Micro-scale sulfur isotope and chemical variations in sphalerite from the Bleiberg Pb-Zn deposit,Eastern Alps,Austria |
| |
| Institution: | 1. Montanuniversität Leoben, Chair of Resource Mineralogy, Peter Tunner-Straße 5, 8700 Leoben, Austria;2. Scottish Universities Research Centre (SUERC), East Kilbride, Glasgow G75 0QF, Scotland, UK;1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;2. Department of Geological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada;3. Scottish Universities Environmental Research Center, East Kilbride G75 0QF, UK;1. Key Laboratory for Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 5106410, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. GeoRessources, Université de Lorraine, CNRS, UMR 7359, Boulevard des Aiguillettes, BP 70239, F-54506 Vandoeuvre-lès-Nancy, France;2. Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine, CNRS, UMR 7358, 15 Rue Notre Dame des Pauvres, BP 20, F-54501 Vandoeuvre-lès-Nancy Cedex, France;3. Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier, 1381 Rue de la Piscine – BP 53, F-38041 Grenoble cedex 9, France;4. European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, France;1. Géosciences Montpellier, UMR CNRS 5243, Université Montpellier, Place E. Bataillon, CC 60, F-34095 Montpellier, France;2. BRGM, Bureau de Recherches Géologiques et Minières, Territorial Direction Languedoc-Roussillon, 1039 Rue de Pinville, 34000 Montpellier, France;3. BRGM, Bureau de Recherches Géologiques et Minières, 3 Avenue Claude Guillemin, BP 36009, 45060 Orléans Cedex 2, France;1. Department of Energy and Resources Engineering, Inha University, Incheon, Republic of Korea;2. Development of Mineral Resources (DMR), Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea;3. Division of Polar Earth-System Sciences, Korea Polar Research Institute (KOPRI), Incheon, Republic of Korea |
| |
| Abstract: | The Bleiberg Pb-Zn deposit in the Drau Range is the type locality of Alpine-type carbonate-hosted Pb-Zn deposits. Its origin has been the subject of on-going controversy with two contrasting genetic models proposed: (1) the SEDEX model, with ore forming contemporaneously with sedimentation of the Triassic host rocks at about 220 Ma vs. (2) the epigenetic MVT model, with ores forming after host rock sedimentation at about 200 Ma or later. Both models assume that, on a deposit or even district scale, a fixed paragenetic sequence of ore minerals can be established. The results of our detailed petrographic, chemical and sulfur isotope study of two key ore-samples from two major ore horizons in the Wetterstein Formation at Bleiberg (EHK02 Erzkalk horizon and Blb17 Maxer Bänke horizon) demonstrate that there is no fixed paragenetic sequence of ore minerals. Small-scale non-systematic variations are recorded in textures, sphalerite chemistry and δ34S. In each sample, texturally different sphalerite types (colloform schalenblende, fine- and coarse-grained crystalline sphalerite) co-occur on a millimeter to centimeter scale. These sphalerites represent multiple mineralization stages/pulses since they differ in their trace element inventory and in their δ34S. Nonetheless, there is some correspondence of sphalerite micro-textures, sulfur isotope and chemical composition between the two samples, with microcrystalline colloform schalenblende being Fe-rich, having high Fe/Cd (15 and 9, respectively) and a light sulfur isotope composition (δ34S −26.0 to −16.2‰). Cadmium-rich and Fe-poor sphalerite in both samples has relatively heavier sulfur isotope composition: in sample EHK02 this sphalerite has Fe/Cd of ∼0.5 and δ34S from −6.6 to −4.6‰; in sample Blb17 Fe/Cd is ∼0.1 and δ34S ranges from −15.0 to −1.5‰. Barite, which is restricted to sample EHK02, has δ34S ≈ 17‰. The large variations in δ34S recorded on the mm to cm-scale is consistent with variable contributions of reduced sulfur from two different sulfur reservoirs. The dominant reservoir with δ34S values <−20‰ likely results from local bacteriogenic sulfate reduction (BSR), whereas the second reservoir, with δ34S about −5‰ suggests a hydrothermal source likely linked with thermochemical sulfate reduction (TSR). Based on this small- to micro-scale study, no simple, deposit-wide paragenetic and sulfur isotope evolution with time can be established. In the Erzkalk ore (sample EHK02) an earlier Pb-Zn-Ba stage, characterized by heavy sulfur isotope values, is succeeded by a light δ34S-dominated Zn-Pb-F stage. In contrast, the several mineralization pulses identified in the stratiform Zn-Pb-F Maxer Bänke ore (sample Blb17) define a broad trend to heavier sulfur isotope values with time. The interaction documented in these samples between two sulfur reservoirs is considered a key mechanism of ore formation. |
| |
| Keywords: | Sphalerite Carbonate hosted Pb-Zn deposits In situ sulfur isotope analysis Trace elements Eastern Alps |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
