Paleoproterozoic Layered Intrusions of the Monchegorsk Ore District: Geochemistry and U–Pb, Sm–Nd, Re–Os Isotope Analysis

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