GEOCHEMISTRY OF HANNIVKA GRANITES (EAST HANNIVKA MONOCLINE, MIDDLE-DNIEPER MEGABLOCK OF THE UKRAINIAN SHIELD)

Abstract

The Middle – Dnieper megablock, which is a fragment of archean craton, differs from other cratons on Earth by a large variety of Archean granitoids (Tok, Mokro-Moscowka, and Demurino complexes) which were formed later than the Mesoarchean TTG of sura complex. In this regard, the Middle – Dnieper megablock is an important area for studying the genesis and geodynamic conditions of Late Archaean granitoid formation. The poorly studied Late Archean granitoids in the Middle – Dnieper block include the Hannivka granites in the East Hannivka monocline of the Kryvyi Rig – Kremenchuk structure, the age and stratigraphic position of which have been the subject of a long debate. The aim of the work is to determine geochemical peculiarities. genesis and U-Pb age of Hannivka granites and to compare them with other archean granitoid complexes of the Middle-Dnieper fragment of the Mesoarchean craton. The LA-ICP-MS method determined the U-Pb age of zircon from Hannivka granite 2827 ± 16 Ma. They are close in time to the granitoids of the Tok and Mokro-Moscowka complexes and were formed much later than the granitoids of the Demurino complex. The Hannivka granites could have been formed in a crustal magmatic source as a result of melting of an older crust. They differ from other Archaean granitoids of the Middle-Dnieper megablock by the increased content of U (56.4 ppm) and the presence of Mo (4.3 ppm). Unsolved problems that require further study include determination of the connection of Hannivka granites with granitoid intrusions of the Mokra-Moscowka and Tok complexes outside the Eastern Hannivka structure and the origin of ore mineralization for uranium and molybdenum.

Keywords

• hannivka granites
• middle-dnieper megablock
• east hanniv monocline
• craton
• u-pb age