Types of analyses
The LA-ICP-MS facility at GEUS mainly performs U-Th-Pb age determination of accessory minerals and trace element analysis of mineral grains and bulk geological samples.

The laser ablation inductively coupled plasma mass spectrometry
(LA ICP-MS) facility at GEUS is designed to address different problems in Earth and Natural Sciences through the generation of isotopic, elemental and U-Th-Pb geochronology information.
The LA-ICP-MS facility at GEUS mainly performs U-Th-Pb age determination of accessory minerals and trace element analysis of mineral grains and bulk geological samples.
Analyses are performed on a routine basis for detrital zircon provenance analysis, formation ages of magmatic and metamorphic rocks, structural and tectonic framework studies and for ore formation investigations. Where core-rim (or other significant growth domains) is observed it is sometimes possible to obtain multiple ages representing events recorded in the core or rim of a single crystal. Analyses are typically performed on mineral separates embedded in epoxy mounts or on thin sections (typically 30-100 µm thick).

zircon crystal with laser ablation pit in centre
Dating of accessory minerals (other than zircon) is a powerful tool for understanding geological processes that may not be recorded in the zircons, e.g. metamorphic or hydrothermal events or the provenance of sediments derived from metamorphic terrains. Thus, we offer U-Th-Pb dating analyses of the mineral phases:
Analyses are performed on request and can include one (single phase dating) or several (multi-phase dating) of the minerals listed above. Please consult the laboratory staff for further information. We are always open to requests concerning dating of other mineral than listed, like
Uraninite, Thorithe, Perovskite, Eudialyte, Steenstrupine ect.
Minerals that can be dated by the U-Th-Pb method (see above) also contain trace elements that can contribute with information about the conditions of formation or alterations that the mineral/rock has experienced.
Concurrently obtaining an age as well and the trace elements content from the very same analysis location offers the opportunity to use these data for a more spatially exact geological interpretation of the mineral or rock.
This analysis method is used for provenance or metamorphic studies, and is a powerful alternative when mineral grains are small in size to maximize data output.
Almost any solid material is in principle possible to analyse by LA-ICP-MS.
We specialize in the analysis of inorganic, naturally occuring materials as well as synthetic products, e.g.:
Analysis of almost any solid material is in principle possible to perform by LA-ICP-MS, but the following materials are not routinely performed at GEUS: metals including sulfide minerals, bones, teeth, paints and plastics, soft tissues and hair.
NB: Major element composition is typically used as internal standard for concentration determinations. Thus, to quantify data the concentration of at least one major element constituent (e.g. Si, Ca or Mg) that is to be used as internal standard must be known prior to laser analysis. Typically, this is obtained by electron probe micro-analysis (EPMA), XRF or akin technique.

Otolith to be analyzed for trace elements content.
When minerals crystallize from a melt or a fluid phase, relics are commonly trapped and preserved as fluid (or melt) inclusions several micrometers in size. Such inclusions are a main and direct source of chemical information about e.g. late-stage magma crystallization, crustal fluid flow, hydrothermal transport processes or ore formation, and can be analyzed by LA-ICP-MS to obtain the trace element content. Methods for fluid inclusion analysis has been established recently, and we are always open for new procedures for the quantitative chemical analysis of such inclusions.

Classification of fluid inclusions (from Fall et al., 2011)
Prior to LA-ICP-MS analysis, usually the samples have been examined by microtextural and microthermomethic analysis to determine the internal age relationship between the potential different generations of fluid inclusions, and to determine the formation-temperature, the salt content in the inclusions and the composition of fluid, gas, salt and crystallised material (melt) in the inclusion.

Equipment used for the microthermometry analyses of fluid inclusions
The facility operates an Element 2 single-collector magnetic sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) from Thermo-Fisher Scientific that is connected to one of our laser ablation system (NWR213 or UP213) from Elemental Scientific Lasers.

The GEUS Staff have extensive experience in preparing samples in our sample preparation laboratories from crushing of the raw rock material to the fabrication of polished mounts. Available mineral separation techniques include heavy liquid separation, water-shaking table, Frantz electro-magnetic separator and high-quality picking microscopes. External users can bring prepared samples (please consult the staff for details).
Imaging or qualitative analysis using GEUS' scanning electron microscopy (SEM) or optical microscopy facilities usually is an integrated part of the preparations for LA-ICP-MS analysis.
Our different sample holders offer a number of options for mounting sample material of different size and shape. In most cases the sample material is prepared by mounting mineral grain separates in standard 1” epoxy mounts or as petrographic thin or thick sections for in-situ analysis. Sample sizes that can be accommodated:
Materials to be analyzed must be dry, cleaned and free of any kind of coating (e.g. carbon, gold, etc.). Any carbon coating from previous microprobe analysis should be removed. Gold coating must be removed thoroughly as residues of gold coating can severely affect LA-ICP-MS data quality.
Preferably, the surface of the material should be sufficiently polished. Samples do not need to have surface preparation, but data quality improves considerably if the samples are polished.
The microscope on the laser instrument is not as good as some of the dedicated microscopes one might be accustomed to, and locating specific spots to analyze can be tricky and time-consuming, in particular on polished sections and for fluid inclusions. Thus, prior to analysis users are strongly encouraged to bring along “sample map” images that will help maneuvering on the surface of the sample. For polished sections optical microscopy images are often required in addition to e.g. BSE, CL or equivalent imaging. Pen markings should be on the lower (glass) side of the thin sections because the section side is cleaned before analysis. The imaging can usually be carried out at the SEM or optical microscopy laboratories at GEUS.
'Appropriate software is available for the data reduction of all types of LA-ICP-MS analyses performed. It is possible for external users to carry out their own analytical work and subsequent data reduction after receiving appropriate training by our experienced laboratory staff.
Please contact the laboratory manager for information.