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A brief description of a low grade regionally metamorphosed region in the Madoc area in Southern Ontario is given. Plagioclase compositions from metamorphosed basic rocks of this region were studied with the intention of finding co-existing plagioclases in the region of peristerite solvus. X-ray diffraction was found useful in determining the presence of two co-existing plagioclase feldspars. Two peaks occurred in the region of the 131 and 131 peaks if this was the case. Compositional determinations for albitic feldspars were found inaccurate as the angular separation (Δ29) between the 131 and 131 peaks was apparently reduced indicating plagioclase composition less than An0. For anorthite rich feldspars the angular separation between 131 and 131 gave relatively accurate compositions. The electron microprobe was used·to determine the plagioclase compositions of samples from the Madoc area. Results compared well for anorthite rich feldspars determined by both X-ray diffraction and. electron microprobe techniques. Only one rock was found to contain two plgioclases related to a peristerite solvus. A zoned nature appears to exist. Albite and oligoclase coexist, the oligoclase grading into andesine. Also, albitic plagioclase is associated with epidote inclusions; a diffusion relationship probably existing between the two. With increased metamorphic grade, epidote disappears and the anorthite content of plagioclase increases. / Thesis / Bachelor of Science (BSc)

This thesis is missing either page 57 or 58. The other copies of this thesis do not have this page either. -Digitization Centre / This study is an investigation of two regions which were once part of the same Proterozoic margin: the Frontenac Axis in the Southeastern Grenville Province of Ontario, and the island of Islay in Scotland. Shieh (1985) performed an oxygen isotopic study on the granitic plutons and surrounding metasediments in the Frontenac terrane. For the granites south of the Rideau Lake Fault, he observed extremely high 18O/16O ratios of +14.0%o (relative to SHOW), whereas north of the fault, the plutons gave ratios of around 10%o. Five of the plutons in Shieh's study have been dated using U-Pb zircon geochronology, with the following results: Battersea -1165 ± 3 Ma, Lyndhurst -1166 ± 3 Ma, Perth Road -1166 ± 3 Ma, Crow Lake -1176 ± 2 Ma, and Westport -1076 ± 2 Ma. The zircon ages are younger than the depleted mantle Nd model ages obtained (1211 to 1480 Ma) and signify that the plutons may be derived from a mantle source with contamination by the older surrounding metasediments which have an average Nd model age of 1790 Ma. Correlation between initial Nd (ENd(t) from +1 to +3) and initial Sr (Esr(t) from +9 to +21) also shows a mixed origin for the plutons. However, oxygen isotopes show that contamination by marble may also have occurred. Two features distinguish the Frontenac terrane southeast of the Rideau Lake Fault (RLF) from the Central Metasedimentary Belt (CMB) to the northwest: 1) the anorogenic (i.e. within plate) chemical signatures of the plutons, which are similar to the Hid-Proterozoic anorogenic granites that occur throughout North America (Anderson, 1983); and 2) the unique zircon ages for the plutons south of the RLF (1166 to 1176 Ha) that occur nowhere else in the CMB. This implies that the two areas define different crustal terranes. However, since Penokean (ca. 1800 Ha) crustal extraction ages are found in both terranes they may represent displaced segments of a single Penokean continental margin. In Scotland, a gneiss terrane on Islay was always inferred to be part of the Archean Lewisian complex. However, isotopic evidence shows that the Islay terrane is early Proterozoic in age (1782 Ha by U-Pb zircon geochronology) and that it is juvenile mantle-derived material, not a reworking of Archean crust during the Proterozoic. As a result, two major implications for the crustal evolution of Northern Britain are: 1) the Grampian terrane, an area directly adjacent to the newly defined Proterozoic Islay block, is probably underlain by Proterozoic basement; and 2) Northern Britain can be included in the Lower Proterozoic reconstruction of the Laurentian Shield. The similar crustal extraction ages observed in the Grenville of Ontario and on Islay give proof that these areas were part of a major 1.8 to 1.9 Ga crustal formation event, stretching from the southwestern U.S. to Finland. / Thesis / Master of Science (MS)

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Entre os principais problemas ambientais e econômicos enfrentados pela mineração está a estocagem de grandes quantidades de resíduos em barragens. Estudos que buscam usos para esses resíduos têm sido realizados com a finalidade de torná-los matérias-primas para fabricação de diversos produtos, como cerâmicas, vidros, argamassas e pedras compostas, entre outros. Tratamentos físico-químicos, como separação magnética a seco e lixiviação ácida, aplicados ao resíduo arenoso proveniente do processo de beneficiamento do mineral itabirito, mostram a possibilidade de sua transformação em matéria-prima para os setores de maior consumo de areia de alta pureza, como as indústrias de sílica metalúrgica, de cerâmicas e de vidros. Verificou-se que a separação magnética com um campo permanente de 21.000 gauss, aplicada ao resíduo arenoso com teor mássico médio de 13% de ferro, foi capaz de gerar uma fração magnética com teor mássico de 37% de ferro e uma fração não-magnética com 0,5% de ferro. A lixiviação ácida da fração não-magnética, realizada em recipientes tubulares de teflon, com pressão de 1,03 MPa e temperaturas em torno de 180C, possibilitou a obtenção de uma sílica com teores de ferro de 0,003%. Foram obtidas amostras de vidro, esmaltes cerâmicos e cerâmicas vermelha e de revestimento com utilização da fração nãomagnética antes e depois da lixiviação, as quais apresentaram características de acordo com os requisitos do mercado. / Among the major environmental and economic problems concerning mining is the large quantities of residues that should be stored in dams. Studies are being carried out seeking uses for these residues as raw materials for manufacturing of products such as ceramics, glass, mortar, and composite stones. Dry magnetic separation and acid leaching were applied to a sandy residue (iron content averaging 13 %) from banded iron formations exploitation to obtain high purity silica. The magnetic separation with a permanent field of 21000 gauss was able to produce a magnetic fraction with content of 37% iron and a nonmagnetic fraction with 0.5% iron. The acid leaching of the non-magnetic fraction was carried out in tubular containers of Teflon (inner pressure 1.03 MPa and temperatures around 180 C) and produced silica with an iron content of 0.003%. Glass, ceramic glazes, and ceramic samples were obtained from the non-magnetic fraction before and after leaching with properties according to market requirements.

名古屋大学年代測定総合研究センターシンポジウム報告