Dr Simon Richards

Lecturer: Structural and Metamorphic Geology, Tectonics and mineralisation

PhD (Newcastle)

Room TG154, Townsville campus

Call: (+61) 7 4781 6340

Fax (+61) 7 4781 4020

Email: simon.richards@jcu.edu.au

EA3200: Deformation, Metamorphism and Hydrothermal fluids

EA1002: Environmental Earth Science

Research Interests

  • Gold, diamonds and 4D plate tectonics

  • 3D model of the Earth

Current Research

1) Cyclic orogenesis

Research focus on microscale to macroscale processes associated with cyclic orogenesis, in particular, the cause of HTLP metamorphism in developing orogens including the Lachlan Fold Belt in eastern Australia and the Barrovian-Buchan terrains in Scotland.

Fields of research:

  • Igneous petrology and magma chamber evolution (stratigraphy and mechanisms of chamber construction in extensional settings)

  • Temporal and spatial evolution of High-Temperature, Low-Pressure (HTLP) metamorphism and metamorphic complexes in eastern Australia (detailed micro-, meso- and macro-scale studies of metamorphic rocks including structural mapping and thin section analysis)

  • Continental margin extension and basin evolution including facies analysis sequence stratigraphy of Palaeozoic basins in eastern Australia

  • Field-based acquisition of geophysical data, 2D and 2.5D inversion (land-based local-scale (<500km2) gravity and magnetics studies across HTLP metamorphic complexes and plutons of the eastern LFB)

  • Geochronology (U/Pb Zircon) of layered plutons and associated metamorphic complexes.

2) Virtual Earth

A 3D digital “Virtual Earth” (VE) model is being created from a variety of global- to outcrop-scale geological and geophysical databases. The aim of the VE project is to construct an interactive, editable and updatable digital 3D model that the geometry of the Earth with a particular focus on the 3D geometry of subduction zones. The principal sources of data being used to create the VE include seismic tomography, earthquake hypocenter data, global geochemical datasets and plate-tectonic reconstructions.

4D evolution of the Indo-Australian Plate

Multiple global-scale datasets including earthquake hypocenters, P- and S-Wave tomography as well as surface geology, active volcano locations and SRTM (Shuttle Radar Topography Mission) digital elevation data are used to construct detailed 3D models of the subducted Indo-Australian plate (oceanic crust and lithosphere) beneath India, Sumatra, Banda and Molucca. The interpreted geometry of the slab (shown below in 3D) illustrates complexity in the slabs geometry that must reflect, at least in part, its complex geological evolution. Plate tectonic reconstructions involving SE Asia, India and Australia are used to help interpret some of the characteristics of the subducted slab. For example, the prominent vertical tear between the northern Molucca section of slab (marked (3)) and the southern Banda-Sumatra section (marked (1) and (2)) appears to have initiated at the time when continental fragments on the northern Australian plate collided with the originally ~E-W trending Indo-Australian subduction zone.Complex plate geometries have also been revealed for the Nazca Slab beneath South America and the Pacific Slab below Tonga. The identification of these highly complex slab geometries is providing a new insight into the geodynamic evolution of, and interaction between, subducting slabs and the overriding plate.

3) Timing and location of porphyry mineralisation.

Research is currently focused on examining the “when and where of porphyry mineralisation”. Detailed 3D slab models generated using the Virtual Earth are used to examine the relationship between slab structure and the location of porphyry mineralisation. Additionally, 4D plate tectonic reconstructions are used to determine when porphyry deposits form. Episodicity in the timing of porphyry mineralisation suggests that particular periods in Earths history appear to be more fertile than others. Why is this the case?By examining the tectonic evolution of subduction systems in 4D, we are able to provide insight into what controls the timing and location of porphyry mineralisation.

4) Tectonic environment of kimberlite emplacement

Research is currently focused on using detailed plate tectonic reconstructions to demonstrate a tectonic control on kimberlite emplacement. Using the 4D Virtual Earth (including seismic tomography for kimberlite-bearing regions), 3D models of the lithosphere below kimberlite-bearing areas around the world are being generated. These are combined with surface observations, rock deformation experiments and plate tectonic reconstructions to determine the tectonic controls on kimberlite emplacement in Angola and Australia. Research has demonstrated that here is a global-scale synchronicity in kimberlite magmatism in which particular periods of time characterised by abundant magmatism while other periods are barren. Using plate tectonic reconstructions it is possible to show that the timing of magmatism is linked to key tectonic processes including incipient continental breakup and major changes in plate motion. The research has involved the integration of information from a variety of geological disciplines including sedimentary geology, igneous petrology, geochemistry, geophysics and both regional and global scale tectonics. Research has also examined the type and timing of structures that facilitate kimberlite emplacement.

5) Geosystems on a global scale

Creation of the Virtual Earth has provided invaluable insight into the interactivity between geological processes on the global scale. The structural geology of subducted slabs is an important aspect of developing geoscience disciplines. This new tool is revealing information that can be used to explain the geodynamic evolution and characteristics of the continental crust that overlies complex subduction systems. The location of earthquakes and volcanism, together with the orientation of structures in developing orogens (e.g. Andes, Himalaya, SE Asia) can be related to the geometry and characteristics of the subducted slab.

Selected Publications:

Richards, S., G. Lister, and B. Kennett., 2007. A slab in depth: Three-dimensional geometry and evolution of the Indo-Australian plate. Geochemistry. Geophysics, Geosystems., 8, Q12003, doi:10.1029/2007GC001657

Richards, S.W. and Collins, W.J., 2004. Gr owth of wedge-shaped plutons at the base of active half-grabens. Transactions of the Royal Society of Edinburgh, 95, 309-317.

Collins, W.J. and Richards, S.W .,2008. Geodynamic significance of S-type granites in circum-Pacific orogens. Geology. 36, 7, 559- 562.

Lister, G., Kennett, B., Richards, S. and Forster, M. 2008.Boudinage of a stretching slablet implicated in earthquakes beneath the Hindu Kush.Nature Geoscience 1, 196-201, doi:10.1038/ngeo132

Richards, S.W . and Collins, W.J., 2002. The Cooma Met amorphic Complex, a low-P, high-T (LPHT) regional aureole beneath the Murrumbidgee Batholith. Journal of Metamorphic Geology, 20, 119-134.

Full list of Publications

Richards , S., G. Lister, and B. Kennett., 2007. A slab in depth: Three-dimensional geometr y and evolution of the Indo-Australian plate. Geochemistry. Geophysics, Geosystems., 8, Q12003, doi:10.1029/2007GC001657

Richards , S.W. and Collins, W.J., 2004. Growth of wedge-shaped plutons at the base of active half-grabens. Transactions of the Royal S ociety of Edinburgh, 95, 309-317.

Richards , S.W. and Collins, W.J., 2002. The Cooma Metamorphic Complex, a low-P, high-T (LPHT) regional aureole beneath the Murrumbidgee Batholith. Journal of Metamorphic Geology, 20, 119-134.

Collins, W.J. and Richards , S.W.,2008. Geodynamic significance of S-type granites in circum-Pacific orogens. Geology. 36, 7, 559-562.

Lister, G., Kennett, B., Richards , S. and Forster, M. 2008.Boudinage of a stretching slablet implicated in earthquakes beneath the Hindu Kush.Nat ure Geoscience 1, 196-201, doi:10.1038/ngeo132

Keller, N., Arculus, R., Herman, J., and Richards , S.W., 2007. Submarine back-arc lava with arc signature: Fonualei Spreading Center, northeast Lau Basin, Tonga, Journal of Geophysical Research, 113, B08S07, doi:10.1029/2007JB005451.

Collins, W.J., Wiebe, R.A., Healy, B. and Richards , S.W., 2006. Replenishment, crystal accumulation and floor aggradation in the megacrystic Kameruka suite, Australia. Journal of Petrology, 47, 2073-2104.

Clarke, B., Dorais, M., Barbarin, B., Barket, D., Cesare, B., Clarke, G., El Baghdadi, M., Erdmann, S., Forster, H.-J., Gaeta, M., Gottesmann, B., Jamieson, R. A., Kontak, D. J., Koller, F., Gomes, C. L., London, D., Morgan VI, G. B., Neves, L. J. P. F., Pattison, D. R. M., Pere ira, A. J. S., C,, Pichavant, M., Rapela, C. W., Renno, A. D., Richards , S., Roberts, M., Rottura, A., Saavedra, J., Sial, A. N., Toselli, A. J., Ugidos, J. M., Uher, P., Villaseca, C., Visona, D., Whitney, D. L., Williamson, B., and Woodard, H. H., 2004, Occurrence and origin of andalusite in peraluminous felsic igneous rocks: Journal of Petrology, 46, 441-472

Healy, B., Collins, W.J., Richards , S.W., 2004. A hybrid origin for Lachlan S-type granites: the Murrumbidgee Batholith example. Lithos, 78, 197-21 6.

Vernon, R.H., Collins, W.J., Richards , S.W., 2003. Contrasting leucosomes in metapelitic and metapsammitic Migmatites in the Cooma Complex, Australia. Visual Geoscience, 8, 45-54

Vernon, R.H., Richards , S.W., and Collins, W.J., 2001. Migmatite-granite relationships: Origin of the Cooma Granodiorite magma, Lachlan Fold Belt, Australia: Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy, 26, 267-271.

Collins, W.J., Richards , S.W., Healy, B.E., and Ellison, P.I., 2000. Origin of heteroge nous mafic enclaves by two-stage hybridisation in magma conduits (dykes) below in and granitic magma chambers: Transactions of the Royal Society of Edinburgh, Earth Sciences, 91, 27-45.P.10

Collins, W.J., Richards , S.W., Healy, B.H., Wiebe, R.A., 2000. Gr anite magma transfer, pluton construction, the role of coeval mafic magmas, and the metamorphic response: south-eastern Lachlan Fold Belt Field Guide, FP3, 142 pp. Geological Society of Australia.

In review

Viete, D.R., Oliver, G.J.H., Richards , S.W., Lis ter, G.S.L., The Grampian orogenic phase and the origin of the Midland Valley Terrane, Scotland. In Review

Richards , S.W., Lister, G.S.L. and Kennett, B.L.N., 2007. The Nazca Slab in the Realm of the Virtual Earth. Earth Science Reviews. In Review

Lister , G.S., Kennett, B.L.N., Forster, M. Richards , S. 2007. Sturctural analysis of aftershock sequences from the 2004-2005 Great Sumatran Earthquakes, GRL. In Review

Beltrando, M., Lister, G.S., Rosenbaum, G., Richards , S.W., 2007 Sedimentological signature o f episodic lithospheric thinning along a convergent plate margin: the Lower Oligocene Alps. Tectonics. In Review

Smith, M. L, Kurtz, J, Richards , S. W., Forster, M., Lister, G., 2006. Re-evaluating the breakup of South America and Africa using deformable mesh reconstruction software. Journal of the Virtual Explorer, Accepted

Richards , S.W. and Lister, G.S.L., 2008. Folding of the Nazca slab during changes in motion of the South American Plate. Tectonics. In Review

Viete, D.R., Richards , S.W., Lister, G.S .L., Oliver, G.H.H., Herman, J. Corvino, A.F., Forster, M.A., 2008 An extensional setting for the classical Barrovian metamorphism of the Grampian Terrane, Scotland: evidence from structural geology, metamorphic petrology, geothermobarometry and 40Ar/39Ar geochronology. Geological Society of London, Special Publication. In Review

Projects

1) Reconstruction of the Southern American – Scotia - Antarctic subduction zone system.

The Mesozoic to present tectonic and magmatic evolution of the South American (Andean) subduction margin has significant implications for our understanding of the evolution of convergent margins. This classic subduction margin is also host to significant mineral (primarily gold) deposits but is also characterised by some complexities in the geometry of the subduction zone. This project utilises seismic tomography, plate tectonic reconstructions and structural geology, igneous geology to address the relationship between the geometry and characteristics of the subduction zone system and mineralisation.

2) Global-scale process-oriented exploration for high-pressure, mantle derived magmas with interest focussed on the potential for diamond exploration.

4D Plate tectonic reconstructions that incorporate interpreted lithosphere geometries, which might arise from mechanisms such as subduction and extension, are used, along with information about kimberlites and related magmas to decipher the paleo-tectonic setting during their emplacement.