EPR and SEM study of organo-mineral associations in Lower Permian evaporite dolomites |
| |
Authors: | Akhmet A Galeev V M Vinokurov F A Mouraviev and Yu N Osin |
| |
Institution: | (1) Kazan State University, Kazan, Russian Federation;(2) Zavoisky Physical-Technical Institute, Russian Academy of Sciences, Kazan, Russian Federation;(3) Faculty of Geology, Kazan State University, 18 Kremlevskaya ulitsa, Kazan, 420008, Russian Federation |
| |
Abstract: | Lower Permian (280 to 300 Ma) evaporite dolomite rocks from the western part of the East European platform were studied by
optical microscopy, scanning electron microscopy with microprobe analysis, and X-band electron paramagnetic resonance (EPR).
Microscopic studies showed that many dolomite grains consist of an aggregation of submicron dolomite crystals (0.2–2 μm) as
a spheroidal nucleus which is overgrown by a larger dolomite rhombohedron (5–20 μm). The EPR spectrum of a raw rock sample
is mainly determined by thermally unstable radiation centers and Mn2+ ions substituted at Ca and Mg sites in the dolomite crystal structure. The presence of dispersed organic matter at low concentrations
was revealed from the backscattered electron images with a microprobe analysis of carbon-enriched areas on cleaved surfaces
and the registration of the carbon-centered free organic radical signal in EPR spectra of heat-treated samples. A model of
two successive growing stages for dolomite grains is suggested: the dolomite (or dolomite precursor) nucleation and aggregation
in the colloidal stage to form suspended organo-mineral particles before the gravitational settling, and early diagenetic
overgrowth at lower temperature and more stable environment of the marine bottom to form a dolomite rhombohedron. The observation
of both growing stages for dolomite grains indicates that there was no recrystallization in the later stages of the rock history. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|