Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography : leaves 213-230. Also available online.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / 1 folded map in pocket. Typescript. Includes bibliographical references (leaves 134-145). Also available on the Internet.

Abstract The gold mineralization event within Archaean granite-greenstone terranes occurred during the late Archaean, and followed the intrusion of syn- to late-tectonic granitic plutons into previously deformed greenstone belts. An Archaean granite/gneiss-hosted gold deposit, in terms of this project, is classified as having a gold-assay cutoff of 1g/metric ton over widths of at least several metres, or higher grades over narrower widths and/or verbal descriptions that indicate such values. Fluid inclusion studies and isotopic data identify two possible origins for the auriferous fluids; namely magmatic and metamorphic. The exploration target according to the magmatic model, is a late-Archaean, hydrothermally altered, mineralized and fractured granitic intrusion preferably with a granodioritic or quartz-dioritic composition. The exploration target according to the metamorphic replacement model is a granitic stock that has intruded a zone of crustal weakness such as a shear zone, active during the late Archaean. Alternatively, the granitic intrusion should be affected by regionally extensive late-Archaean shearing. It should be hydrothermally altered, deformed and mineralized. Five areas within the Pietersburg granite-greenstone terrane were selected for the 'Regional Area Selection' phase of exploration for Archaean granite/gneiss-hosted gold deposits; namely Roodepoort, Waterval, Ramagoep, Moletsie and Matlala. Roodepoort contains a known granodiorite-hosted gold deposit; the Knight's Pluton, and served as an orientation survey for this project. The use and interpretation of LANDSAT images formed an integral part of exploration techniques; to assess their usefulness in the exploration of Archaean granite/gneiss-hosted gold deposits. Area selection criteria for granite/gneiss-hosted gold mineralization at Roodepoort are the major ENE-trending shear zone, the NNW-trending lineament and hydrothermal alteration, shearing, quartz-stockworks and sulphide mineralization within the Knight's Pluton. The origin of the gold within the Knight's Pluton is uncertain; both magmatic and metamorphic models are possibilities. Ongoing exploration is in progress at Roodepoort. The only area selection criterion for granite/gneiss-hosted gold mineralization at Waterval is the sericitized, subcropping granites located within trenches. Gold mineralization is insignificant. No area selection criteria for Archaean granite/gneiss-hosted gold mineralization were located at Ramagoep, Matlala and Moletsie. No further exploration is recommended for all these areas. The MES image interpretations were successful in identifying lineaments, granitic outcrops, greenstones, vegetation and soil cover. The Clay-iron images adequately differentiated betweeen iron-rich and clay-bearing areas. However, not all clay-bearing areas were associated with hydrothermal alteratian; field checks were necessary to discriminate between weathered granites and hydrothermally altered granites. The Wallis images served to locally enhance the contrasts of the MES and Clay-iron images.

The Thor-Odin gneiss dome is one of several structural culminations along the eastern margin of the Shuswap terrain. The gneiss domes have previously been ascribed both to diapiric uprise of granitic gneisses and to interference of late-stage buckle folds. The ages of rocks in the gneiss domes have also been the subject of controversy. Age estimates range from Archean to Mesozoic. This study provides the basis for a detailed model for a new interpretation of the structural evolution of the Thor-Odin gneiss dome. Prior to doming, this area was characterized by the formation of large-scale nappe structures and imbrication of Archean basement rocks with the cover rock sequence. The first period of deformation (Phase One) consisted of large-scale infolding of the cover rock sequence into the basement rocks. The Pingston fold in the core of the dome is a product of this event. The second period of deformation (Phase Two) was marked by the forcing of wedges of basement into the cores of northerly-moving nappes. The third period of deformation (Phase Three) was co-axial with Phase Two and consisted of imbrication and refolding of the upper levels of the stack of Phase Two nappes. Strain analysis based on fold shape, distorted lineation patterns and elliptical strain markers demonstrate that finite strains are highest in the imbricated zone between the Basement Cored Nappe Domain and the Cover Rock Domain. Flattening strains are anomalously low in the Autochthonous Core Gneiss Domain. Analysis of Phase Two fold axes distorted into flattened small circles by Phase Three folds shows that Phase Three strain magnitude √(λ₂/ λ₁) varies from 0.81 to 0.49. Rb-Sr whole rock geochronometry has revealed evidence for three Precambrian events within the basement gneisses. Unmigmatized metasedi-mentary basement gneisses form a six-point errorchron with an age of 2.73±0.20 Ga. Granitic gneisses previously dated at 1.96 Ga by the U-Pb zircon technique, give reset ages for gneiss/vein whole rock suites with ages in the range 750 to 860 Ma. Common lead systematics of stratabound sulfide deposits in the cover rock sequence suggest that the cover rocks are Cambrian in age, in agreement with earlier lithological correlations. The lead isotope ratios suggest the deposits were ultimately derived from an approximately 2.0 Ga basement terrain. The outcropping gneissic basement rocks of the Shuswap are dominantly granitic gneisses which give 2.0 to 2.2 Ga Rb-Sr whole rock dates.; Ductile deformation in the terrain appears to have ended by 150 Ma, as this corresponds to the ages of several post-tectonic intrusions which crosscut Phase Three folds and impose a contact metamorphic overprint on the regional metamorphic pattern. The Nelson Batholith is a post-tectonic batholith which intrudes both the Shuswap terrain and the Kootenay Arc to the east. Two sample suites were collected from the different batho-lithic phases and analyzed by Rb-Sr whole rock methods with the following results: Suite I - Porphyritic monzonite with alkali feldspar megacrysts from the West Arm of Kootenay Lake give a seven-point isochron with an age of 158 ± 16 Ma and an initial ratio of 0.7069 ± 0.0001. Suite I has a Rb-Sr feldspar, date of 153 ± 26 Ma, a K-Ar hornblende date of 143 ± 5 Ma, and a K-Ar biotite date of 60 ± 2 Ma. It seems likely that the K-Ar dates have been disturbed by thermal events subsequent to emplacement of the batholith. Suite II- Medium grained granodiorite from the southern tail of the Nelson Batholith gives a nine-point whole rock isochron with an age of 162 ± 6 with an initial ratio of 0.7065 ± 0.0001. Taken together, these data provide significant new information on the nature and timing of the events that formed the metamorphic core zone of the southern Canadian Cordillera. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

A petrographic study has been made of the contact relations between metagabbro and nepheline gneiss underlain by marble, in Monmouth township, Haliburton County, Ontario. A bad of hornblende nepheline-garnet gneiss about 80 feetwide trending north-south is underlain at a shear contact by marble. Round inclusion up to 18 inches across of red pyroxene with some spinel and rimmed by olivine occur in the marble a few feet below the contact. For a few inches above the contact the nepheline gneiss sometimes is biotite-bearing. To the east the nepheline gneiss grades into a band of hybrid nepheline metagabbro (containing pink augite) about 50 feet wide. This in turn is followed by a zone of garnetiferous clinozoisite metagabbro about 220 feet wide. Clinozoisite persists in the metagabbro for 100 feet beyond this zone and is followed by hornblende-(pyroxene)-plagioclase metagabbro. Pyroxene-garnet-(nepheline) skarn is interlayered with nepheline gneiss at one outcrop ear the fault contact with marble. It appears that gabbroic magma has intruded limestone and developed a skarn at the contact. Assimilation of lime by the magma has developed pink augite (titanaugite ?) , clinozoisite and grossularite in the gabbro. Subsequent injection of a highly fluid nepheline magma, or of solutions containing soda, alumina and iron and not saturated with silica, formed nepheline-bearing rock between marble and gabbro. Soda metasomatism produced a hybrid nepheline gabbro adjacent to the nepheline-bearirg rock. Regional metamorphism later imparted a foliation to the marble and nepheline rock, and produced a metamorphic texture the gabbro. Faulting of a unknown age brought nepheline gneiss and marble into sharp contact and probably trapped the skarn as horses only one of which is now exposed. / Thesis / Doctor of Philosophy (PhD)

No description available.

Thèse doctorat : Sciences e la Terre et de l'Univers : Nancy 1 : 2005. Thèse doctorat : Scienze della Terra : Università degli studi di Bari : 2005. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre.

The tectonometamorphic histories of allochthonous nappe units that were deeply buried and subsequently exhumed during the Scandian orogeny in the Western Gneiss Region (WGR) of Norway are poorly constrained and understood. One such unit is the Blåhø Nappe which underlies northern Harøya and Finnøya, two islands in the Nordøyane ultrahigh-pressure (UHP) metamorphic domain. The Blåhø Nappe contains a lower unit of garnet amphibolite gneiss with interlayered garnet-bearing quartzofeldspathic gneiss and marble, and an upper unit of migmatitic aluminous gneiss. Southern Harøya comprises orthogneisses attributed to the Baltican continental crust, and is separated from the Blåhø Nappe by the Finnøya migmatitic shear zone (FMSZ). Field and petrographic observations from these islands suggest that the Blåhø Nappe experienced peak metamorphism at high pressure amphibolite to granulite facies conditions before being overprinted by relatively lower pressure amphibolite facies conditions. In contrast, the adjacent Baltican basement gneiss contains coesite-eclogite pods, which attests to UHP conditions. However, the basement rocks are also overprinted by an amphibolite facies assemblage. To understand the implications of these observations, the metamorphic history of the Blåhø Nappe was investigated, and compared to that of the basement. This thesis presents thermobarometric and geochronologic analyses used to define a metamorphic pressure-temperature-time (PTt) path for the Blåhø Nappe on Harøya and Finnøya. The results suggest prograde metamorphism between ca. 440 Ma and 415 Ma, peak temperature metamorphism at 860?C and 15 kbar at around 410 Ma, equilibration at amphibolite-facies conditions of 680?C and 9 kbar by 395 Ma, and cooling below Ar-closure T in muscovite by ca. 360 Ma. The PTt data from the Blåhø Nappe demonstrate that these rocks did not share the UHP history of the adjacent basement rocks, but that both experienced similar amphibolite facies metamorphism and deformation. These units were likely juxtaposed along the FMSZ during isothermal decompression from their respective maximum burial depths to ~30 km depth.

Thesis (Ph.D.) - Carleton University, 2005. / Includes bibliographical references (p. 204-221). Also available in electronic format on the Internet.