The mineral Davemaoite (CaSiO3-perovskite, the third most abundant mineral in lower mantle layer of Bumi interior) has been discovered on the surface of the Bumi 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 Bumi under extremely high temperature and pressure conditions. This first-ever discovery of interior bumi mineral in nature is important to geology for better understanding of dynamics of deep Bumi.
Perovskite ialah mineral yang terdiri daripada kalsium titanium oksida (CaTiO3). Mana-mana mineral lain yang mempunyai struktur kristal yang serupa dipanggil perovskite. Ini menjadikan perovskit kelas sebatian yang mempunyai jenis struktur kristal yang sama seperti CaTiO3 (struktur perovskit).
Perovskit kalsium-silikat (CaSiO3-perovskite atau CaPv) adalah mineral penting kerana ia adalah mineral ketiga paling banyak1 (7% mengikut isipadu) dalam lapisan mantel bawah Bumi interior and plays a significant role in the heat dynamics of Bumi interior. To put things in perspective, of the three layers of Bumi, the mantle layer, between dense super-heated core and thin outer crust layer, makes up 84% of Bumi total volume while the lower mantle layer alone comprises 55 percent of the Bumi and extends from 670 and 2900 km in depth. The below table gives a snapshot view of place of perovskite in Bumi dalaman.
Jadual: Tempat lapisan kaya perovskit di pedalaman Bumi
Perovskites along with other minerals in the mantle layer play a key role in the dynamics of deep bumi 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 penemuan 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-Bumi galian.
Pasukan penyelidik yang diketuai oleh Oliver Tschauner menggunakan pembelauan sinar-x synchrotron untuk mengkaji struktur dalaman bintik gelap yang sangat kecil dalam berlian yang dianggap sebagai perovskit dari lapisan mantel bawah dan dapat mencari bukti muktamad bagi CaSiO3-perovskite padu terpelihara secara struktur. di sana2.
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 Bumi 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.
Yang menghairankan, 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.
Penemuan ini, bersempena dengan penemuan lebih banyak mineral pada masa hadapan, seharusnya memperkaya pemahaman tentang evolusi mantel Bumi.
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Rujukan:
- Zhang Z., et al 2021. Kekonduksian terma CaSiO3 perovskit pada keadaan mantel yang lebih rendah. Kajian Fizikal B. Jilid 104, Isu 18 – 1. Diterbitkan 4 November 2021. DOI: https://doi.org/10.1103/PhysRevB.104.184101
- Fei,Y. 2021. Perovskite diambil dari mantel bawah, Sains. Diterbitkan 11 Nov 2021. Jld 374, Keluaran 6569 ms 820-821. Sains (2021). DOI: https://doi.org/10.1126/science.abm4742
- Tschauner, O. et al. Penemuan davemaoite, CaSiO3-perovskite, sebagai mineral dari mantel bawah. Sains. 11 Nov 2021. Jld 374, Keluaran 6569 ms 891-894. DOI: https://doi.org/10.1126/science.abl8568
- Universiti Nevada 2021. Berita – Penyelidikan Secara Ringkas: Mineral Bumi Dalaman Pertama Ditemui di Alam Semula Jadi. [Disiarkan pada 15 November 2021. Boleh didapati dalam talian di https://www.unlv.edu/news/release/research-brief-first-ever-interior-earth-mineral-discovered-nature
- Nestola, F., Korolev, N., Kopylova, M. et al. CaSiO3 perovskite dalam berlian menunjukkan kitar semula kerak lautan ke dalam mantel bawah. Alam 555, 237–241 (2018). https://doi.org/10.1038/nature25972
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