Original Paper

Contributions to Mineralogy and Petrology

, Volume 164, Issue 2, pp 245-259

Open Access This content is freely available online to anyone, anywhere at any time.

Low-temperature zircon growth related to hydrothermal alteration of siderite concretions in Mississippian shales, Scotland

  • Maciej J. BojanowskiAffiliated withInstitute of Geochemistry, Mineralogy and Petrology, University of Warsaw Email author 
  • , Bogusław BagińskiAffiliated withInstitute of Geochemistry, Mineralogy and Petrology, University of Warsaw
  • , Euan ClarksonAffiliated withSchool of Geosciences, University of Edinburgh
  • , Ray MacdonaldAffiliated withInstitute of Geochemistry, Mineralogy and Petrology, University of Warsaw
  • , Leszek MarynowskiAffiliated withFaculty of Earth Sciences, University of Silesia

Abstract

Zircon occurs in voids and cracks in phosphatic coprolites enclosed in siderite concretions in Mississippian shales near Edinburgh, Scotland. The zircon formed during hydrothermal alteration of early-diagenetic concretions and occurs as spherical aggregates of prismatic crystals, sometimes radiating. Vitrinite reflectance measurements indicate temperatures of ~270°C for the zircon-bearing concretions and the host shales. Molecular parameter values based on dibenzothiophene and phenanthrene distribution and occurrence of di- and tetra-hydro-products of polycyclic aromatic compounds suggest that the rocks experienced relatively high-temperature aqueous conditions related to hydrothermal fluids, perhaps associated with neighboring mafic intrusions. The zircon was dissolved from the concretions, transported in fluids, and reprecipitated in voids. This is the first record of the precipitation of authigenic zircon in sedimentary rock as a new phase, not as outgrowths.

Keywords

Zircon Concretions Diagenesis Hydrothermal alteration Vitrinite reflectance PAHs