Earth Sciences 1022A/B Lecture Notes - Lecture 1: Talc, Nonconformist, Thrust Fault

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 1022A/B
• Professor: Stephen R Hicock

Document Summary

Igneous rocks rock that has solidified from mainly molten material (magma) Orthoclase, plagioclase, olivine, pyroxenes, amphiboles, quartz, and mica constitute over 95% of all igneous rocks (they crystallize according to bowen"s reaction series) Felsic magmas rich in silicon and aluminum, produce more quartz, orthoclase and na- plagioclase minerals tend to produce light coloured rocks (granite and rhyolite) Intermediate magma composition between felsic and mafic (diorite and andesite) Mafic magmas rich in iron, magnesium, and calcium produce more olivine, pyroxene, amphibole, ca-plagioclase, and tend to produce darker rocks (gabbro and basalt) Ferromagnesian (mg, fe-rich) minerals like pyroxene and olivine (dunite, peridotite, pyroxenite) Phaneritic interlocking crystals of about equal size that are plainly visible to the unaided eye. Aphantic interlocking crystals are too small to see without a microscope (rocks appear structureless) Porphyritic - >10% of the rock volume comprises large crystals (phenocrysts) surrounded by a matrix of smaller crystals (groundmass) which may be phaneritic or aphantic.