Abstract
The integrated geological analysis of the Tocantins Province greenstone belts allow us to envisage the following stages in the evolution of the greenstone terra ins in Archean times: a . initial rifting of the tonalitic crust followed by komatiitic volcanism (chiefly peridotites) and ending with tholeiitic basalts; b. period of widespread chemical sedimentation (cherts and dolomites); c. recurrency of the volcanic activity but of a calc-alcaline nature; and d . individualization of restricted sites of chemical sedimentation (BIF, cherts, gondites, exhalites) and carbonaceous sediments wich have evolved into progressive more mature deposits (wackes to pelitic sandstones). The tectono-metamorphic evolution starts with: a. the partial replacement of the protoliths trough hidrothermal changes simultaneous to the volcanism (= 2.7 Ga); b. the greesntones sequences were submited by two deformation events, with the metamorphism reaching the greenschists facies; c. emplacement of the granodioritic domes and maior intrusions of plagiogranites into the supracrustal rocks; d . intrusions of diabase and diorites, particularly in the sialic domains, during a distension tectonic stage; and e. development of thrust-faults during a tangential tectonic stage that brought about the internal rupture of the greenstones and the adjacent sialic terrains.
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