Thesis (M.Sc.) --University of Adelaide, Dept. of Geology, 1965. / Typescript.

Thesis (Ph. D.)--University of Wisconsin - Madison, 2005. / (UnM)AAI3186163. Source: Dissertation Abstracts International, Volume: 66-08, Section: B, page: 4128. Supervisor: John W. Valley.

Thesis (Ph.D.)--Yale University, 2006. / (UMI)AAI3243705. Adviser: Mark Thomas Brandon. Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6968.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 218-229).

No description available.

The origin of massif anorthosite is related to Precambrian crustal evolution. The chemical composition of anorthosite is fundamental to an understanding of the geochemical evolution of the earth in the Proterozoic Era. Chemical studies of Proterozoic anorthosite massifs in the Nain Plutonic Suite, Labrador, delineate their composition ranges and variation, and illustrate the variety of magmas and their source characteristics. Three massifs along Tikkoatokhakh Bay (TIK) are mainly noritic anorthosites and show no mineralogical or chemical differences. The Kikkertavak (KIK) and Port Manvers Run (PMR) intrusions are mainly troctolitic anorthosites and contain more mafics than the TIK bodies. Chemically, the TIK bodies can definitely be distinguished from those at KIK and PMR, the former containing a low An content in plagioclase, high alkalies and LIL in rock. The KIK rocks are similar to the PMR ones in most cases, except for lower Rb/Sr and higher K/Rb ratios in the PMR. Based on petrographic and major element data, three different magma types exist in the study area. The sodic noritic magma accumulated plagioclase in TIK. The troctolitic magmas in KIK and PMR are similar to known troctolitic bodies such as the Kiglapait Intrusion, the Hettasch Intrusion and the intrusion at Paul Island, and their feldspar rich cumulates. A moderate clinopyroxene component in the PMR magma suggests that the PMR magma could be gabbroic-troctolitic. The inversion from plagioclase to melt composition via D$\sp{\rm PL/L}$ was used to calculate REE and trace element concentrations in the parental magmas of the Nain anorthosites. The estimated magmas, noritic in TIK, troctolitic in KIK and gabbroic-troctolitic in PMR, are consistent with those indicated from the major element data. The magmas show that their chemical characters seem to have mostly Plume-MORB nature. High Ba, Sr, Ti and low Rb, Nb, Zr appear to indicate incorporation of a lindsleyite phase from the source, which is ascribed to metasomatism of lithosphere from the asthenosphere. Such characters also indicate that the magma source of the mantle in the Nain area must have been depleted in Rb, Nb and Zr before the melting process.

The Nain Anorthosite Complex is a Proterozoic plutonic suite in Labrador. This complex is composed over 24 anorthositic and troctolitic rocks, but its regional geochronology and tectonic environment were uncertain. The $\sp{40}$Ar/$\sp{39}$Ar method was applied to this complex, and the results shed light on these problems. The early anorthositic magmatic activity of the Nain complex is represented by three major anorthosite massifs along Tikkoatokhakh Bay, and their ages are constrained by a reset $\sp{40}$Ar/$\sp{39}$Ar hornblende age of 1328 $\pm$ 10 Ma in the contact aureole, as well as closure ages from other minerals. This age is younger than a previously estimated age of about 1.4 Ga. It signifies the beginning of large scale anorthositic magmatism. Plagioclase $\sp{40}$Ar/$\sp{39}$Ar closure ages from various anorthosite intrusions reveal two stages of emplacement for the Nain anorthosites. These stages correspond to the Older Anorthosite Event and the Main Anorthosite Event as identified from field evidence. This agreement indicates the overall feasibility of the field criteria used to classify the relative ages of anorthosites. Some contradictions between the two results are also observed, raising questions for further study. The cooling history study is largely based on the closure ages and temperatures of minerals from the Kiglapait Intrusion. This troctolitic layered intrusion yields a hornblende $\sp{40}$Ar/$\sp{39}$Ar age of 1298 $\pm$ 15 Ma, very close to a previous Sm/Nd result of 1305 Ma reported by DePaolo. Different minerals from the Kiglapait Intrusion behave surprisingly well and are concordant. Together, they not only allow the reconstruction of the late cooling history for the Kiglapait Intrusion, but, combined with the pre-intrusion country rock temperature and $\sp{40}$Ar/$\sp{39}$Ar age data from other anorthosite intrusions, reveal a continuous, slow cooling of the Nain region. This cooling trend reflects a late uplift during and after the large scale anorthositic magmatism, with an uplift rate dropping continuously from about 0.15 mm/yr to 0.07 mm/yr. This slowing uplift was probably related to the subsidence of a mantle plume upwelling that originally initiated the magmatism.

The manganese mineralization near Kato Nevrokopi, Drama, in the Falakron mountains, is hosted by the Precambrian to Early Paleozoic Upper Marble. The marble and the underlying Lower Schist unit were metamorphosed between the Late Cambrian and the Carboniferous and were extensively deformed during the Alpine orogeny. The Alpine deformation is considered to have occurred between the Early Cretaceous and the Oligocene. Granodiorites and rhyodacites of Oligocene age outcrop also in the area. The mineralization near Kato Nevrokopi is confined to intersecting Alpine fault zones of northeast and northwest trends. Negligible mineralization occurs into the schist, the richest orebodies being present as lateral extensions in the marble. Mineralization diminishes with increasing distance from the fault zones. The shape of the orebodies is irregular with individual offshoots being lenticular, pod-like or tabular. Sizes can be up to 50m in length, 20m in width and 5-10m in thickness. The boundaries between the orebodies and the marble are sharp and replacement and alteration phenomena around the orebodies include: dolomitization of the marble and clay mineral alteration. Two distinctly different mineralizing processes took place at Kato Nevrokopi: a) A hydrothermal process, characterized by mineral zoning in time and space, present as abundant rhodochrosite, ankerite, sphalerite, pyrite, pyrrhotine, chalcopyrite and marcasite in the stratigraphically deeper veins and "black calcite" (mixture of calcite and todorokite) and galena in the upper veins. b) A supergene process, in which the hydrothermal minerals in the veins were weathered. During this process, rhodochrosite in the veins was oxidized to MnO-gel and todorokite and in low altitude karstic cavities the mineral assemblage is: MnO-gel-nsutitechalcophanite. In high altitude karsts the mineral assemblage is: MnO-gel-nsutite-birnessite-cryptomelane-pyrolusite. During weathering Zn derived by dissolution of sphalerite was also mobile, being transported together with Mn to karstic cavities where it substituted for Mn in the Mn-oxides. The minerals pyrrhotine, marcasite, ankerite and birnessite are for first time recorded at Kato Nevrokopi. The lack of useable fluid inclusions severely limited the information on the composition of the hydrothermal fluids. From the mineral pair kaolinite-sericite, the pH of the hydrothermal fluids was estimated to have been between 3-4. Hydrothermal mineral precipitation took place mainly by reaction of the fluids with the marble and pH increase (cf., rhodochrosite) or by mixing of the hydrothermal fluids with near surface aquifers (black calcite). Thermodynamic data for the overall transformation of rhodochrosite to pyrolusite and the contemporaneous decomposition of chalcopyrite to azurite and malachite were used and the oxygen fugacity of the meteoric fluids was calculated to have ranged between 10-22 and 10-17. Mn-oxide precipitation during weathering took place either by oxidation of the primary veins (cf., MnO-gel, todorokite) or by reaction of the groundwaters with the marble in karstic cavities and precipitation of Mn-oxides as layers and encrustations above the local ground water table. Evidence from the whole rock geochemistry of the mineralized samples emphasizes the role of the thrust and fault zones as solution passageways and stresses their importance for the development of hydrothermal and supergene mineralization at Kato Nevrokopi. During weathering, downward percolation of C02-rich oxygenated meteoric waters within the veins, caused the breakdown and dissolution of sulphides and oxidation of rhodochrosite to Mn-oxides. The pH of these meteoric fluids was buffered by the dissolution of sulphides and the formation of karstic cavities was favoured by the high permeability induced by the occurrence of the thrust zone and the percolation of acidic meteoric waters through the marble. Chemical transport of MnZ+ to karstic cavities was possible in reduced meteoric waters at the beginning of weathering (pH"4-5), and as Mn(HCO3)2 in slightly alkaline groundwaters during advanced weathering (pH"6-8). Alkalies (K, Na) and alkaline earths (Ca, Mg, Ba, Sr) where leached away from the ore and the country rocks during weathering and the order of element mobility in the karstic cavities was: Na>K>MgaSr>Mn>As>Ca>Zn>Ba>Al>Fe>Cu>Cd>Pb. The Mn-oxide orebodies near Kato Nevrokopi are located in a northeast trending line parallel to the axes of major Alpine folds and significantly the rhyodacite volcanics outcrop also in a parallel fashion to this line providing evidence of an underlying pluton. This northeast trending line may therefore represent a zone of crustal weakness that was exploited by andesitic magma and subsequently by hydrothermal fluids. An average age of 33 Ma for the Kato Nevrokopi mineralization is provided. This age is similar to that of magmatism in and around the Drama area. It is therefore reasonable to conclude that the hydrothermal activity near Kato Nevrokopi and generally of the northeast Drama area was related to the Oligocene magmatism. On the basis of its age, style, morphology and genesis, the mineralization near Kato Nevrokopi is placed in the metallogenic province of N. Greece/S. Bulgaria which also includes the Madan hydrothermal Pb-Zn-Mn vein deposits and the Chalkidiki Pb-Zn deposits which have Mn-oxides in their upper parts.

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Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography : leaves [75]-77. Also available online.