Tholeiite
“The basalt that builds ocean floors”
Tholeiite is the most abundant volcanic rock type on Earth, forming the vast majority of oceanic crust at mid-ocean ridges. It's a type of basalt with a specific chemistry — lower alkali content and higher silica than alkaline basalts — and it also dominates large igneous provinces and shield volcanoes.
plagioclase (labradorite), augite, pigeonite, olivine (minor), magnetite, ilmenite
Mid-Atlantic Ridge, East Pacific Rise, Hawaii (shield stage), Deccan Traps (India), Columbia River Basalt (USA), Iceland
5.5-6.5
Tholeiitic basalt covers more of Earth's surface than any other rock type — the entire ocean floor is built from it, making it the foundation of approximately 60% of the planet's crust.
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Approximately what percentage of Earth's crust is built from tholeiitic basalt forming the ocean floors?
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