The mineral Davemaoite (CaSiO3-perovskite, the third most abundant mineral in lower mantle layer of Zemljin interior) has been discovered on the surface of the Zemlja for the first time. It was found trapped inside a diamond. Perovskite is found naturally ONLY in lower mantle layer of the interior of the Zemlja under extremely high temperature and pressure conditions. This first-ever discovery of interior Zemlja mineral in nature is important to geology for better understanding of dynamics of deep Zemlja.
Perovskit je mineral, sestavljen iz kalcijevega titanovega oksida (CaTiO3). Vsak drugi mineral s podobno kristalno strukturo se imenuje perovskit. Zaradi tega je perovskit razred spojin, ki imajo enako vrsto kristalne strukture kot CaTiO3 (perovskitna struktura).
Kalcijev silikat perovskit (CaSiO3-perovskit ali CaPv) je pomemben mineral, ker je tretji najbolj razširjen mineral1 (7 % prostornine) v spodnji plasti plašča Zemljin interior and plays a significant role in the heat dynamics of Zemljin interior. To put things in perspective, of the three layers of Zemlja, the mantle layer, between dense super-heated core and thin outer crust layer, makes up 84% of Zemljin total volume while the lower mantle layer alone comprises 55 percent of the Zemlja and extends from 670 and 2900 km in depth. The below table gives a snapshot view of place of perovskite in Zemljin znotraj.
Tabela: Mesto plasti bogate s perovskitom v Zemljini notranjosti
Perovskites along with other minerals in the mantle layer play a key role in the dynamics of deep Zemlja involving heat transfer from core towards surface, called mantle convection. Despite its abundance and importance, perovskite has never been retrieved from the lower mantle layer, because it loses its structure on being removed from its high-pressure conditions.
Researchers have now reported Odkritje of calcium silicate perovskite as a diamond inclusion in a natural sample. The diamond was found in Orapa mine, Botswana decades ago and was purchased by a mineralogist of USA in 1987. The team of researchers had been studying the diamond for few years for any entrapped deep-Zemlja mineralna.
Raziskovalna skupina pod vodstvom Oliverja Tschaunerja je uporabila sinhrotronsko rentgensko difrakcijo za preučevanje notranje strukture neskončno majhnih temnih pik v diamantu, ki naj bi bil perovskit iz spodnje plasti plašča, in je lahko našla dokončne dokaze o strukturno ohranjenem kubičnem CaSiO3-perovskitu. tam2.
Further structural and chemical studies indicated that the mineral had large amounts of trapped potassium implying that this perovskite could host three of the major heat-producing elements (uranium and thorium were previously known) which influence heat generation in Zemljin interior. They named the mineral “davemaoite” (after geophysicist Ho-kwang “Dave” Mao) which was approved as a new natural mineral. The researchers think that the mineral may have originated from lower mantle layer between 650 and 900 km deep below the Earth’s surface 3,4.
Presenetljivo je CaSiO3 perovskite was reported to be discovered in a deep-Earth diamond from South Africa in 2018 however the research team had not claimed official discoveryhttps://www.scientificeuropean.co.uk/sciences/biology/discovery-of-nitrogen-fixing-cell-organelle-nitroplast-in-a-eukaryotic-algae/ of a new mineral 5.
To odkritje bi v povezavi z nadaljnjimi odkritji več mineralov v prihodnosti moralo obogatiti razumevanje evolucije Zemljinega plašča.
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Reference:
- Zhang Z., sod 2021. Toplotna prevodnost CaSiO3 perovskit v pogojih nižjega plašča. Physical Review B. Letnik 104, številka 18 – 1. Objavljeno 4. novembra 2021. DOI: https://doi.org/10.1103/PhysRevB.104.184101
- Fei, Y. 2021. Perovskit pridobljen iz spodnjega plašča, Znanost. Objavljeno 11. novembra 2021. Letnik 374, številka 6569, str. 820-821. Znanost (2021). DOI: https://doi.org/10.1126/science.abm4742
- Tschauner, O. sod. Odkritje davemaoita, CaSiO3-perovskita, kot minerala iz spodnjega plašča. znanost. 11. november 2021. letnik 374, številka 6569 str. 891-894. DOI: https://doi.org/10.1126/science.abl8568
- Univerza v Nevadi 2021. Novice – Kratka raziskava: v naravi odkrit prvi notranji zemeljski mineral. [Objavljeno 15. novembra 2021. Dostopno na spletu na https://www.unlv.edu/news/release/research-brief-first-ever-interior-earth-mineral-discovered-nature
- Nestola, F., Korolev, N., Kopylova, M. sod. CaSiO3 perovskit v diamantu kaže na recikliranje oceanske skorje v spodnji plašč. Narava 555, 237–241 (2018). https://doi.org/10.1038/nature25972
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