Naslov
Organic geochemistry of Ljubija siderite ore deposit, NW Bosnia

Autori
Strmić, Sabina ; Spangenberg, Jorge E. ; Palinkaš, Ladislav

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Geochimica et Cosmochimica Acta, v. 68, Special Supplement / - , 2004

Skup
Goldschmidt Geochemistry Conference

Mjesto i datum
Kopenhagen, Danska, 05.06.2004. - 11.06.2004

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
siderite; replacement; organic matter; biomarkers

Sažetak
The Ljubija ore field (44.55° N, 16.3° E), NW Bosnia, is presented by siderite replacement of Middle/Upper Carboniferous carbonates and siderite-polysulfide shales. The results of molecular and isotopic analyses of the hydrocarbons (HC) extracted from ore and host rock samples give insights into the ore fluid composition and ore deposition. The gas chromatography of the saturated HC of all samples are dominated by few low molecular-weight homologous series, including normal alkanes with 11 to 25 C atoms and isoprenoids with 15, 18, 19 and 20 C atoms (farnesane, norpristane, pristane, phytane). Mineralized samples display unimodal distribution centered on normal alkanes with 13 to 16 C atoms. Barren samples, display both bimodal (centered on normal alkanes with 13 to 16 C atoms and an unresolved complex mixture (UCM) in region between n-C30 and n-C40) and unimodal (centered on normal alkanes with 13 to 16 C atoms) distributions. Differences in the hydrocarbon distribution can result from variations in biological sources, thermal maturity and as a consequence of hydrothermal alteration. Variation in biological sources is the most likely cause of the varied normal alkane distributions. The normal alkanes n-C13-19 are typical for a source rock derived from marine plankton and algae. Another possibility is that the hydrocarbon distribution reflects hydrothermal alteration of kerogen to lower molecular weight normal alkanes as a result of hydrous pyrolysis during mineralization. The biomarkers hopanes and steranes were detected only within barren samples. The presence of hopanes indicates on bacterial activity during deposition of host rocks. The absent of hopane TM and the presence of TS suggest mature organic matter. High ratio C27 / C29 steranes indicates on strong marine input of organic matter. The maturation of organic matter is estimated by high bb to aa sterane ratios. In barren and mineralized samples the individual normal alkanes have uniform d13C values (-29.8 to - 25.9 ‰ , VPDB) across the C-number range. Shorter-chain hydrocarbons are slightly enriched on 13C what can be caused by cracking of longer-chain hydrocarbons from common marine phytoplanktonic origin. Contribution of isotopically light alkanes, by ore forming fluid, can not be excluded.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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