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Enigmatic super-reduced phases in corundum from natural rocks : Possible contamination from artificial abrasive materials or metallurgical slags. / Litasov, Konstantin D.; Kagi, Hiroyuki; Bekker, Tatyana B.
In: Lithos, Vol. 340-341, 01.09.2019, p. 181-190.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Enigmatic super-reduced phases in corundum from natural rocks
T2 - Possible contamination from artificial abrasive materials or metallurgical slags
AU - Litasov, Konstantin D.
AU - Kagi, Hiroyuki
AU - Bekker, Tatyana B.
N1 - Publisher Copyright: © 2019
PY - 2019/9/1
Y1 - 2019/9/1
N2 - Recently a number of reports claimed enigmatic appearance of high-pressure and super-reduced minerals in ophiolitic chromitite and peridotite. Diamond, moissanite, various metal alloys, and native metals, carbides and nitrides were found in mineral separates from bulk rock probes of chromitite and peridotite from Tibet, Polar Ural and other localities. Similar findings of super-reduced phases were reported for pyroclastic rocks and alluvial deposits of Mt. Carmel in Israel. We performed the study of microinclusions in corundum grains from abrasive materials produced industrially in an electric arc furnace and found that they are very similar to microinclusions in corundum grains from natural samples. The key similar phases are Ti 3+ 4 Al 2 (Zr,Ti 4+ ) 4 O 11 carmeltazite, Ti 2 O 3 tistarite, TiN 1-x , TiC 1-x , Fe–Si and Fe-Si-Ti alloys, hibonite, grossite, anorthite, and residual feldspatic glass. Although some differences between abrasive corundum and corundum from Tibet and Mt. Carmel are obvious, the morphology of melt pockets and amount of mineralogical similarities is more than critical to suggest that they can be of the same origin. The additional possible source of corundum grains with super-reduced inclusions is various Al-bearing slags after aluminothermic reactions during steelmaking. Moreover, taking into account the spectacular similarity of diamonds from ophiolite with synthetic diamonds, we claim for a thorough reconsideration of ultrahigh-pressure and super-reduced phases in natural rocks and argue that we need to find criteria for discrimination between natural and artificial samples. One of the strongest criteria would be textural and structural features that clearly demonstrate the indigenous character of the host minerals.
AB - Recently a number of reports claimed enigmatic appearance of high-pressure and super-reduced minerals in ophiolitic chromitite and peridotite. Diamond, moissanite, various metal alloys, and native metals, carbides and nitrides were found in mineral separates from bulk rock probes of chromitite and peridotite from Tibet, Polar Ural and other localities. Similar findings of super-reduced phases were reported for pyroclastic rocks and alluvial deposits of Mt. Carmel in Israel. We performed the study of microinclusions in corundum grains from abrasive materials produced industrially in an electric arc furnace and found that they are very similar to microinclusions in corundum grains from natural samples. The key similar phases are Ti 3+ 4 Al 2 (Zr,Ti 4+ ) 4 O 11 carmeltazite, Ti 2 O 3 tistarite, TiN 1-x , TiC 1-x , Fe–Si and Fe-Si-Ti alloys, hibonite, grossite, anorthite, and residual feldspatic glass. Although some differences between abrasive corundum and corundum from Tibet and Mt. Carmel are obvious, the morphology of melt pockets and amount of mineralogical similarities is more than critical to suggest that they can be of the same origin. The additional possible source of corundum grains with super-reduced inclusions is various Al-bearing slags after aluminothermic reactions during steelmaking. Moreover, taking into account the spectacular similarity of diamonds from ophiolite with synthetic diamonds, we claim for a thorough reconsideration of ultrahigh-pressure and super-reduced phases in natural rocks and argue that we need to find criteria for discrimination between natural and artificial samples. One of the strongest criteria would be textural and structural features that clearly demonstrate the indigenous character of the host minerals.
KW - Abrasive
KW - Chromitite
KW - Corundum
KW - Fused alumina
KW - High-pressure
KW - Ophiolite
KW - Peridotite
KW - Subduction
KW - Super-reduced phases
KW - PODIFORM CHROMITITES
KW - ULTRAHIGH-PRESSURE
KW - CRYSTAL-STRUCTURE
KW - LUOBUSA OPHIOLITE
KW - DIAMOND-BEARING
KW - UPPER-MANTLE
KW - ORIGIN
KW - METAL-ALLOYS
KW - SUTURE ZONE
KW - UNUSUAL MINERALS
UR - http://www.scopus.com/inward/record.url?scp=85065904693&partnerID=8YFLogxK
U2 - 10.1016/j.lithos.2019.05.013
DO - 10.1016/j.lithos.2019.05.013
M3 - Article
AN - SCOPUS:85065904693
VL - 340-341
SP - 181
EP - 190
JO - Lithos
JF - Lithos
SN - 0024-4937
ER -
ID: 20164098