Early proterozoic margin-continental complexes of the Angara fold belt andtheir metallogeny

Complex geological, petrological, and geochemical studies have given new da ta an Lower Proterozoic margin-continental metasedimentary, metasedimentary -volcanogenic, and granitoid complexes of the Angara fold belt (southwester n margin of the Siberian craton). The contents and distribution of trace, r adioactive, and rare-earth elements in the rocks, together with isotope-geo chronological data, provide a base for interregional correlation. According to geological and isotope-geochronological data, the Early Proter ozoic evolution of the Earth's crust in the Angara fold belt passed through two large periods - early (similar to 2.3-2.0 Ga BP) and late (2.0-1.65 Ga BP). The former involved accumulation of sedimentary, mainly terrigenous, deposits in epicontinental rift-type basins. The latter was associated with formation of volcanogenic complexes with features of Andes-type margin-con tinental volcanic belts. The collision that occurred similar to 1.95-1.9 Ga BP gave rise to granite-gneiss domes and granitoid plutons as well as suba lkalic and leucocratic intrusive granites (1.8-1.75 Ga BP) similar in petro geochemical composition to postorogenic and within-plate formations. Much attention is given to the major features of the metallogeny of the Ang aro fold belt. It Is shown that the specific rare-metal composition of the belt is due to the Archean highly differentiated mature sialic basement and the first, most intense, K-granite formation in the Early Proterozoic.