Geochronology and ore mineralisation of the Dzheltula alkaline massif (Aldan shield, South Yakutia)
The Dzheltula alkaline massif is located in the Tyrkanda ore region of the Chara-Aldan metallogenic zone of the Aldan-Stanovoy Shield (S. Yakutia). Within the region the placer gold objects were found, which are exploring today, as well as ore-bearing Mesozoic alkaline intrusions were established, which have been poorly studied due to its inaccessibility. The Dzheltula massif is the largest multiphase annular intrusion on the surface of the Tyrkanda ore region, therefore it is considered as a typical object for geological, petrological, geochronological and metallogenic studies. The Dzheltula massif consists of five alkaline magmatic phases of the syenite composition. The 40Ar-39Ar data show that the earliest leucocratic phase of syenite porphyries, pulaskites, has the age of 121.1 ± 1.3 Ma. The age of crystallization of dike phases (laurvikites, pulaskites) ranges from 120.1 ± 2 to 118.3 ± 2.1 Ma. The latest final trachyte phase has the age of 115.5 ± 1.6 Ma. According to mineralogical and geochemical studies within the Dzheltula massif, two types of ore mineralization have been identified: gold (Au) and uranium-thorium-rare earth (U-Th-REE). Gold mineralization is found in quartz-chlorite-pyritized metasomatites. Mineralization is confined to the linear fault zones of NNE and NNW directions and coincides with the direction of the intrusion of the syenite-porphyry dike belt. Uranium-thorium-rare-earth mineralization was established in quartz-feldspar metasomatites, localized in exocontact areas of the massif. Within the Dzheltula syenite massif, the areas of combined mineralization have been identified, which increase the ore potential of the investigated object within the Tyrkanda ore region.