Abstract
Relevance of the study is due to the importance of composition and maturity of the dispersed organic matter (DOM) as indicators of rock forming conditions, which may contribute to the paleoecological reconstruction of sedimentation conditions for rocks in the ore-bearing stratum of the Safyanovskoe deposit. Objective: to analyze the composition and characteristics of DOM in carbon-siliceous rocks of the ore-bearing stratum of the Safyanovsky copper-pyrite deposit. The obtained characteristics of the DOM make it possible to reveal the source of original accumulation and the level of its transformation under the influence of various geological processes. Methods. A detailed study of DOM was carried out by the EPR method (electron paramagnetic resonance) for powder preparations. EPR spectra were recorded at room temperature on X-band spectrometers DX-70, ESR 70-03 DX/2, and SE/X-2547 RadioPAN. The analytical procedure for studying organic matter (OM) included: determination of insoluble residue and C org content in the rock, extraction of the chloroform bitumoids (CB) and the alcohol-benzol bitumoids (ABB), humic acids (HA), determining the group composition of CB and hydrocarbons (HC), chromatographic fractionation with determination of the sum of methane-naphthenic and aromatic fractions of hydrocarbons, GC-MS analysis of n-alkanes, cyclic and polyaromatic hydrocarbons (PAHs). GC-MS analysis was performed on the complex Hewlett Packard 6850/5973 with a quadrupole mass detector and analytical information processing software. Results. Analysis of the EPR spectra of carbon-siliceous rocks of the Safyanovskoe deposit showed the presence of the two types of carbon signal (C-org), characteristic of the plant and the animal residues. It was also found that the DOM has never been exposed to temperatures greater than 300 °C. Geochemical analysis of OM indicates that DOM is at a high maturation stage (residual organic matter (ROM) > 99%). But the type of distribution of polyaromatic hydrocarbons (PAHs) suggests that the primary OM was specifically altered at elevated temperatures. Conclusions. DOM of carbon-siliceous rocks of the Safyanovsky deposit is genetically the same, its type is mainly sapropelic and accumulation is associated with marine conditions. A characteristic feature is, on the one hand, its high polymerization, which is typical for DOM of the stage of late mesocatagenesis, and, on the other hand, its molecular composition does not allow us to talk about the maturation of DOM in the process of natural regional metamorphism.
Highlights
Safyanovskoe deposit is located within the East Urals rise in the southern part of the Rezhevskaya structural-formational zone (Fig. 1)
In order to determine the genesis of dispersed organic matter (DOM) we studied limestone opened by drift and carbon-bearing-siliceous rocks drift and quarry
The signal characteristics after annealing at 300 °C: g ~ 2,0031 ± 0.0001 and line width ∆B ~ 0.5–0.7 mT, indicating the presence of organic matter (OM) plant residues metamorphosed at relatively low-temperature conditions [8]
Summary
Safyanovskoe deposit is located within the East Urals rise in the southern part of the Rezhevskaya structural-formational zone (Fig. 1). It is localized in the altered volcanic and volcano-sedimentary rocks of acid-medium composition, which opened in the career of the Main ore deposit. Main ore body of massive pyrite ores has a length of 400 m and a width of up to 140 m. The southern flank of the ore body rapidly tapers out, and the northern passes in a series of apophyses, which are represented by massive pyrite, copper-zinc and vein-disseminated sulfide ores [1]. Host rocks tectonically elaborated, brecciated and hydrothermally altered. Ore-hosting strata has a capacity of approximately 500 m
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