ВОЗРАСТ ЗОЛОТОГО ОРУДЕНЕНИЯ КЕТКАПСКО-ЮНСКОЙ МАГМАТИЧЕСКОЙ ПРОВИНЦИИ, ФОРМАЦИОННАЯ ПРИНАДЛЕЖНОСТЬ ЗОЛОТОНОСНЫХ КОМПЛЕКСОВ И РАЗНОВРЕМЕННОСТЬ ПОЗДНЕМЕЗОЗОЙСКОГО МАГМАТИЗМА В РАЗНЫХ ЧАСТЯХ АЛДАНСКОГО ЩИТА

Abstract

The first 40Ar/39Ar isotopic age data for hydrothermal vein gold mineralization in the late Mesozoic Ketkap-Yuna igneous province of the Aldan shield confirm the correlation between this style of mineralization and the Early Cretaceous sub-alkali magmatism, which was established by geological observations. The combination of geological characteristics and U-Pb data on magmatites enabled us to indirectly determine the age of the highly productive bimetasomatic «massif-skarn» type of mineralization associated with sub-alkali magmatogenic formations of the province. The isotopic dating of magmatites and gold mineralization in the Ketkap-Yuna igneous province and other late Mesozoic igneous provinces of the Aldan shield shows consistency in the ages of ore-bearing magmatites and associated ores. The delay in time of the Late Mesozoic magmatism manifestations in the Ketkap-Yuna igneous province and the associated gold mineralization relative to the intensification of tectonomagmatic processes in the Western and Central Aldan, as well as differences in the correlations of different types of igneous formations in the provinces, are explained by the characteristics of the regional tectonic structure and, as a consequence, the specific nature of the Late Mesozoic magmatism development in different parts of the Aldan shield. Two large areas of the late Mesozoic intensification of tectonomagmatic processes are identified in the Aldan shield that differ both in the time of the onset of polyformational magmatism and the accompanying different-type mineralization, and in the dominant formational type of magmatites: West-Central Aldan, on the one hand, and East Aldan, on the other. The former is characterized by continuous magmatic activity from the Berriasian to the early Albian (≈ 30 Ma) and predominance of the leucitite–alkali-(foid)-syenite formation, and the latter by manifestations of magmatism over a timeframe half of the above period (≈ 15 Ma) and predominance of the subalkaline diorite-granodiorite-granite formation. The termination of the late Mesozoic magmatism in both areas was subsynchronous. A «set» of magmatogenic formations in them is also similar: leucite-alkaline-(foid)-syenite with alkali granites, monzonite (shonkinite)-syenite and subalkaline diorite-granodiorite-granite. The Coniacian–Santonian outbreak of alkali volcano-plutonism during the intensification of tectonomagmatic processes is characteristic of the East Aldan region, which manifested itself in the Ketkap-Yuna igneous province after a long (about 30 Ma) period of amagmatism.