GEOL 1001 Lecture : GEOL Lecture 8
Document Summary
Igneous rock names: based on texture and mineralogy. Rocks with olivine, pyroxene- mafic (mg, fe) Variation in mineralogy reflects variation in magma composition. Different minerals form at different temps during cooling, melt change composition. Andesitic and rhyolitic magmas are produced by altering the composition of basaltic magma through other processes. Crystals removed from the melt as they form ( for ex. Basaltic magma can also assimilate crustal material and change composition. Mixing of basaltic and granitic magma produces magmas of intermediate composition (andesite/diorite) Melting in the mantle- the origin of magmas. Temperatures along the geotherm are too low to cause melting in the mantle. Melting ensues when mantle material moves to lower pressure or shallower depth.
