4C - XRF Fusion - XRF
To minimize the matrix effects of the samples, the heavy absorber fusion technique of Norrish and Hutton (1969, Geochim. Cosmochim. Acta, volume 33, pp. 431-453) are used for major element (oxide) analysis. Prior to fusion, the loss on ignition (LOI), which includes H
2
O+, CO
2
, S and other volatiles, can be determined from the weight loss after roasting the sample at 1050°C for 2 hours. The fusion disk is made by mixing a 0.5 g equivalent of the roasted sample with 6.5 g of a combination of lithium metaborate and lithium tetraborate with lithium bromide as a releasing agent. Samples are fused in Pt crucibles using an automated crucible fluxer and automatically poured into Pt molds for casting. Samples are analyzed on a Panalytical Axios Advanced wavelength dispersive XRF
The intensities are then measured and the concentrations are calculated against the standard G-16 provided by Dr. K. Norrish of CSIRO,
Australia
. Matrix corrections were done by using the oxide alpha - influence coefficients provided also by K. Norrish. In general, the limit of detection is about 0.01 wt% for most of the elements.
Code 4C
Oxides and Detection Limits (%)
|
Oxide
|
Detection
Limit
|
|
SiO2
|
0.01
|
|
TiO2
|
0.01
|
|
Al2O3
|
0.01
|
|
Fe2O3
|
0.01
|
|
MnO
|
0.001
|
|
MgO
|
0.01
|
|
CaO
|
0.01
|
|
Na2O
|
0.01
|
|
K2O
|
0.01
|
|
P2O5
|
0.01
|
|
Cr2O3
|
0.01
|
|
LOI
|
0.01
|
|