ITRAX - High-resolution XRF analysis of sediment cores
The ITRAX™ Core Scanner collects element profiles in the range Si-U downcore from split core sections up to 12 cm in diameter and 1.8 m in length. Core sections are first scanned to achieve a constant working distance from the X-ray detector using a laser finder to map the topography of the cut core surface. Then scanned at a step-size that is defined by the user to obtain an ED-XRF spectrum at each step. A digital continuous-strip X-radiograph, 22 mm in width, can be collected immediately prior to the XRF scan using a charge-coupled (CCD) line camera located below the core. The count time for each measurement is also user-definable but should not be less than 30 seconds if minor elements are to be well-detected. The X-ray beam used to irradiate the core is generated using a 3kW Mo X-ray tube (typically run at 55kV and 50 ma for x-radiography and 30kV and 50ma for the XRF scan) and focused through a flat capillary wave guide. The recorded spectra are deconvolved in live time to construct profiles of peak area integrals for individual elements and Rayleigh and Compton scattering peaks. The element peak area will reflect element abundances within the sediment.
- High-resolution geochemical proxy data for measuring environmental change
- Bed provenance and correlation
- Distribution of contaminants and diagentic relocation
- Identification and characterisation of palaeosols, volcanic ash and ice-rafted debris
Comparison between ITRAX and conventional WD-XRF
|Optical image and high-resolution X-radiograph provided||YES||NO|
|Sample preparation and preparation requirement||Non-destructive, flat exposed surface required, 6-1.5 µm polypropylene film used to inhibit drying during analysis||Semi-destructive (pellets) or destructive beads, requires 3g or more of sample, involves subsample removal, drying, grinding and pelletization|
|Practical scanning resolution||> 200 µm||5000 µm|
|Time to acquire major and minor element data from a 1 m long core at 500 µm scanning increments||7 hours||10 working days|
|Normal detection limits (100 s)||
300 ppm Si
3 ppm Ti
15 ppm Sr
50 ppm Si
10 ppm Ti
0.5 ppm Sr
The ITRAX can be used on a range of materials besides marine sediment cores, examples shown are a black smoker sectioned in the rock prep lab, and multiple bone samples set in clay.
ITRAX methods paper:
Croudace, I.W., Rindby, A. and Rothwell, R.G. (2006) span class="title">ITRAX: description and evaluation of a new multi-function X-ray core scanner. In, Rothwell, R.G. (ed.) New techniques in sediment core analysis. London, UK, Geological Society of London, 51-63. (Geological Society Special Publication 267).
Itrax overview article: