments (i.e. weeks or better months), in order to
understand how textural equilibration evolves in such systems.
Moreover, there have been only few attempts to perform deformation
experiments on such systems. Furthermore, the study of the only
natural samples, which could be representative of this stage of the
evolution of planets, such are Pallasite meteorites, have been so far,
not taken into the appropiate account, while their study could bring
insights within this topic. A different case is, when we are in presence of a partial silicate melt.
We, for the first time, have performed metal segregation experiments,
in partially molten peridotite aggregates (Bagdassarov et al., 2009 b),
thanks to the usage of the
newly developed ‘centrifuging piston cylinder’ (see Schmidt
et al., 2006). Our results indicate that only for large fraction of
silicate melt, segregation velocity of metal melt is
large enough to accomplish for terrestrial bodies core formation times.
The debate stays open regarding, how much metal
could segregate, and how it would be possible to
remove the metal remnants. Numerical modelling, seems nowadays, the
best answer to solve the quarrel.
The project has been realized in collaboration with Gregor
Golabek and supervised by Prof. Max Schmidt
Dr. Nikolai Bagdassarov, who also collaborated to the experimental
4. Percolation of MORB melt in middle
oceanic ridge areas
Gravitational segregation of basalt melt in Middle
Oceanic Ridge areas is another topic in which I am deeply involved. The
permeability of asthenospheric mantle controls the time scale for transport of MORB
melt to the ocean bottom surface, thus it controls the timing for
formation of Earths
crust. Our experiments (Connolly et al., 2009), performed with the
‘centrifuging piston cylinder’ on olivine aggregates added
with 4-14 vol% of basalt melt, allowed to calculate much larger permeabilities than
previously accepted (e.g. Richardson and McKenzie,
1994 and Wark et al., 2003). Such large permeabilities accomplish for
dramatically higher transportation velocities of basalt melt via
The project has been
supervised by: Prof. Max Schmidt,
Dr. Nikolai Bagdassarov and Prof. James Connolly
5. Cumulates formation in mafic layred
The problematic of the formation of cumulate
layer is very interesting for people studying Mafic Layred Intrusions.
In fact, there exist cumulus layers containing up to 80-90 vol%
of solid grains, but it is still poorly understood whether they form by
simple gravitational settling and mechanical compaction, or if chemical
compaction is required, and how long do these processes extend. In our
experiments, we have observed that pure
gravitational settling of olivine
grains can generate a layer with a residual melt fraction
slightly larger than 50 vol% (preventive results were presented at EMPG
conference EMPG XII ).
At this stage, grains are in mutual contact and chemical
compaction starts to play a role in addition to mechanical
gravitational one. A theoretical 100 vol% solid grain aggregate could
then form. We have computed formation
times, for olivine cumulates, with 20-30 vol% residual porosity
(typical for mafic intrusions sub-metric layers), spanning over a few months to a few
years. However it his crucial to understand wheter grain
or dissolution-precipitation is the dominating process during chemical
The project has been
supervised by: Prof. Max Schmidt,
Dr. Nikolai Bagdassarov and is part of the current Ph.D. project
The numers in figure could be read as: e.g. '3 h 200g' means that
sample ZOB-6 was kept at T, P, and
an acceleration of 200 times g, for 3 hours.
6. Slab penetration
at '660' discontinuity
of my master thesis, consisted in the individuation of phase
assemblages in subducting oceanic crust at depths of the transition
zones of the mantle. The subject has been widely treated in the last 5
years; however, there is at list one point, which has not been fully
cleared yet. Tackley (1993), pointed out that if density contrast
between the subducting oceanic crust and the surrounding mantle is
larger than 8-9%, then, single mantle convection is promoted, however,
this seems not to overcome 2-3%. The individuation of the abundances of
different phases (e.g. majoritic_
garnet, stishovite, K-hollandite,
Fe-Ti-oxide, etc.) at 660 km depth is critical for calculating the
density contrast, thus, it would be important to further investigate
this subject. Furthermore, we can nowadays compute density of single
mineral phases at the desired temperature and pressure through series
of databases and codes, which allows for more meaningful calculations.
The project has been
supervised by: Prof.
Stefano Poli and Dr. Kazuaki
Bagdassarov, N., Golabek, G., Solferino,
G., Schmidt, M.W. Constraints
on the Fe-S melt connectivity in mantle silicates from electrical
impedance measurements. Physics of
the Earth and Planetary
vol. 177, pag. 139-146, 2009. doi:10.1016/j.pepi.2009.08.003
Bagdassarov, N., Solferino, G.,
Golabek, G., Schmidt, M.W. Centrifuge
assisted percolation of Fe-S melts in partially molten peridotite: Time
constraints for planetary core accretion. Earth and
Planetary Science Letters, vol. 288, pag. 84-95, 2009. doi:10.1016/j.epsl.2009.09.010
Connolly, J.A.D., Schmidt, M.W., Solferino, G.,
Permeability of asthenospheric mantle and melt extraction rates at
mid-ocean ridges. Nature,
vol. 462, pag. 209-212, 2009. doi:10.1038/nature08517.
Roberts J. J., Kinney J. H., Siebert J., Ryerson, F.J., 2007. Fe-Ni-S
melt permeability in olivine: Implication for planetary core formation.
Geophys. Res. Lett. 34,
L14306, doi: 10.1029/2007GL030497.
Richardson, C. and McKenzie, D., 1994. Radioactive disequilibria from
2d models of melt generation by plumes and ridges. Earth and Planetary
Science Letters, 128: 425-437.
Schmidt M. W., Connolly, J.A.D., D. Gunther, D., Bogaerts, M., 2006.
Element Partitioning: The Role of Melt Structure and Composition,
Science 312, 1646 – 1650.
Tackley, P.J., Stevenson, D.J., Glatzmaier, G.A., Schubert, G. Effects
of an endothermic phase transition at 670 km depth in a spherical model
of convection in the Earth’s mantle. Nature, 361, 699-704.
Walte N. P., Becker J. K., Bons P. D., Rubie D. C., Frost D. J., 2007.
Liquid-distribution and attainment of textural equilibrium in a
partially-molten crystalline system with a high-dihedral-angle liquid
phase. Earth Planet. Sci. Lett.
262, 517-532, doi:
Wark, D.A., Williams, C.A., Watson, E.B., 2003. Reassessment of pore
shapes in microstructurally equilibrated rocks, with implications for
permeability of the upper mantle. Journal
of Geophysical Research
– Solid Earth, 108: 18,320-18,338.
Yoshino T., Walter M. J., Katsura, T., 2004. Connectivity of molten Fe
alloy in peridotite based on in situ electrical conductivity
measurements: implications for core formation in terrestrial planets.
Earth Planet. Sci. Lett. 222,