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Isotope Geochemistry Laboratory

The NAWI Graz Central Lab for Water, Minerals and Rocks is part of the NAWI Graz Geozentrum and one of its key areas, the isotope facility, is located in the premises of Graz University of Technology (TU Graz). Our expertise lies in in-situ dating and trace element analysis of accessory minerals to decipher igneous and metamorphic histories and processes.

Equipment

- NWR 193 nm ArF Excimer laser
- NuPlasmaII multi-collector ICP-MS
- Agilent 7500 quadrupole ICP-MS

Principle

The NWR 193nm ArF Excimer laser (Elemental Scientific Lasers) can be used to ablate any material of interest. It is commonly operated at 5-10 Hz repetition rate, with a fluence of about 2-3 J/cm² and for circular spot diameters between 2 and 50 µm (nominal value). Ablated material is carried to the mass spectrometers in a mixed gas flow of Helium and Argon.

Applications

Two inductively coupled plasma-mass spectrometers (ICP-MS) are available for isotope analyses.

-The Agilent 7500 quadrupole ICP-MS is mostly used for trace element analyses in minerals. It is able to quickly scan through a large number of masses.

- The Nu PlasmaII high resolution-multi collector-ICP-MS (Nu Instruments) is currently used for U-Pb geochronology on zircon, monazite, allanite and uraninite. The Nu PlasmaII is equipped with five Ion Counters that simutaneously measure the masses 208, 207, 206, 204 and 202 while 238U and 232Th isotopes are measured on Faraday cups.

 

Common targets:

  • silicates (e.g. garnet, biotite, feldspars, pyroxene, quarz…), phosphates (apatite), oxides (magnetite, ilmenite …)
  • magmatic, metamorphic and detrital zircon
  • magmatic and metamorphic monazite, xenotime
  • magmatic and metamorphic allanite, epidote
  • uraninite


Available reference material:

  • NIST610, NIST612, NIST614, MACS-3, MAPS-4, BCR-2G, BHVO-2G, various G-Probe Glasses…
  • Zrn – GJ1, 91500, Plešovice, OD3, MudTank
  • Mnz – 44069, Moacyr, Elk Mts, Madmon
  • Xtm – in progress…
  • Urn – Mitterberg
     

Use case : Geochronological study of cm-large zircon grains (D. Gallhofer)

Relatively large zircon crystals can be found in a weathered carbonatite from Sri Lanka. They offer the possibility to study the ablation behaviour of U-poor zircon and the grain-scale variation of U-Pb dates.

 

Figure 1. Euhedral zircon grains from Sri Lanka, with well-visible (a) crystal faces and (b) oscillatory zoning.

Figure 2. Composite reflected light picture showing the dimensions of laser ablation pits ranging from 15 to 50 µm in diameter.

Figure 3. Concordia diagram with age dating results for zircon grain SZR 5.

Selected publications

Nong, Anh T.Q.; Hauzenberger, Christoph; Gallhofer, Daniela; Dinh, Sang Q.
Geochemistry and zircon U\\Pb geochronology of Late Mesozoic igneous rocks from SW Vietnam – SE Cambodia: Implications for episodic magmatism in the context of the Paleo-Pacific subduction. In: Lithos. 390-391,390-391. 2021. 20pp. doi:10.1016/j.lithos.2021.106101

Brandl, Michael; Hauzenberger, Christoph. Geochemical Sourcing of Lithic Raw Materials from Secondary Deposits in South Serbia. Implications for Early Neolithic Resource Management Strategies. In: Archaeologia Austriaca. 102. 2018. 55-70.

Schantl, Philip; Hauzenberger, Christoph; Finger, Friedrich; Mueller, Thomas; Linner, Manfred
New evidence for the prograde and retrograde PT-path of high-pressure granulites, Moldanubian Zone, Lower Austria, by Zr-in-rutile thermometry and garnet diffusion modelling.
In: Lithos. 342. 2019. 420-439. doi:10.1016/j.lithos.2019.05.041

Konzett, Jürgen; Hauzenberger, Christoph; Krenn, Kurt; Joachim-Mrosko, Bastian; Stalder, Roland; Gröbner, Katharina; Sieberer, Anna-Katharina; Khoi, Nguyen Ngoc
Neogene Metasomatism in the Subcontinental Lithosphere beneath SE Asia—Evidence from Modal and Cryptic Phosphorus Enrichment in Peridotites and Pyroxenites from Southern Laos.
In: Journal of Petrology. 60,12. 2020. 2413–2448.
 

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