Mémoire (M.P.M.O.)-- Université du Québec à Chicoutimi, 1985. / Document électronique également accessible en format PDF. CaQCU

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Augmitto-Bouzan est un segment de 12 km de long à Rouyn-Noranda (Québec, Canada) de la zone de déformation Cadillac Larder-Lake (ZDCLL) caractérisé par une minéralisation aurifère inégalement distribuée, dans des veines de quartz-carbonate±tourmaline. L'étude compare les conditions de circulation passées des fluides entre les secteurs enrichis et pauvres en or afin d'identifier les processus responsables de l'enrichissement en or du segment. Les veines de quartz (δ¹⁸O: 11.3-16.8‰) tourmaline (δ¹⁸O: 8.5-11.9‰; δD: -59- -18‰) et carbonate (δ¹⁸O: 11.3-15‰; δ¹³C: -6.2- -2.8‰) sont principalement encaissées dans les roches ultramafiques-mafiques altérées du Groupe de Piché, reconnus comme étant l'expression physique de la ZDCLL. Le quartz et la tourmaline présentent des températures d'équilibre (228-420°C) qui définissent un gradient thermique vertical élevé (~30°C/100m) au sein du Groupe de Piché. La covariation entre la température et les valeurs δ¹⁸O[indice H2O] et δD[indice H2O] est interprétée comme représentant un mélange entre un fluide métamorphique profond de haute température (>420°C), haut δ¹⁸O[indice H2O] (>10.8‰) et bas δD (<-29‰) et un fluide interstitiel de la croûte supérieure de plus basse température (<230°C), bas δ¹⁸O (<4‰) et haut δD (~0‰). Les valeurs plus élevées de δD[indice H2O] sont probablement liées aux cycles d'évaporation-condensation associés au mécanisme faille-valve dans les veines. Des remontées locales de fluide métamorphique, mises en évidence par l'interpolation du δ¹⁸O[indice H2O], sont observées dans les blocs Augmitto-Cinderella et Astoria et ont probablement été canalisées dans des structures de perméabilité plus élevée. Les secteurs moins minéralisés présentent des δ¹⁸O[indice H2O] et des rapports fluide/roche plus faibles, reflétant probablement une plus grande proportion de fluide poral et des changements d'écoulement des fluides. La modélisation de l'écoulement des fluides montre que la plus grande proportion de fluide de la croûte supérieure dans les secteurs moins minéralisés est due à 1) un écoulement moins volumineux de fluide métamorphique dans le Groupe de Piché plus mince et 2) la présence de roches plus poreuses au nord de la ZDCLL, à partir desquelles une quantité plus importante de fluide poral s'infiltre dans la faille. Nous suggérons donc que la majorité des variations des teneurs aurifères est liée à la variation du flux de fluide métamorphique le long du segment. Un écoulement de fluide métamorphique moins abondant ou dilué diminue le potentiel aurifère le long de la ZDCLL. / Augmitto-Bouzan is a 12 km long segment of the Cadillac Larder-Lake deformation zone (CLLDZ) in Rouyn-Noranda (Québec, Canada) characterized by an uneven gold mineralization distribution, hosted in quartz-carbonate±tourmaline veins. This study compares the past fluid flow conditions between the variable gold-endowed sectors to identify processes responsible for gold endowment in the area. Quartz (δ¹⁸O: 11.8-16.8‰), tourmaline (δ¹⁸O: 8.5-11.9‰; δD: -59- -18‰) and carbonate (δ¹⁸O: 11.3-15‰; δ¹³C: -6.2- -2.8‰) veins are mainly hosted in the ultramafic-mafic Piché Group recognized as the physical expression of the CLLDZ. Quartz and tourmaline display equilibrium temperatures (228-420°C) that define a high vertical thermal gradient (~30°C/100m) within the host lithologies Covariation between temperature and computed δ¹⁸O[subscript H2O] and δD[subscript H2O] is interpreted to result from mixing between a high temperature (>420°C), high δ¹⁸O (>10.8‰), and low δD (<-29‰) deep-seated metamorphic fluid, and a low temperature (<230°C), low δ¹⁸O (<4‰) and high δD (~0‰) upper crustal pore fluid. The higher δD[subscript H2O] (up to 43‰) values are likely associated with flash vaporization and condensation cycles related to fault-valve mechanisms in the veins. Local upwellings of deep-seated fluid, evidenced by interpolation of δ¹⁸O[subscript H2O], are observed in the Augmitto-Cinderella and Astoria blocks and were likely focused along deformation-related pathways of higher permeability. Sectors of low gold endowment have lower δ¹⁸O[subscript H2O] and fluid/rock ratios, likely reflecting a larger proportion of upper crustal fluid and fluid-flow changes. Modelling of fluid flow shows that the larger proportion of upper crustal fluid in the less endowed sectors is due to 1) the less abundant metamorphic fluid that flowed in the thinner band of Piché Group rocks and 2) the presence of more porous rocks north of the CLLDZ, from which a larger quantity of pore fluid was drawn into the fault. We suggest that most of the variation of gold endowment is related to the variation of the gold-bearing metamorphic fluid flow along the segment. Less abundant or diluted metamorphic fluid flow decreases the gold potential along the CLLDZ.

Trembling aspen (Populus tremuloides Michx.) were observed growing along roads far north from the area where it dominates, in sites dominated by black spruce (Picea mariana (Mill.) B.S.P.) forests. This study examined the distribution of aspen at an early development stage and the conditions in which they are growing in a black spruce/feathermoss forest type in northwestern Abitibi, Quebec six years following harvesting. In this region, aspen are appearing in logged and burned areas that had been previously dominated by black spruce. The relationship of aspen growth with Ca availability and mineral soil access is the main focus of the study. Soil and foliar samples from aspen seedlings were collected from roadside, slash and cutover locations during the summer of 2003. Trees were also measured for height and basal diameter. Microsites where aspen was growing and where it was absent were compared to determine whether aspen was associated with specific microsites soil properties. The results suggest that there are differences in the growing conditions for aspen between different locations but that the trees are growing successfully in all of the three location types. In the cutovers, aspen seedlings were consistently found in association with patches of Polytrichum moss. All the sets of data indicate that Ca availability and access to mineral soil are not the main factors influencing the distribution of aspen but that soil pH, or a factor relating to pH, may be important.

Mole drainage is an inexpensive form of drainage particularly suited to clay soils. / Mole drainage is approved by Le Conseil des Productions Vegetales du Quebec to drain clay soils with low hydraulic conductivity. A few known trials on this technique of drainage have been done in Ontario and Alberta. In England and New Zealand, this technique is widely used. The large surface of heavy clay soil cultivated in Abitibi-Temiscamingue makes this region an excellent choice for trying this technique. / Two sites established on two soil series (Palmarolle, Roquemaure) have been moled in Abitibi-Temiscamingue. These soils represent 21% of the cultivated land in this region. Twelve plots have been moled at varied depths, spaces and lengths. Physical and chemical soil properties have been measured to identify their influence on mole drainage stability. Water table, rainfall and the stability of the mole drains were monitored for three summers. Mole drain stability was observed with a borescope. Maturity growth and yield of a hay crop, and three types of cereals were measured. / The mole drainage technique is satisfactory in heavy clay. The organic matter (${>2 %}$), the water content of the soil (${>40 %}$) at moling time and a small amount of rainfall (${<6}$ mm) in the first week after moling positively influenced the stability of the mole drains. Some mole drains have kept 75% of their initial opening after three years of life. The water table was lower on one mole drained site. The yield of the hay and the three cereals were higher on the moled parcels. (Abstract shortened by UMI.)

Thèses (M.A.)--Université de Sherbrooke (Canada), 2002. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

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I examined saproxylic beetle responses in two silvicultural systems of the eastern mixedwood boreal forest of Quebec. I first investigated habitat-use and aspen-host use of saproxylic and bark and wood-boring beetles in remnant forest patches (cut-bock separators and small patches) left after harvest, theorized to resemble natural post-fire residual trees and snags. A second study focused on effects of partial cutting, a method that may serve to imitate natural succession dynamics. / Remnant forest patches had the highest saproxylic and bark and woodboring beetle species richness and relative abundance. Although non-significant, higher larval densities were also collected from remnant forest patches. In the second study, partial cut patches had an intermediate saproxylic beetle assemblage compared to uncut forest and clearcuts. / This research has brought new information on the effects of alternative harvesting practices on saproxylic beetles, supporting the hypothesis that biodiversity is best preserved based on forest management that is diversified and based on natural disturbance dynamics.