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| Titel |
Conditions of crystallization of the Ural platinum-bearing ultrabasic massifs: evidence from melt inclusions |
| VerfasserIn |
Vladimir Simonov, Victor Puchkov, Vladimir Prikhod’ko, Sergey Stupakov, Alexey Kotlyarov |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078017
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| Zusammenfassung |
| Conditions of the Ural platinum-bearing ultramafic massifs formation attract attention of
numerous researchers. A most important peculiarity of such plutons is their dunite cores, to
which commercial Pt deposits are related. There are a different opinions about genesis of
these massifs and usual methods not always can solve this question.
As a result of melt inclusions study in the Cr-spinel the new data on physical and
chemical parameters of dunite crystallization of the Nizhnii Tagil platinum-bearing ulrabasic
massif (Ural) was obtained. The comparative analysis of Cr-spinels, containing melt
inclusions, has shown essential differences of these minerals from chromites of the ultrabasic
ophiolite complexes and of modern oceanic crust.
Contents of major chemical components in the heated and quenched melt inclusions are
close to those in the picrite and this testifies dunite crystallization from ultrabasic (to 24 wt.%
MgO) magma. On the variation diagrams for inclusions in Cr-spinel the following changes of
chemical compositions are established: during SiO2 growth there is falling of FeO, MgO, and
increase of CaO, Na2O contents. Values of TiO2, Al2O3, K2O and P2O5 remain as a whole
constant. Comparing to the data on the melt inclusions in Cr-spinel from the Konder massif,
we see that values of the most part of chemical components (SiO2, TiO2, K2O, P2O5)
are actually overlapped. At the same time, for the Nizhnii Tagil platinum-bearing
massif the big maintenances of FeO and CaO in inclusions are marked. Distinct
dependence of the majority of components from the MgO content in inclusions is
observed: values TiO2, Al2O3 FeO, CaO and Na2O fall at transition to more magnesia
melts.
On the peculiarities of distribution of petrochemical characteristics melt inclusions in
considered Cr-spinels are co-ordinated with the data on evolution of compositions of melts
and rocks of model stratified ultramafic plutons during their crystallization in the magmatic
chambers. On the diagrams an association of melt inclusions with the data on inclusions in
Cr-spinels from the Konder platinum-bearing and Karashat ophiolite massifs is clearly
visible.
Our computer simulations on the basis of melt inclusion compositions by the
PETROLOG program package (Danyushevsky, Plechov, 2011) allowed to evaluate the
crystallization temperature of dunites of the Nizhnii Tagil platinum-bearing massif in the
intrusive chamber. The most part of olivine was formed from 1430 to 1360°C and continued
to crystallize until to 1280°C. Cr-spinel crystallized from melts in the range of temperatures
from 1345 to 1310°C.
The investigations were supported by the Russian Foundation for Basic Research (project
No 12-05-00959) and by Projects N 2.1 and N 50. |
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