The Age of Gold Mineralization of the Ketkap-Yuna Magmatic Province, the Formation Affiliation of Gold-Bearing Complexes, and Stages of the Late Mesozoic Magmatism in Different Parts of the Aldan Shield

摘要

Thefirst data on the 40Ar/39Ar isotope age of hydrothermal stringer-disseminated gold mineralization of the Late Mesozoic Ketkap-Yuna magmatic province (KKYuMP) of the Aldan Shield (AS) confirm the connection of this mineralization type with the Early Cretaceous sub alkaline magmatism, which has been identified by geological observations. The combination of geological features and U/Pb data of igneous rocks indirectly indicates the age of highly productive bimetasomatic massive skarn mineralization type associated with KKYuMP subalkaline igneous rocks. The isotope ages of the KKYuMP igneous rocks and gold mineralization, as well as other AS igneous provinces, show consistent ages of ore-bearing igneous rocks and accompanying ores. The temporal delay of the Late Mesozoic magmatism of the KKYuMP and related gold mineralization relatively to those of zones of tectono-magmatic activation (TMA) of the West and Central Aldan, as well as the different proportions of the volumes of various formations of igneous rocks of the province, are explained by the peculiarities of the regional tectonic structure and related specific evolution of the Late Mesozoic magmatism in various AS parts. Two large areas of the Late Mesozoic AS TMA that are distinct in both the beginning of the polyformational magmatism and accompanying mineralization of various types and dominant type of igneous rocks are distinguished: West-Central Aldan from one side and East Aldan from another side. The first one is characterized by long magmatic activity from the Berriacian to the Early Albian (similar to 30 million years) and predominance of the leucitite-alkali (foido)-syenite formation and the second one exhibited magmatic activity for a two times shorter period (similar to 15 million years) at a dominant formation of subalkali diorites-granodiorites-granites. The end of the Late Mesozoic magmatism in both areas was almost synchronous. The assemblage of igneous formations in them is also similar: leucitite-alkali (foido)syenite with alkali granites, monzonite(shonkinite)-syenite, and subalkali diorite-granodiorite-granite. The East Aldan TMA area is characterized by a Coniacian-Santonian explosion of alkaline volcanoplutonism in the KKYuMP after a continuous (similar to 30 million years) amagmatic period.