Search Results (3)

Large-scale layered intrusions of a peridotite–pyroxenite–gabbronorite complex, to which Cr, Ni, Cu, and PGE deposits and ore occurrences are confined, were emplaced into the Baltic paleocontinent 2.50–2.45 Ga. Layered intrusions in the Monchegorsk Ore District, including the Monchepluton and Imandra–Umbarechka Complex, as well as the gabbro-anorthosite complex of the Main Ridge, were analyzed earlier geochemically and isotopically. In the present paper, the authors analyze layered intrusions in the Kola region (Mount Generalskaya) and Karelia (Kivakka, Kovdozero, and the Burakovsky Pluton). The primary composition of mantle magmas for the layered intrusions is assumed to be identical to that of the komatiitic basalts making up the volcanogenic units of the Vetreny Belt and the Imandra–Varzuga zone. A general model for the formation of layered intrusions includes superplume uplift in the early Paleoproterozoic, the generation of mantle magmas and their injection into the lower portion of the earth crust, the formation of deep-seated and intermediate magma chambers, and the intense contamination of the granulite–metamorphic complex followed by the generation of magma chambers provoked by single or multiple injections. Full article

The paper concerns the geochemical analysis of rocks from the ore-bearing layered intrusions that belong to two age groups of the Monchepluton and the Imandra–Umbarechka Complex (2.50 and 2.44 Ga) and the largest gabbro-anorthosite of the Main Ridge Complex (2.51–2.45 Ga). The intrusion of these complexes happened at different depths when the endogenous and geodynamic settings changed at the beginning of the Paleoproterozoic Era. Five megacycles are distinguished in a generalized cross-section of the two-chamber Monchepluton. The megacycles differ in rock composition, rock geochemical features, and mineralization types, i.e., the chromite, sulfide Cu–Ni–PGE and low-sulfide PGE types. The abrupt changes in isotope indicators (εNd, ⁸⁷Sr/⁸⁶Sr) mark their boundaries. At a depth of 2037–2383 m, the M-1 borehole intersects a standalone intrusive body that is essentially a magma feeder channel. The intrusive body’s geochemical characteristics and U–Pb isotope age correlate to the Monchepluton rocks. The gabbro-anorthosite massifs united in the Main Ridge Complex were intruded in the following order: the Monchetundra, Chunatundra, Volchetundra, and Losevo–Medvezhye tundras. The largest Monchetundra massif was formed as a result of multiple intrusions of mafic magmatic melt from the deep reservoirs. The melts intruded in two stages, i.e., 2.51–2.49 Ga and 2.48–2.47 Ga, and their composition changed gradually. The gabbro-pegmatites and coeval harrisite dykes are more recent ones (2.46–2.45 Ga). The summarized results of the U–Pb, Sm–Nd, and Re–Os systems research allowed us to establish genetic relations between the studied geological objects. We proposed a model where there was an uplift of a mantle plume to the lower crust area at the age of 2.5 Ga, the deep mantle reservoirs were formed, and a large-scale interaction happened between the parental magma and granulite–eclogite complex rocks. Local contamination and assimilation processes took place during the uplifting of magmas in areas where the magmatic feeding system contacted the host amphibolite–gneiss Archean complexes. Full article

Monchegorsk is an intrusion complex of basic and ultrabasic rocks of the Paleoproterozoic age. This complex formed during active magmatic mobility that took place in NE Scandinavia 2.5 Ga years ago. These were the subject of intensive exploration and exploitation at the beginning of the 20th century, the latter carrying on through to the beginning of the 21st century. This contributed to the creation of some different forms of post-industrail mining infrastructure in the area. Many mining settlements, including Monchegorsk, mining plants, adits and quarries were established during this time, the relics of which are still present today. The Monchegorsk intrusions complex is formed by several fragmented massifs: Traviannaya, Kumuzhia, Nittis, Sopcha, Nyud, Poaz, and Monchetundra, the highest elevations of which reach up to 1000 m above sea level. These massifs form a landscape of “islands” and mountain ranges that have influence upon the regional landscape over several tens of kilometers. Their geography is characterized by numerous reliefs, glacial cirques, rocky thresholds with waterfalls and trough lakes. The potential of this region lies in the heritage of historical exploitation, numerous monuments of which have been preserved to this day. An important value is a landscape resulting from the relief of these mountains, highlighted by glacial activity in the Pleistocene. There are also interesting examples of Arctic fauna and flora, and of the rocks that form the bedrock in this intrusion. Some of the mineralization of these outcroppings can also be admired in the collections of the local museum that serves as a geocenter. The possibility of admiring relatively easily accessible views (the international route St. Petersburg–Murmansk–Kirkenes passes through the middle of the hills) and the interesting geology of the area abounding in rocks of mineralogical significance, their exposures, and history, along with the possibility of observing various post-industrail forms, make this area of great tourist potential. This article describes the most interesting exposures of outstanding tourist value and proposes routes connecting these points. It also discusses the problem of securing these exposures and the necessary tourist infrastructure, which is currently lacking. Full article