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4C - Laterite - XRF Fusion - XRF

Samples are dried at 105°C prior to LOI or fusion as laterites can easily absorb water from air. 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) is used for major element (oxide) analysis.  Prior to fusion, the loss on ignition (LOI), which includes H2O+, CO2 , S and other volatiles, can be determined from the weight loss after roasting the sample at 1000°C for 2 hours. The fusion disk is made by mixing a 0.75 g equivalent of the roasted sample with 9.75 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 Ausmon standard which adjusts the calibration. Control standards are run to verify the procedure. 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-Laterite Oxides and Detection Limits (%)

Oxide

Detection

 Limit

Al2O3

0.01

CaO

0.01

Co3O4

0.005

Cr2O3

0.01

CuO

0.005

Fe2O3

0.01

K2O

0.01

MgO

0.01

MnO

0.001

Na2O

0.01

NiO

0.003

P2O5

0.01

SiO2

0.01

TiO2

0.01

V2O5

       0.003

LOI

0.01

 


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