GEOL 1425 1st Edition Lecture 6Outline of Last Lecture I. RocksII. Overview of different kinds of rocks/formationsOutline of Current Lecture I. Igneous rocksII. MagmaIII. Different types of igneous rocksCurrent Lecture- "Igneous" : processes that involve liquid rock (magma) Melting of rock; Intrusion of magma into crust; Extrusion of magma onto surface; Flow and freezing of magma; Chemical changes in magma- Magma: mixture of liquid rock, dissolved gases and a few minerals and other solids- Volcanos erupt magma and are a common source for the formation of igneous rocks- Composition based on amount of SiO2 (silica) and heavy elements Fe, Mg, Ca- 4 different types:- 1. Ultra-mafic magmas < 50% SiO2 – Relatively rare in crust – present in mantle. Very high concentrations of Fe, Mg, Ca; very low concentrations of Na, K, Al - 2. Mafic magmas: 50 to 60% SiO2 (80% of all magmas) high concentrations of Fe, Mg, Ca;low concentrations of Na, K, Al - 3. Intermediate magmas: 60 to 70% SiO2 . (10% of magmas) Intermediate concentrations of Fe, Mg, Ca; intermediate concentrations of Na, K, Al - 4. Felsic Magmas: > 70% SiO2 (10% of magmas) Low concentrations of Fe, Mg, Ca and high concentrations of Na, K, Al- As a general rule, minerals with heavier elements (Fe, Mg, Ca) tend to have higher melting temps. - Mafic minerals (pyroxene, olivine, plagioclase) melt and crystallize at high temperatures- Felsic minerals (quartz, orthoclase feldspar, mica) melt and crystallize at lower temperaturesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a
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