Large igneous provinces of Northern Eurasia and their PGE-Cu-Ni ore deposits
|Location||International Geological Congress,oslo 2008|
|Author||Sharkov, Evgenii; Dyuzhikov, Oleg|
|Holding Date||03 September 2008|
The most important type of ore mineralization are large and unique sulfide PGE-Cu-Ni ore deposits, related to mafic-ultramafic intrusions of large igneous provinces (LIPs). They have widely represented in geological history of the Earth from the Paleoproterozoic to Cenozoic. However, despite of huge sizes of these provinces, such deposits are very rare. We will discuss this problem on example of the Phanerozoic Siberian and two Paleoproterozoic Fennoscandian large igneous provinces on the Russian territory on examples of large and unique ore deposits of Noril’sk district (SW of Siberian LIP), Pechenga district (Kola Peninsula) and large mafic-ultramafic layered intrusions in eastern Fennoscandian Shield (Monchegorsky, Burakovsky, Lukkulaisvaara, etc. complexes.
In spite of wide spread expansion of the same kind of magmatic rocks on the vast territory, in all cases is fixed only one large occurrence of the sulfide PGE-Cu-Ni ore deposits. These occurrences are characterized by combination by at least three similar features:
(1) long term (more than 300 myr) formation of the structures where ore deposits located.
(2) presence beneath them ancient high-depleted mantle where the PGE were accumulated in residuals during former multiple episodes of melting;
(3) presence of the S- and Cl-bearing sediments in these places: Neoproterozoic and Paleozoic evaporites in the Noril’sk district; early Paleoproterozoic sulfide-bearing metasediments into the Pechenga structure and in it’s basement, as well as metamorphosed sulfide-bearing metasediments of the Archean Kola Fm, which enclose ore-bearing Monchegorsky and Pana-Fedorova Tundras complexes.
Thus, the type of tectonomagmatic activity is not the only reason for appearance of large and unique PGE-Cu-Ni ore deposits, but it is necessary to presence of other factors, especially mentioned above. Only their combination could provide it. In places, where such combination is absent, no large ore deposits in spite of the same character of the proper magmatic activity. Moreover, for case of large mafic-ultramafic layered intrusions it is necessary take into account that appearance of platineferous reefs, which appearance was linked with replenishment of fresh portions of magmas, enriched in ore components, is unpredictable. So, cross-section of each large layered intrusion should be studied carefully during prospecting works as reef could be found in any place.
Work was supported by grant RFBR # 07-05-00496