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
V.N. Sharapov1,2, M.P. Mazurov1, K.V. Chudnenko3, K.E. Sorokin1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
Keywords: traps, modeling, fluids, infiltration metasomatism, Siberian Platform
Abstract
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 p O2 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.
DOI: 10.15372/RGG2019052
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