Practical aspects of estimating the quantitative mineral composition of copper-bearing sedimentary rocks on the basis a calculation procedure analogical to the CIPW norm

Abstract

The paper presents a possibility of estimating the content of ore minerals based on chemical analyses of copper-bearing sedimentary rock samples from the North-Sudetic Synclinorium and from the Fore-Sudetic Monocline using a calculation procedure similar to the CIPW norm. The mineralogical data was obtained by means of an optical microscope and an electron microprobe (EPMA). The quantitative composition of gangue minerals was determined using the XRD method, and of the ores by the computer microscopic image analysis (CAMI). The actual set of gangue and ore minerals, their chemical composition, and proportions of copper ores were determined in the samples. Elements that are the main components of identified minerals were selected. The calculation procedure has been developed in accordance with the mineralogical and chemical data. The set of ore minerals determined based on the calculation of the weight ratios is consistent with the microscopic observations of copper-bearing rocks. The obtained ore contents are similar or slightly higher in poorly mineralized samples and slightly lower in highly mineralized samples in comparison to the results of the CAMI method. These differences may be due to different methods of averaging samples (powdered, averaged rock samples, and a thin section). The calculated ore proportions are consistent with those obtained by the CAMI method. The study calculations of the quantitative ore mineral composition using the calculation procedure analogical to the CIPW norm can be used to a preliminary approximation of the quantity of ores in geological prospection and exploration studies, but they require testing of more variants of the element partition between the set of minerals.