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The Metamorphic Evolution of the Kolvitsa Complex and The Evolution of mafic rock-types of the Kolvitsa Complex, Kola Peninsula (Russia): Implications for the metamorphic evolution of the Kolvitsa Belt and characterisation of related fluid-rock interactions Dissertation zur Erlangung des Doktorgrades (Dr. rer. nat.) der Mathematischen-Naturwissenschaftlichen Fakultät der Rheinischen Friedrich-Wilhelms-Universität Bonn vorgelegt von Nicol Susann Ecke Bonn 2004 TABLE OF CONTENTS DANKSAGUNG GENERAL INTRODUCTION 1 1. Reaction textures in mafic rock-types: Implication for the metamorphic evolution of the Kolvitsa Belt, Kola Peninsula (Russia) 1.1. Introduction 3 1.2. Lapland-Kola Orogen 4 1.3. Geological setting of the Kolvitsa Belt 5 1.4. Petrography, microstructures and mineral reactions 8 1.4.1. Granulite-facies assemblages from the south-eastern 8 boundary of the Kolvitsa Massif 1.4.2. Corona reactions involving garnet 10 1.4.2.1. Garnet-consuming reaction textures from the south-eastern 10 boundary of the Kolvitsa Massif 1.4.2.2. Garnet-producing corona textures from the central part 12 of the Kolvitsa Massif 1.4.3. Amphibolite-facies assemblages 14 1.5. Mineral chemistry 17 1.5.1. Garnet 17 1.5.2. Clinopyroxene 20 1.5.3. Orthopyroxene 24 1.5.4. Plagioclase 27 1.5.5. Amphibole 31 1.5.6. Fe-Ti-oxides & minerals 33 1.6. Temperature and pressure estimates 35 1.6.1. Granulite-facies stage for the mylonitic rock types from the 35 south-eastern boundary of the Kolvitsa Massif 1.6.2. Decompressional stage in mafic rock types from the 45 south-eastern boundary of the Kolvitsa Massif 1.6.3. Garnet-producing corona textures in rock types from the 51 central Kolvitsa Massif 1.6.4. Amphibolite-facies stage 54 1.7. Discussion 59 1.7.1. Interpretation of results – P-T path 59 1.7.2. Age constraints 60 1.8. Conclusion 61 TABLE OF CONTENT S 2. Characterisation of fluid-rock interactions during exhumation of mafic granulites of the Kolvitsa-Umba suture zone, Kola Peninsula (Russia) 2.1. Introduction 63 2.2. Geological setting 64 2.3. Examples of fluid infiltration zones 2.3.1. Description of the examined case studies 67 2.4. Major and trace element geochemistry 72 2.4.1. Analytical techniques 72 2.4.2. Geochemical characterisation of the magmatic protoliths 2.4.3. Geochemical characterisation of the hydration zones 80 2.4.4. Mass balance 85 2.4.5. Volume of fluids and estimates of fluid influx 94 2.5. Stable isotope geochemistry 98 2.5.1. Analytical technique 98 2.5.2. Results 98 2.5.3. Interpretation 2.6. Age determination and isotopic data 107 2.6.1. U-Pb dating of titanite 2.6.1.1. Analytical technique 108 2.6.1.2. Results 108 2.6.1.3. Interpretation 111 2.6.2. 40Ar/39Ar mineral ages 112 2.6.2.1. Analytical technique 112 2.6.2.2. Age spectra of hornblende 112 2.6.2.3. Interpretation 120 2.6.3. Cooling history and P-T-t evolution 121 2.6.4. Sm-Nd systematics 124 2.6.4.1. Analytical technique 124 2.6.4.2. Results 124 2.7. Conclusions 127 2.8. References 129 **** Verstand wird Russland nie verstehn, Normales Maß will auch nichts taugen: Es hat ein sonderbares Wesen – An Russland kann man einzig glauben. 28. November 1866, Fjodor Tjutčev **** Умом Россию не понять, Аршином общим не измерить: У ней особенная стать – В Россию можно только верить. ноябрь 28тю 1866, Фйодор Тйутцев Danke! Zum Gelingen dieser Arbeit haben viele Leute beigetragen und allen von ihnen gilt mein persönlicher Dank! Zu Anfang möchte ich den Initiatoren dieses Deutsch-Russischen Projekts, Prof. Dr. M. Raith, Prof. Dr. S. Hoernes, Prof. Dr. V. Glebovitsky und Dr. D. Krylov danken, ohne die diese Arbeit nicht möglich gewesen wäre. Besonders herzlich möchte ich meinem Doktorvater Prof. Dr. M. Raith für die Unterstützung während dieser Arbeit, die kritischen Denkanstöße und die “Ausflüge“ in Kunst, Kultur und Literatur danken. Bei den Geländekampagnen auf der Kola Halbinsel stand er mir aufmunternd und tatkräftig zur Seite. In diesem Zusammenhang möchte ich mich auch bei Prof. Dr. S. Hoernes, Ralf Simmat und Kay Scheffler für ihre Hilfe während der Geländearbeiten bedanken. Für die herzliche Gastfreundschaft und für die Einblicke in ihre langjährige geologische Erfahrung auf der Kolahalbinsel möchte ich Dr. Mischa Yefimov und Dr. Mascha Bogdanova danken. Bei Dr. Dima Krylov möchte ich mich für seine Gastfreundschaft in St. Petersburg und seine Hilfe bei der Sauerstoffisotopenanalytik bedanken. Mischa Yefimov, dem Kapitän der Dora, Walodja und Sergej gilt ein besonderes Dankeschön, da sie uns durch das stürmische Weiße Meer immer sicher ans Land gebracht haben. Für die Verpflegung, weit ab jeglicher menschlicher Zivilisation, sei Mascha und Sergej gedankt, die mit gesammelten Blaubeeren und Pilzen, Blinis, Bortsch und Kascha hervorragend für unser leibliches Wohl gesorgt haben. Bei meinen russischen Kollegen am Institut für Präkambrische Geologie und Geochronologie in St. Petersburg möchte ich mich für die Sm-Nd and U-Pb Analytik bedanken. Ein besonderer Dank gilt dabei Dr. Viktor Kovach und Dr. Katja Salnikova. Prof. Dr. W. Frank möchte ich für die Ar-Ar Analytik am Geologischen Institut in Wien danken und dafür, dass er mir ganz unkompliziert ein Quartier in Wien gegeben hat. Meinem Co-Korrektor, Dr. Ingo Braun, danke ich für die zügige Durchsicht dieser Arbeit. Bei Andrea Beer möchte ich mich für die Präparation der allseits gelobten Dünnschliffe, bei Dorothée Dohle für die Umsätze an der Fluoranlage und Messungen am Massenspektrometer bedanken. Für die zugesandte, umfangreiche Literatur möchte ich Dr. M. Timmerman danken. Meiner Familie möchte ich für die Unterstützung und das Interesse an meiner Arbeit danken, gerade weil die Geowissenschaften für sie fremd waren, und ich trotzt aller Hoffnungen kein Gold und keine Diamanten gefunden habe... Für die vielen Aufmunterungen und die moralische Unterstützung, aber auch für die schöne Zeit während dieser Arbeit, gilt Kay Scheffler ein besonders herzliches Dankeschön. GENERAL INTRODUCTION This study forms part of the German-Russian DFG-RFBR project “The collision suture zone between the Archaean terranes of Karelia and the Kola peninsula” of the Mineralogical-Petrological Institute, University Bonn and the Institute of Precambrian Geology and Geochronology Russian of the Academy of Science, St. Petersburg. Joint field work was undertaken during two campaigns in August 1999 and 2000. Ancient orogenic belts give insights into the metamorphic and tectonic processes operating during orogeny. Granulites exposed in high-grade regional metamorphic belts provide a window into the lower crust and thus are an important clue to the understanding of crust-building processes and continental growth. Shear and thrust zones help to reconstruct the dynamics and mechanisms of mass and fluid transport at middle to deep crustal levels. Within the Lapland-Kola Orogen, situated in the north-eastern Baltic Shield, the Kolvitsa-Umba Belt forms part of a major suture zone. Remnants of this important Svecofennian collision zone separating the Late Archaean Belomorian terrane from crustal plates of the Central Kola terrane are exposed along the north-eastern coast of the White Sea. Whereas the litho-tectonic structures of individual nappe units were studied in detail by Yefimov and Bogdanova (1993), modern petrological and isotope geochemical work is missing or at it beginnings. The mafic rock associations of the Kolvitsa Complex comprise layered gabbro and anorthosite bodies as well as several generations of mafic dykes, all formed in an extensional setting c. 2.45 Ga ago (Frisch et al., 1995, Mitrofanov et al., 1995b). Results from geochronology indicate a polymetamorphic history, comprising an early episode of high-grade metamorphism and ductile shearing c. 2.42 – 2.43 Ga ago and a younger period of metamorphic reworking c. 1.91 Ga ago (Frisch et al., 1995, Kaulina, 1996). In high-strain zones, multiple injection of dykes occurred coeval with pervasive deformation and shearing. In low-strain zones, which escaped ductile deformation, magmatic textures, such as cumulate texture and magmatic layering are well preserved. In unique exposures along the coast, multistage magmatism, primary magmatic textures as well as the imprints of high-grade shearing which occurred during or immediately after solidification can be observed. Prominent strain-gradients across small-scale shear zones with continuous transitions from static magmatic textures to domains of intense ductile deformation with dynamic recrystallisation are exposed. Svecofennian compressional tectonics c 1.91 Ga ago led to the up-thrusting of nappe units and crustal thickening. At the south-eastern boundary of the Kolvitsa Massif, strongly mylonitic granulites form part of a prominent thrust zone, which separates the Kolvitsa Massif from the overthrust nappe units of the Por’ya Guba and Umba Complex. Contrary to the evolution of typical high-grade granulites, mafic rock types in the central part of the Kolvitsa Massif commonly preserve relict igneous minerals and garnet occurs exclusively as a coronitic phase. During tectonic exhumation of the nappe units hydrous fluids infiltrated the high-grade rocks along shear zones and fractures. Zones of amphibolitisation show conspicuous strain and fluid gradients between the centre of hydration and the outer hydration front. The hydration processes were pervasive and resulted in a complete mineralogical and textural re-equilibration at grain-scale. The layered intrusions and the related dyke swarms of the Kolvitsa Complex are an impressive example of the complex and polymetamorphic evolution of the Kolvitsa Belt. In excellent coastal outcrops, the tectonometamorphic imprints on primary magmatic textures and mineralogy can be studied from large to very small scales. Retrograde zones of amphibolitisation are direct evidence of fluid infiltration and provide important clues to the understanding of processes in deep-crustal metamorphic flow systems, such as textural re-equilibration, re-crystallisation, element and mass transfer and help to identify the driving forces of fluid flux.
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