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New models of the structures and compositions of the large kimberlite pipes in Daldyn -Alakite region, Yakutia Igor Ashchepkov (1), Theodoros Ntaflos (2),

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Presentation on theme: "New models of the structures and compositions of the large kimberlite pipes in Daldyn -Alakite region, Yakutia Igor Ashchepkov (1), Theodoros Ntaflos (2),"— Presentation transcript:

1 New models of the structures and compositions of the large kimberlite pipes in Daldyn -Alakite region, Yakutia Igor Ashchepkov (1), Theodoros Ntaflos (2), Vladykin Nikolai (3), Igor Makovchuk (4), Zdislav Spetsius (4), Alla Logvinova (1), Gleb Shmarov (4), and Ravil Salikhov (4) (1) Institute of Geology and Mineralogy SB RAS, Geology, Novosibirsk, Russian Federation (2)UniversityofVienna,Austria,(3) Institute of Geocjemistry SB RAS ,Irkutsk,(4)ALROSA Stock Company,Mirny,Russia New xenoliths from Zarnitsa (27) Udachnaya (30) Komsomolskaya (74) and Sytykanskaya (49) pipe. In Zarnitsa several associations significant part of the xenoliths studied belong to the enriched Fe-Ti deformed peridotites,whicharetracedhotgeothermfrom7-6GPa.Duniteswithsub-calciumgarnetsarefromthecoldlower part together with diamond inclusions.. In GPa garnet harzburgites prevail some of them contain richterites, phlogopitesorIlm-Cpx-Amph-Phlveins.NeartheMohoboundary,variouspyroxenitesincludingAmph-bearing. Among the xenoliths, several metasomatic associations with amphiboles were found near Moho. Clinopyroxenes from peridotite xenoliths are enriched in REE, and some samples with inflections in Eu, Ce, possibly demonstrate the participation of the eclogite material. Cpx, which are low in REE, exhibit complex spectra with very low LREE and strong depletion in Ba and have minima of Zr and Ba and a low content of incompatible elements. Fe- enriched Ilm - Cpx create two branches and give very high-T conditions. TraceelementsforlowCrCpxshowsubparallelTREpatternsbutslightlycrossinginHREEwithoutanomaliesin Zr-Hf but with lower LILE and Nb-Ta. Eclogites mainly refer to the lower part of mantle section. Trace elements show Eu depressions and depletion in HFSE In Udachnaya we especially analyzed ultradepleted associations which sometimes contain pyroxenes refer to the cold branch in lithosphere base,. The garnets and Px show S- tyoe REE and low levels incompatible elements The Ilm bearing peridotites refer to the contact zones of the megacrystalline Ilm aggregates which sometimes include Cpx TRE for Cpx show the enriched HFSE and low in lithophiles, U, Th but high in lithophiles. New seriaes of eclogites belonh to quite different types and differ in REE patterns. Xenoliths from Komsomoslskaya pipe are quite different in the modal compositions from Gar dunites to Cpx enriched compositions most of them contain phlogopites but not in veins but mainly dissiminated type. Several Opx bearing harzburgites and pyroxenites were found referring to the upper SCLM part. SCLM near Moho is highly Fe- enriched.Middle part from 3.2 to 4.5 GPa is also higher in Cpx and refertillized, But the section from 5 to 6.5 it Fe-Ti enriched sometimes similar to porpyroblastic associations from Udachnaya but really deformed peridotites were not detected. The eclogitic associations refer to the two intervals 5.5 – 6.5GPa and 3.5 – 5GPa, the later are more Fe- rich. Trace elements for the peridotite Cpx are enriched in the LREE and high in La/yb rations and high in LiLE higher than those from Sytykanskaya pipe. High amount of new Opx-Ol beraing and xenoliths allowed to detalise the structures of the manle column Most of association refer to the low–T 35 mw/m2 geotherm/ But the high–T associations for the branch 5.5-7GPa. RFBR grant (1) Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences, (2) Novosibirsk State University, (3) Nikolaev Institute of Inorganic Chemistry Siberian Branch Russian Academy of Sciences

2 40Ar/39Ar ages for the mica in xenoliths and xenocrysts
Alakite field Daldyn field Udachnaya Udachnaya Удачнкая Udachnaya Radiogeophysicheskaya Ukrainskaya Yubileynaya Sytykanskaya Ages for the micas from Daldyn field are esentialy more ancient referring to Archean and came from shallow pressure harzburgites. Alakite micas came from the mantle metasomtic veins related to the plumes in Proterozoic and Ventdian time

3 mica-Ilm Amh veins, eclogites and various pyroxenites containing Amph
Mantle xwnolith in Zanitsa Are represented mainly by dinite –harzburgites with metasamtic mica-Ilm Amh veins, eclogites and various pyroxenites containing Amph Zanitsa xenoliths only

4 Zarnitsa porphyric kimberlite
Garnets Zarnitsa black kimberlites contains most deep garnets found in the Yakutia They are referring to lherzolites pyroxenitesharzburgites subjected to the Ti carbonatitic metasomatism Clinopyroxenes Ilmenites Cpx vary from low Cr-Ti diopsides related to protokimberlite metasomatism and more ancient Cr- rich diosides and various augites and om[hacites Ilmenites form th trend which consist of the tree magor steps – referring to different levels in mantle columns The Cr-rich varieties are from the metasomatic veins

5 TRE for high-Cr garnets >8% Cr2O3
TRE for Cr- diopsides TRE for Cr- diopsides Cpx frompyroxenites and low pressure cumuates TRE for Black augites and eclogites TRE for Black augites and Cpx from eclogites TRE for Cpx and some minerals fromxenoliths

6 Udachnaya xenoliths TPX
Udachnaya minerals from xenoliths Trace Elements Clinopyroxenes Garnets

7 Komsomo;skaya minerals from xenoliths Trace Elements

8 Sytyknskaya minerals from xenoliths Trace Elements


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