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| Titel |
New data for paleoprotherozoic PGE-bearing anorthosite of Kandalaksha massif (Baltic shield): U-Pb and Sm-Nd ages |
| VerfasserIn |
Ekaterina Steshenko, Tamara Bayanova, Pavel Serov |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101363
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| Publikation (Nr.) |
 EGU/EGU2015-486.pdf |
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| Zusammenfassung |
| The aims of this researches were to study the isotope U-Pb age of zircon and rutile and
Sm-Nd (rock forming and sulphide minerals) on Kandalaksha anorthosite massif due to study
of polimetamorphic history. In marginal zone firstly have been obtained the presence of
sulphide mineralization with PGE (Chashchin, Petrov , 2013). Kandalaksha massif is located
in the N-E part of Baltic shield and consists of three parts. Marginal zone (mesocratic
metanorite) lies at the base of the massif. Main zone is composed of leucocratic metagabbro.
The upper zone is alteration of mataanorthosite and leucocratic metagabbro. All rocks were
subjected to granulate polymetamorphism. Two fractions of single grains from anorthosite of
the massif gave precise U-Pb age, which is equal to 2450± 3 Ma. Leucocratic gabbro-norite
were dated by U-Pb method, with age up to 2230 ± 10 Ma. This age reflects the time of
granulite metamorphism according to data of (Mitrofanov, Nirovich, 2003). Two
fractions of rutile have been analyzed by U-Pb method and reflect age of 1700 ± 10
Ma. It is known that the closure temperature of U-Pb system rutile is 400-450 ° C
(Mezger et.al., 1989), thus cooling processes of massif rocks to these temperatures was
about 1.7 Ga. These data reflect one of the stages of metamorphic alteration of
the massif. Three stages of metamorphism are distinguished by Sm-Nd method.
Isotope Sm-Nd dating on Cpx-WR line gives the age of 2311 Ma which suggested of
high pressure granulite metamorphism. Moreover Cpx-Pl line reflect the age 1908
Ma of low pressure granulite metamorphism. Also two-points (Grt-Rt) Sm-Nd
isochrone yield the age 1687 Ma of the last metamorphic alterations in Kandalaksha
anorthosite massif. Model Sm-Nd age of the leucocratic gabbro-norite is 2796 Ma
with positive ÉNd (+0.32). It means that the source of gabbro-norite was mantle
reservoir.
All investigations are devoted to memory of academician PAS F. MItrofanov which was a
leader of scientific school for geology, geochemistry and metallogenesis of ore deposits. The
studies are contribution by RFBR OFI-M 13-05-12055, 13-05-00493, Department of Earth
Sciences RAS (programs 2 and 4), and IGCP-SIDA 599. |
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