The origin of organic matter in the Lower Silesia copper-bearing shales

Mariusz J. Rospondek, Anna Fijałkowska, Anna Lewandowska


Pochodzenie substancji organicznej w łupkach miedzionośnych Dolnego Śląska

Stratified Lower Silesian copper deposits, similar to other deposits of this type, are enriched in organic matter. Microscope analyses of this substance occurring in the examined lithofacies of copper-bearing shales indicate that this organic material consists predominantly of structureless organic debris. Recognizable organic debris (vascular bundle, wood remains and palynomorphs) occur in subordinate amounts. The estimation of chemical nature of the quantitatively dominant but microscopically unidentifiable organic matter at the molecular level, was carried out using gas capillary chromatographic analysis of the pyrolysis products of kerogen Py(610ºC)- GC. Kerogen occurring in the copper-bearing shales consists of aliphatic macromolecules (n-alkanes and n-alk-l-enes were identified among the pyrolysis products). Thus composition is characteristic for biopolymers which are highly resistant to (bio)chemical degradation occurring in algae (algaenan) and protective anvelopes of higher plants (subcran and cutan). However, since no such tissues were encountered microscopically, organic matter must be derived from marine algae.

The presence of thiophene structural units in kerogen.indicates anaerobic (H2S) conditions in the sedimentous environment. When compared with other types of organic material, the structureless organic matter is enriched in metal sulphides. The sulphides are directly bound to structureless organic matter and occur as framboids. Organic matter is enveloping the sulphide concentrations. This indicates the important role of this organic malter in framboid formation by the isolation of precipitated iron sulphide phases from sedimentation environment and protection of these sulphides from replacement by copper sulphides due to action of Cu-bearing solutions.

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