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How Does Olivine Affect The Concentration Of Iron Or Silica?

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1. Olivine decreases the concentration of magnesium in the melt. It helps decrease the amount of iron in the melt as well. On the graph of magnesium versus silica cation percentage the Magnesium amount decreases and the silica percent increases in the melt when olivine starts forming. This creates a downward sloping line. This downward slope is also true for the Iron versus silica graph. Plagioclase decreases sodium and potassium concentrations in the melt. Both Plagioclase and Olivine decrease the amount of silica and oxygen in the melt. On the graph of silica versus calcium it also shows a rapid downward trend just like olivine because they are both made up of compatible elements. However, potassium has an upward trend versus silica because …show more content…

The initial rocks are very ultramafic and as time goes on they became more felsic. The magma during the formation of the ultramafic to mafic rocks the magma becomes more felsic until these rocks stop forming. This is because compatible elements were crystallizing into minerals. These minerals then made up rocks after each step finished. Slowly the minerals and rocks formed became more felsic and the melt became less felsic. It will continue to get less felsic until all the magma has crystallized. For example, we went from Dunite (step1) all the way to Granodiorite(step ten). Dunite was very ultramafic while Granodiorite was more felsic since it had more silica in it. The last melt could have formed a Quartzolite or a Quartz-rich Granitoid depending on how much silica, alkaline feldspars, and plagioclase was left. Silica was the most abundant element in the melt so therefore the percentage of it in the melt remained high even after a decent amount of it had been removed. For example, at the end of step six there was still 125 silica atoms left in the melt. The steps that created ultramafic rocks were steps one through six since they had olivine, plagioclase, and pyroxenes in them. The mafic rocks were created in steps seven and eight since they had no olivine or felsic minerals in them, but still had pyroxene and plagioclase in them. The steps nine and ten created felsic rocks since they had felsic minerals (quartz and Alkali feldspars) as well as the mafic minerals in …show more content…

In a magma that is involving equilibrium crystallization only a few minerals if any are not interacting with the melt. In a system with complete equilibrium fractionation the mineral modes would increase from 0% to 100% at the different steps. In fractionalization crystallization, each step adds to 100% on it’s own. For example, step two would not equal 75% Olivine and 25% Plagioclase because these minerals would interact with the two previously crystallized Olivines as well as the melt. Therefore the percent of olivine and plagioclase would be completely different and would be a percentage of the melt that was crystallized. If the whole melt became a rock, then you would have a step that everything is equal to 100%, but you won’t have any earlier step equal 100%. This then will change the types of rocks formed and their IUGS

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