Rock and sediments

Our methods are capable of analysing a full range of rock materials, igneous, metamorphic or sedimentary, including mineralised material. We can adapt our procedures for pure and applied geochemical applications. We are active participants in the GeoPT scheme.

Heavy minerals

Correlation and provenance of geological materials can be achieved through several techniques. A common and popular approach is by the analysis of heavy minerals (density > 2.85 g/cm3). Traditionally this would involve the counting and identification of different mineral species using a petrological microscope, which is time consuming and costly; geochemical analysis of heavy minerals by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) offers a faster and cheaper alternative. The ICP-AES approach establishes the relative or absolute abundance of key elements linked with specific heavy minerals: apatite, chrome spinel, monazite, titanium oxides (rutile, titanite, anatase etc.) and zircon.

Whilst this technique lacks the sensitivity of traditional optical counting using a petrological microscope, it does provide unique mineral-chemical signatures, broad trends in major cation groups and the quantification of specific rare earth elements (REE).

Classification of sediments and their associated source(s) are constructed through the comparison of the geochemistry associated with ultrastable heavy minerals and unstable heavy minerals. Heavy minerals are concentrated using a typical 'sink float' heavy media separation using lithium-heterotungstate adjusted to a specific gravity of 2.85 g/cm3. Analysis is focussed on the 63–125 µm sand fraction. Samples for geochemistry are flash-fused using a lithium-metaborate flux and analysed using a Perkin Elmer 7300 DV ICP-AES for a suite of major, minor and trace elements.

Core profiling and in-situ analyses

Stratigraphic analysis is done using handheld X-ray fluoresence (HH-XRF) to analyse drill core to identify sedimentary cycles. We also carry out in situ analyses of building stones.

Trace and major elements capability

The facility has two inductively coupled plasma mass spectrometry (ICP-MS) instruments, one Agilent 7500 (UKAS accredited for aqueous samples to ISO 17025) and a Spectro Array ICP-MS.

We have capability for:

  • high throughput survey scale analyses of 55 elements, plus iodine using a TMAH matrix
  • low volume analyses (< 5ml, including IC, pH/Alk, NPOC)
  • elemental speciation of arsenic, chromium and selenium using high performance liquid chromatography ICP-MS
  • isotope ratio analyses for uranium (e.g. DU) and lead (provenancing)

In addition, we have one inductively coupled plasma atomic emission spectroscopy (ICP-AES) instrument for high total dissolved solids solutions.

Gamma emitting isotopes capability

Natural daughter products from uranium and thorium decay, such as 210Pb, may be used as environmental tracers. Occasionally anthropogenic processes such as oil or gas extraction may pre-concentrate these to hazardous levels i.e. radium in barium sulphate-rich brines. Some of these may be measured using our Canberra Broad Energy germanium gamma spectrometers.

Certain artificial isotopes may be found in our environment or industrial processes due to past nuclear releases i.e. 137Cs from atmospheric bomb tests or 60Co from steel irradiation. Some of these may be measured using our Canberra Broad Energy germanium gamma spectrometers.

Contact

Please contact Michael Watts, Charles Gowing or Simon Chenery for further information.