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DISSERTATION / DOCTORAL THESIS Titel der Dissertation /Title of the Doctoral Thesis „Rare metal granites, Central Eastern Desert, Egypt: geochemistry and economic potentiality“ verfasst von / submitted by Mabrouk Sami Mohamed Hassan, M.Sc. angestrebter akademischer Grad / in partial fulfilment of the requirements for the degree of Doktorin der Naturwissenschaften (Dr.rer.nat.) Wien, 2017 / Vienna, 2017 Studienkennzahl lt. Studienblatt / A 796 605 426 degree programme code as it appears on the student record sheet: Dissertationsgebiet lt. Studienblatt / Erdwissenschaften/ Earth sciences field of study as it appears on the student record sheet: Betreut von / Supervisor: Ao. Univ. Prof. Dr. Theodoros Ntaflos TABLE OF CONTENTS TABLE OF CONTENTS Acknowledgements I Abstract II Zusammenfassung IV CHAPTER I: INTRODUCTION General introduction 1 Literature reviews 2 Geological background 3 Objectives of this study 10 Methods 10 Isotopic systems 11 Synthesis 14 References 17 CHAPTER II 22 Sami, M., Ntaflos, T, Farahat, E. S., Mohamed, H. A., Ahmed, A. F., Hauzenberger, C., 2017. Mineralogical, geochemical and Sr-Nd isotopes characteristics of fluorite-bearing granites in the Northern Arabian-Nubian Shield, Egypt: Constraints on petrogenesis and evolution of their associated rare metal mineralization. Ore Geology Reviews 88, 1–22. CHAPTER III 51 Sami, M., Ntaflos, T, Farahat, E. S., Mohamed, H. A., Hauzenberger, C., Ahmed, A. F., 2017. Petrogenesis of Neoproterozoic highly fractionated garnet bearing muscovite granites in the Central Eastern Desert, Egypt: Evidence from LA-ICP-MS of garnet, whole-rock geochemistry and Sr-Nd isotopic systematics. (In Revision stage) CHAPTER IV 98 Sami, M., Ntaflos, T, Farahat, E. S., Mohamed, H. A., Ahmed, A. F., Hauzenberger, C., 2017. Origin of spessartine and rare metal minerals in garnet bearing muscovite granites, north Arabian-Nubian Shield, Egypt; Evidence from whole-rock geochemistry and in situ EMPA and LA-ICP- MS data. (Submitted manuscript) Published Abstracts 148 CURRICULUM VITAE 157 ACKNOWLEDGEMENTS Acknowledgements First and foremost, I would like to thank the Almighty ALLAH for his compassion, grace and carefulness, without which accomplishing this work would have been impossible. The Egyptian Ministry of Higher Education and State for Scientific Research has to be gratefully acknowledged for the financial support for two years (2014-2015). Thanks to the International Association of GeoChemistry (IAGC) for the PhD student research grant to perform the geochemical analyses. My heartfelt gratitude to my supervisor, Prof. Theodoros Ntaflos, for his untiring effort, commitment, encouragement, support, fruitful discussions, guidance and help in writing scientific publications. Without his support and help this work would never have been in this level and shape. One simply could not wish for a better or friendlier supervisor. Then, I want to thank co-supervisor Prof. Esam S. Farahat for many very fruitful discussions and also detailed comments on my paper manuscripts, which helped me to find my way through the complex subject. Thank you for all your support! Big thanks go to Prof. Haroun A. Mohamed from Minia University, for helping in field work and sample collection from the studied area. I want to thank prof. Christoph Hauzenberger for numerous (LA-) ICP-MS analyses. Last but not least, to Wencke Wegner, for putting so much time and effort into analyzing samples for Sr and Nd isotopic composition. Thank you to all my co-authors for the very helpful reviews and constructive discussions. The staff members of the Department of Geology (Minia University) are sincerely thanked particularly, Prof. Awad F. Ahmed for advices and honest support. I am also very grateful to Franz Kiraly (microprobe), Peter Nagl (XRF), Marianne Schwarzinger (sample preparation) and Monika Horschinegg (clean lab) for their assistance and help. The Last but not the least, I would like to express my deepest thanks to my beloved family especially to my parents for their continuous help and support in all my life. They have made their best efforts to teach us good manners and proprieties and offering us best education. My brothers and my sisters thank you for your support and my sincere gratitude to my faithful loving wife (Dr. Douaa Fathy), my daughters (Retal, Razan and Rovan) for love and patience. It was their unconditional love, understanding and sacrifice that allowed me to complete this work. My family, I am really very proud of being a member of you. My biggest thanks go out to my family for their unconditional love and encouragement throughout the years! I am very grateful for all your support! Mabrouk Sami I ABSTRACT Abstract The present PhD-thesis uses petrological, mineralogical and geochemical methods to document and evaluate the highly fractionated rare metal-bearing granites in the northern Arabian-Nubian Shield in Egypt. Two areas (Gabal El-Ineigi and Gabal Abu- Diab), located in the Central Eastern Desert of Egypt, are discussed in detail. Gabal El-Ineigi is a composite pluton consisting of porphyritic syenogranites (SGs) and coarse- to medium-grained highly evolved alkali-feldspar granites (AFGs), intruded into older granodioritic and metagabbroic-dioritic rocks. Several rare metal minerals, including columbite-(Fe), fergusonite-(Y), rutile, zircon and thorite occur in the AFGs. Allanite and epidote are present as accessory phases in the SGs. The mineralogical and geochemical characters of the AFGs are typical of rare metal bearing granites. The AFGs are metaluminous, highly fractionated calc-alkaline granites that contain high amounts of Rb and HFSE (e.g. Nb, Y, U, Th and Ta) and are extremely depleted in Sr and Ba. Their REE patterns are characterized by enrichment in light rare-earth elements (LREE) with a pronounced negative Eu anomaly and tetrad effect, indicating that the granites were affected by late- to post- magmatic stage fluids during their magmatic differentiation. In contrast, the SGs have high Sr and Ba contents, while their REE patterns show moderate enrichment in LREE and a weak negative Eu anomaly. The AFGs are characterized by extremely high 87Rb/86Sr and 87Sr/86Sr ratios, reflecting a clear disturbance of the Rb- Sr isotopic system and which may be an indication for high temperature magma-fluid interaction. In contrast, the SGs have relatively low initial 87Sr/86Sr ratios, giving a Rb-Sr age of 569±15 Ma. Both SGs and AFGs have a positive εNd(t) value, ranging from +7.40 to +5.17, and young Nd-TDM2 ages, from 707 Ma to 893 Ma, reflecting the juvenile crustal nature of the Gabal El-Ineigi granites and precluding the occurrence of pre-Neoproterozoic continental crust in the Arabian-Nubian Shield. The two studied granites in this composite pluton are genetically not associated with each other and indicate a complex origin, involving two compositionally distinct parental magmas that were both modified during magmatic fractionation processes. The SGs were formed by partial melting of a mid-crustal source, with subsequent crystal fractionation, whilst the AFGs were generated by partial melting and fractionation of Nb- and Ta-rich amphibole and/or biotite in the lower crust. The appreciable amounts of fluorine in the magma appear to be responsible for the formation of the rare metal element complexes in the Gabal El-Ineigi AFGs. Gabal Abu-Diab constitute a multiphase pluton, largely consisting of two-mica granites (TMGs) enclosing microgranular enclaves and intruded by garnet bearing muscovite granites (GMGs) and muscovite granites (MGs). These granites are weakly peraluminous, post-collisional and show high SiO2 and alkali contents, with a highly fractionated A-type affinity. Compared to their host TMGs, the microgranular enclaves are strongly peraluminous, with low SiO2 and contain high abundances of TiO2, FeO, MgO, P2O5, F, Li, Nb, Rb, Th, U, Zr, Y and REEs. The TMGs are depleted in Ba, Nb, P and Ti and are enriched in LREEs relative to HREEs, with a II ABSTRACT weak negative Eu anomaly. In contrast, the GMGs and MGs are extremely depleted in Ba, Sr and Ti and have tetrad-type REE patterns, with pronounced negative Eu anomalies, like rare metals-bearing granites from the Central Eastern Desert of Egypt. The crystallization age of the TMGs was 585±24 Ma (Rb-Sr method). Moreover, the TMGs are characterized by restricted and relatively low initial 87Sr/86Sr ratios, suggesting that they were derived from a depleted mantle source, with insignificant contamination from the older continental crust. The GMGs and MGs have extremely high 87Rb/86Sr and 87Sr/86Sr ratios that reflect a disturbance of the Rb-Sr isotopic system and may give an indication for magmatic-fluid interaction. However, all the granitoids display positive εNd(t), from +4.41 to +6.57, and depleted mantle model ages, with TDM2 from 777 Ma to 956 Ma, which indicate a derivation from a mantle source. The microgranular enclaves likely represent remnants of mantle-derived mafic magmas injected into the more felsic TMGs magma. Geochemical and isotopic data, along with petrogenetic modelling, suggest that TMGs were formed by a low degree of partial melting (25 %) of the pre-existing I- type granodiorites, followed by extensive fractional crystallization and fluid fractionation, to produce the geochemically specialized rare metals GMGs and MGs in the outer part of Abu-Diab pluton. Due to lithospheric delamination process during the post-collisional stage of the evolution of the Arabian-Nubian Shield, the underplated fluid/volatile rich mantle magma interplated and migrated upward to shallow crustal levels, through extensional faults/shear zones, and enhanced the partial melting and fractionation of the granodiorites, to eventually form the Abu-Diab A-type granites. In this study, we focus on the GMGs, due to their enrichment in rare metal accessory minerals, including garnet, columbite, zircon ilmenorutile, rutile and thorite. The garnet (Sps61–72Alm25–35Prp1–4Adr0–1) is strongly enriched in HREE (∑HREE= 681- 2494 ppm with Y= 1616-2827 ppm) with a strong negative Eu anomaly. Zircon contains high Hf, Y, U, Th and Yb contents.
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  • The Texas Grenville Orogen, Llano Uplift, Texas

    The Texas Grenville Orogen, Llano Uplift, Texas

    THE TEXAS GRENVILLE OROGEN, LLANO UPLIFT, TEXAS Fieldtrip guide to the Precambrian Geology of the Llano Uplift, central Texas by Sharon Mosher, Mark Helper, and Jamie Levine Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin TRIP 405 for THE GEOLOGICAL SOCIETY OF AMERICA ANNUAL MEETING, HOUSTON, TX, FALL 2008 Cosponsored by GSA Structural Geology and Tectonics Division THE TEXAS GRENVILLE OROGEN, LLANO UPLIFT, TEXAS Fieldtrip guide to the Precambrian Geology of the Llano Uplift, central Texas by Sharon Mosher, Mark Helper, and Jamie Levine Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin TRIP 405 for THE GEOLOGICAL SOCIETY OF AMERICA ANNUAL MEETING, HOUSTON, TX, FALL 2008 Cosponsored by GSA Structural Geology and Tectonics Division Cover: Robert M. Reed Copyright by Sharon Mosher 2008 GEOLOGY OF THE LLANO UPLIFT by Sharon Mosher INTRODUCTION The Llano Uplift of central Texas consists of multiply deformed, 1.37-1.23 Ga metasedimentary, metavolcanic and metaplutonic rocks intruded by 1.13 to 1.07 Ga, syn- tectonic to post-tectonic granites (Fig. 1) (Mosher, 1998). An early high-pressure eclogite-facies metamorphism is overprinted by dynamothermal, medium-pressure metamorphism at upper amphibolite-facies conditions and a subsequent low-pressure, middle amphibolite-facies metamorphism associated with widespread intrusion of late granites (Carlson et al., 2007). These rocks are exposed in a gentle structural dome exposing ~9000 km2 of Middle Proterozoic crystalline basement in an erosional window through Phanerozoic sedimentary cover (Muehlberger et al., 1967; Flawn and Muehlberger, 1970). Normal and oblique-slip faults related to the Ouachita Orogeny affect Precambrian to Pennsylvanian rocks and juxtapose Paleozoic strata with the Precambrian exposures.