Adakite
“Melted oceanic crust from a subducting slab”
Adakite is a sodium-rich volcanic or plutonic rock with a distinctive geochemical signature — high strontium and low yttrium — that indicates it formed by partial melting of young, hot oceanic crust as it subducts into the mantle. Most magmas form from melting the mantle above the slab, making adakites unusual.
plagioclase, hornblende, biotite, quartz, magnetite, garnet (residual in source)
Adak Island (Alaska, USA — type locality), Mindanao (Philippines), Ecuador, Kamchatka (Russia), Patagonia (Chile/Argentina)
6-7
Adakites may have been far more common on the early Earth when the planet was hotter and subducting oceanic crust was young enough to melt — they could hold clues to how the first continents formed.
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