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| Titel |
Ore genesis dating: implication of Sm-Nd method using sulfide minerals for mafic-ultramafic layered intrusions of Fennoscandian Shield |
| VerfasserIn |
Pavel Serov, Tamara Bayanova, Ekaterina Steshenko, Nadezhda Ekimova |
| 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 |
250101375
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| Publikation (Nr.) |
 EGU/EGU2015-501.pdf |
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| Zusammenfassung |
| The main method of dating the ore process was the Re-Os method of sulfides (Luck, Allegre,
1983; Walker et. al., 1991). However, studies of Re-Os systematics of sulfide minerals do not
always give the correct ages and showing the disturbances of the Re-Os systematics. At
the same time, Sm-Nd age of sulfides in good agreement with the U-Pb dating on
zircon and baddeleyite and suggests that the Sm-Nd system of sulfides is more
resistant to secondary alteration processes. Our studies have shown that along with
rock-forming, ore minerals (sulfides) can be used to determine the ore genesis time of
industrially important geological sites, since exactly with the sulfides the industry
Pt-Pd mineralization is closely connected. In to Sm-Nd measurements steadily
introduce new minerals-geochronometers (i.e. titanite, burbancite, eudialite etc.). Of
these, sulfides of PGE-bearing layered intrusions are quite important in terms of
dating the process of ore origin. Studying the REE distribution in the sulfides of
MOR hydrothermal sources has shown possible REE presence in the sulfide lattice
(Rimskaya-Korsakova et. al., 2003). These are difficult to carry out because the
concentrations of Sm and Nd isotopes in sulfides are much lower than those in
chondrites (Rimskaya-Korsakova et. al., 2003). In (Kong et. al., 2000) sulfides from
two metamorphosed chondrites were studied by instrumental neutron activation
analysis (INAA) and ion probe. As shown, the level of REE in the sulfide phase
determined by the ion probe is quite similar to that obtained by INAA. Although the
concentrations of REE in the enstatite and the Fe, Si, Cr-rich inclusions are comparable to
those in sulfide, estimates based on mass balance calculations show that the silicate
inclusions would not noticeably contribute to the REE budget in sulfides (Kong et. al.,
2000). For the first time in Russian geochemistry laboratories using sulfide and
rock-forming minerals and WR in Sm-Nd method have been dated impregnated and
brecciform ores of the following objects - Pilguyarvi Cu-Ni deposits, Pechenga
(1965±87 Ma); impregnated (2433±83 Ma) and redeposited (1903±24 Ma) ores of
Ahmavaara intrusion (Finland); Kolvitsa massif metagabbro (1990±92 Ma, which reflect
the age of Sm-Nd system closure in sulfide minerals); olivine orthopyroxenites
of Sopcha “Ore bed” (2442±59 Ma); ore gabbronorites of Penikat PGE-bearing
layered intrusion (2426±38 Ma (Ekimova et.al., 2011); Pt-Pd gabbro-pegmatite
ores (2476± 41 Ma, which agrees well with the U-Pb zircon age - 2470±9 Ma
(Bayanova, 2004) and gabbronorites (2483±86 Ma) of PGE Kievey deposit and Fedorova
Tundra metagabbroids (2494±54 Ma); Monchetundra gabbronorites – 2489±49
Ma.
All investigations are devoted to memory of academician RAS, professor F. Mitrofanov
(Russia), he was a leader of scientific school for geology, geochemistry and metallogenesis of
ore deposits.
The studies were supported by the RFBR 13-05-00493, OFI-M 13-05-12055, Department
of Earth Sciences RAS (programs 2 and 4), IGCP-599. |
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