The lavas and pyroclastics of Ascension Island contain a suite of coarse grained igneous blocks which range in composition from olivine-gabbro to peralkaline-granite paralleling, but extending beyond the compositional range of the volcanics. The lavas range from alkali-basalt through hawaiite, trachybasalt, trachyandesite and trachyte to comendite. True basalt is relatively rare and there is a scarcity of analyses with 57 < Si02 < 63 wt %. No high pressure mineral assemblages and hence no possible mantle fragments have been found. Petrographic and isotopic data suggest that a suite of gabbros from Dark Slope Crater crystallised from a magma derived from a MORB-like source. The remaining blocks and all the lavas evolved from magmas derived from a less depleted source. The chemical variation seen in the lavas and blocks is best explained by crystal fractionation mechanisms in a relatively shallow magma chamber. The gabbroic blocks exhibit cumulus textures suggesting that they formed by accumulation of settling crystals. The intermediate to acid blocks compare much more closely in composition with the evolved lavas and are probably their slowly cooled equivalents. There is petrographic evidence that partial melting of intermediate coarse grained material gave rise to melts of granitic composition but these are not chemically equivalent to the acid lavas and blocks. A pegmatoid body crystallised in situ and closed system crystal fractionation alone resulted in a very similar sequence of mineral assemblages to the blocks and lavas and a peralkaline final liquid. High 87 S4/ 86 Sr ratios in the evolved lavas and blocks are attributable to contamination by a small quantity of highly radiogenic oceanic sediment. Comparison with other oceanic volcanoes suggests that these differentiation processes are much less important in determining the evolutionary path of the magma than its apparent starting composition.

The Metchosin Igneous Complex, a partial ophiolite exposed on southern Vancouver Island, is the most northerly exposure of the Eocene Crescent Terrane. The role of the Crescent Terrane in crustal genesis and Cordilleran tectonics would be affected by its tectonic setting, however that setting is in debate. Analysis of trace element compositions of basalt from the Metchosin Igneous Complex by ICP-MS was used to determine the tectonic setting in which the complex formed. REE and HFSE compositions are transitional between N-MORB and E-MORB and do not suggest a unique tectonic setting. Strong enrichments of Nb and Ta relative to N-MORB are contrary to formation in a subduction zone. In conjunction with existing plate motion data, this makes a rifted-margin origin unlikely. Interaction at a distance between the Yellowstone hot spot and the Kula-Farallon ridge is proposed to satisfy all the geological and geochemical data. Many studies of ophiolites have interpreted high-temperature phases as hydrothermal in origin despite high permeability and low temperatures in sea floor volcanics. Metamorphic assemblages and compositions of metamorphic minerals were used to determine if alteration in the Metchosin Igneous Complex was related to sea floor alteration or obduction. Chlorite geothermometry and amphibole compositions show that peak metamorphic temperatures increase from east to west across the complex. The metamorphic facies increase from prehnite-actinolite and greenschist in the east to amphibolite in the west, corresponding with the temperatures inferred from mineral compositions. The temperature gradient is perpendicular to stratigraphy, whereas hydrothermal patterns are expected to be parallel to stratigraphy. Therefore the pattern of alteration in the Metchosin Igneous Complex is unrelated to sea floor alteration. Metamorphism during obduction has overprinted any hydrothermal alteration patterns. The east-west thermal gradient is attributed to tilting of the complex, either by tectonic forces or by unequal exhumation due to orographic effects.

No description available.

Thesis. 1979. M.Arch.A.S.--Massachusetts Institute of Technology. Dept. of Architecture. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Bibliography: leaves 173-176. / M.Arch.A.S.

Thesis (Ph. D.)--University of Chicago, Dept. of Anthropology, August 2002. / Includes bibliographical references (p. 251-260). Also available on the Internet.

Texte remanié de: Thesis--New York University, 2001. / Bibliogr. p. 189-203.

Thesis (Ph. D.)--University of Chicago, 2002. / Includes bibliographical references (leaves 251-260). Also available on the Internet.

Field evidence for density-driven free convection, a potentially important groundwater transport process, has been examined at Padre Island National Seashore to determine if this phenomenon can develop under natural environmental conditions. Hitherto, this process had not been conclusively detected or measured in field scale hydrogeology. Field methods, including nested monitoring wells and time-lapse 3-D resistivity surveys, reveal evidence of variable-density groundwater flow in the wind-tidal flats. Evaporative concentration of groundwater near the water table resulted in unstable inverted density gradients, reduced groundwater levels, and reduced hydraulic gradients. These factors allowed plumes of dense fluid to migrate downward into less dense fluid which were observed in monitoring wells and 3-D resistivity surveys. This shows that the development and flow of variable-density fluids in groundwater can be detected and monitored through field techniques. It demonstrates that the development of density inversions may overcome the dissipating forces of dispersion and diffusion to create a sufficiently large unstable gradient to induce free convection. / text

This thesis explores twenty years of community based tourism policy and planning in the Baffin Region. This rise of local participation in tourism development is reviewed. Such an approach is seen as being potentially beneficial to marginalized aboriginal people in remote areas. This, combined with political support for Inuit self determination, formed the rationale behind community based tourism policy in Baffin. / With its extensive community participation program, the planning process formed a strategy for sustainable tourism. Since then, the industry has grown but some of the strategy's goals have not been met. The number of Inuit involved in the industry initially increased, but is now beginning to decline and turnover is high. Interest in the industry, and initiatives such as training, need to arise from inside communities rather than the government. To complement traditional subsistence hunting, the tourism industry must support short term employment.

During the summers of 1961 through 1964 field parties of the Geographical Branch, Department of Mines and Technical Surveys, conducted studies in the physical geography of north-central Baffin Island. While field research emphasized the glacial geomorphology of the area about the northwest margin of the Barnes Icecap, air photo interpretation over a much wider area revealed the existence of a series of major terminal and lateral moraines stretching for 640 km. (400 miles) in a belt roughly parallel to the heads of the Baffin Bay fiords (Map 1). [...]