Summary of Lead Isotope Data from Ore Deposits of the Eastern and Southern Alps: Some Metallogenetic and Geotectonic Implications

Köppel, V.

doi:10.1007/978-3-642-68988-8_18

Cited by 24 publications

(15 citation statements)

References 8 publications

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“…The deep burial carbonate cements (e.g., saddle dolomite III) are not shown. Köppel, 1983;Köppel and Schroll, 1988) during high heat flow in the initial phase of the Middle and/or Upper Anisian (Old Slovene) extensional tectonic phase recognized in other regions of the Southern Alps by Buser (1978) and in the Drau Range by Bechstädt et al (1978). The Mežica deposits formed in Late Triassic to Early Jurassic by thermally driven fluid flow during the crustal extension of the Penninic/Ligurian ocean .…”

Section: Previous Geochemical Studiesmentioning

confidence: 96%

Hydrocarbon Biomarkers in the Topla-Mezica Zinc-Lead Deposits, Northern Karavanke/Drau Range, Slovenia: Paleoenvironment at the Site of Ore Formation

Spangenberg¹,

Herlec²

2006

Economic Geology

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The Mississippi Valley-type zinc and lead deposits at Topla (250,150 metric tons (t) of ore grading 10 wt % Zn and 3.3 wt % Pb) and Mežica (19 million metric tons (Mt) of ore grading 5.3 wt % Pb and 2.7 wt % Zn) occur within the Middle to Upper Triassic platform carbonate rocks of the northern Karavanke/Drau Range geotectonic units of the Eastern Alps, Slovenia. The ore and host rocks of these deposits have been investigated by a combination of inorganic and organic geochemical methods to determine major, trace, and rare earth element (REE) concentrations, hydrocarbon distribution, and stable isotope ratios of carbonates, kerogen, extractable organic matter, and individual hydrocarbons. These data combined with sedimentological evidence provide insight into the paleoenvironmental conditions at the site of ore formation. The carbonate isotope composition, the REE patterns, and the distribution of hydrocarbon biomarkers (normal alkanes and steranes) suggest a marine depositional environment. At Topla, a relatively high concentration of redox sensitive trace elements (V, Mo, U) in the host dolostones and REE patterns parallel to that of the North American shale composite suggest that sediments were deposited in a reducing environment. Anoxic conditions enhanced the preservation of organic matter and resulted in relatively higher total organic carbon contents (up to 0.4 wt %). The isotopic composition of the kerogen (δ 13 Ckerogen = -29.4 to -25.0‰, δ 15 Nkerogen = -13.6 to 6.8‰) suggests that marine algae and/or bacteria were the main source of organic carbon with a very minor contribution from detrital continental plants and a varying degree of alteration. Extractable organic matter from Topla ore is generally depleted in 13 C compared to the associated kerogen, which is consistent with an indigenous source of the bitumens. The mineralization correlates with δ 15 Nkerogen values around 0 per mil, 13 C depleted kerogen, 13 C enriched n-heptadecane, and relatively high concentrations of bacterial hydrocarbon biomarkers, indicating a high cyanobacterial biomass at the site of ore formation. Abundant dissimilatory sulfate-reducing bacteria, feeding on the cyanobacterial remains, led to accumulation of biogenic H2S in the pore water of the sediments. This biogenic H2S was mainly incorporated into sedimentary organic matter and diagenetic pyrite. Higher bacterial activity at the ore site also is indicated by specific concentration ratios of hydrocarbons, which are roughly correlated with total Pb plus Zn contents. This correlation is consistent with mixing of hydrothermal metal-rich fluids and local bacteriogenic sulfide sulfur. The new geochemical data provide supporting evidence that Topla is a low-temperature Mississippi Valley-type deposit formed in an anoxic supratidal saline to hypersaline environment. A laminated cyanobacterial mat, with abundant sulfate-reducing bacteria was the main site of sulfate reduction.

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Section: Previous Geochemical Studiesmentioning

confidence: 96%

Hydrocarbon Biomarkers in the Topla-Mezica Zinc-Lead Deposits, Northern Karavanke/Drau Range, Slovenia: Paleoenvironment at the Site of Ore Formation

Spangenberg¹,

Herlec²

2006

Economic Geology

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“…Compared to the Lengenbach mineralisation, the average isotopic composition of Pb-Zn deposits in Triassic host rocks from the Eastern and Southern Alps as well as the Massif Central and the Betic Cordillera are less radiogenic and yield anomalous high model ages (Brevart et al 1982;K6ppel 1983;Le Guen et al 1991;Arribas and Tosdal 1994). Pb isotope analyses proved that Pb and other metals were leached from basement rocks (K6ppel 1988;K6ppel and Schroll t988).…”

Section: Pb Isotopes Of the Stratiform Mineralisationmentioning

confidence: 96%

Geochemistry and genesis of the Lengenbach Pb-Zn-As-Tl-Ba-mineralisation, Binn Valley, Switzerland

Hofmann

Knill

1996

Mineral. Deposita

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Abstract. The Lengenbach Pb-Zn-As-TI-Ba mineralisation is located in Triassic dolostones of the Penninic zone in the Swiss Alps where Alpine metamorphism reached upper greenschist to lower amphibolite grade. Geochemical data are used to constrain the origin of this unique occurrence. Two metamorphic redox environments are present: the As(III)-rich zone is controlled by barite-pyrite while the reduced zone contains graphite or pyrrhotitepyrite and formally zerovalent As. The As(III)-rich zone is characterised by a mineral assemblage consistent withfO2 in the stability field of barite + pyrite. An As-(Pb, T1)-rich sulphide melt coexisted with a hydrothermal fluid at > 300 °C in this zone. Mineralised dolostones are anomalous in As, Pb, Ag, T1, Hg, Zn, Ba, Cd, Fe, Cu, Mo, U, V, B, Ga, Cr and possibly Sn and Au (in order of decreasing enrichment). As, Pb and Zn are present in the 0.1 to 1% range, T1 and Ag reach several hundred ppm. Uraninite is concentrated in silicate-rich bands and yields a late Alpine U-Pb age of 18.5 + 0.5 Ma. Pb-and S isotopic variations are interpreted by metamorphic overprinting and re-equilibration within an isochemically metamorphosed mineralisation. Hydrothermal sulphides are more strongly affected by uranogenic Pb than massive Pb-As-sulphides representing a former sulphide melt. The least overprinted mineralisation is characterised by 2°6pb/2°*pb = 18.44 -18.56, 2°TPb/2°4Pb = 15.60 -15.75, 2°Spb/2°4pb = 38.44 -38.84 and ~534S (sulphide) = -25 + 2%0. S isotopic variations are largely a result of sulphide-sulphate re-equilibration yielding temperatures of 450 + 30°C. SVSr/86Sr ratios of mineralised samples are lower than or equal to host dolostones, precluding major infiltration of basement-derived fluids during Alpine metamorphism. The Sr source (87Sr/86Sr close to 0.708) probably was seawater with a radiogenic, detrital mineral component. The genesis of the unique Lengenbach mineralisation is interpreted as the result of isochemical metamorphic overprinting of a carbonate hosted stratiform sulphide mineralisation. Well-crystallised sulphide minerals in Correspondence to: B.A. Hofmann fissures and druses formed during retrograde cooling of a sulphide melt in equilibrium with a hydrothermal fluid. The primary mineralisation was probably formed at or close below the sea floor and fed by sulphide-poor hydrothermal fluids. Sulphide was largely derived from seawater by open system bacterial sulphate reduction. U, V and Mo may be seawater-derived.

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“…In addition, the ore lead is isotopically different from host-rock lead. However, according to Köppel (1983), basement rocks and upper Carboniferous to Permian magmatic rocks of the Southern Alps exhibit similar characteristics as the lead in the Triassic Pb-Zn deposits, whereas the lead of feldspars from Triassic volcanics shows significant differences. The syndiagenetic Pb-Zn deposits in Triassic carbonates could have obtained lead from lower crustal rocks, or material thereof, by leaching processes (Köppel, 1983).…”

Section: Sedex Depositsmentioning

confidence: 99%

“…They predominantly contain epigenetic replacement bodies and minor but extensive syngenetic stratiform orebodies in carbonate rocks (Schneider, 1964). Klau & Mostler (1986) regard the deposits as MVT based on the Pbisotope data of Köppel (1983) which, according to them, shows no relation between magmatic rocks and mineralization. In addition, the ore lead is isotopically different from host-rock lead.…”

Section: Sedex Depositsmentioning

confidence: 99%

Carbonate-Hosted Base Metal Deposits

Kamona¹

2011

Earth and Environmental Sciences

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Summary of Lead Isotope Data from Ore Deposits of the Eastern and Southern Alps: Some Metallogenetic and Geotectonic Implications

Cited by 24 publications

References 8 publications

Hydrocarbon Biomarkers in the Topla-Mezica Zinc-Lead Deposits, Northern Karavanke/Drau Range, Slovenia: Paleoenvironment at the Site of Ore Formation

Hydrocarbon Biomarkers in the Topla-Mezica Zinc-Lead Deposits, Northern Karavanke/Drau Range, Slovenia: Paleoenvironment at the Site of Ore Formation

Geochemistry and genesis of the Lengenbach Pb-Zn-As-Tl-Ba-mineralisation, Binn Valley, Switzerland

Carbonate-Hosted Base Metal Deposits

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