| Galen Halveson
Applied Geology, Curtin University The Neoproterozoic record of Rodinia break-up and biospheric evolution in Northwestern Canada Abstract Northwestern Canada preserves an exceptional stratigraphic record that spans from the time of the purported assembly of Rodinia ca. 1.0 Ga to Laurentia’s definitive break-out from the supercontinent sometime close to the Precambrian–Cambrian boundary. It has long bean appreciated that western Laurentia’s Neoproterozoic history involved more than a simple Wilson cycle, but details of its tectonostratigraphic evolution have remained obscure. The Neoproterozoic succession in Yukon reveals a complex history of basin development, punctuated by Cryogenian snowball glaciation. Multiple phases of continental extension occurred in the early Neoproterozoic, prior to regional uplift and tilting associated with emplacement of the c. 779 Gunbarrel large igneous province (LIP). Subsequent extrusion of the c. 720 Ma Franklin LIP in northern Laurentia was temporally closely associated with mafic volcanism in western Yukon, transtension, which generated thick pull-apart basins filled by Rapitan glacial deposits, and transpression, which resulted in the localized Corn Creek orogeny in eastern Yukon. Snowball glaciation subsequently stripped northwestern Canada of its abundant basalt carapace. Final opening of a passive margin in northwestern Laurentia did not occur until the late Ediacaran–early Cambrian. This convoluted history is reflected in the Nd isotope record preserved in fine-grained clastic sediments. This isotopic record, which reveals a prominent peak in εNd prior to the Rapitan glaciation, can addtionally be applied to testing palaeogeographic models of Laurentia’s place within a Rodinian supercontinent and its possible role in the initiation of snowball glaciation. The global seawater Sr isotope record also reflects the interplay of continental break-up, extensive early–mid Neoproterozoic flood basalt magmatism, and the profound influence of snowball glaciation on continental weathering. A new calibration of the Neoproterozoic stratigraphic record based in part on new ages from northwestern Canada can be used to apply approximate ages to key horizons in other age equivalent successions, including those of the Centralian Superbasin in Australia. Dr. Galen Halverson, an Associate Professor from McGill University of Canada (http://www.mcgill.ca/eps/halverson). He is visit Curtin as a CCFS-sponsored visitor between 4–15 November, 2013. Galen’s research integrates sedimentology, stratigraphy, and isotope geochemistry to reconstruct ancient environments within the context of secular and progressive tectonic, biospheric, and climatic evolution of the earth. The underlying theme of his research is to reconstruct paleoenvironmental change spanning from the late Proterozoic to the early Phanerozoic (~ 1200 to 500 ma) and to understand the interconnections between tectonics (i.e., super continental break-up and assembly), seawater chemistry and ocean redox, severe climatic fluctuations (including snowball Earth), and the origin and diversification of animals. This research is fundamentally field-based and geared around detailed geological studies of sedimentary basins that formed during this time. |
Galen Halveson Applied Geology, Curtin University The Neoproterozoic record of Rodinia break-up and biospheric evolution in Northwestern Canada
Chemistry@Curtin seminar series – A/Prof Keith Stubbs – 4PM Friday 1st November – Bld 500 exhibition space
RACI Athel Beckwith Lectureship
Glycobiology: The Development of Chemical Tools to Study Carbohydrates
Assoc/Prof Keith Stubbs
School of Chemistry and Biochemistry, The University of Western Australia
Glycobiology is the study of the structures and roles of carbohydrates in biology. Carbohydrates are present in every living system and traditionally, have been known for their role in structural integrity and as energy sources. Recently, however, carbohydrates have been shown to be involved in a variety of fundamental biological processes such as protein folding and trafficking, as well as cellular signaling and regulation. As a result glycoconjugates continue to be uncovered as important factors in health and disease.
As we gain greater understanding into the roles that carbohydrates play at the cellular level, chemists need to develop carbohydrate-based tools to investigate the specific roles that a single mono- or polysaccharide plays in the dynamics of the cell. This seminar will describe examples from my laboratory of the development of chemical-based tools to study specific carbohydrate-processing enzymes and how they can be used in the field of glycoscience.
Carbonate spots: understanding the relationship to gold mineralization in Central Victoria.
Carbonate spots: understanding the relationship to gold mineralization in Central Victoria.
Abstract
Carbonate spots are ubiquitously associated with gold mineralization in the central Victorian gold-fields and they provide the most obvious visual sign of hydrothermal alteration. However, the absolute timing of the growth and change in composition of these spots is not so obvious and commonly misconstrued. Understanding the relationship between these spots and gold mineralisation can be used as an exploration tool by providing a larger hydrothermal footprint to these systems. This talk is based on research conducted within the pmd*CRC project T6: Dugdale A.L., Wilson C.J.L., Leader L.D., Robinson J.A. & Dugdale L.J. 2009. Carbonate spots: understanding the relationship to gold mineralization in Central Victoria, southeastern Australia. Mineralium Deposita 44, 205-219.
Bio
Allison is currently a coordinating Applied Geology Post Graduate coursework for students at Curtin. She has a PhD from UWA on the Bronzewing gold deposit and spent 6 years in Stawell, Victoria working as an imbedded researcher for The University of Melbourne linked to an ARC-Linkage and pmd*CRC projects. She also has 10 years’ experience in the mining industry.
E&A – NO SEMINAR on Tuesday Oct 22nd 4pm
NO SEMINAR on Tuesday Oct 22nd at 4pm, 300.219 at Curtin University
Next week: Tuesday Oct 29th at 4pm, 300.219 at Curtin University
Chemistry@Curtin seminar series – Dr Katy Evans – 4PM Friday 25th October – Bld 500 exhibition space
Some constraints on the redox budget of subduction zones
Dr Katy A. Evans
Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
A number of lines of evidence suggest that the sub-arc mantle is 1-2 log units more oxidised than mantle elsewhere, though this conclusion is controversial, and the processes that may contribute to sub-arc mantle oxidation are poorly understood.
A simple analytical model was used to constrain the evolution of sub-arc mantle oxidation state as a function of redox-budget fluxes into, and out of, subduction zones. The model shows that plausible Archean and Proterozoic redox budget fluxes would not have created oxidised sub-arc mantle. Phanerozoic redox budget fluxes, on the other hand, which are dominated by the sulfate component, could increase sub-arc fO2 by up to three log10 units. The paucity of Cu and Au deposits associated with oxidised magmas in the Precambrian may be explained as a consequence of a lack of subducted oxidised material, rather than simply as a consequence of preservation potential. The redox budget of arc lavas is related to arc characteristics; samples from seven arcs show a significant correlation (P < 0.0005) between redox budget, subduction zone convergence rate, and subduction zone age.
Sulfate may be present in altered ocean crust in significant quantities, and even the most conservative model calculations suggest that sulfate is likely to dominate Phanerozoic subduction zone redox budget inputs. However, little is known of the relative stability or solubility of sulfur-bearing phases under subduction conditions, so large uncertainties are associated with absolute fluxes.
Sulfur isotopes provide one way to investigate sulfur sources, and the processes that affect sulfur during subduction. In-situ sulfur isotope measurements of pyrite associated with high pressure mineral parageneses in high pressure mafic rocks from the Eastern Alps and from New Caledonia were performed. The New Caledonia samples contain pyrite with δ34S in excess of 5‰, while samples from Pfulwe pass in the Eastern Alps contain pyrite with δ34S up to 15‰. These elevated δ34S values suggest that sulfur ultimately derived from seawater is preserved in these rocks to depths greater than 60km.
Chemistry@Curtin special seminar – Prof Keene (JCU) – 1PM Thursday 24th October – Bld 500 exhibition space
Polypyridyl ruthenium(II) complexes as cytotoxic lipophilic cations: new paradigms for old molecules?
Emeritus Professor F. Richard Keene
School of Pharmacy & Molecular Sciences, James Cook University School of Chemistry & Physics, University of Adelaide
There has been considerable interest in the use of inert polypyridyl ruthenium(II) complexes for biological applications. The ability of such complexes to bind nucleic acids with some degree of specific sequence and structure recognition has highlighted their potential as diagnostic and therapeutic agents. In most cases, the cytotoxicity of the ruthenium(II) complexes has been attributed to their interactions with nucleic acids.1
We have synthesised a series of dinuclear ruthenium polypyridyl complexes where the two ruthenium centers are linked by a chain of 2-16 methylene groups: these species have a high affinity for non-duplex DNA structures,1,2 and are highly cytotoxic to leukaemia cells where the cytotoxicity is proportional to chain length.3 Interestingly, the DNA affinity trends show little correlation with the cytotoxic properties. A detailed study on their cytotoxicity, uptake mechanism and localisation has shown they act as highly cytotoxic lipophilic cations, entering the cell by passive diffusion (with a minor protein- mediated active transport component), poisoning the mitochondria and causing cell death by apoptosis.3
This genre of complexes also exhibited high levels of antimicrobial activity against a range of pathogens, including multi-drug resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa.4-6 However, they showed low levels of
toxicity against human cell lines.4
The seminar will look at the synthesis of these compounds, their interactions with nucleic acids, cell uptake studies and aspects of their particularly significant antimicrobial behaviour.
References
- “MetalComplexesasStructure-SelectiveBindingAgentsforNucleicAcids”,F.R.Keene,J.A. Smith and J.G. Colllins, Coord. Chem. Rev. 2009, 253, 2021-2035.
- “Anapproachtotherapeuticagentsthroughselectivetargetingofdestabilisednucleicacidduplex sequences”, F. Li, D.K. Weber, J.L. Morgan, J.G. Collins and F.R. Keene, Dalton Transactions 2012, 41, 6528-6535.
- “Mechanismofcytotoxicityandcellularuptakeoflipophilicinertdinuclearpolypyridylruthenium(II)comple xes”,M.J.Pisani,P.D. Fromm, R.J. Clarke, Y. Mulyana, H. Körner, K. Heimann, J.G. Collins and F.R Keene, ChemMedChem 2011, 6, 848-858.
- “Theantimicrobialactivityofinertoligonuclearpolypyridylruthenium(II)complexesagainst pathogenic bacteria, including MRSA”, F. Li, Y. Mulyana, M. Feterl, J. Warner, J.G. Collins and F.R. Keene, Dalton Trans. 2011, 40, 5032-5038.
- “Invitrosusceptibilityandcellularuptakeforanewclassofantimicrobialagents:dinuclear ruthenium(II) complexes”, F. Li, M. Feterl, Y. Mulyana, J.M. Warner, J.G. Collins and F.R. Keene, J. Antimicrob. Chemother. 2012, 67, 2686-2695.
- Chlorido-containingruthenium(II)andiridium(III)complexesasantimicrobialagents”M. Pandrala,F.Li,M. Feterl, Y. Mulyana, J. M. Warner, L. Wallace, F. R. Keene, and J. G. Collins, Dalton Trans. 2013, 42, 4686-4694.
- “Dinuclearpolypyridylruthenium(II)complexes:flowcytometrystudiesoftheiraccumulationin bacteria and the effect on the bacterial membrane”, F. Li, M. Feterl, J.M. Warner, F.R. Keene and J.G. Collins, J. Antimicrob. Chemother. 2013; DOI: 10.1093/jac/dkt279.
Curtin Applied Geology Seminar – 23rd Oct – Tony Kemp on “Lies, Damned Lies and Crust Formation Ages” 12pm, room 312.222
Tony Kemp
Centre for Exploration Targeting, University of Western Australia
Lies, Damned Lies and Crust Formation Ages
Abstract
Radiogenic isotopes have been used to gain spectacular insights into the differentiation of the Earth and the growth of continental crust through time. That said, indiscriminant application of model ‘crust formation ages’ can lead to a spectacularly inaccurate view of Earth evolution. In this talk I discuss the good, the bad, and (mostly) the downright ugly of crust formation ages derived from hafnium isotope analysis of zircon – and why it might be time to pull in the reins on the detrital zircon juggernaut.
Biographical Details
Tony Kemp remains stuck in a geo-vortex that has dragged him from PhD studies at the ANU (Canberra), to research positions in Bristol (UK), Niigata (Japan), Townsville (QLD), Pullman (Washington, USA) and now Perth. He is currently an ARC Future Fellow based in the CET at UWA, where he is cultivating an obsession for old bits of crust and arcane black minerals in pegmatites, and trying to convince people that minute variations in the isotope composition of obscure elements are important.
E&A seminar – TUE OCT 15th 4pm 300.219 – Dr J Ramsay (Hlth Sc, Curtin)
Dr Josh Ramsay
Biomedical Sciences, Curtin University
Regulation of horizontal gene transfer through integrated molecular circuitry
Abstract: The symbiosis island (ICEMlSymR7A) of Mesorhizobium loti is a 502-kb integrative and conjugative DNA element that confers on its bacterial host the ability to form a N2-fixing symbiosis with Lotus legumes. It was first discovered through its ability to convert non-symbiotic M. loti to symbionts of Lotus in New Zealand soils. Mobile genetic Read more…
Chemistry@Curtin seminar series – Prof Jayatilaka – 18th Oct at 4PM – Bld 500 exhibition space
Pushing X-ray diffraction to the limit using “experimental” wavefunctions
Prof. Dylan Jayatilaka
School of Chemistry and Biochemistry, The University of Western Australia
Our objective is to obtain the most accurate structural parameters and electron densities from X-ray experiments. The idea is to refine the parameters in a model wavefunction in order to fit the X-ray diffraction data. Two applications will be considered:
- First, we show that for a dipeptide, hydrogen atom positions and ellipsoids can be obtained in agreement with neutron diffraction measurements. This is the first time it has been done, quantitatively, and was thought to be impossible.
- Second, I will report on the ability to obtain accurate anharmonic vibration parameters for a drug-like molecule YQ28. Such information can be used to obtain the effective potential of mean force for the atom concerned. Obtaining anharmonic constants reliably was thought to be impossible due to model cross contamination between the bonding-electron and atomic displacement parameters. The electron densities obtained are about an order of magnitude more accurate than obtained before, without any special improvements in data measurement.
Chemistry Seminar: Prof von Gunten, 27th September, 4PM Bld 500, exhibition space
Interaction between natural organic matter and oxidants: Reactivity, competition, oxidation by-product formation and precursor control
Prof Urs von Gunten
Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland EPFL, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
Natural organic matter (NOM) plays an important role in all water treatment processes and typically leads to a reduction of their efficiency. The interaction with oxidants are manifold, but mostly, they result in a consumption of oxidants leading to a lower performance related to disinfection and oxidation. At the same time, the interaction with NOM may directly lead to the formation of oxidation by-products or affect their formation (in)directly (shift of reactive species, precursor control). The reactivity of NOM with chemicals has often been related to UV-Vis absorption spectra, because they give information on aromatic and conjugated moieties in NOM, which are related to the oxidisability of NOM. Recently, we also investigated the electron donating capacity (EDC) of NOM as a new parameter to characterize its reactivity with various oxidants, such as chlorine, chlorine dioxide and ozone. A combination with the UV absorption enables drawing conclusions on reactive sites in NOM.
The talk will give an overview over the interactions between NOM and chemical oxidants and their effect on micropollutant abatement, oxidation by-product formation and precursor removal and try to rationalize the observations in terms of NOM character related to UV absorption and EDC.
