Host rock is, simply, the rock surrounding the ore deposit. Host rocks, as the definition suggests, may be found as a host to any kind of ore deposit, from gold to uranium. Host rock may also be defined as the type of rock where mineralization occurs. Host rocks are significant in identifying the age of the mineral deposit.
The type of host rock influences the mining method, to an extent. For example, an ore body that is hosted in a self-supporting rock may be mined by using an open stoping method. On the other hand, an ore body that is hosted in a poor rock may require a cut and fill method. Adopting this method ensures that the void created during mining is continuously filled.
During mining operations the host rock undergoes alteration. Host rocks that surround hydrothermal mineral deposits tend to exchange elements with hydrothermal fluids, thereby producing alteration minerals. These mineralogical alterations affect the volume and density of the host rock, which in turn alters the ensuing hydrothermal reaction. Such host rock alterations result in volume increases This seals the fault fractures that form the principal conduits for hydrothermal flow.
Radioactive Significance of Host Rocks
Host rocks are of three types. Namely, clay rocks, salt rocks, and crystalline rocks. In cases of radioactive ore deposits, their safe enclosure is influenced by the geological, geo-technical, and technical barriers. The type of barrier system is dependent on the host rock. Each type of host rocks - clay, salt and crystalline - provide varied radioactive disposal systems.