Petrogeochemical reconstruction of the nature of metamorphic rocks and thegeodynamic settings of formation of their protoliths (new approaches and restrictions)

A method for reconstructing the protonature of metamorphic rocks and the se ttings of formation of their protoliths is proposed. It is a system approac h to analysis of the geological and geochemical features of rocks. It impli es a petrogeochemical modeling of the settings of formation of Phanerozoic and Precambrian rock complexes, which takes into account their possible dif ferences according to the compositions of heterochronous structures, thus p roviding more correct reconstructions. The parameters of the settings are p resented as functions of the chemical characteristics of rocks. The multist age multilevel reconstruction of the protonature of metamorphic rocks inclu des elucidation of the regimes of formation of their protoliths. The propos ed approach was tested on some Phanerozoic structures of different regions of the world and on some Precambrian metamorphic complexes of the northeast ern Baltic Shield. It is concluded that the proposed method provides the mo st adjustable and reliable reconstructions than various diagram methods use d at present.