According to the San Diego State University (SDSU) webpage Unusual Lava Types, komatiite is

ultramafic volcanic rocks, having very low silica contents (~40-45%) and very high $\ce{MgO}$ contents (~18%). These lavas are exceptional not only for their compositions, but also for their very old, restricted ages. These lavas have no modern analogs.

The vast majority of komatiite deposits, according to the SDSU webpage, are about 3 Ga or older in age, due to

These ancient lava flows erupted at a time when the Earth's internal heat was much greater than today, thus generating exceptionally hot, fluid lavas with calculated eruption temperatures in excess of 1,600 degrees C (2,900 degrees F).

However, with many things in Science, there are exceptions - according to the SDSU webpage, Gorgona Island, Colombia has komatiite deposits that are Cretaceous in age (around 90 Ma). The presence of young komatiite hints at higher temperatures at formation - something that has not been seen in any significant amount since the Archaean.

What caused the high temperatures that resulted in the Cretaceous aged komatiite lavas of Gorgona Island, Colombia?


There are some suggestions in the recent paper in Nature Geoscience about Tortugal lava suite. The suite formed 89 million years ago and recorded mantle temperatures as high as Archaean komatiites. The mantle plumes are chemically and thermally heterogeneous, so the researchers interpret these rocks as the result of melting the hot core of the plume head that produced the Caribbean large igneous province. Their results imply that a mantle reservoir as hot as those responsible for some Archaean lavas has survived eons of convection in the deep Earth and is still being tapped by mantle plumes.

The link: https://www.nature.com/ngeo/journal/v10/n6/full/ngeo2954.html


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