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| Titel |
Radiogenic and stable isotope study of the Dyumptaley and Binyuda ultramafic-mafic intrusions and associated Ni-Cu-PGE sulfide ores (Russian Arctic) |
| VerfasserIn |
Kreshimir Malich, Inna Badanina, Elena Belousova, Norman Pearson, Andrey Romanov, Sergey Sluzhenikin |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097510
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| Publikation (Nr.) |
 EGU/EGU2014-13102.pdf |
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| Zusammenfassung |
| It is commonly assumed that ultramafic-mafic intrusions and associated PGE-Cu-Ni sulphide
deposits of Northern Siberia represent a small component of a major episode of mafic activity
at ~250 Ma, which included formation of the most extensive flood-basalt province on Earth
[1]. Recent studies, however, advocated protracted evolution of the ore-forming magmas
parent to the Noril’sk-type intrusions [2, 3, etc.]. Understanding the processes behind the
formation of economically important ore deposits is crucial for locating additional deposits in
areas that have not been previously considered. This study, therefore, aimed to provide
isotope-geochemical fingerprinting to be used in exploration for Ni-Cu-PGE sulfide
ores.
We firstly present geochronological and Hf-Nd-Sr-Cu-S isotope data for the same suite of
lithologies and associated PGE-Cu-Ni sulphide ores from the Dyumptaley and Binyuda
ultramafic-mafic intrusions located in the limits of the Taimyr Peninsula (Russian Arctic).
The rocks investigated comprise sulphide-rich varieties of ferrogabbro (i.e. gabbro
abnormally high in Fe) and melanocratic troctolite occurring in bottom parts of the
Dyumptaley and Binyuda intrusions, respectively.
Zircons are characterized by similar U-Pb ages (256.2±0.9 Ma at Dyumtaley, and
245.7±12 Ma at Binyuda). In contrast, silicate materials show distinct Hf-Nd-Sr isotope
signatures (ÉHf=8.3±3.7, ÉNd=3.5±0.7 and 87Sr/86Sri=0.70493±0.00021 at Dyumptaley,
and ÉHf=-5.2±0.6, ÉNd=-3.4±0.3 and 87Sr/86Sri=0.70585±0.00004 at Binyuda). The
determined Hf-Nd-Sr variability is interpreted to represent a primary source signature of the
lithological units. An important role of the juvenile component is clearly pronounced for the
Dyumptaley intrusion, whereas a major contribution from a SCLM or essentially crustal
source is inferred for the Binyuda intrusion.
These signatures clearly manifest deviation from those typical of the ore-bearing
intrusions from the Noril’sk Province, characterized by a significant time span of zircon and
baddeleyite U-Pb ages (from ca. 350 to 230 Ma), relatively constant ÉNd values (ca. +1±0.5)
and heterogeneous radiogenic ÉHf (from -2.3 to 16.3) and 87Sr/86Sri (from 0.70552 to
0.70798) [2,3].
In terms of Cu-isotopes, the majority of the analyzed sulfide samples fall within a tight
cluster of δ65Cu values (from -1.2 to -0.2o with a mean of -0.65oand a standard deviation
of 0.25oat Dyumptaley, and from -0.6 to -0.2o,-0.43±0.09oat Binyuda),
characteristic of the ores from the economic Ni-Cu-PGE deposits at Talnakh and
Stillwater [4]. In contrast, notable difference in δ34S values typifies sulfide ores at
Dyumptaley (11.4±0.2o) and Binyuda (2.1±0.5o), respectively. We suggest that
the Cu-S isotope characteristics of the sulfide ores reflect their primary signature
rather than a result of mixed sources or magmatic fractionation of stable isotopes.
However, the latter option cannot be ruled out for heavy S isotope composition of
sulfide at Dyumtaley. Samples of the disseminated sulfide ore from the Dyumptaley
intrusion approach δ34S-δ65Cu parameters of the economic ores at Talnakh and
may be considered as most promising in targeting the massive Ni-Cu-PGE sulfide
ores.
Integrated radiogenic and stable isotope data provide new constraints on baseline isotope
signatures of sulfide ores of the Russian Arctic, demonstrating a potential in combined
petrologic and isotope-related mineral deposit studies.
The study was supported by RFBR (grant 13-05-00671) and the Uralian Division of
Russian Academy of Sciences (grant 12-5-9-019-Arctic).
References: [1] Campbell et al. (1992) Science 255, 1760-1763. [2] Malitch et al. (2010)
Contrib. Mineral. Petrol. 159, 753-768. [3] Malitch et al. (2013) Lithos 164-167, 36-46.
[4] Malitch et al. (2013) Geophysical Research Absracts 15, EGU2013-4506-1. |
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