Kimberlites and megacrystic suite: Isotope-geochemical studies

Kostrovitsky, Sergey; Solov’eva, L. V.; Yakovlev, D. A.; Suvorova, L. F.; Sandimirova, G. P.; Травин, А. В.; Yudin, D. S.

doi:10.1134/s0869591113020057

Cited by 22 publications

(8 citation statements)

References 26 publications

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“…Recent U-Pb perovskite and macrocrystic-zircon age determinations for six other kimberlite pipes from the Upper Muna field gave a narrow interval of kimberlite magmatism from 367 to 345 Ma [2,47,[51][52][53], corresponding to Late Devonian-Early Carboniferous. The emplacement age of KM is estimated as 334-382 Ma based on bulk groundmass K-Ar of kimberlite breccia [42,54]; Rb-Sr ages of phlogopite megacrysts from the pipe yielded 400-402 Ma [55]. These data are generally consistent with the Late Devonian-Early Carboniferous age of the Upper Muna field.…”

Section: Geological Settingmentioning

confidence: 72%

Thermal State, Thickness, and Composition of the Lithospheric Mantle beneath the Upper Muna Kimberlite Field (Siberian Craton) Constrained by Clinopyroxene Xenocrysts and Comparison with Daldyn and Mirny Fields

et al. 2020

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To gain better insight into the thermal state and composition of the lithospheric mantle beneath the Upper Muna kimberlite field (Siberian craton), a suite of 323 clinopyroxene xenocrysts and 10 mantle xenoliths from the Komsomolskaya-Magnitnaya (KM) pipe have been studied. We selected 188 clinopyroxene grains suitable for precise pressure (P)-temperature (T) estimation using single-clinopyroxene thermobarometry. The majority of P-T points lie along a narrow, elongated field in P-T space with a cluster of high-T and high-P points above 1300 °C, which deviates from the main P-T trend. The latter points may record a thermal event associated with kimberlite magmatism (a “stepped” or “kinked” geotherm). In order to eliminate these factors, the steady-state mantle paleogeotherm for the KM pipe at the time of initiation of kimberlite magmatism (Late Devonian–Early Carboniferous) was constrained by numerical fitting of P-T points below T = 1200 °C. The obtained mantle paleogeotherm is similar to the one from the nearby Novinka pipe, corresponding to a ~34–35 mW/m2 surface heat flux, 225–230 km lithospheric thickness, and 110–120 thick “diamond window” for the Upper Muna field. Coarse peridotite xenoliths are consistent in their P-T estimates with the steady-state mantle paleogeotherm derived from clinopyroxene xenocrysts, whereas porphyroclastic ones plot within the cluster of high-T and high-P clinopyroxene xenocrysts. Discrimination using Cr2O3 demonstrates that peridotitic clinopyroxene xenocrysts are prevalent (89%) among all studied 323 xenocrysts, suggesting that the Upper Muna mantle is predominantly composed of peridotites. Clinopyroxene-poor or -free peridotitic rocks such as harzburgites and dunites may be evident at depths of 140–180 km in the Upper Muna mantle. Judging solely from the thermal considerations and the thickness of the lithosphere, the KM and Novinka pipes should have excellent diamond potential. However, all pipes in the Upper Muna field have low diamond grades (<0.9, in carats/ton), although the lithosphere thickness is almost similar to the values obtained for the high-grade Udachnaya and Mir pipes from the Daldyn and Mirny fields, respectively. Therefore, other factors have affected the diamond grade of the Upper Muna kimberlite field.

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Section: Geological Settingmentioning

confidence: 72%

Thermal State, Thickness, and Composition of the Lithospheric Mantle beneath the Upper Muna Kimberlite Field (Siberian Craton) Constrained by Clinopyroxene Xenocrysts and Comparison with Daldyn and Mirny Fields

et al. 2020

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“…The emplacement age of the KM pipe is roughly estimated as 334-382 Ma based on the bulk groundmass K-Ar data of kimberlite breccia [43,44]. The Rb-Sr ages of phlogopite megacrysts from the pipe yielded 400-402 Ma [45].…”

Section: Geological Settingmentioning

confidence: 99%

Oxidation State of the Lithospheric Mantle Beneath Komsomolskaya–Magnitnaya Kimberlite Pipe, Upper Muna Field, Siberian Craton

et al. 2020

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The oxidation state of the mantle plays an important role in many chemical and physical processes, including magma genesis, the speciation of volatiles, metasomatism and the evolution of the Earth’s atmosphere. We report the first data on the redox state of the subcontinental lithospheric mantle (SCLM) beneath the Komsomolskaya–Magnitnaya kimberlite pipe (KM), Upper Muna field, central Siberian craton. The oxygen fugacity of the KM peridotites ranges from −2.6 to 0.3 logarithmic units relative to the fayalite–magnetite–quartz buffer (∆logfO2 (FMQ)) at depths of 120–220 km. The enriched KM peridotites are more oxidized (−1.0–0.3 ∆logfO2 (FMQ)) than the depleted ones (from −1.4 to −2.6 ∆logfO2 (FMQ)). The oxygen fugacity of some enriched samples may reflect equilibrium with carbonate or carbonate-bearing melts at depths >170 km. A comparison of well-studied coeval Udachnaya and KM peridotites revealed similar redox conditions in the SCLM of the Siberian craton beneath these pipes. Nevertheless, Udachnaya peridotites show wider variations in oxygen fugacity (−4.95–0.23 ∆logfO2 (FMQ)). This indicates the presence of more reduced mantle domains in the Udachnaya SCLM. In turn, the established difference in the redox conditions is a good explanation for the lower amounts of resorbed diamonds in the Udachnaya pipe (12%) in comparison with the KM kimberlites (33%). The obtained results advocate a lateral heterogeneity in the oxidation state of the Siberian SCLM.

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“…In the Siberian Platform, zircon xenocrysts derived from crustal material originate predominantly from granulite xenoliths in the lower crust of the Siberian Craton (Buzlukova et al, 2004;Neymark et al, 1992;Rosen et al, 2002;Shatsky et al, 1990). Favoured by the physical stability and chemical and thermal resistance of zircon, such xenocrysts may yield a wealth of information on their primary rocks, and the milieu of conditions of kimberlite-magma formation (Koreshkova et al, 2009;Kostrovitsky et al, 2013;Vladykin and Lepekhina, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Recent analyses yielded 170-150 Ma for Kuoika kimberlites, and two formation intervals for Ary-Mastakh kimberlites (Sun et al, 2014). Almost all pipes of the Kuoika and Ary-Mastakh fields were found to contain notable amounts of zircon xenocrysts in their heavy mineral fractions (Kostrovitsky, 1986;Kostrovitsky et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Retention of radiation damage in zircon xenocrysts from kimberlites, Northern Yakutia

Nasdala

Kostrovitsky

Kennedy

et al. 2014

Lithos

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We have studied zircon xenocrysts from Mesozoic kimberlites from the Kuoika and Ary-Mastakh fields in Northern Yakutia. Zircon xenocrysts are assumed to originate from crustal rocks. Our SHRIMP (Sensitive High mass Resolution Ion MicroProbe) analyses yielded predominantly concordant U-Th-Pb ages (up to~3570 Ma; Paleoarchean) that clearly predate kimberlite formation. The general U-Th-Pb concordance observed excludes notable disturbance of the zircon xenocrysts U-Th-Pb isotope system during kimberlite ascent and emplacement. In addition, zircon xenocrysts were found to be significantly more radiation-damaged than would correspond to damage accumulation only since the time of kimberlite formation. This observation first indicates that zircon crystals were sampled by the kimberlite magma at comparably shallow depths not exceeding 10-12 km. If, in contrast, zircon crystals originated from deeper levels of the Earth's crust, they would have been exposed to temperatures of 250-300°C or more. This in turn would have caused long-term thermal annealing of the radiation damage, which was however not observed in our study. Second, our observation contradicts the hypothesis that high temperatures experienced by zircon xenocrysts during kimberlite ascent will cause notable structural reconstitution by short-term thermal annealing. Consequently, zircon crystals cannot have spent more than a few hours at temperatures exceeding ca. 700-800°C, or more than a few days at temperatures exceeding ca. 500-600°C. This in turn suggests that (i) temperatures of the ascending kimberlite magmas were rather moderate, and (ii) kimberlite ascent is a comparably short process followed by rapid cooling.

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Kimberlites and megacrystic suite: Isotope-geochemical studies

Cited by 22 publications

References 26 publications

Thermal State, Thickness, and Composition of the Lithospheric Mantle beneath the Upper Muna Kimberlite Field (Siberian Craton) Constrained by Clinopyroxene Xenocrysts and Comparison with Daldyn and Mirny Fields

Thermal State, Thickness, and Composition of the Lithospheric Mantle beneath the Upper Muna Kimberlite Field (Siberian Craton) Constrained by Clinopyroxene Xenocrysts and Comparison with Daldyn and Mirny Fields

Oxidation State of the Lithospheric Mantle Beneath Komsomolskaya–Magnitnaya Kimberlite Pipe, Upper Muna Field, Siberian Craton

Retention of radiation damage in zircon xenocrysts from kimberlites, Northern Yakutia

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