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Chemical weathering of feldspars happens by hydrolysis and produces clay minerals, including illite, smectite, and kaolinite. Hydrolysis of feldspars begins with the feldspar dissolving in water, which happens best in acidic or basic solutions and less well in neutral ones. [30]
Physical weathering, also called mechanical weathering or disaggregation, is the class of processes that causes the disintegration of rocks without chemical change. Physical weathering involves the breakdown of rocks into smaller fragments through processes such as expansion and contraction, mainly due to temperature changes.
Chemical weathering of igneous minerals leads to the formation of secondary minerals, which constitute the weathering products of the parent minerals. Secondary weathering minerals of igneous rocks can be classified mainly as iron oxides, salts, and phyllosilicates. The chemistry of the secondary minerals is controlled in part by the chemistry ...
Clay minerals most commonly form by prolonged chemical weathering of silicate-bearing rocks. They can also form locally from hydrothermal activity. [ 16 ] Chemical weathering takes place largely by acid hydrolysis due to low concentrations of carbonic acid , dissolved in rainwater or released by plant roots.
Above the water table the environment is oxidizing, and below it is reducing. [7] Solutions traveling downward from the leached zone react with other primary minerals in the oxidised zone to form secondary minerals [5] such as sulfates and carbonates, and limonite, which is a characteristic product in all oxidised zones. [3]
In inorganic chemistry, mineral hydration is a reaction which adds water to the crystal structure of a mineral, usually creating a new mineral, commonly called a hydrate. In geological terms, the process of mineral hydration is known as retrograde alteration and is a process occurring in retrograde metamorphism .
Hydrothermal mineral deposits are accumulations of valuable minerals which formed from hot waters circulating in Earth's crust through fractures. They eventually produce metallic-rich fluids concentrated in a selected volume of rock, which become supersaturated and then precipitate ore minerals. In some occurrences, minerals can be extracted ...
The process of formation is called laterization. [2] Tropical weathering is a prolonged process of chemical weathering which produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. The majority of the land area containing laterites is between the tropics of Cancer and Capricorn.