Zbigniew SAWŁOWICZ 1 , Thomas G. KAYE 2 REPLACEMENT OF IRON SULPHIDES BY OXIDES IN THE DINOSAUR BONE FROM THE LANCE FM. (WYOMING, USA) - PRELIMINARY STUDY. Abstract: A unique aggregate of framboidal pyrite and iron oxides was found in the vascular canals of dinosaur bone from the Lance Fm. and was studied using SEM/EDS. Various types of pyrite, massive and framboidal, and their subsequent oxidation and replacement by iron oxides are described. The proposed sequence of events is as follows: 1: formation of pyrite framboids and framboidal aggregates; 2: infilling of the interstices between pyrite crystals by massive pyrite; 3: oxidation of former sulphides. Keywords: dinosaur bones, pyrite, iron oxides, framboids, replacement INTRODUCTION Pyritized organic remains are common in the sedimentary record. Pyrite and iron oxides generally fill open voids, and can replace organic matrix or “soft parts”. Pyrite can adopt various forms, from massive to aggregated, euhedra, or framboids. Excellent descriptions of the mechanisms for fossil pyritization were given, for example, by Canfield and Raiswell (1991) and Raiswell et al. (1993). Infilling by iron oxides are quite common, although detailed studies are rare (Pfretzschner 2001a,b). Pawlicki and Nowogrodzka-Zagorska (1998) and recently Schweitzer et al. (2005) suggested that small mineral structures could be exceptionally preserved blood which stirred an especially hot discussion on the possible implications. Schweitzer and Horny (1999) presented iron and oxygen-rich microstructures in the bone tissues of Tyrannosaurus rex but rejected the structures as framboids due to their composition of iron oxides. This paper documents various stages of framboidal pyrite replacement by oxides in dinosaur bone. SAMPLING AND METHODS OF INVESTIGATIONS Four to five cm size fragments of large dinosaur long bones most likely from Hadrosaur or Triceratops were collected from the dark shales of the Lance Formation near the town of Lance Creek Wyoming. Several small (0.2-0.7 mm) pieces, were fractured from the bone, mounted and carbon coated for analysis. Equipment used was a field-emission SEM (HITACHI S-4700), equipped with YAG (BSE) detector and EDS analyzer (NORAN Vantage). 1 Institute of Geological Sciences, Jagiellonian University, Oleandry 2A, 30-063 Krakow; email: zbyszek@ing.uj.edu.pl 2 404 Hillcrest, Prospect Heights, Illiniois, USA, 60070; email: tom@tomkaye.com