A UNIQUE DIAMONDIFEROUS PERIDOTITE XENOLITH FROM THE UDACHNAYA KIMBERLITE PIPE (Yakutia): ROLE OF SUBDUCTION IN DIAMOND FORMATION

This paper describes the tectonic features of the Alakit-Markha kimberlite field, regional factors of kimberlite magmatism control in this area, structural and tectonic preconditions for kimberlite pipe prospecting. The paper highlights kimberlite pipe formation features and the role of tectonics in this process. The most promising areas are those related to low-amplitude negative structures (e.g. depressions), especially transverse low-amplitude complications of the opposite sign for the main plicative structure: for antiforms (elevations), these are saddle-shaped depressions, and antiform elevations are for synforms (depressions).

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Role of accelerated electrons in diamond formation processes during electron-assisted chemical vapor deposition

Diamond and Related Materials ◽

10.1016/0925-9635(94)90202-x ◽

1994 ◽

Vol 3 (4-6) ◽

pp. 452-456 ◽

Cited By ~ 6

Author(s):

H. Saitoh ◽

H. Mima ◽

T. Ishiguro ◽

Y. Ichinose

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Chemical Vapor ◽

Formation Processes ◽

Diamond Formation ◽

Accelerated Electrons

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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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FEATURES OF GARNET AND CLINOPYROXENE IN DIAMONDIFEROUS ECLOGITES FROM THE UDACHNAYA KIMBERLITE PIPE, YAKUTIA: METASOMATOSIS EVIDENCE

Ores and metals ◽

10.47765/0869-5997-2020-10027 ◽

2021 ◽

pp. 45-53

Author(s):

Zdzislaw Spetsius ◽

Ludmila Liskovaya ◽

Alexander Ivanov ◽

Irina Bogush

Keyword(s):

Partial Melting ◽

Kimberlite Pipe ◽

Diamond Formation ◽

Two Phase ◽

N Content ◽

Total N ◽

Garnet Composition ◽

Mantle Fluids ◽

Time Gap ◽

Multiple Stages

Mineralogy of diamondiferous eclogite xenolites showing metasomatosis evidence from the Udachnaya kimberlite pipe is discussed. The paper also reviews features of diamonds they contain, compositions of primary garnets and omphacites as well as alteration of structural and species compositions of original garnets and clinopyroxenes during metasomatosis. Based on pyrope structure update, two-phase garnet composition is suggested, which is mostly represented by complex pyrope associated with Ca-pyrope. In all samples, primary omphacite is replaced by another clinopyroxene variety depleted in Na2O, which is typical of partial melting products. Geothermometry results suggested that the eclogites formed within a temperature range of 1,000–1,2000 °C. Based on diamond morphology, data on total N content in diamonds and its aggregation, multiple stages of diamond formation in eclogites and the most probable growth of later diamond generations impacted by metasomatizing mantle fluids containing carbon are postulated. It is suggested that certain diamond formation stages probably had a time gap of several hundred million years.

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