
TY  - JOUR
A1  - Tchen, T. 
A1  - Eisler, P. 
T1  - Accurate borehole probe calibration
JF  - Exploration Geophysics
JO  - Explor. Geophys.
Y1  - 1992
VL  - 23
IS  - 2
SP  - 343
EP  - 352
KW  - 
UR  - https://doi.org/10.1071/EG992343 
N2  - The In Situ Minerals Analysis Group in the CSlRO Division of Geomechanics has developed quantitative borehole logging techniques applicable to iron-ore and coal deposits. They are used currently to determine the formation density, either the iron-ore grades or the raw coal-ash contents, as appropriate, and the borehole diameter. The in-situ analyses depend on probe-calibration equations which were formulated by linear regression analysis that related the probe's spectral outputs with the required geological variables. Calibration equations consisting of a linear combination of first-order terms gave excellent assaying accuracy. The group achieved further improvements in assaying accuracy by developing a more generalised calibration model based on second-order terms and cross-product terms of the probe's spectral parameters. The logging data used for the statistical analysis were recorded in mine development boreholes at three Pilbara iron-ore mines and at a Queensland coal mine. Application of the generalised model, in place of the first-order model, resulted in a reduction of the root mean square (RMS) deviation between assays obtained in the laboratory and by logging, of about 15% relative for iron-ore grades and of about 8% relative for raw coal-ash content. The study also shows that the accuracy obtained using the conventional, non-spectrometric calibration model is inferior to that obtained by using either of the two spectrometric models, where the comparisons made are based on the same set of logging data. 
ER  -

