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Science Seminars

David Kelsey (GSWA) on: Thorium in monazite: A forward modelling approach

By Hugo Olierook 21 October 2020 Applied Geology Comments off

Wed 28th October 2020 @ 12:00 nn at 312.222 and via Webex (Meeting number (access code): 170 306 4530, Meeting password: C692PeVx9Fg)

Abstract:

Integrating monazite into existing pressure–temperature frameworks is an essential step towards fully realising the significant potential of this mineral in petrochronology. To further this endeavour, we present a predictive and readily adaptable equilibrium thermodynamic calculation framework involving solid solution for monazite, apatite, allanite, xenotime and Y+LREE+P+F+Th-bearing silicate melt. This framework comprises over 90 wt% oxide of the elemental components of these phases (Y, La, Ce, Nd, Th, P, Si, Ca) and includes all of the major end-member substitutions. We investigate the response of monazite and other accessory phases to closed and open system melting processes and changes to the major and trace element composition of the whole rock. We find that the incorporation of additional elements into monazite (La, Nd, Th, Ca, P and Si) displaces both the lower and upper bounds of monazite stability to higher temperatures relative to previous estimates. Exploration of bulk composition changes reveals that both Al and Ca affect the size and shape of the accessory mineral stability fields, in line with previous studies. We also show that increases to bulk LREE increase the mode and stability of monazite and decrease the proportion of the Th endmembers, cheralite and huttonite, in monazite. Changes to bulk Th have limited effect on the mode or stability field of monazite due to the generally low fraction of Th-endmembers in monazite, but do significantly change the total amount of Th-in-monazite.

Our modelling shows that monazite can be stable to much higher temperatures than previously modelled, to >1100°C in both open and closed systems, consistent with the natural rock record. Our models replicate the compositions and compositional trends from a natural dataset of over 5000 pressure–temperature-linked monazite analyses and present the first predictions of monazite growth above the solidus. We also present models for specific natural rock and monazite compositions which show considerable promise for the application of this framework to natural examples. The provision of this readily adaptable phase equilibria calculation framework adds an important new tool to the petrochronology toolbox.

Short bio:

This work is part of ARC project DP160101006 awarded to Dave Kelsey, Daniela Rubatto and Frank Spear. Dave was a Senior Lecturer at the University of Adelaide, where this research commenced, and is now a Senior Geologist at the Geological Survey of Western Australia. His research has focused on metamorphic petrology and petrochronology, particularly involving ultrahigh temperature metamorphism and phase equilibria of accessory minerals. The research presented here was part of a PhD thesis by Dr Megan Williams.

Claudio Delle Piane (CSIRO) on: Diagenetic pathways of the Proterozoic Velkerri Fm, implications for rock properties prediction

By Hugo Olierook 13 October 2020 Applied Geology Comments off

Wed 21st October 2020 @ 12:00 nn at 312.222 and via Webex (Meeting number (access code): 170 169 8534, Meeting password: p4nFqGiTH64)

Abstract:

The Proterozoic (~1.43 Ga) Velkerri Formation (Beetaloo Basin, Northern Territory) hosts one of the world’s oldest petroleum systems, sourced and reservoir within organic-rich black shale deposited in a marine setting. A comprehensive characterisation of the Amungee Member of the Velkerri Formation was carried out to shed light on how the mineral and organic components in the Velkerri Formation are affected by post-depositional mechanical and chemical processes. This presentation will highlight the main diagenetic pathways identified via micro and nano-structural analysis, discuss their mechanisms in the context of Proterozoic oceans and biosphere and their effects on the bulk physical properties of the sediment.

Short bio:

Claudio Delle Piane is a Research Scientist at the Commonwealth Scientific and Industrial Research Organization (CSIRO). He is a geologist with background in structural geology and rock deformation; his research interests lie in the qualification and quantification of microstructure and its influence on the geomechanical, petrophysical and elastic properties of rocks.

His technical expertise is in the experimental evaluation of rock properties and microstructures by means of multiphysics laboratory measurements combined with analytical methods including optical and electron microscopy, X-ray and neutron diffraction and cathodoluminescence. These techniques have been used to gain better understanding of rock/fluid interactions, elastic anisotropy, stress/permeability evolution, frequency dependent seismic attenuation in rocks and fault reactivation.

Luc Doucet (Curtin University) on: Distinct formation history for deep-mantle domains reflected in geochemical differences

By Hugo Olierook 29 August 2020 Applied Geology Comments off

Wed 26th August @ 12:00 nn via Webex (WATCH RECORDING HERE)

Abstract:

The Earth’s mantle is currently divided into the African and Pacific domains, separated by the circum-Pacific subduction girdle and each domain features a large low shear-wave velocity provinces (LLSVPs) in the lower mantle. However, it remains controversial as to whether the LLSVPs have been stationary through time or dynamic, changing in response to changes in global subduction geometry. Here we compile radiogenic isotope data on plume-induced basalts from ocean islands and oceanic plateaus above the two LLSVPs which show distinct Pb, Nd and Sr isotopic compositions for the two mantle domains. The African domain shows enrichment by subducted continental material during the assembly and breakup of the supercontinent Pangaea, whereas no such feature is found in the Pacific domain. This deep-mantle geochemical dichotomy reflects the different evolutionary histories of the two domains during the Rodinia and Pangaea supercontinent cycles and thus supports a dynamic relationship between plate tectonics and deep mantle structures.

Short bio:

Luc Doucet got his Ph.D. in St Etienne, France (2012), after a short time as Lecturer in St Etienne, he got a three years fellowship from the Belgium Fund for Scientific Research. Luc moved to Brussels to apply the “non-traditional” stable-isotope systematics on the mantle and crustal rocks to study the formation of both oceanic and continental lithosphere. After an academic career break, he moved to Curtin University, Perth in March 2018 to join Professor Li and the Earth Dynamics Research Group to work on the Oceanic Large Igneous Provinces project to decipher the present-day and past connections between Earth’s mantle, supercontinent and superocean cycles. His tools are fieldwork, clean lab, various instruments and data mining to obtain petrological, geochemical and isotopic data on mafic and ultramafic rocks. He is currently co-supervising two PhD students (one in Brussels and one in Perth), teaches mineralogy and geochemistry at Curtin University, and he proudly serves as a guinea pig for the first seminar in the online seminar series.

Timmons Erickson (NASA, USA) on: Discovering Earth’s oldest asteroid strike

By Hugo Olierook 13 March 2020 Applied Geology Comments off

Wed 25th March @ 6:30 pm, Tim Winton Lecture theatre, Building 213, Level 1

Abstract:

Dr Erickson will talk about the discovery of the oldest asteroid strike on Earth, called Yarrabubba, which is located on the road to Meekatharra in Western Australia. The impact site was discovered nearly 20 years ago, however, the age of impact was not known until now. Using research techniques and equipment, the team were able to determine the age and impact of Yarrabubba – 2.229 billion years old, making it the oldest known asteroid to strike. Dr Erickson will also discuss the impact the asteroid could have had to cause the end of one of the Earth’s oldest ice ages.

Short bio:

Dr. Timmons Erickson is a Jacobs-JETS Research Scientist in the Astromaterials Research and Exploration Science Division, NASA Johnson Space Center. Prior to joining JSC, he was a Postdoctoral Fellow at the Lunar and Planetary Institute in Houston, Texas and a Research Associate within Curtin University’s School of Earth and Planetary Sciences. He completed his PhD at Curtin University, and received an MSc from the University of Puerto Rico Mayagüez and a Bachelors from Oberlin College.

Steve Barnes (CSIRO) on: Timescales and lengthscales in magmatic nickel sulfide ore deposits with special reference to the Nova-Bollinger system, Albany-Fraser Orogen

By Hugo Olierook 12 March 2020 Applied Geology Comments off

Wed 18th March @ noon, Rm 312.222

Abstract:

Ore forming processes involve the redistribution of heat, mass and momentum by a wide range of processes operating at different time and length scales. The fastest process at any given length scale tends to be the dominant control. Applying this principle to the array of physical processes that operate within magma flow pathways – e.g. thermal aureole formation, country rock assimilation, sulfide liquid equilibration – leads to some key insights into the origins of magmatic Ni-Cu-PGE sulfide ore deposits. This talk explains the approach, and considers how it applies to the understanding of the most recent major nickel sulfide discovery in Australia, the Nova-Bollinger system in the Albany-Fraser Orogen. Processes operating on timescales from days to millions of years can be identified in the ores and host rocks at length scales from kilometres to hundreds of metres.

Short bio:

Dr Steve Barnes is an economic geologist with particular interests in magmatic ore deposits, layered intrusions and Archean volcanism. He has been with CSIRO in Perth since 1985, with a brief interlude in the exploration industry, and leads the Ore Deposit Petrology team in CSIRO Mineral Resources. He has published over 180 journal papers and book chapters covering ore deposits and host rocks on six continents. He was the recipient in 2011 of the Gibb-Maitland Medal of the Geological Society of Australia WA Division for services to Western Australian geology.

 

Katherine Bermingham (University of Maryland, USA) on: Building blocks of the Solar System

By Denis Fougerouse 9 January 2020 Applied Geology Physics & Astronomy Comments off

Wed 15th January @ noon, Rm 312.222

Abstract:

What is the Solar System made of? How did the Solar System evolve? One way to investigate these fundamental questions is through the study of meteorites. Many meteorites display isotope anomalies that have been attributed to the heterogeneous distribution of star dust in the protoplanetary disk. Active research is directed at documenting the stars from which the dust originated, the composition of the dust, and the process(es) that led to its heterogeneous distribution in the disk. Understanding these features would permit the identification of the stellar building blocks of the Solar System and place observationally derived constraints on processes of disk dynamics which influenced planet formation. In the present study, the identity of the stellar events and the chemistry of the dust are investigated and interpreted in the context of recent nucleosynthesis models.

 

Short bio:

My research interests lie in using the distribution of isotopes in meteorites and terrestrial materials to constrain the early Solar System evolution and the building blocks of the Earth and Moon. I use a combination of high precision cosmochemical isotope data and astrophysical modelling to constrain the different stellar contributors to the early Solar System and how these components were mixed into the early disk.

Kai Wünnemann (Museum für Naturkunde and Freie Universität, Berlin) on: The role of impact processes in the formation and early evolution of the Earth-Moon system

By Denis Fougerouse 21 November 2019 Applied Geology Comments off

Wed 27th November @ noon, Rm 312.222

Abstract:

The accretion of planets and their thermochemical evolution, the formation of the Moon, cratered landscapes, and the origin of habitable environments and atmospheres, are consequences of hypervelocity collisions of asteroids and comets with planetary bodies including the Earth. Impacts may be considered as one of the most fundamental processes in the solar system and it is a key question whether stochastic impacts of large bodies (giant collision) may have significantly changed the course of the evolution of individual planets or whether the evolution of planets was more or less determined after its formation. The presentation comprises examples of multi-scale numerical modelling, laboratory impact experiments and morphological and geophysical observations on the Moon to disentangle the collision history of the inner solar system and to quantify the role of impacts in the formation and early evolution of the Earth-Moon system.

 

Short bio:

Kai Wünnemann is Professor for “Impact and Planetary Physics” at Museum für Naturkunde (MfN) and Freie Universität (FU) Berlin. He is the deputy head of the Science Programme “Evolution and Geoprocesses” and head of the section “Impact and Meteorite Research” at MfN.

He has been studying impact processes for more than 20 years by numerical modelling, laboratory experiments, and geophysical exploration to improve our understanding of the collision history of planets and its implications for the evolution of lithospheres and biospheres. He is one of the lead developers of the iSALE software (http://www.isale-code.de) that is used by more than 200 users around the world to simulate impact and shock wave processes on all scales. He used different methodological approaches to study several craters on Earth and planetary surfaces during his PhD thesis at the University of Münster (2001), as postdoc at Imperial College London and University of Arizona (2002-2005), and as senior researcher and head of the Meteorite Impact Research section at the Museum für Naturkunde (MfN) in Berlin (since 2006).

Bill Collins (Curtin University) on: The critical role for water in the formation of continental crust

By Denis Fougerouse 15 November 2019 Applied Geology Comments off

Wed 20th November @ 11 am, Rm 312.222

Abstract:

The talk discusses how water modulates crustal temperatures during continental arc magmatism. It proceeds to show the role that hydrous basaltic arc magmas have in exsolving water during fractionation and underplating at the Moho, and consequently on melting the overlying crust.  A holistic petrological model is presented that focusses on the role of water through the subduction factory, from slab to surface, and how it facilitates the formation of continental crust.

 

Short bio:

Professor WJ Collins began his work on A-type granites at ANU with Bruce Chappell, before moving to La Trobe University for a PhD on Archean granites with Prof Allan White. A post-doc on high-grade Proterozoic terranes in central Australia ensued with Prof. Ron Vernon at Macquarie University before moving to the University of Newcastle as a lecturer. He moved to James Cook University as a Professor before returning to Newcastle as Director of the NSW Institute for Frontiers Geoscience. He became a Curtin Professorial Fellow last year.

Nicholas Christie-Blick (Lamont-Doherty Earth Observatory) on: Why Extensional Detachment Faults Are Still A Problem

By Denis Fougerouse 17 October 2019 Applied Geology Comments off

Wed 23rd Octover@ noon, Rm 312.222

Abstract:

The Basin and Range Province of the western United States has been influential in the development of ideas concerning the extension of continental crust. New structural, geophysical and geochronological data from several field sites in eastern California, southern Nevada, Utah and southeastern Idaho call into question the role of regional detachment faults in engendering large-scale extension of the upper crust. Our data are instead consistent with the now-40-year-old interpretation of Proffett (1977) in the Yerington district, Nevada, that mid- to late Cenozoic extension was accommodated in brittlely deformed rocks by moderately to steeply inclined normal faults that tilted to lower dip during deformation, and were cut by one or more generations of younger, more favorably oriented faults. The application of critical Coulomb wedge theory to the still-contentious Sevier Desert detachment of west-central Utah implies a friction coefficient as low as 0.13. Our data have profound implications for the interpretation of detachment faults in other extensional and passive margin settings.

 

Short bio:

Nicholas Christie-Blick is a professor at Lamont-Doherty Earth Observatory, on sabbatical leave in Perth until June, 2020. His research deals with sedimentation processes, crustal deformation, and deep-time Earth history, with particular reference for the last several years to the low-angle normal fault paradox. He was an undergraduate at Cambridge (1974), and completed his PhD at the University of California, Santa Barbara with John Crowell (1979). He is best known in Australia for his work on the Ediacaran Period, with a new project under way in the Flinders Ranges of South Australia.

Marco JL Coolen (Curtin University) on: Subseafloor microbiomes provide long-term genomic archives of the paleodepositional environment

By Denis Fougerouse 26 September 2019 Applied Geology Comments off

Wed 2nd October @ noon, Rm 312.222

Abstract:

Deep marine sediments host ~2.9 × 1029 microbial cells, equivalent to up to 3.6% of the total living biomass on the planet with Archaea accounting for ~37% of that population. These subsurface microbial communities are generally considered to be structured through in situ environmental conditions such as the availability of electron acceptors and donors, porosity and sediment lithology. Yet, recent studies have shown that a subset of subseafloor microbial communities were present at the time of deposition and formed a genetic archive originally referred to as “the Paleome” and reflect the paleo-depositional environment. However, additional highly resolved profiling of subseafloor microbiomes are required to substantiate this claim. In this talk I will show that up to 15% of subseafloor bacterial communities in the Arabian Sea subsist through fermentation but originated from the overlying water column during the last glacial interglacial cycle where they were involved in denitrification during periods of strong oxygen minimum zone conditions. This fraction of subseafloor Bacteria underwent weak postburial selection and therefore formed a living long-term genomic record of the paleodepositional environment. To explore the global potential of sedimentary Archaea to also record changes in the paleodepositional environment, we performed a highly-resolved 16S rDNA survey of subseafloor archaeal communities in up to 140 kyr-old sediments of the northern Red Sea covering the last six Marine Isotope Stages (MIS) when alternating glacial low stands and interglacial highstands caused drastic changes in sea level and salinity in the Red Sea. Our results revealed a strong significant response of subseafloor archaeal communities to changes in paleodepositional conditions associated with MIS stages and their transitions and only a moderately significant response to changes in sediment lithology. This suggest that a substantial part of the subseafloor archaeal communities would have been present at the time of deposition and that they no longer play a highly active role in the cycling of sedimentary organic matter. This claim was substantiated by the parallel finding that the majority of buried archaeal lipid biomarkers (GDGTs) that comprise the TEX86 paleothermometry were derived from ancient marine Thaumarchaeota and not from e.g. methanogenic archaea that were identified from the Red Sea paleome.

 

Short bio:

Associate Prof. Marco Coolen is a geomicrobiologist who is best known for his studies on ancient DNA signatures preserved in lake and marine sediments to reconstruct terrestrial and aquatic ecosystem responses to long-term climate variability or to more recent human environmental impact. In addition, Coolen studies the activity, limitations, and evolution of the deep biosphere and is exploring to what extent microbes buried in the geologic record can form long-term genomic records of ecosystem-climate interactions. He is also using similar technologies to study the diversity and functioning of active microbes in modern environments such as the role that bacteria play in human gallstone formation, the functioning of Shark Bay microbial mats, and the degradation of oceanic plastic waste as well as industrial-derived persistent organic pollutants.

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