ERS120H5 Lecture Notes - Lecture 9: Intrusive Rock, Diorite, Mafic
Document Summary
Composition: silicic (rick in silica, intermediate, mafic (rich in magenesium and iron (fe), ultramafic. Texture (depends on cooling rate: extrusive (volcanic) cools fast which means there are small crystals, intrusive (plutonic) cools slowly which means there are large crystals. The rocks high in density have a lower silica content. The order the rocks are made is important. *understand figure 4. 13 when studying for the test. Obsidian volcanic glass (cools instantaneously it cools so fast that no minerals get to grow, it is a felsic extrusive rock, old spears and knifes could be made from this rock) Pumice volcanic glass with bubbles (can be used to take off dead skin, when its made gas is trapped in the rock, so it"s a very low density rock) Why do intermediate and silicic rocks even exist? (melted mantle = mafic) Partial melting release of silicic components first of rock melts. Fractional crystallization formation and settling of mafic minerals first as rock cools.
