Mining in Manitoba |
Secondary Mineral Deposits |
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Return to Geological Considerations
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Primary deposits through the
action of weathering give rise to secondary deposits. Weathering includes both mechanical
weathering or the breaking down of rock masses by changes of temperature, the expansion of
water as it freezes in cracks, the growth of roots and abrasion from moving solid
particles, and chemical weathering caused by the solvent action of surface waters. These deposits are divided into 3 groups: 1) Sedimentary rocks These include the plastic sedimentary rocks, such as slate, sandstones and quartzite, formed from the products of mechanical weathering and chemical precipitation. This group includes organic deposits, such as certain iron ores, phosphate deposits, and coal. 2) Secondarily Enriched Deposits These are formed by the dissolving or leaching of the metal from the upper part of the deposit close to the surface, the metal content of the solutions collecting on the metallic minerals below, forming an enriched zone. 3) Residual and Detrital Deposits By the removal of soluble material from the original substance the insoluble material remaining may form valuable residual deposits. |
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