Transcript Slide 1

Petrology of Oceanic Crust
Mark Gorenc John Solder
Components of Oceanic Lithosphere
Layer 1 (>1 km)
•Sediment Layer
Layer 2 ( up to 2.8 km)
• Pillow Basalts, Sheeted
Dikes
Layer 3 (up to 5 km)
•Gabbro
Mid Oceanic Ridge Basalts
Heterogeneous Basalts
• Textures controlled by
cooling Histories
• Heterogeneous mantle
• Fractionation
• Tholeiites
• Phenocryst Rich Basalts
– Plagioclase, Olivine
MOR Metamorphism
• Hydrothermal Metasomatism
• Low Grade – mostly Zeolite and Greenschist
• Olivine & Pyroxene => Hydrated Silicates
Tale of Two Circulation Systems
• Active - High T, alteration of fresh basalt and underlying magma
chamber
– Greenschist and Prehnite-Pumpellyite Facies
– Cholrite, Actinolite, Talc, Albite, and Epidote
• Passive – Lower T, alteration of sediments
– Basalt cools over millions of years as evidenced by continued
hydrothermal circulation
– Zeolite Facies => Hydrated Clays, Calcite, Cholrite, and Zeolites