Abstract
The article presents new Sm–Nd and U–Pb geochronological data on rocks of the poorly studied Pados-Tundra Cr-bearing complex. It is part of the Notozero mafic–ultramafic complex (western Kola Peninsula) and occurs at the border of the Paleoproterozoic Lapland Granulite Belt and the Archean Belomorian composite terrain. The Pados-Tundra complex hosts two major zones, the Dunite and Orthopyroxenite Blocks. Dunites are associated with four levels of chromite mineralization. Isotope Sm–Nd studies of dunites, harzburgites, and orthopyroxenites from the central part of the complex have been carried out. The isochron Sm–Nd age on 11 whole-rock samples from a rhythmically layered series of the complex is 2485 ± 38 Ma; the mineral Sm–Nd isochron for harzburgites shows the age of 2475 ± 38 Ma. It corresponds with the time of large-scale rifting that originated in the Fennoscandian Shield. When the rhythmically layered series of the intrusion and its chromite mineralization were formed, hornblendite dykes intruded. The U–Pb and Sm–Nd research has estimated their age at ca. 2080 Ma, which is likely to correspond with the occurrence of the Lapland–Kola Ocean. According to isotope Sm–Nd dating on metamorphic minerals (rutile, amphibole), the age of postmetamorphic cooling of rocks in the complex to 650–600 °C is 1872 ± 76 Ma. The U–Pb age on rutile from a hornblendite dyke (1804 ± 10 Ma) indicates further cooling to 450–400 °C. The conducted research has determined the early Proterozoic age of rocks in the rhythmically layered series in the Pados-Tundra complex. It is close to the age of the Paleoproterozoic ore magmatic system in the Fennoscandian Shield that developed 2.53–2.40 Ga ago. Later episodes of alterations in rocks are directly related to main metamorphic episodes in the region at the turn of 1.9 Ga. Results of the current study expand the geography of the vast Paleoproterozoic East Scandinavian Large Igneous Province and can be applied for further studies of similar mafic–ultramafic complexes.
Highlights
In the northeastern Baltic Shield, large-scale mafic–ultramafic deposits of Cu-Ni-Co, platinum group elements (PGE), and Fe-Ti-V are economically significant, in particular, concerning critical raw materials, such as PGE and V
An Sm–Nd isochron was constructed based on 11 whole-rock samples
The newly obtained dates indicate an older age for the Pados-Tundra complex than the until not admitted age 2.15 Ga age, which is the age of the Paleoproterozoic mafic–ultramafic
Summary
In the northeastern Baltic Shield, large-scale mafic–ultramafic deposits of Cu-Ni-Co, platinum group elements (PGE), and Fe-Ti-V are economically significant, in particular, concerning critical raw materials, such as PGE (platinum group metals) and V These are major Cu-Ni-Co-Cr + PGE deposits in the Monchegorsk ore area [1,2,3,4,5] and Pechenga [6,7,8], Fe-Ti-V Kolvitsa deposit [9,10], PGE and Cu-Ni. Fedorovo-Pana layered complex [11,12,13,14] and Burakovsky intrusion [15], Cu-Ni-Co + PGE deposits in Finland: Kemi [5,16], Penikat [17,18], Akanvaara, Koitelainen [19], Tornio [20], and so forth. Its study is both scientifically and economically important, considering the acceleration of the raw material potential of the Russian Arctic
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
