GEO CHEMICAL CYCLE

Generally geochemical cycle is a developmental path followed by materials or group of materials of the earth in different layers of the earth. 

The process of geochemical cycle involves geochemical differentiation. This means natural separation and concentration of the materials of the earth. In the lithosphere (crust + upper mantle) , geochemical cycle starts from the crystallization of magma at the surface of the crust or at the depth . After magma crystallized at the surface it becomes igneous rock. Then these rocks undergoes series of physical and chemical alternation (weathering) and results in breakdown into smaller materials. Now this process is followed by transportation and deposition of resulting materials as sediments. Then the sediments becomes lithified which results in the formation of sedimentary rocks. These sedimentary rocks under high temperature and pressure gradually becomes metamorphic rocks. But maximum temperature and pressure in metamorphic rock leads to anatexis(partially melting of rock) into magma. This ideal cycle can be affected at any point. Each element may be affected differently as cycle progresses. For example: during the weathering of igneous rocks, minerals containing iron , calcium, magnesium break down and more resistant minerals like quartz and feldspar are transported as sediments. Then the resultant sedimentary rocks are dominated by quartz and feldspar and others are by calcium and magnesium containing the ppt. of calcium and magnesium carbonates. Elements like sodium remains in the solution until precipitation of water under extreme condition. When the partial melting of the rock occurs ,the elements are separated according to their melting properties , volatiles are released to atmosphere and physical movement of chemically separated body occurs. So, starting from lithosphere the chemical process continues in various zones on the earth with their own chemical cycle. And this chemical alternation in various layers of the earth makes the geochemical cycle complete.