PETROLOGICAL-GEOCHEMICAL FEATURES OF ROCKS AND POTENTIAL CU-NI SULPHIDE MINERALIZATION IN LATE PRECAMBRIAN MAFIC DYKE SWARM OF THE ANABAR SHIELD

Late Precambrian mafic rocks form dike swarms of various directions up to 200-300 km long and several tens of km wide on the Anabar Shield. According to U-Pb dating data, three main directions of dike belts of different ages were identified: the Chieress swarm of a northwestern direction with an age of 1385 Ma: Kuonamka swarm of sublatitudinal dikes - 1500 Ma and north-northwestern dikes of the East Anabar swarm - 1774-1750 Ma. In terms of geochemical features, the Anabar Precambrian mafic rocks correspond to intraplate basalts. In the dolerites of the Kengede and East Anabar belts, manifestations with disseminated veinlet and nodular sulfide Cu-Ni mineralization were established. The main minerals in sulfide ore occurrences are pyrrhotite and chalcopyrite; pentlandite, siegenite, gersdorffite, galena, sphalerite and other small unidentified phases are less common. Also found are segregations consisting of close intergrowths of many melted amoeboid titanomagnetite individuals, which are associated with drop-shaped pyrrhotite and prismatic apatite crystals. Rounded formations of sulfide nodules indicate their segregation nature, when, already at the early magmatic stage, a sulfide melt enriched in Cu and Ni is separated from the sulfur-saturated mafic magma. The presence in mafic rocks of apatite-sulfide-magnetite segregations with melted rounded forms of sulfides and magnetite also indicates the segregation nature of the separation of highly phosphate sulfide-oxide liquids. Thus, with the differentiation of large volumes of Precambrian mafic melts in deep intermediate chambers, magmatic PGE-Au-Cu-Ni sulfide and phosphate-iron phoscorite deposits can be formed. Such deposits are one of the potential sources of areal complex placers in the Leno-Anabar province.