GEOL107 Lecture Notes - Lecture 5: Igneous Rock, Feldspar, Mica
24 Sep 2017
School
Department
Course
Professor
Document Summary
Examined ways minerals crystallized from magma by taking intermediate composition igneous rocks (think diorite or andesite) and under pressure melting it to produce magma and allowing magma to cool. Observed two major types of processes taking place as magma in lab cooled. Discontinuous reaction series different minerals formed formed was olivine. Distinct silicate minerals being formed within distinct temp ranges - as temp decreased. At highest temperatures (where initial crystallization (solidification) occurred), mineral. As temp dropped, olivine stopped forming and next pyroxene formed. As temp dropped further, pyroxene stopped forming and next amphibole formed. As temp dropped further, amphibole stopped forming and next biotite mica formed. As temp dropped further, final mineral to form was quartz. As temp decreased same mineral, plagioclase feldspar, was forming, but composition. Ca-rich plagioclase feldspar called anorthite na-rich plagioclase feldspar called albite was changing slightly from calcium (ca) - rich to sodium (na)-rich. Calcium leaves magma (goes to rock) earlier (at higher temperatures) than sodium.
