THE PALEOPROTEROZOIC IMANDRA-VARZUGA RIFTING STRUCTURE (KOLA PENINSULA): INTRUSIVE MAGMATISM AND MINERAGENY

• Published in: Geodynamics & Tectonophysics
• Main Authors: V. V. Chashchin, F. P. Mitrofanov, В. В. Чащин, Ф. П. Митрофанов
• Other Authors: Исследования выполнены при финансовой под­ держке РФФИ (грант № 13­05­12055).
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Institute of the Earth's crust of the Russian Academy of Sciences, Siberian Branch 2015
• Subjects: малосульфидное Pt-Pd оруденение; mantle plume; layered intrusions; minerageny; low-sulfide Pt-Pd mineralization; мантийный плюм; расслоенные интрузии; минерагения; Kola Peninsula; Monchegorsk; Imandra; Varzuga; Fennoscandian; kola peninsula
• Online Access: https://www.gt-crust.ru/jour/article/view/88; https://doi.org/10.5800/GT-2014-5-1-0126

The article provides data on the structure of the Paleoproterozoic intercontinental Imandra-Varzuga rifting structure (IVS) and compositions of intrusive formations typical of the early stage of the IVS development and associated mineral resources. IVS is located in the central part of the Kola region. Its length is about 350 km, and its width varies from 10 km at the flanks to 50 km in the central part. IVS contains an association of the sedimentary-volcanic, intrusive and dyke complexes. It is a part of a large igneous Paleoproterozoic province of the Fennoscandian Shield spreading for a huge area (about 1 million km2), which probably reflects the settings of the head part of the mantle plume. Two age groups of layered intrusions were associated with the initial stage of the IVS development. The layered intrusions of the Fedorovo-Pansky and Monchegorsk complexes (about 2.50 Ga) are confined to the northern flank and the western closure of IVS, while intrusions of the Imandra complex (about 2.45 Ga) are located at the southern flank of IVS. Intrusions of older complexes are composed of rock series from dunite to gabbro and anorthosites (Monchegorsk complex) and from orthopyroxenite to gabbro and anorthosites (Fedorovo-Pansky complex). Some intrusions of this complexes reveal features of multiphase ones. The younger Imandra complex intrusions (about 2.45 Ga) are stratified from orthopyroxenite to ferrogabbro. Their important feature is comagmatical connection with volcanites. All the intrusive complexes have the boninite-like mantle origin enriched by lithophyle components. Rocks of these two complexеs with different age have specific geochemical characteristics. In the rocks of the Monchegorsk and Fedorovo-Pansky complexes, the accumulation of REE clearly depends on the basicity of the rocks, the spectrum of REE is non-fractionated and ‘flat’, and the Eu positive anomaly is slightly manifested. In the rocks of the Imandra complex, the level of REE accumulation is relatively higher. The spectrum of REE here ...