Magmatic underplating

[1] Geophysical seismic studies (as well as igneous petrology and geochemistry) utilize the differences in densities to identify underplating that occurs at depth.

Geochemistry allows geologists to determine levels of association between igneous units: in the Karoo Province of southern Africa, large volumes of rhyolite along the continental margin were produced from melts with initially basaltic compositions.

Studies of geomorphology in the Karoo Province have identified regional uplift,[1] associated with the underplating and consequent thickening of the crust.

Seismic studies of the crust at depth have done a great deal to identify magmatic underplating, but without direct samples to look at, it can be problematic for geologists to agree on the source of an anomaly.

Seismic studies of the Laccadive Islands in the Indian Ocean revealed a high-velocity layer of thickened crust between 16 and 24 km below the surface;[3] these were corroborated with tomographic work in the nearby Kutch District, which identified a large mafic body at depth, close to the mantle.

[6] The morphology of the lower crust was not conclusively identified as magmatic underplating, and may in fact be the remnants of the Caledonian root.

Modeling of data brought on by studies of the British Isles shows that a large amount of high velocity material occurs around the Mohorovičić discontinuity under the Irish Sea.

[11] It was also shown that magmatic underplating during a time period of about thirty million years was strong enough to erase all tectono–metamorphic history in the Ivera Verbano Zone.

The assemblage of minerals remaining behind are typically mafic or ultramafic, and are responsible for the observed seismic anomaly which indicates underplated material.