EOSC 118 Lecture Notes - Lecture 18: Alkali Basalt, Lamprophyre, Corundum

• School: UBC
• Department: Earth and Ocean Sciences
• Course: EOSC 118
• Professor: David Turner

Document Summary

Corundum is found in many rock types around the world. Corundum requires environments with low silica in order to form: high silica content allows the aluminum needed for corundum to go into aluminosilicate minerals instead, and not have enough left for corundum to form. The combination of silica and aluminum (aluminosilicate) inhibits the growth of corundum: primary metamorphic corundum in gneisses and marbles. Metamorphic corundum deposits have the most gem corundum from primary sources. Primary deposit type corundum produces the most significant quality of rubies & sapphires. Gneisses and marble are the metamorphic rocks that can host corundum mineralization: these rocks take up most si and become enriched in al which allows it to produce corundum rather than aluminosilicates. High degree of metamorphism is required: ~9kbar and ~750 c. These extreme environments are called granulite facies by geoscientists. These conditions occur with continent-continent collisional boundaries: and sometimes in continent-ocean subduction related zones.