Western Australian Argon Isotope Facility

The facility uses a high-powered laser gas-extraction system for geochronology and thermochronology applications. We can date the following minerals:

• Micas – muscovite, biotite, phengite
• Feldspars – K-feldspar and plagioclase
• Amphiboles – hornblende, glaucophane
• Whole rocks – volcanic groundmass, slates, phyllites
• Pyroxenes – augite, orthopyroxene, clinopyroxene
• Feldspathoids – leucite, nepheline
• Clays – celadonite (hard aggregates)
• Sulphates – alunite (hard aggregates), jarosite
• Evaporites – polyhalite, langbeinite
• Glass – obsidian, tektites, pseudotachylite, chondrule
• Manganese oxides – cryptomelane, hollandite
• Tourmaline – schorl, dravite, elbaite

The argon-argon method utilises the natural decay of Potassium-40 (⁴⁰K) to ⁴⁰Ar and the induced conversion of the ³⁹K isotope to gaseous AR (in a nuclear reactor), which enables simultaneous measurement of the parent and daughter isotopes in the same aliquot.

The method is used to measure the age of samples, such as meteorite samples as old as the Earth (4.5 billion years), and date historical geological events, such as the Vesivius eruption (79 AD). Using ⁴⁰Ar/³⁹Ar dating, researchers can date geological events related to volcanism, such as tectonic plate movements, mountain-building rates, sediment formation, weathering and erosion, hydrothermal fluid movements, and the alteration and diagenesis of minerals.

Specific applications include:

• Timing of volcanic eruptions and magmatic episodes
• Dating igneous rock crystallisation ages and thermal histories
• Determining ages of terrestrial impact craters
• Dating of deformation events
• Dating of sediments: sedimentary provenance studies
• Determining thermal histories of metamorphic rocks
• Dating paleaomagnetic sequences
• Dating meteorite and lunar samples
• Dating of hydrothermal and alteration events
• Dating of authigenic growth events
• Determining ages and thermal events of sandstone feldspar cements

⁴⁰Ar/³⁹Ar dating allows much smaller samples to be dated, and offers more age and composition information. Minerals that can be analysed at the WAAIF include:

• Amphiboles: hornblende, glaucophane
• Clays: celadonite (hard aggregates)
• Evaporites: polyhalite, langbeinite
• Feldspars: K-feldspar and plagioclase
• Feldspathoids: leucite, nepheline
• Glass: obsidian, tektites, pseudotachylite, chondrule
• Manganese oxides: cryptomelane, hollandite
• Micas: muscovite, biotite, phengite
• Pyroxenes: augite, orthopyroxene, clinopyroxene
• Sulphates: alunite (hard aggregates), jarosite
• Tourmaline: shorl, dravite, elbaite
• Whole rocks: volcanic groundmass, slates, phyllites

The WAAIF has a range of sample preparation tools, including a Selfrag machine that uses high voltage pulses to break rock along mineral boundaries), a Frantz magnetic separator, and high-resolution binocular picking microscope and cameras.

Argus VI multi-collector noble gas mass spectrometer

The WAIFF has an ARGUS VI (ThermoFisher Scientific), a new generation low-volume multiple collector noble gas mass spectrometer (MC-NG-MS) equipped with five Faraday cups and an CDD multiplier. Our ARGUS VI set-up has:

• 10^12 (on mass 40, 38 and 37) and 10^13 (on mass 39) -ohm resistor faraday collectors and an ultra-low background CDD (ion counter) multiplier on mass 36.
• A dedicated ultra-low volume custom noble gas extraction line equipped with a PhotonMachine CO2 laser capable of delivering a homogeneous laser beam of up to 6mm wide.
• Two AP10 and a GP50 SAES getters and an electric cryocooler, to purify a range of gas loads (from single grain extraterrestrial sample to hundreds of mg of thousand years old samples).

The advantages of the set-up include:

• Better sensitivity that allows the measurement of a larger dynamic range of the Ar ion beam signal on much smaller (thus likely purer) and younger sample aliquots, and provides analytical precision 4–10 times better than previous generation instruments.
• Analysis of phases that are poor–ultra-poor in K (e.g. pyroxene, chondrules), due to the 10^13 ohm resistor equipped on the Faraday associated with mass 39.
• Much faster sample analysis (30–35 analyses/day compared with 10–12 analyses/day for single collector instruments)
• Automated operation that can be controlled remotely via VNC iPhone technology.

The WAAIF recently received an Australian Research Council LIEF grant for the purchase and installation of a second ARGUS VI, which has technological improvements (retrofittable). The new instrument is expected to be installed in early 2022.

Rates are in AUD and are ex-GST. (GST is applicable for Australian clients.)

Conventional step-heating analysis

• Consortium (Curtin University/UWA/LIEF partners only): $695 * (plus processing costs)
• Collaborative research: $1,050 (plus processing costs)
• Commercial (step-heating analysis and sample preparation): $3,995 (flat rate)

Sample preparation and processing

Sample preparation: $200–$690, depending on time required. Processing costs can be reduced significantly if crushed rock or a concentrate of the target mineral is supplied.

Examples:

• Processing/picking typical plagioclase from basalt rock: $690.00 max
• Processing/picking typical ground mass from basalt rock: $460.00 max

For an estimation or quote, please email the laboratory manager, Celia Mayers, on celia.mayers@curtin.edu.au