METASOMATIC EVENTS IN THE LITHOSPHERIC MANTLE BENEATH THE V. GRIB KIMBERLITE PIPE (Arkhangelsk diamondiferous province, Russia)

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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Mantle xenoliths from the Komsomolskaya-magnitnaya kimberlite pipe (Upper Muna kimberlite field, Siberian Craton) Evidences of the composition of the SCLM

10.5194/egusphere-egu2020-12666 ◽

2020 ◽

Author(s):

Igor Iakovlev ◽

Vladimir Malkovets ◽

Anastasiya Gibsher

Keyword(s):

Rare Earth ◽

Lithospheric Mantle ◽

Kimberlite Pipe ◽

Mantle Xenoliths ◽

Coarse Grained ◽

Peridotite Xenoliths ◽

Rare Earth Element Distribution ◽

Group 2 ◽

Kimberlite Field ◽

Group 1

Peridotite xenoliths from kimberlites provide important information about the composition, structure and thermal regime of the lithospheric mantle of ancient cratons. In this paper, we present the results of mineralogical studies of peridotite xenoliths from kimberlites of the Upper Muna field. The Middle Paleozoic (D3-C1) high diamondiferous kimberlite pipe Komsomolskaya-Magnitnaya was chosen as the object of research.We studied a collection of 180 peridotite xenoliths of the Komsomolskaya-Magnitnaya pipe, of which 104 belong to dunite-harzburgite paragenesis, 74 to lherzolite and 4 websterites.The chemical composition of basic minerals from xenoliths was determined using JEOL JXA-8100 electron microprobe. Chemical analysis of xenolith garnet compositions was also performed using the Agilent 7700cs LAM-ICPMS method.Based on a study of the collection of deep xenoliths, we found that the lithospheric mantle under the Upper Muna kimberlite field is composed mainly of garnet-bearing and chromite-bearing dunites and harzburgites, as well as coarse grained garnet lherzolites.The olivine Mg# varies from 88.4 to 94.12%, while the magnitude of the majority (60%) of the studied olivines does not exceed 92% and 30% of olivines have Mg#> 93%. We identified 2 groups according Mg # olivine from xenoliths. Group 1 with &#8220;typical&#8221; mantle values Mg # 88.39-90.70mol%, it is characteristic for fertile peridotites. And group 2 with highly depleted compositions Mg # 91.20-94.12mol%. A high proportion (~ 30%) of peridotites with high magnesian olivines (Mg #> 93 mol%) indicates the presence of a block of highly depleted rocks in the lithospheric mantle beneath the Upper Muna kimberilte field.According to the distribution of calcium and chromium in garnets, 10 out of 35 studied garnets from xenoliths belong to diamondiferous harzburgite-dunite paragenesis. According to the distribution of rare-earth elements, we distinguish two groups of garnets. Group 1 includes garnets with typical rare earth element distribution spectra typical for fertile garnets, and group 2 garnets with S-shaped spectra that are characteristic of garnet mineral inclusions in diamonds. We noted a high proportion of garnets with S-shaped REE distribution spectra (~ 66%), as well as garnets belonging to the harzburgite-dunite paragenesis, it indicate a moderate role of metasomatic changes associated with silicate melts, as well as interaction with carbonatite melts enriched in LREE.Using clinopyroxene monomineral thermobarometry, we found that the &#8220;diamond&#8221; window in the lithosphere mantle beneath the Upper Muna field, at the time of kimberlite magmatism (~ 360 Ma) was significant (about 95 km) and was located at a depth of 125 to 220 km.The study was supported by the Russian Science Foundation (grant No. 18-17-00249).

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Sulfur isotopic compositions of the lithospheric mantle sulfides from the Udachnaya pipe (Yakutia)

10.5194/egusphere-egu2020-21171 ◽

2020 ◽

Author(s):

Olga Ilyina ◽

Alexey Agashev ◽

Bertrand Moine

Keyword(s):

Lithospheric Mantle ◽

Sulfur Isotopes ◽

Basic Research ◽

Kimberlite Pipe ◽

West African ◽

Udachnaya Pipe ◽

Depleted Mantle ◽

Isotope Ratio Mass Spectrometer ◽

Isotope Study

Sulfide inclusions in Neoproterozoic West African diamonds have revealed mass-independently fractionated sulfur isotopes in them [Smit et.al., 2019]. This feature is a sign of Archean surface changes traced in the mantle. Here we present an S isotope study of the unique fresh mantle deep-seated peridotites, eclogites and pyroxenites with rare or without any secondary alterations from the Udachnaya-East pipe. This research will give better understanding the role of subduction in the formation of the lithospheric mantle under the Siberian craton. Sulfur isotopes (34S/32S which is denoted as &#948;34S) were measured in the sulfides from eclogites, peridotites and pyroxenites using an Isoprime isotope ratio mass spectrometer (IRMS) with classic configuration with 4 collectors. The sulfides from eclogites are pyrrotite, pentlandites and chalcopyrites. They have &#948;34S values from +0,67 to +3,08 per mil (&#8240;). Sulfides in peridotites are pyrrotite-pentlandite-chalcopyrites assemblages and they have &#948;34S values from +0,22 to +3,55 &#8240;. These &#948;34S values from eclogites and peridotites are broadly overlap with the field for depleted mantle and chondrites (-1,9 to +0,35&#8240;) [Labidi et.al., 2013; 2014]. Sulfides from pyroxenites are pyrrotite and they have &#948;34S values from -3,62 to +1,49 &#8240;. These &#948;34S values have a wider range than the estimates for depleted mantle. The &#948;34S values in our samples are close to those in the depleted mantle, but still have deviation from it and do not fractionated. Our data did not detect mass-independently fractionated sulfur isotopes in the mantle samples from the Udachnaya pipe. Thus subduction of the earth&#8217;s crust did not play role in the values of sulfur isotopes of the lithospheric mantle sampled by Udachnaya kimberlite pipe. The source of sulfur in these rocks probably was the astenospheric mantle.References<ol><li>Smit et. al., 2019</li> <li>Labidi et. al., 2013; 2014</li> </ol>This study was supported by the Russian Foundation for Basic Research &#8470; 18-05-70064

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Petrology of the Yubileynaya kimberlite pipe: application to the variation of kimberlites composition with the depth

10.5194/egusphere-egu2020-8541 ◽

2020 ◽

Author(s):

Zdislav Spetsius ◽

Alexander Ivanov

Keyword(s):

Lithospheric Mantle ◽

Original Data ◽

Kimberlite Pipe ◽

Essential Difference ◽

Mineral Phases ◽

Diamond Crystals ◽

Essential Input ◽

Indicator Minerals ◽

Different Levels ◽

Large Diamond

In this paper are summarized investigation results on the chemistry, petrography and mineralogy of kimberlitic rocks of the upper and deep levels of the Yubileynaya pipe. There are given original data on mineral phases contents in kimberlite ground mass,distribution of indicator minerals and olivine and its pseudomorphoses as well as autoliths (pyroclasts) in kimberlite drill cores of different levels (-)280 &#8211; (-)680m.Petrologic evidence suggest that for the kimberlites of the Yubileynaya pipe is characteristic the prevalence garnet association of indicator minerals with the relatively low their whole content, predominance oflherzolitic pyropes, low content of titanium garnets, two types of ilmenites and chromespinelides.The particularity of this pipe is the presence, both eclogite and garnet websterite xenoliths as well as their diamondiferous varieties. This evidence is confirmed also by the composition of the paragenic associations of indicator minerals that is indicative of essential difference of lithospheric mantle under this given pipe in contrast with nearby kimberlitic pipes. It is possible to speculate that these peculiarities are specific for the kimberlite pipes of the middle diamond productivity.Results of the garnets chemistry and the data of the distribution of eclogitic and ultramafic garnets in kimberlite concentrate of this pipe with the taking in account quantity of garnet variety potentially associated with diamonds suggest anincreased prevalence of eclogitic garnets among indicator minerals. This allowed making a statement about essential input of eclogitic paragenesis diamonds in the whole diamond production of this pipe. In our opinion these peculiarities also determine the increased content of large diamond crystals in kimberlites of the Yubileynaya pipe.&#160;&#160;&#160;&#160;

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Coarse peridotite xenoliths of Udachnaya kimberlite pipe, Yakutia: garnetization of peridotites of the central Siberian platform lithospheric mantle

International Kimberlite Conference Extended Abstracts: 2003 ◽

10.29173/ikc3118 ◽

2019 ◽

Keyword(s):

Siberian Platform ◽

Lithospheric Mantle ◽

Kimberlite Pipe ◽

Peridotite Xenoliths

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Origin of water in the mantle eclogites from the V. Grib kimberlite pipe, NW Russia

10.5194/egusphere-egu2020-298 ◽

2020 ◽

Author(s):

Elena Shchukina ◽

Mariya Kolesnichenko ◽

Elena Malygina ◽

Aleksey Agashev ◽

Dmitry Zedgenizov

Keyword(s):

Water Content ◽

Lithospheric Mantle ◽

Water Saturation ◽

Kimberlite Pipe ◽

Mantle Xenoliths ◽

Coarse Grained ◽

Infrared Spectrometry ◽

Tetrahedral Position ◽

Equilibrium Pressure ◽

Hydrous Minerals

The study of water content in the rock-forming minerals of mantle xenoliths, entrained in kimberlites, provides information about the water storage of the lithospheric mantle of ancient cratons. In mantle xenoliths, the water can be identified as several percentages by weight in hydrous minerals (e.g. phlogopite and amphibole) and up to 2000&#160;ppm in nominally anhydrous minerals (NAMs; olivine, pyroxene, and garnet). Since the hydrous phases occur sporadically in mantle xenoliths, their NAMs reserve the main water content in the lithospheric mantle.The water content in garnet and clinopyroxene from the mantle eclogites from the V.&#160;Grib kimberlite pipe (Arkhangelsk Diamondiferous Province, NW Russia) was analysed using Fourier transform infrared spectrometry. The studied samples are coarse-grained (grain sizes from 0.5&#8211;1.3&#160;cm) bimineralic (garnet and clinopyroxene) eclogites with accessories of phlogopite, ilmenite, and rutile. The samples include high-MgO (three samples) and low-MgO (six samples) groups. The eclogites are interpreted as metamorphosed fragments of oceanic crustal rocks (basalt and gabbro for low-MgO eclogites and picritic/MgO basalt and troctolite for high-MgO eclogites) emplaced into the lithospheric mantle via a subduction event at 2.8 Ga. Based on pressure-temperature estimates (44&#8211;78 kbar; 940&#176;C&#8211;1275&#176;C), eclogites were transported by kimberlite from the range of depths of about 160 to >200&#160;km.The results show that all clinopyroxene grains contain structural water in the amount of 39 to 111&#160;ppm, whereas only two garnet samples have detectable water in the amount of 211 and 337&#160;ppm. The water incorporation into the clinopyroxene is mostly linked to M2 sites and aluminium in the tetrahedral position. The water content in the majority of eclogite clinopyroxene positively correlates with the jadeite component. The low-MgO eclogites with oceanic gabbro precursor contain significantly higher water concentrations in omphacites (70&#8211;111&#160;ppm) and whole rock (35&#8211;224&#160;ppm) compared to those with the oceanic basalt protolith (49&#8211;73&#160;ppm and 20&#8211;36&#160;ppm, respectively). The proposed observation is also confirmed by the negative correlations of water content in clinopyroxenes with a La/Yb ratio in clinopyroxene and WR water content versus the WR Yb concentration. The equilibrium pressure could be an additional factor that controls the water incorporation into the clinopyroxene of the high-MgO group.Our results show that water content in the V.&#160;Grib pipe eclogites is not from the mantle metasomatism and therefore can reflect the water saturation of their protoliths. The eclogite portion of the lithospheric mantle beneath the V.&#160;Grib kimberlite pipe can have at least twice the water enrichment compared to peridotite sections, indicating that an Archean subduction event played an essential role in the water saturation of the mantle.This work was supported by the Russian Science Foundation under grant no. 16-17-10067

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Thermal perturbations in the lithospheric mantle as evidenced from P-T equilibrium conditions of xenoliths from the Udachnaya kimberlite pipe

Doklady Earth Sciences ◽

10.1134/s1028334x14010231 ◽

2014 ◽

Vol 454 (1) ◽

pp. 84-88 ◽

Cited By ~ 10

Author(s):

N. S. Tychkov ◽

A. M. Agashev ◽

E. V. Malygina ◽

E. I. Nikolenko ◽

N. P. Pokhilenko

Keyword(s):

Lithospheric Mantle ◽

Kimberlite Pipe ◽

Equilibrium Conditions ◽

Thermal Perturbations

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Origin of Water in Mantle Eclogites from the V. Grib Kimberlite Pipe, NW Russia

Lithosphere ◽

10.2113/2021/7866657 ◽

2021 ◽

Vol 2021 (1) ◽

Author(s):

Elena V. Agasheva ◽

Maria V. Kolesnichenko ◽

Elena V. Malygina ◽

Alexey M. Agashev ◽

Dmitry A. Zedgenizov

Keyword(s):

Fourier Transform ◽

Water Content ◽

Lithospheric Mantle ◽

Kimberlite Pipe ◽

Infrared Spectrometry ◽

Residual Water ◽

Fourier Transform Infrared Spectrometry ◽

Tetrahedral Position ◽

Structural Water ◽

Oceanic Basalt

Abstract The water content in the garnet and clinopyroxene in the mantle eclogites from the V. Grib kimberlite pipe (Arkhangelsk Diamondiferous Province, NW Russia) was analysed using Fourier transform infrared spectrometry. The results show that all clinopyroxene grains contained structural water at concentrations of 39 to 247 ppm, whereas two garnet samples contained detectable water at concentrations of 211 and 337 ppm. The low-MgO eclogites with oceanic gabbro precursors contained significantly higher water concentrations in the omphacites (70–247 ppm) and whole rock (35–224 ppm) compared to those with oceanic basalt protoliths (49–73 ppm and 20–36 ppm, respectively). The incorporation of water into the clinopyroxene may be associated with vacancies at the M2 site, Al in the tetrahedral position, and the elements that filled the M2 site (mostly Na and Ca). The highest water content in the omphacite was detected in a nonmetasomatised sample and was assumed to represent residual water that survived during subduction. Other eclogite samples showed signs of modal and/or cryptic metasomatism and contained less water in the omphacites compared to the nonmetasomatised sample. The water content was heterogeneous within the eclogite section of the sampled lithospheric mantle. The lack of distinct and uniform correlations between the indices of eclogite modification and their water content indicated that the saturation with water was disturbed during their residence within the lithospheric mantle.

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