Oceanic crust and Ophiolites

What is adiabatic melting?

When rifting occurs, there is a rapid decompression down the crust to the mantle, causing melting of the mantle.

What is in Layer 2 of the ophiolite sequence?

Pillow basalts and sheeted Dykes. The dykes may cut into the pillow basalts or another dyke.

What is in layer 3?

Differential Gabbro’s - some are isotropic & foliated, and some are layered and exhibit cumulate textures.They are 5km thick.

What is in layer 4?

Cumulate wehrlite and gabbro with cumulate dunites with harzburgite xenoliths below.

Where do the harzburgite and dunite originate?

They are unmelted residuum of the original mantle.

What are “Normal” Mid ocean ridge basalts depleted in?

They are slightly depleted in light Rare earth elements.

What are “enriched” mid ocean ridge basalts elevated in?

They are enriched in Light rare earth elements.

What are ophiolites?

Ophiolites are sections of ancient oceanic lithospheric crust emplaced onto a continental margin during orogenic events, found along suture zones.

What are supra-subduction zones?

They are more easily obducted oceanic crust during collision and can be preserved on land. Common during ocean closure and various types of orogeny.