Geodynamic process and its geologic manifestations in the continents

• Date: 2018
• Main Author: Usenko, O.
• Format: Article
• Language: Russian
• Published: S. Subbotin Institute of Geophysics of the NAS of Ukraine 2018
• Subjects: plume; asthenosphere—lithosphere border; mantle; crust; fluid currents; interactions in the system crystals-melt-fluid; geodynamic process; folded area; rift; trap province; magmatic rocks; flysch stratum
• Online Access: https://journals.uran.ua/geofizicheskiy/article/view/147477
• Journal Title: Geofizicheskiy Zhurnal

The data on the composition of the mantle and crust, results of experimental studies on melting under the pressure interval 0,5—0,7 GPa and temperatures 500—2000 °C have been integrated. Theoretical model of deep process behaviour has been proposed which is based on geophysical thermal model and in addition takes into account physical-chemical interactions in the system crystals-melt-fluid and their alterations with the increase of pressure and temperature. The melts crystallize on the surface as magmatic rocks and some part of the fluid forms the chemogenic component of the sedimentary strata. Composition, thickness and structure of sedimentary stratum are determined by the processes occurred at the border of melting layer (asthenosphere) and the lithosphere (LAB). Analysis of complex geological information has been conducted, including age and composition of magmatic and synchronous sedimentary rocks, tectonic structure, metamorphism and hydrothermal activity of phanerozoic structures. Comparison of deep process predictable by theoretical model with its geologic manifestations on the surface allows to affirm that there is some relationship between the change of occurrence of melting layer in geodynamic process and geological events specified. Basic regimes have been distinguished with each of them specified by its own set of magmatic and volcanogenic-sedimentary complexes. In the regime of “folded area” ultrabasite (lertsolite) complexes arrear at first, then volcanogenic picrites (not compulsory) are formed and then — basalts or alkaline rocks complexes. At the last stage multiphase massifs with gabbro, andesites, granites are produced. Special feature of this regime is formation of thick (rhythmic strata). Its metamorphism was realized later as a result of formation of melting focus in the crust. Rift regime is characterized by smaller integrated thickness of sediments. Constituents of these strata preferably are lavas of ultrabasites and basalts as well as of andesites and liparites. Dominance of chemogenic-sedimentary rocks is specific and minor development of metamorphic transformations. Trappe regime is manifested by magmatic rocks. Spatial connection with kimberlites and carbonatites is often observed. Magmatic ultrabasites are close to comatiite standard, basalts are widely distributed and andesites are negligibly low by amount. Sedimentary rocks are practically not represented. Dependences determined give possibility to use material composition and structural features of rocks for reconditioning of paleogeodynamic processes.