Genetic linkage of corundum plagioclasites–kyshtymites and miaskites of the Ilmenogorsky–Vishnevogorsky complex, South Urals, Russia: new Rb–Sr and Sm–Nd isotopic, geochemical and mineralogical data

Filina, M. I.; Sorokina, E. S.; Rassomakhin, M.A.; Kononkova, N. N.; Kostitsyn, Yu. A.; Somsikova, A. V.

doi:10.31857/s0016-7525647742-749

Cited by 1 publication

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References 7 publications

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“…Figure S5. Diagram εSr (T) vs. εNd (T) for kyshtimte and miascite of the Ilmenogorsky-Vishnevogorsky complex modified after [18,25], the diagram shows mantle reservoirs DMM, HIMU, EM1, EM2, MORB and OBI [65].…”

Section: Discussionmentioning

confidence: 99%

“…% in kyshtymites and up to 22.76 wt. % in miascites [25]). Moreover, these rocks have similar accessory minerals (i.e., Y-bearing phases, apatite group minerals, and monazite-(Ce) [49]).…”

Section: Genetic Models Of Corundum Anorthosites-kyshtymitesmentioning

confidence: 99%

“…At the beginning of the 20th century, the studied vein of kyshtymites of a lenticular body ( Figure 2) was explored from the surface by quarry extended currently to the depth of about 3-4 m. The meta-ultramafic host rocks (initial orthopyroxenites) were composed mainly of enstatite, which undergone metasomatism (serpentinization). The reaction rim with a thickness of 10-25 cm consisting of chrysotile-asbestos was detected at the contact of the meta-ultramafic host rock with the kyshtymites [25]. nepheline (20-30 wt.…”

Section: Geological Settingmentioning

confidence: 99%

“…Our previous studies have shown a possible genetic link between kyshtymites (corundum anorthosites), miascites (nepheline syenites), and carbonatites of the Ilmenogorsky-Vishnevogorsky complex [25]: similar REE patterns, i.e., enrichment of LREE compared to HREE ( Figure 13); anomalies in U, Nb, P;, Sr, and Ti ( Figure S3); moderate and highly fractionated distributions of REE (La/Yb) N = 4.20-48.12, and a small Eu maximum (Eu/Eu* = 1.02-1.32). Both miascites and kyshtymites are extremely enriched in Al 2 O 3 (up to 42.94 wt.…”

Section: Genetic Models Of Corundum Anorthosites-kyshtymitesmentioning

confidence: 99%

“…However, the genesis of the contact zone is difficult to reconstruct since there is no clear evidence for a magmatic contact and there is no indication for any metasomatic zonation. Kyshtymites demonstrate Rb-Sr and Sm-Nd isotopic signatures ( 87 Sr/ 86 Sr of 0.70637-0.706936 and εNd from −5.3 to −10.7) corresponding to the signature of the low-crustal material [25], whereas miascites and carbonatites show mantle-derived values [18]. The data lie on the miascites-carbonatites trend of the Ilmenogorsky-Vishnevogorsky complex and show increasing contribution from the crust ( Figure S5).…”

Section: Magmatic Vs Metamorphic Origin Of Kyshtymitesmentioning

confidence: 99%

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Corundum Anorthosites-Kyshtymites from the South Urals, Russia: A Combined Mineralogical, Geochemical, and U-Pb Zircon Geochronological Study

et al. 2019

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Kyshtymites are the unique corundum-blue sapphire-bearing variety of anorthosites of debatable geological origin found in the Ilmenogorsky-Vishnevogorsky complex (IVC) in the South Urals, Russia. Their mineral association includes corundum-sapphire, plagioclase (An61–93), muscovite, clinochlore, and clinozoisite. Zircon, churchite-(Y), monazite-(Ce), and apatite group minerals are found as accessory phases. Besides, churchite-(Y) and zircon are also identified as syngenetic solid inclusions within the sapphires. In situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb zircon geochronology showed the ages at about 290–330 Ma linked to the Hercynian orogeny in IVC. These ages are close to those of the syenitic and carbonatitic magmas of the IVC, pointing to their syngenetic origin, which is in agreement with the trace element geochemistry of the zircons demonstrating clear magmatic signature. However, the trace element composition of sapphires shows mostly metamorphic signature with metasomatic overprints in contrast to the geochemistry of zircons. The reason for this discrepancy can be the fact that the discrimination diagrams for sapphires are not as universal as assumed. Hence, they cannot provide an unambiguous determination of sapphire origin. If it is true and zircons can be used as traces of anorthosite genesis, then it can be suggested that kyshtymites are formed in a magmatic process at 440–420 Ma ago, most probably as plagioclase cumulates in a magma chamber. This cumulate rock was affected by a second magmatic event at 290–330 Ma as recorded in zircon and sapphire zoning. On the other hand, Ti-in-zircon thermometer indicates that processes operated at relatively lower temperature (<900 °C), which is not enough to re-melt the anorthosites. Hence, zircons in kyshtymites can be magmatic but inherited from another rock, which was re-worked during metamorphism. The most probable candidate for the anorthosite protolith is carbonatites assuming that metamorphic fluids could likely leave Al- and Si-rich residue, but removed Ca and CO2. Further, Si is consumed by the silicification of ultramafic host rocks. However, kyshtymites do not show clear evidence of pronounced metasomatic zonation and evidence for large volume changes due to metamorphic alteration of carbonatites. Thus, the obtained data still do not allow for univocal reconstruction of the kyshtymite origin and further investigations are required.

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Section: Discussionmentioning

confidence: 99%

“…% in kyshtymites and up to 22.76 wt. % in miascites [25]). Moreover, these rocks have similar accessory minerals (i.e., Y-bearing phases, apatite group minerals, and monazite-(Ce) [49]).…”

Section: Genetic Models Of Corundum Anorthosites-kyshtymitesmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Genetic Models Of Corundum Anorthosites-kyshtymitesmentioning

confidence: 99%

Section: Magmatic Vs Metamorphic Origin Of Kyshtymitesmentioning

confidence: 99%

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