Basalt is a type of volcanic rock that is formed when lava with a high content of mafic minerals (such as pyroxene and olivine) solidifies and cools. Basalt lava eruptions happen when this molten rock is appeared from a volcano and comes into contact with the Earths surface area. These eruptions can be explosive, producing ash and tephra, or they can be more effusive, flowing slowly and progressively over long durations of time. Basalt lava is generally more fluid than other types of lava, which enables it to stream easily and cover big areas.
n the past, enormous lava eruptions have actually caused the production of big floods of basalt lava on the continents. It was formerly thought that these types of eruptions might only occur in locations where the continental tectonic plates are thin, permitting deep mantle material to increase near the surface area. The low pressure in these areas permits the melting of hot mantle, which can generate a significant amount of magma.
Nevertheless, a new research study by scientists from the University of Helsinki and Aarhus University challenges this standard understanding.
” The idea that flood basalt eruptions normally require melting of the mantle under low-pressure conditions is mainly based on the trace aspect structures of the emerged magmas”, discusses Dr. Jussi Heinonen, University of Helsinki, the lead author of the recent Journal of Petrology post explaining this research study.
Basalt is a type of volcanic rock that is formed when lava with a high content of mafic minerals (such as pyroxene and olivine) cools and solidifies. Basalt lava eruptions take place when this molten rock is erupted from a volcano and comes into contact with the Earths surface. Basalt lava is normally more fluid than other types of lava, which allows it to stream quickly and cover large areas.
It was formerly thought that these types of eruptions might only happen in locations where the continental tectonic plates are thin, enabling deep mantle product to increase close to the surface.
He defines further that the relative amounts of unusual earth components in many flood basalts indicate magma formation in the existence of low-pressure mantle minerals.
The flood basalts in Dronning Maud Land, Antarctica, originate from an incredibly deep mantle source. Credit: Arto Luttinen
Assistance from computer simulation
The new study was performed as part of a research study job focusing on the origin of flood basalts that emerged in southern Africa and Antarctica when these continents were connected to each other as parts of Pangaea some 180 million years earlier.
” We ended up being curious about the incident of most flood basalts in areas where the African and Antarctic tectonic plates are thick instead of thin”, describes Dr. Arto Luttinen, leader of the University of Helsinki group. “Moreover, we found that numerous flood basalts that have unusual earth aspect structures, suggesting high-pressure development conditions, are really located in thin areas of the tectonic plates.”
The concept of an alternative hypothesis started forming after the teams discovery of a kind of flood basalt in Mozambique that shows compositional evidence for remarkably high eruption temperatures.
” These flood basalts made us think about the possibility that melting of exceptionally hot mantle could result in the formation of high-pressure magmas with micronutrient features comparable to those of low-pressure magmas”, adds Ph.D. trainee Sanni Turunen from the University of Helsinki.
The researchers decided to evaluate their hypothesis using the geochemical modeling tool REEBOX PRO, which makes it possible for reasonable simulation of the behavior of minerals, melts and their micronutrient contents throughout mantle melting.
” We were thrilled to discover out that the simulations supported our hypothesis by forecasting total consumption of garnet, a diagnostic mineral of high-pressure conditions when mantle melting took place at the heats indicated by the flood basalts”, states Dr. Eric Brown, Aarhus University, a co-author of the short article and among the designers of the REEBOX PRO tool.
Magmas formed at high pressure can therefore chemically look like low-pressure lavas when the mantle source is really hot. Furthermore, the outcomes showed the survival of garnet at relatively low pressures when a various sort of mantle source was selected for the modeling.
” Our outcomes assist us to understand the obvious debate between the events of southern African and Antarctic flood basalts and their trace aspect qualities. Most notably, we reveal that voluminous flood basalts can form in regions of thick tectonic plates which the trace component structures of flood basalts are undependable messengers of lava generation depths unless the influences of mantle temperature and composition are represented,” the authors conclude.
Recommendation: “Heavy Rare Earth Elements and the Sources of Continental Flood Basalts” by Jussi S. Heinonen, Eric L. Brown, Sanni T. Turunen and Arto V. Luttinen, 27 September 2022, Journal of Petrology.DOI: 10.1093/ petrology/egac098.