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UMI @ National Library Bibliothèque nationale 191 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wdington Stræt 395, rue Weilington ûthwaON K1AOM OtrewaON K1A ON4 camda Canade The author has granted a non- L'auteur a accordé une licence non exclusive Licence allowing the exclusive permettant la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or seii reproduire, prêter, distribuer ou copies of this thesis in microfom, vendre des copies de cette thèse sous paper or dectronic formats. la forme de microfiche/film, 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 from it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT The Hess Offset is a steeply dipping dyke located 12-15 km north of the 1.85 Ga Suc?huryigneous complex (SIC) within the 200-250 km diameter Sudbury impact structure. It is up to 60 m wide and strikes subconcentricaily to the SIC for at least 23 km. The Hess Offset consists of more than one phase. The main phase of the dyke is granodioritic, but it conforms with what is locdly referred to as quartz diorite: a term used for al1 the Offset dykes of the Sudbury impact structure. Rare earth element data shows that the Hess Offset is genetically related to the SIC and that it is most cloaely affiliated with an evolved felsic norite component the Main Mass and not bulk impact melt. This indicates that Hess was emplaced during fiactionation of the impact melt sheet, rather than immediately following impact. The main Quartz Diorite phase of the dyke comprises plagioclase + homblende + biotite * pyroxene, with minor quartz and granophync intergrowths of quariz and alkali feldspar. Pyroxenes are rarely preserved intact; most occur as uralitized relicts. Unaltered clino- and orthopyroxenes do survive in both Hess and especially the Foy adjacent Offset, but are rare and only occur in small isolated patches within the Offsets. The extensive alteration of the pyroxene implies metasomatic alteration. Metasomatism may have ken caused by the ingress of hot fluids fiom the wall rocks during their dehydration due to frictional heating and pseudotachylyte formation. Alteration was not pervasive, as discrete areas of more pristine dyke have been pteserved. Critically, the Hess Offset occupies a fault system that marks the northern limit of a pseudotachylyte-nch, shatter cone-bearing annulus about the SIC. This fault system was active during the modification stage of the impact process. ACKNOWLEDGMENTS Funding for this work was provided through NSERC Research/Operating and INCO/NSERC Collaborative Research and Development grants to my supervisor John Spray. Logisticai support was provided by the Ontario Geological Survey (OGS) and inco Exploration. 1am particularly grateful to the OGS for the use of one of their vehicles and for the helicopter time. Help and advice from Inco staff (and ex-staff), especidly Andy Bite, Hadyn Butler, Bob Martindaie, Everett Makela, Gord Morrison, Mars Napoli, Ed Pattison, Walter Peredery, Rick Lacroix, Peter Lightfoot and Dick Alcock. Many aspects of this project would not have been possible without the many years of experience and knowledge from the Inco geologists. Inco technical staff are also thanked for their cosperation and advice. Clive Karnichaitis and Neil Pettigrew acted as very able field assistants for the 1996 and 1997 field seasons, respectively. John O'Connor, Wes Marsaw and Ron Nerpin are thanked for helping us to recover our truck from the Onaping River. The Barringer Crater Company and the Geological Society of Arnerica, are thanked for travel awards that facilitated participation in conferences at Denver, Sudbury and Houston. Discussion with many geologist at these conferences proved invaluable. Constructive reviews by Alex Deutsch, Peter Lightfoot and Bruce Marsh helped to improve an earlier version of the Meteroitics manwript, helped shap some of the idea presented in this thesis. This project would not have been possible without the support of my supervisor John III Spray and the many discussions on impact geoiogy we have had (yes 1 did spell cheque this). 1 also wish to thank Richard Grieve for taking the time out of his busy schedule to be on my supervisory cornmittee and to both Ted Bremner and Amie McAllister for doing such a thomugh job on my examining cornmittee. Al1 the graduate students at WB are thanked for advice, fiiendship and entertainment value, discussions on al1 aspect of rocks and the meaning of life (42). In particular 1 wish to thank Jürgen Kraus (for his 'J' waves), Yvette Kuiper, Heather Gibson, Lucy Thompson, James Whitehead, hdyStumpf, Bill Gray, Ali Ahrnadi, Geoff Allaby, Lindsey Dunn, Ron Scott and John O'Comer etc etc ... Dave Huntley's thought-provoking letters were appreciated and inspirational. The technicai staff at UNB are thank for their help with many aspects of this project. In particular 1 wish to thank, Calvin Nash and Anse1 Murphy for the excellent thin sections, Jack of al1 trades Pirie for a bit of everything, Angel Gomez for Ming of figure Cor the Meteoritics paper and Bob McCulloch for the plethora of photos. The help of the staffof the Electron Microscopy Unit was invaiuable, in particular Douglas Hall. The office staff, Merrill Beatty and Christine Lodge are thanked for keeping the department ming. Many members of the faculty are thanked for their advice, enthusiasm. Nina Chrzanowski is thanked for her inspiration and fiiendship. 1 wish to thank al1 my fnends spread around the four corners of the globe for their support and encouragement fiom afar, in particular Geoff, for encouraging me to start this Master degree in the fmt place and having the faith in me to complete it. ktbut definitely not least, my family, for their support understanding and encouragement can not be thanked enough, for without you none of this would have been possible. LIST OF CONTENTS AJ3STMCT......................................................................................................................... II ACKNOWLEDGEMENTS.......................................... ......................................................... LIST OF CONTENTS........................................................................................................ VI LIST OF TABLES .............. .. ............................................................................................... X LIST OF FIGURES ................ ...... .............................................................................. ........XI cn~rfER ONE .LNTRODUCTION... ............................................................................. 1 INTRODUCTION........................................ ,,., ............................................ 1 GENERAL GEOLOGY OF THE SUDBURY BASEMENT............. ......**..**.*..*...*... 1 Supenor Province ...................................................................................... I Early Proterozoic Southern Province ..............................................................3 THE SUDBURY STRUCTURE............................................................................... S The Sudbury Igneous Cornplex.. ..................................................................... 5 The Main Mass of the SIC ............................................................................. 6 The Sublayer.................................................................................................. 8 Associated ores ..............................................................................................9 Footwall breccia ............................................................................................9 Sudbury breccialPseudotachylyte...................................................... ........ 10 Whitewater Group............ .. .........~*..........*.................................................10