No description available.

No description available.

No description available.

M.A. / Hematized iron formation known as the Manganore iron formation is slumped into sinkhole structures in the Campbellrand Subgroup, Transvaal Supergroup, on the Maremane dome. These iron deposits are underlain by manganiferous breccias known as the Wolhaarkop Breccia. Known iron and manganese deposits of this type occur in an arc from Sishen in the north to Postmasburg in the south. The area is not being mined for manganese at the moment due to the relatively high grade of the Kalahari manganese field situated to the north of this area. The iron deposits, though, are some of the richest in the world. The aim is to establish the mode of origin for the Wolhaarkop Breccia. The Wolhaarkop Breccia is interpreted as being a residual ancient manganese wad from a karst environment in manganese rich dolostones of the Campbellrand Subgroup. This siliceous breccia contains authigenic megaquartz and angular poorly sorted clasts of chalcedony and quartz, set in a braunite-hematite matrix. Fluid inclusions in the authigenic quartz of the Wolhaarkop Breccia have been studied to establish the source of the fluid responsible for quartz precipitation in the Wolhaarkop Breccia, and indirectly, for the formation of the Wolhaarkop Breccia. Thermometric data was used to determine the maximum possible pT and depth conditions under which the quartz might have been precipitated. Fluid chemistry was determined using the bulk crush-leach method to shed some light on the fluid origin. It was established that the fluid responsible for chert recrystallization and precipitation of authigenic quartz and chalcedony had a meteoric source. Considering the results of the above-mentioned analysis, it was concluded that the iron and manganese deposits were formed during a cycle of uplift followed by subsidence. During the period of uplift, erosion in a karst environment and enrichment of iron formation in a supergene environment concentrated manganese as a manganese wad, and iron as a residual iron-oxide laterite. Meteoric water was the main fluid present during this period. Later, during a stage of subsidence, the Wolhaarkop Breccia underwent diagenesis and later lower greenschist-facies metamorphism. During a final stage of uplift the deposit was exposed to the atmosphere again, the dolostones were weathered away and the residual Manganore iron formation and Wolhaarkop Breccia were exposed to supergene alteration.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 179-192). Also available in print.

Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1924. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed February 23, 2010) Includes bibliographical references (p. [101-105]) and index (p. [106-107]).

The Hekou Group in the Kangdian region, SW Yangtze Block is a metavolcanic-metasedimentary succession hosting the giant Lala Fe-Cu-(Mo, REE) deposit. Mafic volcanic rocks of the Hekou Group and nearby gabbroic intrusions have identical zircon U-Pb ages of ~1700 Ma. The sedimentary and mafic rocks are suggested to have formed in an intra-continental rift, similar to those of the North Australian Craton. Such a similarity suggests that the Yangtze Block was likely linked with the North Australian Craton in the Columbia supercontinent during late Paleoproterozoic. Overlying the Hekou Group is a thick sedimentary sequence of the Julin Group containing basaltic layers with zircon U-Pb ages of ~1050 Ma. The basalts and other coeval igneous rocks in the region have geochemical affinity of within-plate rocks, representing a ~1.05-1.1 Ga rifting event. Occurrence of the within-plate rocks does not support existence of a Grenvillian orogenic belt in the region, and thus agrues against previous hypothesis that proposed the Yangtze Block to be located in the interior of the Rodinia supercontinent on the basis of the so-called Grenvillian orogenic belt. The Lala deposit contains 200 Mt of ores with an average grade of 13 wt.% Fe, 0.92 wt.% Cu, 0.018 wt.% Mo, 0.022 wt.% Co, 0.25 wt.% REE2O3 and 0.16 ppm Au, and is one of the largest IOCG deposits in the region. The ores are hosted mostly in meta-vocalnic rocks (albitite) and schists, and are characterized by abundant low-Ti magnetite with subordinate chalcopyrite, pyrite, molybdenite and REE minerals. The paragenetic sequence includes Stage I of Na-alteration, Stage II of Fe mineralization, Stage III of Cu-Mo-REE mineralization, Stage IV of chalcopyrite-pyrite-calcite veins and Stage V of hematite-calcite-quartz veins. Molybdenite of Stage III has a Re-Os isotopic age of 1086 ± 8 Ma, similar to U-Pb ages of the primary allanite as 1067 ± 41 Ma, suggesting that mineralization of the Lala deposit is coeval with the ~1.05-1.1 Ga within-plate magmatism in the region. The secondary allanite has U-Pb ages of 880-850 Ma, comparable to Ar-Ar and Pb-Pb ages of undeformed Stage IV and V veins, representing a younger hydrothermal event. C-O-S isotopes suggest that the Fe and Cu mineralization stages (II and III) at Lala have formed from high temperature magmatic-hydrothermal fluids (385-430ºC). However, compositions of fluid inclusions and minerals demonstrate that the Fe and Cu mineralizing fluids have different compositions. Strontium isotopic compositions of apatite and calcite suggest that the Fe mineralizing fluid has formed from magmatic fluids interacted with late Paleoproterozoic host rocks, whereas the Cu mineralizing fluid with much higher 87Sr/86Sr ratios has possibly involved magmatic fluids that have interacted with older basement beneath. Close association of monazite-bearing apatite, Cu-sulfides and REE-minerals at Lala suggests that REE mobilization and mineralization is genetically related to the Cu mineralizing fluid. This study suggests that the Cu mineralizing fluid contains Cl-, K, CO2, F-, PO43- and CO32- with low Na activity, and is thus responsible for mobilization, transportation and deposition of LREEs in the Lala deposit. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Στην πρώτη ενότητα της έρευνας, σκοπός μας είναι ο προσδιορισμός των λιθοτύπων και του πετροτεκτονικού περιβάλλοντος εναπόθεσης του πλουτωνίτη. Για το λόγο αυτό χρησιμοποιούνται πετρογραφικές, πετροχημικές καθώς και ορυκτοχημικές μέθοδοι ταξινόμησης. Μελετώνται οι συνθήκες πίεσης και θερμοκρασίας κάτω από τις οποίες εναποτέθηκε ο πλουτωνίτης με τη χρήση γεωβαρομέτρου και γεωθερμομέτρου. Διερευνάται, επίσης η γεωχημεία των περιβαλλόντων πετρωμάτων του πλουτωνίτη καθώς και οι πιθανοί τους πρωτόλιθοι. Η δεύτερη ενότητα της έρευνας περιλαμβάνει τη μελέτη της, συνδεδεμένης με τον πλουτωνίτη, μεταλλοφορίας οξειδίων του σιδήρου (αιματίτη, μαγνητίτη) και σουλφιδίων. Μελετάται η θερμοκρασία κάτω από την οποία έγινε η κοιτασματογένεση, καθώς και η πιθανή πηγή προέλευσής της. Για το σκοπό αυτό χρησιμοποιούνται στοιχειομετρικές, γεωχημικές και ιστολογικές μέθοδοι για τις μεταλλικές παραγενέσεις. Γίνεται, επίσης, προσδιορισμός της θερμοκρασίας εναπόθεσης των σουλφιδίων καθώς και της πηγής προέλευσης του υδροθερμικού ρευστού από το οποίο αποτέθηκαν. Για το σκοπό αυτό χρησιμοποιείται η μέθοδος των σταθερών ισοτόπων 34S. Απαντάμε επίσης στο ερώτημα αν η μεταλλοφορία των σουλφιδίων και οξειδίων προϋπάρχει της διείσδυσης του πλουτωνίτη ή δημιουργήθηκε εξαιτίας αυτής. Τέλος, ως τρίτη, εξίσου σημαντική ενότητα της έρευνας θεωρείται η αναφορά στις αρνητικές επιδράσεις της μεταλλοφορίας οξειδίων του σιδήρου και σουλφιδίων στο περιβάλλον. Στην ενότητα αυτή περιλαμβάνεται και η πρόταση πιθανών τρόπων αντιμετώπισής τους. / The aim of the first part of this study is the determination of the lithotypes of the studied area and also the definition of the petro-tectonic environment of the emplacement of the pluton. Petrographic, petrochemical and mineralogical methoda of classification have been used to accomplish this aim. The conditions of pressure and temperature of the pluton emplacement have been determined with the use of geobarometric and geothermometric methods. In this part of the study, the geochemistry of the country rocks of the pluton and their possible protoliths are also presented. The second part of the study refers to the mineralization of iron oxides (hematite, magnetite) and sulfides related to the pluton emplacement. Stoichiometric, geochemical and textural methods have been used to identify the paragenesis of the mineralization in order to determine the temperature of the mineralization and assume the possible heat origin. the sulfides emplacement temperature, as well as the origin of their hydrothermal fluid is determined, using the method of the stable isotope 34S. We also adress to the question if the sulfides and oxides ores prexisted the pluton inavsion or were created because of it. Finally, as athird equally important aspect of this study is considered the reference to the negative effects of the sulfides and oxides ores in the environment. This unit includes recomendations of possible solutions.

No description available.

Thesis (Ph. D.)--University of New South Wales, 2005. / Also available online.