Mapping potential mineralization : a geostatistical study of B-horizon soil samples from the Rajapalot-Rompas project area in northern Finland

Abstract

The Rajapalot-Rompas area in South Lapland is part of the Peräpohja Schist Belt and contains several gold- and cobalt-bearing mineralized zones. This thesis aims to examine a set of B-horizon soil samples collected primarily between the Rompas and Rajapalot prospects to define areas of interest that could be indicators for nearby mineralisation. The dataset contains 538 samples that were analysed using Ionic Leach. To identify areas of interest, pathfinder elements were defined using 17 samples from the entire sample set, which were taken above or close to the known mineralisation of Raja. These baseline samples were analysed using different evaluation methods, including Principal Component Analysis (PCA) and Pearson correlation. After defining the pathfinder elements, different geostatistical methods were combined to define the areas of interest. Primarily, two clustering techniques were applied to group sample points based on shared characteristics. Additionally, percentile values and combined elemental concentrations were used to further refine the target areas.

With these methods, seven high-priority areas were defined. Comparing these high-priority areas with different background data and by singling out samples that are particularly highlighted, several of these high-priority areas seem to be especially indicative of nearby mineralisation. The analysis of baseline samples identified pathfinder elements well-suited to the deposit style and surrounding country rock. Moreover, similar pathfinder elements were highlighted in the analysis of both the baseline samples and the full dataset.

From the data collected in this thesis, it can be concluded that soil sampling combined with geostatistical analysis is an effective method for evaluating large areas. The areas of interest highlight a space in between the known Rajapalot and Rompas areas, which is an underexplored space that could bear a high potential for mineralisation. To further analyse and refine target areas, glacial till movement should be considered alongside other methods, such as geophysics, base-of-till sampling, or RAB drilling. If these methods define promising target areas, diamond drilling can then be used to test these hypotheses.