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Regional Geology of Ecuador

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Regional Geology of Ecuador Thesis Geochronology, geochemistry, and isotopic composition (Sr, Nd, Pb) of Tertiary porphyry systems in Ecuador SCHUTTE, Philip Abstract This thesis presents geochronologic, geochemical, and isotopic data on Tertiary arc magmas associated with porphyry-related ore deposits in the northern Andes of Ecuador. In detail, ages on host and porphyry intrusion emplacement (U-Pb zircon) and hydrothermal alteration/mineralization (U-Pb titanite, Re-Os molybdenite) were obtained, combined with whole-rock geochemical analysis of least altered igneous rock samples. These data are discussed in a regional frame with respect to the geodynamic context. The following main conclusions apply: (1) porphyry-related ore deposits in Ecuador are mainly Miocene in age, and represent the northern extension of the Miocene metallogenic belt of northern-central Peru; (2) intrusions associated with mineralization are compositionally highly variable; a systematic association of mineralization with a specific trace element signature cannot be observed; (3) flat slab settings produce favorable exposure conditions for porphyry-related ore deposits; a systematic association of ore deposit formation and seamount chain (Carnegie Ridge) subduction is not observed. Reference SCHUTTE, Philip. Geochronology, geochemistry, and isotopic composition (Sr, Nd, Pb) of Tertiary porphyry systems in Ecuador. Thèse de doctorat : Univ. Genève, 2009, no. Sc. 4166 URN : urn:nbn:ch:unige-63675 DOI : 10.13097/archive-ouverte/unige:6367 Available at: http://archive-ouverte.unige.ch/unige:6367 Disclaimer: layout of this document may differ from the published version. 1 / 1 UNIVERSITÉ DE GENÈVE FACULTÉ DES SCIENCES Département de Minéralogie Prof. Urs Schaltegger Dr. Massimo Chiaradia Geochronology, Geochemistry, and Isotopic Composition (Sr, Nd, Pb) of Tertiary Porphyry Systems in Ecuador THÈSE présentée à la faculté des sciences de l'Université de Genève pour obtenir le grade de Docteur ès sciences, mention Sciences de la Terre par Philip SCHÜTTE de Allemagne GENÈVE 2010 TABLE OF CONTENTS Acknowledgements ...........................................................................................................................................iii Abstract ..............................................................................................................................................................v Resumen...........................................................................................................................................................vii Résumé étendu..................................................................................................................................................xi CHAPTER I – THEORETICAL BACKGROUND AND AIMS OF THESIS Introduction....................................................................................................................................................... 1 References......................................................................................................................................................... 3 CHAPTER II – GEODYNAMIC CONTROLS ON TERTIARY ARC MAGMATISM IN ECUADOR: CONSTRAINTS FROM U‐PB ZIRCON GEOCHRONOLOGY OF OLIGOCENE‐MIOCENE INTRUSIONS AND REGIONAL AGE DISTRIBUTION TRENDS Abstract ............................................................................................................................................................. 5 Introduction....................................................................................................................................................... 6 Regional Geology of Ecuador ............................................................................................................................ 6 Tertiary arc segmentation and geology of investigated magmatic centers...................................................... 8 Analytical techniques and sample material .................................................................................................... 14 Results ............................................................................................................................................................. 18 Discussion ........................................................................................................................................................ 25 Conclusions...................................................................................................................................................... 34 References....................................................................................................................................................... 34 Appendix I – Accommodation of convergence obliquity at the Ecuadorian margin throughout the Tertiary...................................................................................................................................................... 39 Appendix II – Overriding plate structural controls on the spatio‐temporal distribution of Tertiary plutons in Ecuador........................................................................................................................................... 42 Appendix III – Accuracy of published K‐Ar (and ZFT) ages of Tertiary intrusions in Ecuador.......................... 48 Appendix IV – Data tables ............................................................................................................................... 54 CHAPTER III ‐ THE MIOCENE METALLOGENIC BELT OF ECUADOR: CONSTRAINTS FROM NEW RE‐OS MOLYBDENITE AND U‐PB TITANITE AGES OF PORPHYRY‐RELATED ORE DEPOSITS Abstract ........................................................................................................................................................... 65 Introduction..................................................................................................................................................... 66 Regional geology and geodynamic setting...................................................................................................... 68 Local geology of Miocene Ecuadorian ore deposits investigated in this study............................................... 69 Sampling and analytical techniques ................................................................................................................ 73 Results ............................................................................................................................................................. 74 Discussion ........................................................................................................................................................ 76 Conclusions...................................................................................................................................................... 92 References....................................................................................................................................................... 92 i CHAPTER IV ‐ CRUSTAL BASEMENT ARCHITECTURE IN ECUADOR EXPLORED BY SR, ND, AND PB ISOTOPIC COMPOSITIONS OF TERTIARY‐QUATERNARY ARC MAGMAS Abstract ........................................................................................................................................................... 97 Introduction..................................................................................................................................................... 98 Geological framework ................................................................................................................................... 100 Methodology ................................................................................................................................................. 100 Results ........................................................................................................................................................... 103 Discussion ...................................................................................................................................................... 106 Conclusions.................................................................................................................................................... 112 References..................................................................................................................................................... 112 Appendix: Data tables ................................................................................................................................... 115 CHAPTER V ‐ ADAKITE‐LIKE FEATURES IN LATE OLIGOCENE TO LATE MIOCENE ECUADORIAN ARC MAGMAS AND THEIR SIGNIFICANCE FOR PORPHYRY‐RELATED ORE DEPOSITS Abstract ......................................................................................................................................................... 119 Introduction................................................................................................................................................... 120 Tertiary‐Quaternary adakite‐like magmatism in Ecuador............................................................................. 120 Regional geology and geodynamic setting.................................................................................................... 122 Sampling and analytical techniques .............................................................................................................
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