Research output: Contribution to journal › Article › peer-review
Retrograde phases of former bridgmanite inclusions in superdeep diamonds. / Zedgenizov, Dmitry; Kagi, Hirioyuki; Ohtani, Eiji et al.
In: Lithos, Vol. 370-371, 105659, 01.10.2020.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Retrograde phases of former bridgmanite inclusions in superdeep diamonds
AU - Zedgenizov, Dmitry
AU - Kagi, Hirioyuki
AU - Ohtani, Eiji
AU - Tsujimori, Tatsuki
AU - Komatsu, Kazuki
N1 - Publisher Copyright: © 2020 Elsevier B.V. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - (Mg,Fe)SiO3 bridgmanite is the dominant phase in the lower mantle; however no naturally occurring samples had ever been found in terrestrial samples as it undergoes retrograde transformation to a pyroxene-type structure. To identify retrograde phases of former bridgmanite single-phase and composite inclusions of (Mg,Fe)SiO3 in a series of superdeep diamonds have been examined with electron microscopy, electron microprobe, Raman spectroscopy and X-ray diffraction techniques. Our study revealed that (Mg,Fe)SiO3 inclusions are represented by orthopyroxene. Orthopyroxenes in single-phase and composite inclusions inherit initial chemical composition of bridgmanites, including a high Al and low Ni contents. In composite inclusions they coexist with jeffbenite (ex-TAPP) and olivine. The bulk compositions of these composite inclusions are rich in Al, Ti, and Fe, which are similar but not fully resembling Al-rich bridgmanite produced in experiments on the MORB composition. The retrograde origin of composite inclusions due to decomposition of Al-rich bridgmanite may be doubtful because each of observed minerals may represent coexisting HP phases, i.e. bridgmanite or ringwoodite.
AB - (Mg,Fe)SiO3 bridgmanite is the dominant phase in the lower mantle; however no naturally occurring samples had ever been found in terrestrial samples as it undergoes retrograde transformation to a pyroxene-type structure. To identify retrograde phases of former bridgmanite single-phase and composite inclusions of (Mg,Fe)SiO3 in a series of superdeep diamonds have been examined with electron microscopy, electron microprobe, Raman spectroscopy and X-ray diffraction techniques. Our study revealed that (Mg,Fe)SiO3 inclusions are represented by orthopyroxene. Orthopyroxenes in single-phase and composite inclusions inherit initial chemical composition of bridgmanites, including a high Al and low Ni contents. In composite inclusions they coexist with jeffbenite (ex-TAPP) and olivine. The bulk compositions of these composite inclusions are rich in Al, Ti, and Fe, which are similar but not fully resembling Al-rich bridgmanite produced in experiments on the MORB composition. The retrograde origin of composite inclusions due to decomposition of Al-rich bridgmanite may be doubtful because each of observed minerals may represent coexisting HP phases, i.e. bridgmanite or ringwoodite.
KW - Bridgmanite
KW - Jeffbenite
KW - Lower mantle
KW - Superdeep diamonds
KW - MATO-GROSSO
KW - JUINA AREA
KW - ALMANDINE-PYROPE PHASE
KW - DEEP MANTLE
KW - HETEROGENEITY
KW - LOWER-MANTLE
KW - MINERAL INCLUSIONS
KW - SUBDUCTED BASALTIC CRUST
KW - PEROVSKITE
KW - TRANSITIONS
UR - http://www.scopus.com/inward/record.url?scp=85087308164&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2020.105659
DO - 10.1016/j.lithos.2020.105659
M3 - Article
AN - SCOPUS:85087308164
VL - 370-371
JO - Lithos
JF - Lithos
SN - 0024-4937
M1 - 105659
ER -
ID: 24633077