Dynamics of metasomatic transformation of the rocks of the lithospheric mantle and Earth's crust in deep-fault zones controlling the Siberian Platform trap magmatism

• Published in: Russian geology and geophysics Vol. 60; no. 8; pp. 833 - 844
• Main Authors: Sharapov, V. N, Mazurov, M. P, Chudnenko, K. V, Sorokin, K. E
• Format: Journal Article
• Language: English
• Published: Allerton Press 01.08.2019
• Subjects: Aldan Shield; alteration; Asia; basalts; basement; carbonate rocks; chemically precipitated rocks; Commonwealth of Independent States; computer programs; crust; crust-mantle boundary; crystalline rocks; data processing; deep-seated structures; evaporites; fault zones; faults; fluid flow; fluid phase; Geophysics; igneous and metamorphic rocks; igneous rocks; infiltration; intraplate processes; lithosphere; lower crust; Lower Triassic; mantle; Mesozoic; metamorphic rocks; metasomatic rocks; metasomatism; numerical models; Paleozoic; Permian; Petrology; plate tectonics; rifting; Russian Federation; sedimentary rocks; Siberian Platform; Siberian Traps; solid Earth (tectonophysics); sulfates; thermodynamic properties; trap rocks; Triassic; upper mantle; Upper Permian; volcanic rocks
• ISSN: 1068-7971; 1878-030X
• DOI: 10.15372/RGG2019052

For a multirate approximation, we have determined the dynamics of rock heating by a magmatic-fluid flow in a flat permeable zone cutting the cratonic lithosphere of the Siberian Platform from a magma chamber at a depth of 50 km to the Earth's surface. This dynamics is compared with the dynamics of infiltration metasomatism in a three-layer lithosphere section: (1) harzburgitic mantle (depth 50-40 km), (2) crystalline basement (39-7 km), whose composition was simulated by the section of rocks hosting the skarn deposits of the Aldan Shield, and (3) platform cover (6-0 km), with its simplified rock compositions specified on the basis of the rock compositions in the southern and northern parts of the trap area of the Siberian Platform. Numerical modeling of the metasomatic transformation of rocks was performed in a multireservoir flow reactor, using the Selektor software. The initial composition of fluids in a magmatic source varied from highly reduced (water-methane) to ordinary (water-acid) (lg pO2 from -13.0 to -12.0). The obtained balances of the interacting phases show no significant change in the mass of aluminosilicate rocks in the mantle and Earth's crust sections and a significant loss of their mass under replacement of carbonate and sulfate deposits.