Research Assistant Professor
Centre for Exploration Targeting (CET)
Robert Street Building, Rm 213
Centre for Exploration Targeting (CET)
The University of Western Australia (M006)
35 Stirling Highway
CRAWLEY WA 6009
+618 6488 2675
- In June 2011 joined CET as a part of a Linkage Grant “Multiscale Dynamics of Ore Body Formation”
- Feb 2008 - Sep 2010 worked at CSIRO as numerical modeler/geologist;
- Sept 2004 – Dec 2007 PhD in numerical modeling of subduction zone processes at Geological Institute, ETH-Zurich, Switzerland,
- PhD title: Dynamic processes above the subducting slab.
- 1998 – 2003 MSc. in Structural Geology, Jagiellonian University, Krakow, Poland,
- Master Thesis: Geological structure of the Zegocina Tectonic Window in Polish Flysh Carpathians.
Lithospheric scale modeling of long-term tectonic processes.
(1) Subduction zone:
Dynamics of dehydration/hydration and partial melting in the mantle wedge due to dehydration reactions, such as f.e. serpentinite decompression. Hydration and partial melting along the slab can create a situation in which a Rayleigh-Taylor instability may develop atop of the subducting slab and leads diapiric structures colder than asthenosphere by 300-400oC. Partial melting of mantle wedge and subducting slab components lead to intensive melt mixing in the wedge.
(2) Intra-cratonic deformation:
Dynamics of intra-continental deformation, strain localization and interaction between asthenosphere. Intra plate deformation can be caused by forces transmitted through the lithosphere from plate boundaries or by spatially independent of plate boundaries led by interaction between mantle lithosphere and asthenosphere (delamination or “dripping”).
(3) Lithospheric-scale shear localization and fluid migration:
Initiation of localized shear in visco-elasto-plastic materials, applicable to continental lithosphere and fluid transfer from the mantle to the crust.
Lithospheric scale modeling is a useful tool that can help to develop a geological, geodynamical and mechanically consistent model for a given tectonic region and be verify by geological and geophysical data.
Regions I’m working at the moment are:
- Musgrave (collaboration with GSWA)
- Gawler Craton (collaboration with DMITRE (former PIRSA))
- Albany-Fraser belt (collaboration with GSWA)
This work is done using I2ELVIS – numerical code based on finite difference method combined with marker in cell technique.
Numerical technique: The numerical code, I2ELVIS, is based on finite differences schemes and marker-in-cell techniques combined with multigrid approach. The code is designed for realistic complex elasto-visco-plastic rheology of rocks and account for changes in topography due to erosion-sedimentation processes and for changes in physical properties of rocks due to phase transformations. The model includes a spontaneously bending retreating slab with a free surface water transport and partial melting.
Governing Equations: The equations for the conservation of mass, momentum and energy, are used describing multiphase viscoplastic flow in Cartesian coordinate frame. The Lagrangian temperature equation includes latent heat effects of phase transformations in the crust and mantle by using effective values of heat capacity and (de)compression heating/cooling [Gerya et al., 2004a].
The viscosity of mantle rocks dependent on strain rate, pressure and temperature is defined in terms of deformation invariants [Ranalli, 1995].The ductile rheology together with a brittle/ plastic rheology yields an effective viscoplastic rheology. For this purpose the Mohr-Coulomb yield criterion [Ranalli, 1995] is implemented by a limiting creep viscosity. The presence of water affects the mantle rheology in a binary fashion inducing steplike change of the flow law from ‘‘dry’’ to ‘‘wet’’ olivine rheology (compare hydrated/serpentinized and dry mantle). The reason for this approach is that the mantle hydration model requires saturation of the water content (up to 2 wt %, ) in the mantle before aqueousfluids can penetrate further. This creates relatively sharp changes in the water content across the hydration front [e.g., Nikolaeva et al., 2008, Figure 5] which, in turn, results in sharp changes in the rheological behavior. More sophisticated hydration models (e.g., water diffusion [Richard and Bercovici, 2009]) may result in a smoother water distribution above slabs for more gradual changes in rheology.
Petrological-Thermochemical Model: Mineral phase transformation, such as dehydration reactions and melting, can affect the physical properties of rocks during the subduction process. The petrological-thermomechanical numerical modeling approach [Gerya et al., 2004b, 2006; Nikolaeva et al., 2008; Ueda et al.,2008] incorporates with all in situ rock properties: effective density, isobaric heat capacity, thermal expansion, adiabatic and latent heating as well as equilibrium water and melt content. All these rock properties are calculated for the Lagrangian rock markers at every time step based on Gibbs free energy minimization [Connolly and Petrini, 2002; Connolly, 2005] as a function of the local pressure, temperature and rock composition. In particular, the in situ rock density is interpolated for every marker at each time step from the look-up density tables (in P-T space) precomputed with PERPLE_X program for the four rock compositions.
Thermodynamics properties of fluids, melts, and minerals for this calculation are taken from an internally consistent thermodynamics database. In the model, water is expelled from the subducted oceanic crust as a consequence of both dehydration reactions and compaction. The additional connate water content of the basaltic and sedimentary crust is assumed as a linear function of depth.
To simulate the migration of water released by dehydration process, we use independently moving rock and fluid markers [Gorczyk et al., 2007a]. A fluid marker with respective water amount is generated and moves upward until it reaches a lithology that assimilates water, which can account for water transport.