The Noble Gas Geochronology research group at the University of Melbourne specialises in high-precision 40Ar/39Ar dating of geological events (spanning thousands to billions of years). 40Ar/39Ar geochronology has a range of geological applications including constraining timing of magmatism, volcanism, deformation and tectonism.
Our current research focus is dating Plio-Pleistocene tuff sequences within the Omo-Turkana Basin, Kenya. Other research focuses include 40Ar/39Ar flux monitor minerals, development of high precision 40Ar/39Ar methods for dating of young (basaltic) volcanoes, geochronology of kimberlites and related rocks, the timing of various ore mineralisation (e.g. gold) events, orogenesis (e.g. Cape Fold Belt) and detrital mineral provenance studies.
The Ar-Ar Laboratory, supported by AuScope, has been at the forefront of high-precision Ar-Ar geochronology, supported by our cutting-edge technology. We currently have 2 running ARGUSVI mass spectrometers and a VG3600 mass spectrometer.
Contact
For enquiries, please email Prof. David Phillips - argon-geochronology@unimelb.edu.au
Services we offer
Ar-Ar Laboratory offers service 40Ar/39Ar geochronology for external researchers and organisations at competitive rates.
In addition to 40Ar/39Ar geochronology services, we also offer mineral separation, thin sectioning, petrographic characterisation, and electron microprobe sample characterisation.
Collaboration and confidentiality
For work undertaken at standard commercial rates, we will provide a confidential report of analyses performed and results obtained. For collaborative projects, we will prepare necessary results for publication in journals or presentation at conferences. We operate on three levels of confidentiality and collaboration, corresponding to individual client needs and budgets:
Research collaborative
‘Research collaborative’ projects represent joint research between partner researchers and Ar-Ar Laboratory researchers. There is an expectation that such work will lead to a scientific publication with co-authorship by the relevant Ar-Ar Laboratory collaborator/s. Depending on the research topic and the analytical requirements, significant discounts may apply.
Commercial collaborative
‘Commercial collaborative’ projects represent joint research between clients and Ar-Ar Laboratory researchers where projects are initiated by clients. There is an expectation that such work will lead to a scientific publication with co-authorship by the relevant Ar-Ar Laboratory collaborator/s.
Commercial in confidence
Projects that are ‘commercial in confidence’ remain the proprietary information of the client. Our staff are bound by that confidentiality.
Get in touch
We are happy to discuss any research you may have and to suggest a suitable, cost-effective program to meet your needs.
Please email argon-geochronology@unimelb.edu.au for any enquiries.
40Ar/39Ar dating workflow and timeline
Total time 8-18 months
Sample preparation 2-6 weeks
- Petrologic characterisation
- Polished section preparation: In some cases, we need to prepare petrographic thin-sections or grain mounts to carry out this characterisation if suitable or accurate information is not provided.
- Bulk crush/sieve
- Gravity/density/magnetic sorting
- Acid leaching
- Hand-picking of K-rich phases
Irradiation 2-6 months
- Co-irradiation w/flux monitor
- Nucleogenic isotope production
Noble gas analysis 2-4 weeks
- Fusion/step heating/laser ablation
- Gas clean-up/purification
- Characterisation of blanks and baselines
- Analysis of air or cocktail standards
- Ar isotope data reduction
Data interpretation 1-3 weeks
- Release spectra
- Statistical analysis
The Ar-Ar Laboratory currently operates three instruments for dating of geological materials.
ARGUSVI & ARGUSVI+
Fully automated multi-collector Thermo Fisher Scientific Argus VI mass spectrometer linked to a Photon Machines Fusions 55W 10.6 CO2 laser system, enabling high-precision step-heating of single grains or bulk samples. Specifications as follows:
- Mass spectrometer volume is ~700 cm3; Gas extraction/purification line volume is ~240 cm3
- Sensitivity: ~3.55 × 10-17 moles/fA
- Five high-gain Faraday detectors (two with 1015 Ω resistors, three with 1013 Ω resistors) and one CDD detector
- Analytical precision: <0.1% for most samples
VG3600
A VG3600 mass spectrometer connected to a double-vacuum niobium resistance furnace and a Synrad Firestar v40 W CO2 laser system. Step-heating of bulk samples or single grains is possible (depending on sample age). Specifications as follows:
- Mass spectrometer + gas extraction (furnace)/purification line total volume: 2,600 cm3
- Sensitivity: ~4.00 × 10-17 moles/mV
- Daly detector
- Analytical precision: <1% for most samples
Equipment is operated and maintained at the highest standard.
Meet the academics and researchers in the Noble Gas Geochronology research group.
Group members
Prof David Phillips
Professor Phillips recent research focus has been precise geochronology of early human evolution in Kenya, the timing and formation of ore deposits, particularly gold and diamond deposits, and the dating of young volcanic rocks less than 1 million years in age. Prof Phillips is also an expert on diamonds, mineral inclusions in diamonds and diamond host rocks, kimberlites and lamproites.
dphillip@unimelb.edu.auDr Hayden Dalton
For his PhD, he focused on kimberlites, the deepest derived magmas on Earth and the volcanoes responsible for transporting diamonds from the deep Earth to the surface. He uses these rocks as a means to probe the geochemical evolution of the physically inaccessible parts of the planet. More recently, he has been investigating hundreds of past volcanic events in east Africa to understand when these eruptions occurred, where they came from, and the insights these can yield into the timing of human evolution.
hayden.dalton@unimelb.edu.au +61383448651
Mr Stan Ssczepanski
Stan has been the technical officer for the Noble Gas Laboratory since its inception in 2005, he is highly skilled in maintaining our lab facilities, data and high standard of precision.
scsz@unimelb.edu.au
Saini Samim
Saini is a PhD researcher undertaking research on the volcanic tuffs within the Omo-Turkana Basin. Saini has developed novel techniques for trace-element geochemistry and dating of young volcanic tuffs.
Ssamim@student.unimelb.edu.au
Ashley Savelkouls
Ashley currently manages the day-to-day processes in the Noble Gas Laboratory and is a PhD researcher. Her current focus is in developing precise stratigraphy of the Okote Tuff Complex in the Omo-Turkana Basin.
ashley.savelkouls@unimelb.edu.auOur recent publications
An improved methodology for high-resolution LA-ICP-MS trace-element fingerprinting of tephra layers: Insights from the Upper and Lower Nariokotome Tuffs, Turkana Basin, Kenya ( link - https://doi.org/10.1016/j.chemgeo.2024.122084)
Kimberlites the deepest geochemical probes on Earth (https://.doi.org/10.1016/b978-0-323-99762-1.00064-4)
40Ar/39Ar eruption ages of Turkana Basin tuffs: millennial-scale resolution constrains palaeoclimate proxy tuning models and hominin fossil ages (https://doi.org/10.1144/jgs2022-171)