Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2014 Stable tellurium isotope variability in ore-forming systems: A theoretical and experimental approach Andrew Fornadel Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Geochemistry Commons Recommended Citation Fornadel, Andrew, "Stable tellurium isotope variability in ore-forming systems: A theoretical and experimental approach" (2014). Graduate Theses and Dissertations. 14075. https://lib.dr.iastate.edu/etd/14075 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Stable tellurium isotope variability in ore-forming systems: A theoretical and experimental approach by Andrew P. Fornadel A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Geology Program of Study Committee: Paul G. Spry, Major Professor Carl E. Jacobson Alan D. Wanamaker Halil Ceylan Aaron D. Sadow Iowa State University Ames, Iowa 2014 Copyright © Andrew P. Fornadel, 2014. All rights reserved. ii TABLE OF CONTENTS Page Acknowledgements .................................................................................................. v Abstract………………………………. .................................................................... vi CHAPTER 1: PRECISE ANALYSIS OF STABLE TELLURIUM ISOTOPE COMPOSITION OF MINERALS IN THE SYSTEM AU-AG-TE AS DETERMINED BY MC-ICP-MS .......................................................................... 1 Abstract ............................................................................................................... 1 Introduction ......................................................................................................... 2 Sample Preparation .............................................................................................. 5 Preparation of labware ................................................................................... 5 Standard selection .......................................................................................... 6 Sample selection ............................................................................................ 7 Making of epoxy mounts ............................................................................... 7 Petrography and electron microprobe for mineral identification .................. 8 Micromilling .................................................................................................. 10 Sample digestion and reconstitution .............................................................. 10 Ion Exchange Chromatography ........................................................................... 11 Yield splits ..................................................................................................... 11 Procedure for ion exchange chromatography ................................................ 11 Determination of Te isotope fractionation by ion exchange .......................... 13 Multiple-collector inductively coupled plasma mass spectrometry..................... 14 System configuration ..................................................................................... 14 Measurement protocol ................................................................................... 15 Assessment of Cd polyatomic interferences .................................................. 16 Data reduction ................................................................................................ 17 Results and discussion ......................................................................................... 20 Fractionation during ion exchange chromatography ..................................... 20 Use of cadmium as a dopant for mass-bias correction .................................. 21 Comparison of wet and dry plasma techniques ............................................. 23 Results from natural samples ......................................................................... 23 Conclusions ......................................................................................................... 25 Acknowledgements .............................................................................................. 26 References ......................................................................................................... 26 Figures ................................................................................................................. 30 Figure 1 ......................................................................................................... 31 Figure 2 ......................................................................................................... 32 Figure 3 ......................................................................................................... 32 Figure 4 ......................................................................................................... 33 Figure 5 ......................................................................................................... 34 iii Figure 6 ......................................................................................................... 34 Figure 7 ......................................................................................................... 34 Tables ............................................................................................................ 36 Table 1 .......................................................................................................... 36 Table 2 .......................................................................................................... 37 Table 3 ......................................................................................................... 38 Table 4 .......................................................................................................... 39 Table 5 .......................................................................................................... 40 Table 6 .......................................................................................................... 41 CHAPTER 2. THEORETICAL AND MEASURED STABLE TE ISOTOPE FRACTIONATION IN TELLURIUM-BEARING MINERALS FROM PRECIOUS METAL HYDROTHERMAL ORE DEPOSITS ........................... 44 Abstract ......................................................................................................... 44 Introduction ......................................................................................................... 45 Tellurium in terrestrial settings ............................................................................ 47 Stability of Au and Te species in hydrothermal solutions ................................... 49 Stable tellurium isotopes ...................................................................................... 51 Isotope fractionation determined by theoretical calculations ........................ 51 Te isotope studies using TIMS and N-TIMS ................................................. 53 Te isotope studies using MC-ICP-MS ........................................................... 54 Meteorites and terrestrial sulfides ......................................................... 54 Biological fractionation ........................................................................ 55 Abiotic fractionation in native tellurium and tellurides ........................ 56 Samples ............................................................................................................. 57 Sample preparation methods and isotope analysis ............................................... 57 Theoretical fractionation calculations .................................................................. 61 Results .................................................................................................................. 62 Theoretical fractionation ................................................................................ 62 Overall isotopic ranges and trends ................................................................. 63 Te mineral pairs ............................................................................................. 64 Discussion ............................................................................................................ 65 Crystallographic effects on fractionation ....................................................... 65 Redox effects on fractionation ....................................................................... 66 Te isotopes discriminated by deposit ............................................................. 67 Temperature of formation ..................................................................... 68 Phase separation .................................................................................... 69 Genetic model ....................................................................................... 69 Te fractionation during Au-(Ag-) telluride mineralization ............................ 70 Comparison to Se isotopes in ore-forming systems ....................................... 72 Conclusions .........................................................................................................