Abstract:
The Archean metamorphic basement is developed in Carajás area of Brazil, which is one of the most abundant mineral deposits and the highest degree of resource accumulation deposits in the world. A large amount of charnockite, (trondhjemite-tonalite-granodiorite,TTG) rock series and metamorphic plutons that haven't completely disintegrated exsit in the crystalline basement of Archean granite-greenstone, with large perception diffe-rence. The correct division and fine study of igneous rocks are important means to further understand the evolution of South American Craton. Based on the investigation of metamorphic basement intrusive rocks, and combined with previous data, the authors decomposed it into the charnockite of Paleoarchean, the mafic-ultramafic rocks and the TTG gneiss suite of Mesoarchean, and the mafic-ultramafic rocks, the TTG gneiss suite, the syntectonic granite and the post-tectonic granite of Neoarchean, and the alkaline granite of Paleoproterozoic. The granitic plutons in Carajás area were comprehensively analyzed with geological, geochemical and geochronological methods. The
207Pb/
206Pb surface ages of granite by Zircon U-Pb method is concentrated in three periods: 2 899~2 831 Ma, 2 742~2 622 Ma and 1 919 Ma. After the formation of continental nucleus in Paleoarchean and continental hyperplasia in Mesoarchean, South America craton experienced two stage cratonic consolidation process in Late Archaean and Paleoproterozoic, and it began to destroyed in Mesoproterozoic and Neoproterozoic. Comparing the similarities and differences between North China Craton and South America Craton, the authors presumed that the mechanism of tectonic evolution was controlled by mantle plume tectonics in the early continental tectonics, and transformed into tectonics accretion mechanism dominated by plate motion. This research is beneficial to deepening knowledge and comparison of metallogenic process and its effects in ore concentrate area.