Abstract
The intermediate rocks classified as diorite-gneisses occur within the southern part of the Monchegorsk (2.5 Ga) layered mafic-ultramafic complex (Kola Peninsula, Russia). These diorite-gneisses belong to a block historically known as the diorite window (DW) block. The same rocks occur in a framing of the Monchegorsk complex. The DW block is predominantly composed of diorite-gneisses and, to a lesser degree, of amphibolites. Multi-ordinal banding, complex folding, boudinage and metamorphic transformations, garnet porphyroblasts, and tourmaline veinlets are typical of the diorite-gneisses. In accordance with the U-Pb isotope data, the age of the diorite-gneisses in the DW block is 2736.0 ± 4.6 Ma. The Sm-Nd mineral (garnet, biotite, and tourmaline) isochron for the DW rocks has yielded an age of 1806 ± 23 Ma (related to the processes of the Svecofennian orogeny). The DW diorite-gneisses are compared with the metadiorites of the Gabbro-10 massif. The latter is a part of the Monchegorsk complex, with U-Pb crystallization age of 2498 ± 6 Ma. On the basis of geological and isotope-geochemical data, it is shown that the DW rocks belong to the Archean basement while the Gabbro-10 metadiorites probably represent one of the late-magmatic phases of the Monchegorsk complex.
Highlights
The Monchegorsk layered mafic-ultramafic complex occupies the Monchegorsk region in the central part of the Kola Peninsula (Figure 1)
It is interesting from the viewpoint of geology and petrology for the multi-order igneous layering, availability of features confirming the multiphase nature of its emplacement, and several genetic types of ore mineralization
Our research investigated the most exposed part (200 m × 200 m) of the diorite window (DW) block near the southwestern flank of the Nude-Poaz massif
Summary
The Monchegorsk layered mafic-ultramafic complex (hereafter the Monchegorsk complex) occupies the Monchegorsk region in the central part of the Kola Peninsula (Figure 1). The Monchegorsk complex is primarily known for its complex Cu-Ni-PGE-Cr-Fe-Ti-V mineralization. It is interesting from the viewpoint of geology and petrology for the multi-order igneous (including rhythmic) layering, availability of features confirming the multiphase nature of its emplacement, and several genetic types of ore mineralization (contact, vein, and reef). Minerals 2020, 10, x FOR PEER REVIEW. Gabbro-10 massif, which is a part of the Monchegorsk layered complex. It is noteworthy that some researchers considered the metadiorites of the Gabbro-10 massif to be products of metasomatic. Minerals 2020, 10, 848 alteration of the Archean basement diorites [1].
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