Wed 18th August 2021 @ 12:00 nn in 312.222 and online via Webex (meeting #: 1849 67 0138 and password: ZDtDZNaZ374)

Abstract:

The limited preservation of ancient crustal material poses a challenge for understanding the composition of Earth’s early crust. As a result of poor preservation and near-ubiquitous overprinting by later geological events, deciphering the early evolution of our planet often relies on the isotopic composition of resistive minerals, such as zircon. Although the isotopic information recorded by zircon grains has proved an invaluable asset to workers seeking to understand the geological evolution of the Earth, it is limited by the range of elements easily incorporated into the structure of the mineral. One way to overcome these limitations is by analysing inclusions of other minerals that were trapped within the zircon during crystallisation. Apatite has great potential in this respect, as it is commonly found as inclusions in magmatic zircon and records a variety of useful isotopic information. Here I present a new approach for investigating igneous petrogenesis and crustal evolution by combining ⁸⁷Sr/⁸⁶Sr measurements of apatite inclusions with U–Pb and Hf isotope analysis of their host zircon crystal. The Sr isotope information contained in the apatite can be accessed by applying a novel SIMS technique we developed for this purpose. Case studies applying this new approach to Archean igneous rocks from West Greenland and the Narryer Terrane (northern Yilgarn) demonstrate how this can be used to understand the evolution of these key localities, with implications for both regional geology and the growth of the continental crust.

Short bio:

Jack is an isotope geochemist and geochronologist. His current work is part of a Discovery Project (DP190103849) awarded to Pete Kinny, Alexander Nemchin, and Aaron Cavosie. Prior to his current postdoctoral position at Curtin, he completed a PhD at the University of Adelaide focussed on understanding the development of intracontinental mountain ranges in Central Asia via low-temperature thermochronology.

Wed 17th March 2021 @ 12:00 nn in 312.222 and online via Webex (meeting #: 184 504 2665 and password: NZtPPEpY842)

Abstract:

The diverse clan of ore deposits classed iron oxide copper-gold (IOCG) systems are among the most heavily studied type of deposit, yet, there is little consensus on the fluid sources, mechanisms and timescales by which they form. This is due to their geology; intense metasomatic alteration and auto brecciation of ostensibly any host rock type, whereby, conventionally dateable phases that precipitate at the prevailing conditions during ore formation do not survive or simply do not form. The archetypal example of an IOCG system sensu stricto is the 1.59 Ga Olympic Dam deposit, the world’s largest published U, 3^rd largest Au and 5^th largest Cu resource.

We show that IOCG formation, using Olympic Dam and related deposits as case studies, can be dated at high-precision repeatably via application of the hematite-zircon U-Pb geochronometers with (CA)-ID-TIMS. Hematite U-Pb systematics are investigated down to the nanoscale to confirm U and radiogenic Pb is lattice bound and unaffected by post crystallization processes. Constraints highlight the timescales of magmatic to hydrothermal transition and possible mineralization lifespans in IOCG systems. This transition is also recorded at the nanoscale in magmatic zircon, often manifest as pervasive Fe-Cl alteration products, which can coexist with metallic-Pb nanospheres produced via high-T metamorphism. New findings on the nature of metallic-Pb nanospheres within and around ore systems applying FIB-HAADF S/TEM techniques will be discussed.

Short bio:

Liam received a M.Sci. in Geoscience from Royal Holloway, University of London (2015), and a Ph.D. from the University of Adelaide (School of Chemical Engineering and Advanced Materials; 2019). His doctoral research centred upon development and application of iron-oxide U-Pb geochronology and synthesis/characterization of U-Pb reference materials. He began a postdoc at the JdLC in November 2019 addressing the geochemistry and chronology of iron ores in the Hamersley Province, WA.

Wed 11th November 2020 @ 9:00 am on Webex (Meeting #: 176 783 7775, password: J2XrX8PRnP7)

Abstract:

Quartz cementation is a major factor in the evolution of bulk properties in the common sandstone types of conventional reservoirs (quartzo-feldspathic sandstones). Is the same true of unconventional reservoirs? High-resolution compositional imaging such as EDS elemental mapping and cathodoluminescence imaging by field-emission scanning electron microscopy allows the examination of mudrock components at scales appropriate for discriminating different forms of quartz in mudrocks. Results from a growing number of case studies show that silt-size detrital quartz of extrabasinal origin is the dominant form of quartz in mudrocks overall.  Locally however, grain assemblages in organic-rich mudrocks, especially ones deposited under conditions of relatively slow sediment accumulation, may contain biogenic silica of intrabasinal origin that is prone to dissolve and re-precipitate as grain-binding microquartz cement. Where present, such cement tends to be abundant (30-40% of rock volume). A given unit however, typically contains a mix of cemented and uncemented muds. This talk will illustrate the relative simplicity of discriminating and quantifying detrital versus authigenic pore-filling quartz using examples of mudrocks that are and are not prospective for oil and gas. Similar to quartz cement content in sandstone, quantitative estimates of cement content to can be used to partition the causes of porosity decline in mudrocks.

Short bio:

Kitty L. Milliken is a Senior Research Scientist at the Bureau of Economic Geology, University of Texas at Austin. She received a B.A. in geology (1975) from Vanderbilt University and M.A. (1977) and Ph.D. (1985) degrees from UT Austin. Her research focuses on diagenesis of siliciclastic sediments and the evolution of rock properties in the subsurface. She has authored and co-authored over 100 peer-reviewed papers and also digital resources for teaching sedimentary petrography. Her current work is focused on the application of electron microbeam imaging and analysis to interpret chemical and mechanical histories of mudrocks (oil and gas shales).

Wed 4th November 2020 @ 12:00 nn at 312.222

Abstract:

Exceptionally preserved fossils from the Late Devonian Gogo Formation, in the Canning Basin, Western Australia have provided the earliest record of 3D muscle preservation. The use of synchrotron and neutron micro tomography reveals the presence organs (eye, stomach, liver and guts) and provides the first evidence for the internal body plan within early jawed vertebrates. This information has enabled the field of vision to be calculated, diet to be determined and swimming ability. Geochemical analyses of the vertebrate fossils has provided data on the pathways involved in the exceptional preservation of this Devonian Konservat-Lagerstätte.

Short bio:

Kate has been working as a palaeontologist in Western Australia for the last 20 years. She was awarded Malcolm McIntosh Prize for Physical Scientist (2010) one of the prestigious Prime Minister’s Prizes for Science for her work using synchrotron and micro CT to investigate and interpret soft tissues preserved in fossil fish. With colleagues she discovered fossil embryos and presented the earliest evidence of live birth within jawed vertebrates. This work was internationally recognized with the discovery being awarded as one of the Top 10 Species Discoveries for 2009.

Wed 28th October 2020 @ 12:00 nn at 312.222

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.

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.

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.

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.

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.