The geochemical and genetic role of organic substances in postmagmatic derivatives of alkaline plutons |
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Authors: | V N Ermolaeva N V Chukanov I V Pekov L N Kogarko |
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Institution: | 1.Vernadsky Institute of Geochemistry and Analytical Chemistry,Russian Academy of Sciences,Moscow,Russia;2.Institute of Problems of Chemical Physics,Russian Academy of Sciences,Chernogolovka, Moscow oblast,Russia;3.Faculty of Geology,Moscow State University,Moscow,Russia |
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Abstract: | Solid bituminous substances (SBS) are common components of the late hydrothermal mineral assemblages of peralkaline pegmatites.
SBS are formed in a reductive setting as a result of progressive sorption of minor carbon-bearing molecules (CO, CO2, CH4, C2H6, C2H4, etc.), their polymerization, transformation into aromatic compounds (reformation), and selective oxidation on microporous
zeolite-like Ti-, Nb-, and Zrsilicates serving as sorbents and catalysts. The oxygen-bearing aromatic compounds with hydrophile
functional groups (−OH, −C=O, −COOH, −COO) act as complexing agents with respect to Th, REE, U, Zr, Ti, Nb, Ba, Sr, Ca, resulting
in transfer of these bitumenophile elements under low-temperature hydrothermal conditions in the form of water-soluble macroassociates
of the micelle type. Th, REE, and to a lesser extent, U, Zr, Ti, and Nb concentrate at the late stage of the hydrothermal
process as microphases impregnating SBS or macroscopic segregations of Th and REE minerals. At the final stage, homogeneous
SBS break down into organic (partly together with Ca, Sr, Ba, and Pb) and mineral (with Th, Ln, Y, Ti, Nb, Ca, Na, K, Si)
microphases. |
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