GEOMORPHOLOGY REPORT - CRC LEME

Table 2. Range of EC and pH values for different geomorphic units in the Lindsay-Wallpolla and
Lake Victoria-Darling Anabranch study area
Geomorphic Unit pH (1:5) EC1:5 (dS/m)
6.3 XRF geochemistry
6.3.1 Methodology
Fm1 4.45-6.03 0.049-1.050
Fm2 4.7-6.54 0.036-0.897
Fm3 6.11-7.71 0.062-1.092
T 6.22-9.45 0.047-5.880
U 7.41-8.95 0.088-1.376
The primary purpose of the XRF analyses was to obtain measurements of the abundances of
K, Th, and U, should detailed interpretation of the gamma-ray radiometric data be required.
The radiometric data was essential in mapping the distribution of different classes of surface
materials, in particular differentiating between floodplain, terrace, and uplands in areas of
poor DEM control.
1. The samples were pulverized using a tungsten carbide mill and the elements were
analyzed by XRF. For major element determination (SiO 2 , TiO 2 , Al 2 O 3 , Fe 2 O 3 , MnO,
MgO, CaO, Na 2 O, K 2 O, P 2 O 5 , and S), samples were prepared as fused discs following
the method of Norrish & Hutton (1964), with the exception that the flux used
consisted of 12 parts lithium tetraborate to 22 parts lithium metaborate. The glass
discs were analyzed on a PW2400 wavelength dispersive X-ray fluorescence (XRF)
spectrometer. The 35 trace elements were determined on pressed powder samples
using a SPECTRO X-Lab energy dispersive XRF spectrometer. The powders were
also measured on a PW1400 wavelength dispersive XRF spectrometer for Sc, V and
Cr, using methods described in Chappell (1991) and Norrish & Chappell (1967).
Tungsten and Co were probably added to the samples during the milling process, and
hence these elements have not been reported. The major elements and minor element
values are shown as % and ppm respectively.
2. The percentage of volatile materials in the samples was determined using a LECO
RC-412 multiphase carbon and water analyzer. Nitrogen was used as the carrier gas
for combustion and the furnace control system allows the temperature of the furnace
to be stepped and subjected to ramping (from 90 to 1040 o C). Water and carbon
dioxide released from the minerals during combustion are detected by means of
infrared absorption cells (IR-cells) and the results are then calculated as CO 2 and H 2 O
respectively.
6.3.2 Results
Only a limited number of comparisons were made because of time limitations and the
departure of the primary source of soil science expertise within the team (VW). Major
elements correlated reasonably well with what can be predicted from the main minerals
present.
The XRF results reflect the high quartz content of the soils with high SiO 2 concentrations
across all geomorphic units and depths. Higher concentrations of CaO found in the Terrace
and Uplands units are most likely due to the presence of CaCO 3 pisoliths, which were noted
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