LOW-GRADE METAMORPHISM [N THE MEGUMA GROUP, SOUTHERN NOVA SCOTIA by Roberta Jean Hicks Submitted in partial fulfilment of the requirements for the degree of Master of Science Dalhousie University Halifax, Nova Scotia December, 1996 O Copyright by Roberta Jean Hicks, 1996 UIDIIOUI ue nauonaie du Cana7 a Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. nie Wellington mwa ON K1A ON4 Ottawa ON K1A ON4 ~a~da canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sel reproduire, prêter, distribuer ou copies of this thesis in micr~form~ vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/fh, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or othexwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Table of Contents Page Table of Contents ....................................................................................................... iv List of Figures............................................................................................................ vii List of Tables ............................................................................................................. si Abstract................................................... ... .............................................................. sii ... Acknowled~ements.................................................................................................... Xlll Chapter I Introduction........................................................................................... i 1.1 Introduction ............................................................................................... 1 1.2 Previous Work ........................................................................................... 5 . 1.3 Objectives and Approach .......................................................................... 1 1 Chapter 2 Regional Geology, Lithologies, Structure and Gold Mineralization ................................................................................................ 15 7.1 Regional Geoloby ...................................................................................... 15 7.1 Lithologies of the Meguma Group..................... .. ................................... 20 1.2.1 New Harbour Member .................... ..... ............ 22 2-22 Risser's Beach Member................................................................. 23 3.2.3 West Dublin Member................................................................... 24 1.1.4 Tancook Member......................................................................... 34 2.2.5 Moshefs Island Member............................................................... 16 2.2.6 Cunard Mcmber ............................................................................ 30 2.2.7 Feltzen Member............................................................................ 32 2.3 Structural GeoIosy .................................................................................... 33 3.3.1 Defornation History ..................................................................... 34 . 3.4 GoId Mineralrzation .................................................................................. 41 Chapter 3 Petrography and NIineral Chemistry.................................................. 44 3. ! Introduction .............................................................................................. 44 3.2 Mineral Assemblages ................................................................................ 45 3.2. I General Petrogaphy ..................................................................... 45 3.2.2 New Harbour Member.................................................................. 56 3.2.3 Risser's Beach Mem ber ........................ ... .................................... 57 3.2.4 West Dublin Member................................ .. ................................. 58 3.2.54 Tancook Member ........................................................................ 3.2.6 Mosher's Island Member.............. ... ......................................... 3.2.7 Cunard Member......................................................................... 3.2.8 Feltzen Member ........................................................................ q-7 . 2.2 Mineral Chemistry.................................................................................... 3 GeneraI Mineral Chemistry ........................................................ 2.2.2.-7 -7 Muscovite Chemistry.................................................................... 2.2.2-7 -7 -7 Chlorite Cheinistry....................... ....... ......................................... Chapter 4 Diagenesis, Metamorphism, and Cleavage Formation...................... 4.1 Introduction .......... ................................................................................. 4.2 Definitions................................................................................................ 4.2.1 Diagenesis..................................................................................... 4-22 Anchizone and Epizone Metamorphism ............................ ........... 4.3 XRD Illite-Muscovite Cwstallinity Studies .............................................. 4.3. 1 Background Information ............................................................... 4.3.2 Sample Selection........................... .... ............................................ 4.3.3 XRD Illite-Muscovite Crystallinity Results................................. 4.4 Diagenesis and Metamorphism in the Meguma Group, Mahone Bay ...... 4.4.1 Chlorite Porphyroblasts and Chlorite-Mica Stacks...................... 4.5 Cleavage Development and Volume Loss ................................................ 4.5.1 General Pnncipies ..................................................................... 4.5.2 Clcavagc in Mcguma Group Rocks .............................................. 4.5.3 Volume Loss in Slaty Cleavase.................................................... 4.5.4 Measuring Volume Loss in Meguma Group Rocks ..................... 4.6 Summary ................................................................................................... Chapter 5 411 ~r/"~rDating ............................................................................ - ........ 5.1 Introduction ........................................................................................... 5.2 JI1 ~ri"')~rSysternatics .............................................................................. 5.3 Previous Work ....................................................................................... 5.4 Sample Selection............... .. .................................................................. 5.5 Sample Separation .................................................................................... 5.6 Sample Analysis ........................................................................................ 5.7 JO ~r/""ArDating Rcsults............................................................. .. .......... 5.7.1 introduction to Interpretation of Argon Age Spectra................... 5.7.2 Detrital Muscovite Results........................................................... 5-73 Metamorphic Muscovite Results.................................................. 5.8 Discussion of -10 Ar/-19 Ar Ages .................................................................. Chapter 6 Discussion and Conclusions .................................................................. 6.1 Introduction ......................................................................................... 6.2 Low-Grade Metamorphism and Fabric Developrnent.............................. 6.7 Age of Metamorphism in the Megurna Terrane ....................................... 6.4 Late-Stage (Pre-Granite) Regionai Metarnorphic Tectono-Thermal Evolution of the Meguma Group.............. .. ......................................... 6.4.1 Gold in Low-Grade Meguma Group Rocks.................................. 6.5 tnhomogeneous Deformation and Metamorphism of the Megurna Terrane.................................................................................................. 6.6 Recommendations for Future Studies.............................. ... ...................... 6.7 Conclusions......... .. ................................................................................. Appendix A Electron Microprobe Analytical Methods....................................... Appendix B Electron Microprobe Analyses ......................................................... Appendix C Structural Formulae.......................................................... ,............... Appendix D XRD Sample Preparation and Labratory Methods........................ Appendix E XRD Illite-Muscovite Crystallinity (KI) Results and Minerai Analyses.......................................................................................................... Appendix F Range of XRD Crystallinity