Question

question 46
2 pts
which of the following describes the formation of the oceanic lithospheric mantle?
sediment scraped from subducting oceanic lithosphere accumulates in the accretionary prism.
decompression melting of ultramafic asthenosphere produces mafic magma which cools to form mafic rocks.
flux melting in the asthenosphere produces magmas which cool at the base of the crust.
gradual cooling of the uppermost mantle beneath oceanic crust.

Explanation:

The oceanic lithospheric mantle is formed by the gradual cooling of the uppermost mantle beneath the oceanic crust. The other options describe processes related to accretionary prisms, magma - formation mechanisms (decompression and flux melting) rather than the formation of the oceanic lithospheric mantle itself.

Answer:

Gradual cooling of the uppermost mantle beneath oceanic crust.