ACCURACY OF MEASUREMENTS OF DEPOSIT PARAMETERS AND ESTIMATION OFSULPHURDEPOSITS RESERVES

Summary

Errors which may occur in estimations of sulphur deposit resources fall into four groups:

1 – technical errors connected with measurements of deposit parameters, 2 – errors of representativity connected with incomplete information on deposit parameters, because of their variability, 3 –geometrization errors connected with the accepted mode of geometrical presentation in the course of estimating deposit resources, 4 – errors of analogy, connected with acceptation of a definite concept of interpretation of deposit structure.

Technical errors may be random and systematic. Error in thickness measurement results from incomplete retrieval of core (Fig. 1), equalling 70%. It am mounts up to0,2 m. Random errors connected with estimating sulphur content may result during sample collecting due to complete retrieval of core), its preparation to analysis, and from the analysis itself; they equal about 2%, 1%, 4%, respectively. Cumulative error in estimating sulphur content in a sample may be estimated at about 4.5%. Error in estimations of sulphur content in a deposit profile is inversely proportional to the number of section samples collected and it equals 1–1.5%. Estimations of sulphur content may be encumbered with systematic errors resulting from crumbling away sulphur from the core (Table 1) and from weathering of core (formula 3); the systematic error mag approach to up 10%.

Accuracy of estimations of bulk density, equalling 0.03 – 0.06 t/m³. It may be also encumbered by systematic error resulting from spatial differentiation of that parameter, approaching 0.4 t/m²

Accuracy of surface measurement depends on that of location of points on map as well as on measurement accuracy itself, depending on map scale and size of the surface measured (Fig. 4). Relative accuracy of estimation of resources may approach 10% on account of technical errors introduced.

Accuracy of geometrization, estimated by comparing reserves results of calculations by various techniques (Table 5) may approach 7%.

Representativeness error, resulting from incomplete information about deposit parameters depends on natural variability of these parameters and on the knowledge of the deposit (number of reconnaissance points). If there is a random variability of deposit parameters and the number of reconnaissance boreholes equals 40 – 50 the accuracy estimated using the formula [17] will be equal 10 – 20% (Table 6). The exploitation practice gives support to such estimation (Fig. 5). When there is a marked non-random component in the observed variability of deposit parameters, the accuracy of estimations will increase (Table 7).

Errors of analogy are of secondary importance in the case of sulphur deposits. Figures 7 present the cases when such errors may be expected. The appears to be connected with areas subjected to the action of secondary karst processes.