Massifs of Disintegrated Granitoids in the Junction Zone of the East European and West Arctic Platforms: Composition, Age, and Hydrocarbon Potential

Abstract

In the Trollfjord–Rybachy–Kanin fault zone, the major convergent suture between the East European and West Arctic platforms, on the isthmus of Cape Vestnik located between the Sredny and Rybachy peninsulas, in the Riphean terrigenous sequence, massifs of disintegrated granitoids have been identified, primarily belonging to the Archean crystalline basement and which subsequently underwent tectonic extrusion to the upper horizons in the form of protrusions. Petrographic studies of disintegrated rocks from the Vestnik granitoid massif and the surrounding rocks indicate their high permeability and porosity in shattering zones. The positive Eu anomaly and decrease in content of light rare earth elements indicates the reducing nature of the fluids that affected disintegrated rocks, contributing to their formation under decompression conditions. The buried massifs of disintegrated granites may have reservoir properties. U–Pb and Sm–Nd isotopic studies of disintegrated plagiogranites with a model age of 2966 Ma has made it possible to correlate them with the rocks from the Murmansk block of the Baltic Shield. According to Sm–Nd data, the dolerite dike that cuts the plagiogranite massif has an age of 1333 ± 160 Ma (Middle Riphean) on pyrite and plagioclase, which corresponds to fragmentation of the basement at the initial continental rifting stage, which led to the formation of the White Sea paleorift system. East of Cape Vestnik, within the water area of the Barents Sea, a chain of linear–arched contrasting negative anomalies has been recorded in the gravity field. They are interpreted with high probability as reflections of the plate-shaped massifs of disintegrated granitoids included in the Riphean sedimentary sequence along the Trollfjord–Rybachy–Kanin shear zone, which may suggest a promising hydrocarbon potential of this zone under certain conditions.