Marine Geosciences

X-RAY FLUORESCENCE SPECTROMETRY

General view of the laboratory

Wavelength X-ray fluorescence spectrometry (WD-XRF) is a powerful multi-elemental and non-destructive analytical technique. This method allows to determine with accuracy the global chemical composition of a solid sample, in major elements and in trace elements at the µg/g^-1 level. Its domain of investigation lies from Boron (N=5) to Uranium (N=92). It presents following advantages, simple sample preparation, rapid analysis, good reproducibility and low cost in use.

• Principle of functioning

• The container-laboratory

• Applications to geological samples study

Principle of functioning: When the matter is bombarded with appropriate energetic X-ray photons, characteristics radiations of same nature are emitted by its chemical elements. This is X-ray fluorescence phenomena. Emitted X-rays are first collimated and then selectively separated on the analysing crystal by diffraction (application of Bragg’s relationship). Number of emerging X-ray photons are measured with a proportional detector. Corrected intensities from inter-element effects are linearly correlated with certified concentrations of reference materials.

Equipment: In lab, measurements are performed with a wavelength X-ray fluorescence sequential spectrometer SIEMENS SRS 303, equiped with a ten-positions sample holder and a front window tube (Rh and Au anodes). The instrument is fully computer-controlled. Another X-ray spectrometer is installed in a container-laboratory embarking on research vessels.

The container laboratory: For the first time in 1972, it was shown during the GIBRACO cruise of the R.V. Jean Charcot (1), the possiblity to produce rapidly onboard ship chemical analysis of geological samples with an embarked X-ray fluorescence apparatus. The geochemical container in which is installed an X-ray fluorescence spectrometer SIEMENS VRS, and required equipments  for sample prepration, is a standard 8 x 8 x 16 ft transport container. This equipment was shipped on numerous french and foreign oceanographic vessels, notably as analytical support of  the Deep Sea Drilling Project (DSDP)  onboard the R.V. Glomar Challenger from 1974 to 1982. Its last use were in 1998 on the R.V. l’Atalante during TRIATNORD campaign.

(1) H. Bougault and P.Cambon, Dispersive X-ray fluorescence analysis on board oceanographic vessel, Mar. Geol., 37-41, 1973.

Visit inside the container

Applications to geological samples study:

Examples of recents analytical developments

• Appropriate sample preparation for elemental analysis of  difficult geological matrix as massive sulfides with strong concentrations of  Iron, Copper, Zinc and Lead.

• Precise analysis of Niobium directly on rock powder according to an addition method below the µg/g^-1 level.

• Determination of Gold and Platinum in rock samples after separation by ion-exchange chromatography.

Collaborations:

• Electron microprobe laboratory (CNRS)

• Mass Spectrometry laboratory (spectromètre de masse) (CNRS)

• Weak radio-activity laboratory (CEA)

Contacts: P.Cambon (pcambon@ifremer.fr), J. Etoubleau (etoublo@ifremer.fr)