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| Titel |
Titanium in garnets as indicator of inhomogeneous composition of lithosphere mantle |
| VerfasserIn |
S. Kostrovitsky, D. Yakovlev, Z. Spetsius |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064612
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| Zusammenfassung |
| The inhomogeniety of lithosphere mantle under platforms is the well known fact
considered by numerous researchers (Sobolev, 1976; Griffin et al, 1999), who primarily
dwell upon the ratio of different parageneses of rocks composing the mantle, e.g.
pyroxenite, eclogite, lherzolite and dunite-harzburgite. In this paper the garnets with
a high content of TiO2 (>0.2%) are discussed. The low-Tigarnets are found in
many kimberlite pipes both in the northern and southern fields of the Yakutian
Province. This fact agrees with assumption about high-Mg and low-Ti composition of
lithosphere mantle. The garnet composition from two neighboring northern fields of
the Yakutian province shows that they embrace the Ti-rich blocks of lithosphere
mantle.
We studied the composition of high-pressure minerals from heavy fraction of kimberlites
for Chomurdakh (pipes: Chomur, Svetlaya, Snezhnaya, Druzhba, Ural’skaya, Olimp,
dyke Pereval’naya) and Ogoner-Yuryah (pipes: Vasileostovskaya, Baltiyskaya,
Aerogeologicheskaya) fields. The heavy fraction of kimberlites of these pipes basically
consists of magnesian ilmenite; the number of garnet grains is less 1/100 parts of total
number of ilmenite grains. The garnet from these pipes belongs to pyroxenite-vebsterite and
eclogite associations. Garnets of diamondiferous dunite-harzburgite paragenesis are absent or
occur as single grains.
The remarkable feature of garnets from almost all explored pipes, but pipe Ural’skaya, is
their high-Ti composition. From 50 to 100 % of all garnets from heavy fraction of kimberlites
are characterized by the TiO2 content more than 0.2 % (to 1.9 %). Such unusually high
content of high-Ti garnets in the kimberlites of Chomurdakh and Ogoner-Yuryah fields
possibly reflects profound metasomatic transformations of separate blocks of lithosphere
mantle in the north of Siberian platform.
In the conclusion it should be marked that the high content of Ti is the feature of
composition of most kimberlites and basic rocks occurring in the northern termination of the
Siberian platform. The question is whether the processes of Ti enrichment of separate blocks
of lithosphere mantle, kimberlite and basic rocks are genetically interrelated. This issue
should definitely be further explored.
References:
Sobolev, N.V., 1977. Deep-seated inclusions in kimberlites and the problem of the upper
mantle composition, Novosibirsk: Nauka, (in Russian). Engl. translation by Brown,
D.A. & Boyd, F.R., (ed.), American Geophysics Union, Washington, D.C., 279
p.
Griffin W.L., Ryan C.G., Kaminsky F.V., O’Reilly S.Y., Natapov L.M., Win T.T., Kinny
P.D., Ilupin I.P. 1999. The Siberian lithosphere traverse: mantle terranes and the assembly of
the Siberian craton. Tectonophysics. V. 310. P. 1-35. |
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