Petrogenesis and Geochronology of The
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PETROGENESIS AND GEOCHRONOLOGY OF THE DELIKTA Ş, SIVRIKAYA AND DEVREKANI GRANITOIDS AND BASEMENT, KASTAMONU BELT-CENTRAL PONTIDES (NW TURKEY): EVIDENCE FOR LATE PALAEOZOIC-MESOZOIC PLUTONISM, AND GEODYNAMIC INTERPRETATION DISSERTATION INSTITUT FÜR GEOWISSENSCHAFTEN UNIVERSITÄT TÜBINGEN-DEUTSCHLAND ODILIA MBONGUH NZEGGE CAMEROON ~~2008~~ PETROGENESIS AND GEOCHRONOLOGY OF THE DELIKTA Ş, SIVRIKAYA AND DEVREKANI GRANITOIDS AND BASEMENT, KASTAMONU BELT-CENTRAL PONTIDES (NW TURKEY): EVIDENCE FOR LATE PALAEOZOIC-MESOZOIC PLUTONISM AND GEODYNAMIC INTERPRETATION DISSERTATION Zur Erlangung des Doktorgrades der Naturwissenschaften der Geowissenschaften Fakultät der Eberhard-Karls-Universität, Tübingen Vorgelegt von ODILIA MBONGUH NZEGGE aus Babubock-Cameroon ~~2008~~ 2 Tag der mündlichen Prüfung 13/12/ 2007 Dekan: Prof. Dr. Peter Grathwohl 1. Berichterstatter Prof. Dr. Muharrem Satir 2. Berichterstatter Prof. Dr. Durmu ş Boztu ğ 3 For my father (Nzegge Francis Akang, † 1984), my mother (Nzegge-Ebong Agnes, † September 2003), sisters (Nzegge Apollonia and Epah Angela, † December 2003), senior brother (Nzegge Charles Onyong, † March 2004) and aunt (Ayuk-Ebong Asumpta, † March 2005). For God almighty ! 4 5 TABLE OF CONTENTS Table of content ....................................................................................................................6 Abstract …………………….................................................................................................8 Kurzfassung ………………………………………………………………………………11 Acknowledgements .............................................................................................................15 1. INTRODUCTION …………………………………………………………………....16 1.1. Tectonic framework .……………………………………………………………............ 19 1.2. Previous studies……………………………………………………………….......20 1.3. Geological setting...…………………………………………………………….....24 1.4. Aims of this study………………………………………………………………....26 2. ANALYTICAL METHODS .………………………………………………………...28 2.1. Determination of major and trace elements concentrations…………………….....28 2.2. Whole-rock Nd-Sr isotopic and Rb-Sr minerals isotopic analyses……………......28 2.3. Oxygen isotopes analytical procedures………………………………………........29 2.4. U-Pb zircon isotope dilution analyses……………………………………………..29 2.5. Pb-Pb zircon evaporation method...……………………………………………….30 2.6. Cathodoluminescence……………………………………………………………..30 - Zircon internal structure…………………………………………………………..30 2.7. Classification of rocks-granite types…………………………………………........32 3. SIVRIKAYA AND DELIKTA Ş GRANITES……………………………………….34 3.1. PETROGRAPHY………………………………………………………………….34 3.2. GEOCHEMISTRY………………………………………………………………...37 3.2.1. Major and trace elements ……….………………………………………….37 3.2.2. Rare earth elements……………………………………………………........43 3.2.3. Sr-Nd-O isotopic compositions……………………………………………..45 3.2.4. Discussion on geochemistry ………………………………………………..49 3.2.4.1. Petrogenetic considerations ………………………………………...49 3.2.4.2. Fractional crystallization……………………………………….........50 3.2.4.3. Nature of parental magma and possible sources…….. ……………...52 3.2.4.4. Tectonic implications……………………………………………......54 3.2.4.5. Conclusion on geochemistry and isotopic systematics……………...56 3.3. GEOCHRONOLOGY…………………………………………………………......59 3.3.1. Zircon internal structure………………………………………………........59 3.3.2. U-Pb, Pb-Pb and Rb-Sr data…………………………………………….....61 3.3.3. Discussion and conclusions on geochronology .………………………........69 6 4. DEVREKANI GRANITOID ……………………………………………………........71 4.1. PETROGRAPHY…………………………………………………………………..72 4.2. GEOCHEMISTRY…………………………………………………………….........74 4.2.1. Major and trace elements geochemistry……………………………….........74 4.2.2. Rare earth elements…………………………………………………………79 4.2.3. Sr-Nd-O isotopic compositions…………………………………………......82 4.3. GEOCHRONOLOGY………………………………………………………………84 4.3.1. Zircon internal structure……………………………………………………84 4.3.2. U-Pb, Pb-Pb and Rb-Sr data……………………………………………......86 4.4. DISCUSSION………………………………………………………………………90 4.4.1. Magma genesis and possible sources ………………………………….......90 4.4.2. Subduction versus mantle wedge components ……………………….........92 4.4.3. Tectonic implications: evidence of slab break-off……………………........93 4.5. CONCLUSIONS…………………………………………………………………...94 4.6. General conclusion on granitoids: geodynamic model…………………….............96 5. EURASIAN-DERIVED BASEMENT COMPLEX ………..................................100 5.1. PETROGRAPHY………………………………..................................................102 5.2. GEOCHEMISTRY………………………………………………………………108 5.3. GEOCHRONOLOGY………………………………………………………........113 5.3.1. U-Pb and Pb-Pb Zircon data.……………………………………………..114 5.3.2. Rb-Sr whole-rock data………………………………………………........126 5.4. DISCUSSION……………………………….........................................................127 5.5. CONCLUSIONS………………………………....................................................128 5.5.1. Regional geological implications ………...................................................128 5.5.2. Precambrian basement………………….....................................................130 6. REFERENCES ……………………………………..................................................132 7. APPENDIX ……………………………….................................................................157 - Deliktas-Sivrikaya granites Rb-Sr mineral ages………..........................................157 - Tables geochemical analyses of basement………...................................................158 - Table isotope analyses for basement………............................................................162 - Table U-Pb zircons isotope dilution analyses ……….............................................164 8. PUBLICATIONS …………………………................................................................165 -First page of published Paper and Manuscripts in review ………....................................166 7 Abstract The Pontides orogenic belt (Ketin, 1966), is the central portion of an extensive belt running from western Bulgaria (Rhodope Mountains) through northern Turkey to the Caucasus. Three tectono-stratigraphically different sectors can be distinguished: the Western Pontides ( Đstanbul zone), the Central Pontides and the Eastern Pontides (Sakarya zone). The Central Pontides, located between the Đzmir-Ankara suture to the south and the Black Sea to the north is the geographical term for the arched central part of the Pontides orogenic belt (Fig. 1.1). The Central Pontides is one of the well preserved areas where the late Early Cretaceous juxtaposition of the Western Pontides ( Đstanbul Zone) and the Eastern Pontides (Sakarya Zone) (Okay and Tüysüz, 1999; Tüysüz, 1999) can be observed ( Şengör and Yılmaz, 1981). Four main units are comprised in the Central Pontides: two major tectonic units, the Devrekani metamorphic unit (Eurasian-derived basement) and the Çangalda ğ arc complex separated by two oceanic basins, the Küre and the Domuzda ğ-Saraycıkada ğ complexes. The study area is marked by the Çangalda ğ arc complex, and numerous granitoids and associated volcanics collectively called the Kastamonu granitoid belt (KGB) (Yılmaz and Boztu ğ, 1986), that pierced the imbricated Palaeotethyan continental and oceanic basement assemblage. The Kastamonu belt documents large scale, multi-episodic magmatism, formed in response to subduction of the Palaeotethys and the subsequent late orogenic tectonics. The occurrence of these plutons and ophiolites in the Central Pontides has attracted geologists for several decades, because of their importance in understanding Palaeotethyan evolution, and the Tethysides-Variscides connection. However, data necessary to identify the type and origin of all the intrusions are not available. On the basis of stratigraphic correlation and a few K-Ar data earlier workers assigned Middle Jurassic emplacement time to all the plutons of the KGB. In an attempt to elucidate the petrogenetic and magmatic evolution of this belt, zircons from Delikta ş, Sivrikaya and Devrekani granitoids and their basement have been analyzed by means of Pb-Pb evaporation and U-Pb isotope dilution combined with isotope and geochemical data. Geochemical compositions, isotopic data and geochronological constraints are presented and interpreted for the evolution of the Palaeotethys in the Central Pontides. The Late Carboniferous Sivrikaya granitoid (SG) comprises biotite-hornblende granodiorite, tonalites and minor two-mica granites. Sivrikaya rocks are slightly metaluminous to peraluminous, and transitional to S-type (ASI= 0.9 to > 1.1). The rocks are characterized by 87 86 variably low initial Sr/ Sr ratios [Sr (i) = 0.705 - 0.708], moderate εNd (t) values (-1 to -3.8) and young Nd-model ages (T DM = 0.75 - 1.05 Ga), suggesting variable degrees of mixing 8 between mantle and crustal components. Chondrite-normalized (cn) rare earth element (REE) patterns are characterized by fractionation between the light (LREE, [La/Yb] cn = 9 - 49) and heavy REEs (HREE, [Gd/Yb] cn = 0.79 - 2.37) and no to strong Eu depletion (Eu/Eu*= 1.19 - 18 0.18). All these characteristics, combined with moderate δ O(whole-rock) values (10 - 11.6 ‰) point to dehydration melting of heterogeneous amphibolites-metagreywackes-type sources with variable mantle contribution. The Early Permian Delikta ş leucogranite (DLG) is host to muscovite-bearing monzogranites. Delikta ş rocks are strongly peraluminous S-type granites (ASI >1.1), as reflected in the mineralogy that includes highly aluminous phases such as muscovite and cordierite. DLG samples exhibit strongly fractionated REE patterns ([La/Yb] cn = 3.6 - 35), rather flat HREE ([Gd/Yb] cn = 0.59 - 0.78)