The correlation-regression method, as one of the indirect sampling methods, is only sporadically used in geological and mining activities. Theoretically, it should be particularly useful for predicting the content of some chemical components in limestone and marl deposits due to the correlation between them. The results of simple and multiple correlation and regression analysis for 5 selected components (CaO, SiO2, Al2O3, MgO, and SO3), determined in samples from exploratory boreholes and blast holes carried out in the Barcin-Piechcin-Pakość deposit, are presented in the article. The determination coefficients were used as a measure of the correlation power and the quality of the regression models. A very strong linear correlation between CaO and SiO2 content and strong linear correlations between CaO and Al2O3 and SiO2 with Al2O3 have been found. The correlation relationships of the remaining pairs of oxides are weak or very weak and do not provide a basis for prediction of their content based on regression models binding them with the content of other components. The use of nonlinear models for these pairs of oxides results in only a slight improvement in the quality of regression, insignificant from a practical point of view. The application of multiple regression models, linking the content of the mentioned components (with the exception of CaO), leads to similar conclusions. Compared to the determination coefficients of a simple linear correlation, a strong increase in determination coefficients obtained in two cases was found to be artificial and caused by a correlation between the content of the selected components acting as independent variables. From the geological and mining point of view, the results of the analysis indicate the possibility of a fully reliable prediction of SiO2 content and the limited reliability of the Al2O3 content prediction when the CaO content is determined using simple linear regression models.
The presented article describes the relationship between lithological and facies development of reservoir rocks in the area of the roof elevation of the Weissliegend sandstones, with a particular emphasis on the influence of elevation on the occurrence of low mineralization zones in the deposit area. To illustrate the variability of the deposit parameters, closely related to the facies and lithological conditions of the host rocks, three-dimensional lithological and geochemical models for two research areas were developed using the geostatistical methods and based on field observations and the sampling of the deposit. The research area includes parts of the Northern Elevation of Rudna and the surrounding depressions within the boundaries of the Sieroszowice and Rudna deposits. Based on cross-sections of the 3D models, a different deposit formation in the roof elevation area of sandstone formations has been characterized; the lithological profile is defined as „atypical” due to the absence of a copper-bearing shale series, the most characteristic layer for copper ore deposits in the Fore -Sudetic monocline. Large variations in the shape of the deposit and the irregular boundaries of both balance mineralization and enclaves of gangue have been confirmed. The presence of large-scale enclaves of igneous rock in the entire profile of the Lower Zechstein rocks (areas without the balance copper mineralization) and small areas of gangue (sandstone) enriched with anhydrite binders adjacent to the parts of balance deposit located in argillaceous sandstone has been revealed. The possibility of the occurrence of gangue, in the area of the roof elevation of the Weissliegend sandstones directly adjacent to the border with calcareous dolomite, and irregular gangue partings in sandstone formations in the balance deposit was indicated. In addition, small areas of strong enrichment in Cu sulphides were observed in the contact zones between sulphate and clay binders in the Weissliegend sandstone series.
In the world-class Cu-Ag deposits of the Legnica-Głogów Copper District (LGCD), constant bulk density values are adopted to estimate the ore and metal resources within them based on the results of previous studies of the LGCD deposits carried out at the stage of their exploration and documentation: 2.6 Mg/m3 for the carbonate series, 2.5 Mg/m3 for the shale series, and 2.3 Mg/m3 for the sandstone series. The main purpose of research was to analyze the range of possible differences at local scale of observation between constant values of bulk densities (hereinafter referred to as reference values) assigned during deposit documentation to the main lithological units and bulk densities of these units determined based on the results of experimental sampling of individual lithological units within the exploited copper and silver deposits (Lubin, Polkowice-Sieroszowice and Rudna). In general, when it comes to Cu-Ag LGCD deposits (or their large parts), the relative diversity of estimates of average bulk densities of ores based on the results of experimental sampling (more than 1,600 samples from different individual lithological units were collected at 500 sampling points in mining excavations) and reference values is low (with a median not exceeding 3%). The results of studies indicate, however, that the application of reference bulk densities at the local observation scale may result in significant underestimation (up to nearly 20%) or overestimation (up to 11%) of real bulk densities of the main lithological units. This may have a noticeable impact on the correct estimation of ore and metal resources in small parts of deposits and, as a consequence, hinder the reconciliation of the planned and actual ore mining production.