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Thesis Reference Thesis Geochronological, structural, isotopes and fluid inclusion constraints of the polymetallic Domo de Yauli district, Peru BEUCHAT, Sebastien Abstract L'origine des gisements polymétalliques du Domo de Yauli est liée au magmatisme Miocène ayant affecté les Andes péruviennes. Cette étude met en évidence les relations géochronologiques et structurales entre les intrusions et les corps minéralisés, ainsi que les caractéristiques des fluides hydrothermaux. Les âges obtenus sur les intrusions et les minéralisations indiquent un système pulsé et répétitif durant 9 Ma, alors que les contraintes associées à la formation des gisements montrent un champ hétérogène probablement lié à l'influence de linéaments crustaux. Les rapports isotopiques de Sr, Pb, O et H associés à l'étude des inclusions fluides, par microthermométrie, spectroscopie Raman et LA-ICP-MS, révèlent l'influence d'au moins trois fluides d'origines et de caractéristiques différentes. Leur mélange a conduit à la formation des gisements, alors que les éléments économiquement intéressants ont uniquement été apportés par le fluide s'étant séparé du magma. Reference BEUCHAT, Sebastien. Geochronological, structural, isotopes and fluid inclusion constraints of the polymetallic Domo de Yauli district, Peru. Thèse de doctorat : Univ. Genève, 2003, no. Sc. 3415 URN : urn:nbn:ch:unige-979762 DOI : 10.13097/archive-ouverte/unige:97976 Available at: http://archive-ouverte.unige.ch/unige:97976 Disclaimer: layout of this document may differ from the published version. 1 / 1 UNIVERSITE DE GENEVE FACULTE DES SCIENCES Département de minéralogie Professeur L. Fontboté Docteur R. Moritz Geochronological, Structural, Isotopes and Fluid Inclusion Constraints of the Polymetallic Domo de Yauli District, Pern THE SE présentée à la Faculté des sciences de l'Université de Genève pour obtenir le grade Docteur ès sciences, mention Sciences de la Terre par Sébastien BEUCHAT de Undervelier (JU) Thèse N° 3415 GENEVE Atelier de reproduction de la Section de physique 2003 La Faculté des sciences, sur le · préavis de Messieurs L. FONTBOTÉ, professeur ordinaire (Département de minéralogie), et R. MORITZ, docteur (Département de minéralogie ) codirecteurs de thèse, U. SCHALTEGGER, professeur adjoint (Département de minéralogie), et R. TOSDAL, professeur (University of British Columbia, Department of Earth and Ocean Sciences, Vancouver - Canada), autorise l'impression de la présente thèse, sans exprimer d'opinion sur les propositions qui y sont énoncées. Genève, le 20 janvier 2003 Thèse - 3415 - Le Doyen, Jacques WEBER Beuchat S.: Geochronological, structural, isotopes and fluid inclusion constrains ofthe polymetallic Domo de Yau li district, Peru. Terre & Environnement, vol. 41 , 130 pp. (2003) ISBN 2-940153-40-X Section des Sciences de la Terre, Université de Genève, 13 rue des Maraîchers, CH-1211 Genève 4, Suisse Téléphone ++41-22-702.61 .11 -Fax ++41-22-320.57.32 http://www.unige.ch/sciences/terre/ Table of content ABSTRACT --------------------------------------------------------1 RESUMEN 5 RÉSUMÉ DES RÉSULTATS 9 Introduction ___________________________________________________ 9 Magmatisme miocène --------------------------------------------11 Métallogénie du Domo de Y auli 12 Le paléo-champs de contraintes miocènes 13 Inclusions fluides 13 Description et microthermométrie des inclusions fluides 13 Analyse des inclusions fluides par LA-ICP-MS 14 Isotopes d'oxygène et d'hydrogène 14 Discussions 15 La répétition d'événements magmatiques et hydrothermaux à Morococha, indique-t-elle la présence d'une large chambre magmatique sous-jacente? 15 L'influence de linéaments crustaux sur les paléo-champs de contraintes et la formation de gisements 16 Modèle génétique des minéralisations polymétalliques de San Cristobal 16 Références -----------------------------------------------------17 CHAPTER 1: RESOLVING MIOCENE MAGMATIC AND MINERALISING EVENTS IN THE ZN-PB-AG-CU DOMO DE YAULI DISTRICT (PERU) BY HIGH-PRECISION GEOCHRONOLOGY 21 Abstract --------------------------------------------------------21 Introduction 22 Geological settin 23 Regional Geology ofthe Domo de Yauli district 23 Miocene igneous activity 23 Ore deposits of the Domo de Yauli district 28 Analytical techniques 31 Microprobe analysis 31 Cathodoluminescence (CL) and secondary electron (SE) images 31 Whole rock analysis 32 Whole rock isotope data 32 U/Pb age and Hf isotope determinations 32 Re/Os age determinations 33 40 ArP9 Ar age determinations 33 Results 34 Whole rock and microprobe analyses ofMiocene intrusions 34 Zircon cathodoluminescence (CL) images 34 U/Pb dating and Hfisotopic composition ofzircons ____________ 37 The Anticona diorite: TIC 39 The San Francisco and the Yantac intrusions: TOR and POR 39 The Chumpe intrusion: CHU 39 Re/Os dating of molybdenite 39 40 ArP9 Ar ages of phlogopite and sericite 41 Discussion 43 Two mining districts of different ages in the Domo de Yauli area 43 Do multiple magmato-hydrothermal events reveal the presence of a large underlying magmatic chamber? 46 Are Precambrian rocks involved in the generation ofMiocene magmatism? 48 Conclusions ------------------------------------------49 Acknowledgments ____________________________ 50 References 50 CHAPTER II: LINEAMENT CONTROL ON MIOCENE ORE FORMATION IN CENTRAL PERU, THE ZN-PB-AG-CU SAN CRISTOBAL EXAMPLE 55 Abstract ----------------------------------------------------55 Introduction 56 Regional Geology ___________________________________ 58 Stratigraphy 58 Tertiary igneous activity 59 Andean deformation 60 Ore deposits of the San Cristobal district 62 Vein ore type 62 Carbonate replacement ore type 66 Paleostress determinations 68 Methodology 68 Results 68 Discussion and conclusions ________________________________________ 69 Acknowledgments _________________________ 71 References 72 CHAPTER III: THE ZN-PB-AG SAN CRISTOBAL DISTRICT, CENTRAL PERU: ISOTOPE AND FLUID INCLUSION CONSTRAINTS 75 Abstract -------------------------------75 Introduction ___________________________ 76 Geological setting 78 Regional Geology 78 V ein ore type 8 0 Carbonate replacement ore type 82 Previous S, Sr and Pb isotopie data 84 Analytical methods 86 Fluid inclusion petrography, microthermometry and Raman spectroscopy 88 Fluid inclusion LA-ICP-MS results 97 H and 0 isotopes 97 Discussion 100 Earl y vein stages 100 Late vein tage 102 Carbonate replacement ore bodies 106 Conclusions 107 Acknowledgments 108 References 108 APPENDIX I: DESCRIPTIVE LIST OF THE STUDIED ROCKS AND CITED ANALYSES -----------------------------------------------------------113 40 39 APPENDIX II: AR/ AR DATING 121 APPENDIX III: MICROTHERMOMETRY AND RAMAN FLUID INCLUSION DATA 123 APPENDIX IV: LA-I CP-MS FLUID INCLUSION DATA 125 REMERCIEMENTS 129 Abstract The Domo de Y auli contains two of the district, there are multiple small apophyses major Zn-Pb±Cu±Ag mining districts of of the very altered Chumpe intrusion. The Peru, the Morococha and the San Cristobal northern monzogranite stocks are related to districts. They are classical intrusion the formation of four different ore deposit related ore districts with high temperature, types: Cu-porphyries, Zn-Pb skarns, Zn­ carbonate-hosted base metal deposits and Pb±Ag carbonate replacement deposits, are a typical of the Miocene metallogenic and veins. In the south, only polymetallic belt of Central Peru. This study is aimed at carbonate replacements and veins are three main topics, a geochronological, a associated to the Chumpe intrusion. structural and an isotope and fluid inclusion study. These three different U-Pb dating of zircons from the northern approaches permit us to constrain the intrusions gives concordant ages of 14.11 ± factors needed to form world-class 0.04 Ma for the Anticona diorite and close deposits. Indeed, formation of such large to 9 Ma for different monzogranite stocks districts are linked to the conjunction and related to Cu-porphyry style and skarn the right timing among magmatic activity deposits. V eins of the Cu-porphyry deposit providing heat and fluids, structural stress have been dated at 7.9 ± 0.1 Ma by Re-Os permitting large fluid circulation and on molybdenite and phlogopite from a Zn­ available fluids and elements sources. Pb skarn gives a 40 Ar/39 Ar plateau age of 7.2 ± 0.2 Ma. U-Pb analyses ofzircons The Domo de Y auli is located 100 km east from the southern Chumpe intrusion result of Lima in the Western Cordillera of Peru. in discordant points defining a lower The area is mainly composed of Paleozoic intercept age about 6.6 (+1;-3.6) Ma, in phyllites of the Excelsior Group, Permo­ agreement with 40Ar/39Ar ages of 4.90 ± Triassic volcanic and sedimentary rocks of 0.15 Ma ·and 4.78 ± 0.16 Ma obtained on the Mitu Group, Triassic-Jurassic sericite from wall rock alteration selvages. limestones of the Pucara Group, and U-Pb, Re-Os and 40Ar/39 Ar Cretaceous sedimentary rocks. Incaic age determinations reveal the existence of compression events of Eocene age have three distinct magmatic events at 14.1, 9.1 produced isoclinal folds, ramp thrusts in and 6.6 Ma, with the two later ones related the sedimentary cover rocks and a NE-SW to a phase of mineralisation. We therefore fracture system which crosscuts the entire conclude that the northern and southem ore Domo de Yauli. Major N 120° W oriented deposits bear a different age and that the lineaments are present in the basement and particularly large abundance of economie affect the morphology of the whole area. ore bodies at Domo de Y auli is the result The positions of these lineaments
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