In 1989 Baltic geologists completed a collaborative work on a joint Latvian, Lithuanian and Estonian mineral resource forecast map up to depths of fifty meters below ground. The work involved a quantitative evaluation of anticipated hard combustible and non-metallic mineral resource deposits (e.g. sand-gravel, clay, dolomite, gypsum and others).
The key factor that guides the general relationship of perspective field placement is the thickness of waste mineral layers that cover the valuable strata. For determining the specific field boundaries, an extensive set of fact material was used—medium and large scale geological mapping data, results of mining attempts and research work as well as borehole sections that were made for the purpose of water distribution systems, without obtaining any core samples. Materials were summarized on a large and medium scale topographic base depending on how thoroughly the specific territory was researched. Perspective field boundaries are natural because they contain mineral layers of uniform content and are, most commonly, simple, horizontally embedded structures. For indication of fields, the relationship of covering mineral layers and valuable mineral layers (cover-layer coefficient) is not greater than one, but for most prospective fields—not greater than 0.5. In determination of perspective field boundaries, apart from geological and technical conditions of mining, nature preservation factors were taken into account: green zones of cities and inhabited areas, natural parks and naturally preserved territories. Buffer corridors along roads and rivers were not included in the perspective fields making the data of this work significantly differ from results of previous works.
All deposit forecasts of valuable resources were divided into categories P1, P2 and P3 according to their geological reasoning, employing a productivity coefficient. The fields of category P1 were assessed and they can be recommended for expanding the mineral resource repository in the future. The forecast category P2 in most of the cases has the potential to expand the already existing mineral resource repository. The fields with category P3 resource forecast have the potential to discover new valuable resource mines.
The range of valuable mineral resources suitable for open mining differs across the three Baltic states as it is dependent on the properties of the geological structure of the territory. There is significant potential for discovering new mines for oil shale and limestone in Estonia and anhydrites as well as sand-gravel in Lithuania, while in the case of Latvia, there is potential for the mining of dolomite, clay and gypsum.
Text: Vija Hodireva