SPATIAL DISTRIBUTION OF ILMENITE AND APATITE IN THE CRYSTALLINE ROCKS OF THE BASEMENT AND WEATHERING CRUST OF THE TORCHYN DEPOSIT

Abstract

The article presents general information on the geological structure of the Torchyn deposit of eluvial apatite-ilmenite ores, which is located within the Korosten pluton of the Volyn megablock of the Ukrainian Shield. Within the deposit, various petrotypes of crystalline basement rocks and their weathering crust contain significant amounts of ilmenite and apatite. The weathering crust has a zonal structure and is represented by a zone of disintegration and leaching; a zone of initial hydrolysis (kaolinite-hydrohydroxide); and a zone of final hydrolysis (kaolinite). Based on the analysis and synthesis of production reports, a targeted attribute database (well coordinates, their description and test results) was created, which was used to study the spatial (lateral) distribution of the average content (kg/t) of ilmenite and apatite in crystalline rocks of the basement, in the weathering crust and in various zones of eluvium. The direction and strength of correlations between the average mineral content in gabbro-norites and different zones of the weathering crust were investigated. The distribution of ilmenite and apatite content in different zones of the weathering crust along the vertical section of the boreholes and the direction and strength of correlations between minerals were studied. The corresponding maps were constructed to show the lateral distribution of the average content of ilmenite and apatite in the crystalline rocks of the basement, in the weathering crust and its zones, as well as the vertical distribution of these minerals in the boreholes. The direction and strength of the correlations of the average ilmenite and apatite content between different zones of the eluvium are investigated. Within the deposit, we selected three longitudinal and two transverse profiles to study changes in the thickness of the weathering crust and the average content of ilmenite and apatite. It was found that within the deposit and in the studied profiles, the thickness of the weathering crust and the average mineral content are characterized by significant contrasts. It was found that the lateral distribution of the average content of ilmenite and apatite has a direct or inverse correlation with the thickness of the eluvium. It has been found that the lateral and vertical distribution of ilmenite and apatite content in the weathered crust is determined by the geological structure of the rocks of the crystalline basement, their ore content and different degrees of eluvium erosion.