Prospecting Flashcards
What is a gravity survey and how does it work?
Rock density varies with mineral composition and pore space, with tighter minerals causing higher gravity. Metals are denser than surrounding rocks, allowing gravity anomalies to detect mineral concentrations. Sedimentary rocks and fluids have lower gravity readings, making it effective for identifying subsurface material like salt domes, fault structures, metal ores, and petroleum.
What is a magnetic survey and how does it work?
Magnetic surveys are a popular geophysical tool in mineral exploration for investigating iron ore, magnetite, and pyrite. They provide quick, cost-effective regional coverage of large areas and identify magnetic materials like magnetite and haematite. These surveys can identify materials of economic importance and identify areas with potential for further exploration.
What is a seismic survey and how does it work?
A seismic survey creates a shock wave on the ground, which travels into the earth, reflects off subsurface formations, and returns to the surface. Geophones record this wave, allowing geophysicists to map subsurface formations and predict oil or gas potential for exploration activities by analysing the time it takes.
What is electrical resistivity and how is it utilised?
Electrical resistivity is a fundamental electrical property of all materials, indicating their resistance to electric current flow. Low resistivity indicates a material that allows current flow, indicating conductive properties. Resistivity surveys can be used to study Earth’s subsurface, including 2D sections and 3D rock volumes. Metals and metallic sulphides, with low resistivity, are particularly useful in mineral exploration for metallic ore bodies. The electrical method is particularly effective in areas with metallic targets and sulphide ores. The conductivity of an ore deposit largely depends on sulphides or graphite.
What is a borehole and how is it utilised?
Boreholes are used to analyse subsurface composition during site investigations to determine resource availability and economic viability. They provide clear rock strata, facilitate inspection, and allow for mineral resource extraction. Drilling can be done up to 6m, but beyond 6m becomes more challenging, requires skilled workers, and increases traffic and noise. The area affected by drilling can also be adversely affected by the equipment’s setup and transportation.
What is geochemical sampling and how is it used?
Geochemical sampling methods involve collecting and analyzing geological materials like soils, stream sediments, rocks, and plants. These methods have historically been highly productive in mineral exploration, as they help identify subtle mineralization in hand specimens. Geochemical surveys use a systematic sampling approach, taking samples of soil, sediment, or water at a specified distance. If high concentrations are found, intervals between sampling spots decrease until focusing on a small area where the ore or mineral deposit may be found.
