Evaluation of the nature of connection of metasomatic rocks and their educts by their acid-base properties
Authors: G. P. Dvornik
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The author developed the systematics of metasomatic rocks according to acid-base properties, expressed by the magnitude of the general basicity. There are four distinguished groups of metasomatites: highly basic (carbonatites, magnesian and calcareous endoskarns and exoscarnas, rodingites, calcite and dolomite-ankerite metasomatites), basic (serpentinites, fenites, gumbaites, microclinites, talcites, microcline-sericite, carbonate-talc and magnesite metasomatites), medium-basic (albitites, listvenites, eisites, propylites, biotite-orthoclase metasomatites), low-basic (berezites, muscovite-quartz greisens, argillizites, secondary quartzites, hematite-magnetite quartzites, jasperoids, quartz-sericite, chlorite-sericite-quartz, diaspore-pyrophyllite and quartz-pyrophyllite metasomatites). The author established signs of difference by the nature of the bond with the educt between metasomatites over aluminosilicate and carbonate rocks. Metasomatic rocks formed along the aluminosilicate substrate (magnesian and calcareous endoskarns, fenites, biotite-orthoclase and microcline-sericite metasomatites, albitites, serpentinites, gumbeites, eisites, greisenes, berezites, argillisites) have a characteristically significant positive correlation by basicity value with the rocks of the educt. The revealed differences are due to the peculiarities of the composition of substituted aluminosilicate and carbonate rocks and the hydrothermal solutions affecting them. The author established a significant positive correlation between the basicity of alkaline metasomatites (albitic, kalispat, feldspathoid), metasomatites of the acid leaching stage (muscovite-quartz greisens, secondary quartzites, berezites, argillisites) from the inner zones of experimental metasomatic columns and the composition of initial solutions expressed by pH. In addition, the basicity of magnesian and calcareous skarns weakly correlates with the pH of hydrothermal solutions.