Long-Lived Mantle Plume and Polyphase Evolution of Palaeoproterozoic PGE Intrusions in the Fennoscandian Shield

Abstract

The NE Fennoscandian Shield comprises the Northern Belt in Finland and the Southern Belt in Karelia. They host mafic-ultramafic layered Cu-Ni-Cr and Pt-Pd-bearing intrusions. Precise U-Pb and Sm-Nd analyses indicate the 130-Ma evolution of these intrusions, with major events at 2.53, 2.50, 2.45, and 2.40 Ga. Barren phases were dated at 2.53 Ga for orthopyroxenites and olivine gabbro in the Fedorovo-Pansky massif. PGE-bearing phases of gabbronorites (Pechenga, Fedorovo-Pansky, Monchetundra massifs) and norites (Monchepluton) are 2.50 Ga old. Anorthosites of Mt. Generalskaya (Pechenga), the Fedorovo-Pansky, and Monchetundra massifs occurred at 2.45 Ga. This event produced layered PGE-bearing intrusions in Finland (Penikat, Kemi, Koitelainen) and mafic intrusions in Karelia. The Imandra lopolith dikes occurred at the final phase (2.40 Ga). Slightly negative εNd and ISr values (0.703–0.704) suggest that intrusions originated from an enriched mantle reservoir. Low 3He/4He ratios in accessory minerals (ilmenite and magnetite) indicate an upper mantle source. Large-scale correlations link the Fennoscandian Shield with the Superior and Wyoming cratons.

The Paleoproterozoic Kandalaksha-Kolvitsa Gabbro-Anorthosite Complex (Fennoscandian Shield): New U–Pb, Sm–Nd, and Nd–Sr (ID-TIMS) Isotope Data on the Age of Formation, Metamorphism, and Geochemical Features of Zircon (LA-ICP-MS)

“…According to geochronological and Nd-Sr isotope data, rocks of the Kandalaksha-Kolvitsa complex seemed to have a common anomalous mantle source with Paleoproterozoic layered intrusions of the Baltic Shield (Figure 9). The obtained data comply with the known isotope-geochemical characteristics of ore-bearing layered intrusions in the northeastern Baltic Shield [40,43,46]. The model age of rocks from the Kandalaksha-Kolvitsa complex varied from 2.8 Ga to 3.3 Ga and corresponded with T DM for rocks in the East-Scandinavian Large Igneous Province [46].…”

“…In general, using sulfides as geochronometers provides positive results for a number of commercially valued objects of the Baltic Shield [42]. The model Sm-Nd age of these gabbroids was close to 3.3 Ga (Table 4), which is typical of the Paleoproterozoic ore-magmatic system of the Baltic Shield [43]. Rutile, garnet, plagioclase, clinopyroxene, and whole rocks from metaanorthosites of the Kandalaksha massif (sample 225/1) displayed the age of 1886 ± 37 Ma on the Sm-Nd plot in isochron coordinates (Figure 8b, Table 4).…”

Metallogenic Setting and Evolution of the Pados-Tundra Cr-Bearing Ultramafic Complex, Kola Peninsula: Evidence from Sm–Nd and U–Pb Isotopes

“…The Sm-Nd age of rocks in the rhythmically layered series of the complex is 2485 ± 77 Ma (whole-rock isochron) and 2475 ± 38Ma (mineral isochron). It coincides with the age of layered intrusions in the Baltic Shield [11,12,15,36,[87][88][89][90][91][92][93][94]. The model Sm-Nd age (TDM) of the analyzed samples is close to 2.7-2.8 Ga.…”

“…The obtained isotope-geochronological data combined with results of previous geochemical, petrological, and mineralogical studies of the complex [43][44][45][46][47][72][73][74] allow referring it to the vast Paleoproterozoic East Scandinavian LIP, which is associated with rich deposits of strategic mineral raw materials (i.e., Cr, Cu-Ni-Co and PGE) [1][2][3][4][5][6][12][13][14][15][16][17][18][19][21][22][23][24][25][26][27][29][30][31][32][33][34][35][36][37][38][39]41,42,54,87,[89][90][91][92]94].…”

Low-Sulfide Platinum–Palladium Deposits of the Paleoproterozoic Fedorova–Pana Layered Complex, Kola Region, Russia

“…It is generally believed that the formation of PGE mineralization in most Russian Paleoproterozoic layered intrusions is related to prolonged igneous activity in response to a long-lived mantle plume [73] affecting the Kola Craton for more than 50 Ma, which is mainly based on ID-TIMS U-Pb age dating [15,49]. This interpretation is generally at odds with the current paradigm of relatively short-lived mantle plume magmatism and the duration of cooling of basaltic magma chambers, such as the Bushveld Complex, which crystallized in less than 1 Ma [74].…”