The mine life cycle begins with the Pre-Feasibility study with the search for minerals and answers to the below questions;
- What is it?
- Where is it?
- How big is it?
- What is the value?
The only way to source the answers for these questions is founded on paper through mapping and modelling and also through field work through rock and soil sampling. The first phase of the mining cycle is called Pre-Feasibility and can take up to between 1 – 5 years to complete. It is the process of finding commercially viable quantities of minerals/ores to mine. With this study comes economic growth and development. Pre-feasibility activities involve land issues and should bring an influx of jobs to the area with the purchase of local goods and services, especially in developing areas. During the pre-feasibility stage we should endeavour to comply with the environmental regulations whilst learning about the local ecosystems and biological diversity in the area, all whilst attempting to establish a safe working environment
Large areas of land are evaluated by airborne surveys or geological surveys of the Earth’s surface. After the review of the found data , if viable, specific areas are targeted for more in depth studies. If further studies are needed, land sampling and mineral sampling are carried out by geologists and prospectors.
The methods used for the mining cycle pre-feasibility phase vary at different stages of the process, dependent on the size of the area which is being explored, as well as the density and type of the information sought after.
In the Pre-Feasibility study, the area to be explored is identified. A few of the methods used in the this Pre-Feasibility stage are;
- Geophysical Surveys: Geophysical survey techniques include magnetic, electromagnetic, electrical, radiometric and gravity techniques, and surveys can be conducted from the air or on the ground. These surveys provide information on potential targets for ground-based exploration.
- Prospecting and Geological Mapping: This can involve the mapping and sampling of targets identified in airborne geophysical surveys, regional-scale mapping and more detailed mapping of areas of particular interest. The objective is to provide a preliminary assessment of the potential for mineralization over a relatively large area.
- Geochemical Surveys: A range of materials may be sampled, most commonly rocks and soil. Samples are sent for chemical analysis for metals of interest. Results of the analyses are compiled and compared with the results obtained from other exploration methods.
- Diamond Drilling: Diamond drills recover a core of rock, and cores from several holes allow geologists to build a three-dimensional picture of the local geology. Core samples are also subjected to chemical analysis.
- Trenching: Trenches may be dug or areas of outcrop stripped of vegetation and soil to enable mapping of near-surface geology and for bulk sampling where ore and other geologic units may be very near the surface.
The primary goal now would be to define the quantity and quality of the potential minerals/ore and the geometry of the deposit and to determine the most appropriate mining and processing methods. Larger amounts of rock are removed during bulk sampling as part of the Pre-Feasibility study. Valuable information can be obtained through this process. Bulk sampling is commonly accompanied by extensive diamond drilling, the results of which are used to improve the understanding of the geometry of the mineral deposit, as well as the quantity, characteristics and delineation of the potential ore body.
If the quantity and quality of potential ore present are adequate to proceed to a feasibility study, the data extracted is used for preliminary planning of mine layout, ore processing design, and estimating the cost of developing and operating a mine, and this is how the next stage of the mining cycle begins : Feasibility.
