The computer simulations did not show a mantle plume
rising to the surface.
Traditionally, alkalic lavas in oceanic settings are associated with Hawaiian-type mantle plumes
that tap enriched mantle sources (e.g.
These lavas emerge from a mantle plume
(hotspot), which may or may not be situated at a spreading center or plate boundary.
Referring to a time when present-day Africa and South America - two of the world's highest gold-producing regions - were one landmass, part of the supercontinent Gondwana, GonzAaAaAeA lez JimAaAaAeA@nez said the as of a mantle plume
- it can be thought of as a narrow stream of hot or molten rock that rises through the mantle and spreads out under the crust, like a mushroom - caused the erstwhile supercontinent to break up.
This fuels the discussion about the competing role of mantle plumes
and tectonic processes.
More broadly, the researchers wrote, mantle plumes
push up against the earth crust, shifting water to continents, thereby producing sea-level rise, and precipitating volcanic activity, which produces additional CO2, leading to a warmer climate.
Traditionally, most petrologists have accepted that during the Archean and Paleoproterozoic, komatiite melting temperatures ranged from 1600-1900[degrees]C, so komatiitic magmas were therefore related to deep-seated mantle plumes
(Campbell et al.
However, during the past ten years, the mantle plume
explanation has been the source of vigorous debate (see Hotspot theory feels the heat).
Here researchers examine a theory which explains its existence, namely that it was created by the rapid decompression and melting of an inordinately hot mantle in the heads of newly ascended mantle plumes
. The topics of their 19 integrated studies here include the motion of the plateau in the hot-spot frame of reference, modeled palaeolatitudes for a hot spot, a lower Cretaceous planktonic foraminiferal and nannofossil biostratigraphy, evidence of partial melting below the plateau, implications of a petrology experiment on differentiation processes, submarine basaltic glasses and their implications for magmatic processes and source region compositions, and several papers on the composition and distribution of volcaniclastic rocks and other materials.
Hawaii is notable for being both the largest of all mantle plumes
(as measured by total volcanic output over the millennia) and by far the most intensively studied by geochemists.
"The experiments show that mantle plumes
have an important local impact on the ice sheet, with basal melting rates reaching several centimeters per year directly above the hotspot.