GEOL 101 1nd Edition Lecture 8 Outline of Last Lecture I Naming Igneous Rocks a Felsic b Intermediate c Mafic d Ultramafic II Origin of Magma Outline of Current Lecture I Evolution of Magma II Bowen s Reaction Series Current Lecture Short Lecture Evolution of Magma Geologists have observed several magmas of different composition coming from the same volcano Then a Geologist by the name of N L Bowen explained it by saying as magma cools different minerals crystalize based on their melting points Bowen s Reaction Series o During the process where it crystalizes the composition of the liquid part of the magma continually changes o It can change by early forming minerals removing the elements in the chamber Mafic minerals are first to crystalize o The liquid portion is filled with Silica as crystallization continues In a magma chamber the magma cools and it forms minerals and depending on the melting point it will form sooner than later Olivine has highest melting point so it crystalizes first Then Pyroxene and Calcium Plagioclase forms and all the others until Quartz the final formation cools and crystalizes to completely solidify the chamber See picture below These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute The Bowen Reaction Series can also be referred to as Magmatic Differentiation Separation of a melt from earlier formed crystals to form a different composition of magma Composition can change by including host rock bits of the surrounding crust Also called assimilation Composition can ALSO change if the chamber knocks and goes into a second chamber This is called Magma Mixing Two chemically different magmas can produce something entirely different from the original chambers
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