The Guano-Guayes property, in the Pelly Mountains of the Yukon Territory, covers a rare earth element (REE) bearing contact metamorphic aureole which developed around a syenite stock during Mississippian time (319 ± 10 Ma phlogopite K-Ar date, 333 ± 10 Ma Rb-Sr skarn mineral isochron). Sedimentary rocks consist of several hundred metres of Ordovician dark gray shale which are faulted upward adjacent to 450 m of Silurian interbedded impure calcite and dolomite marbles and quartzites overlain by at least 500 m of Silurain quartzite. Sedimentary rocks are on the steeply, west-dipping limb of a regional anticline (the axis bears 162 degrees and plunges 24 degrees south). The syenite, at the southeast end of a northwest-trending belt of syenite stocks and associated volcanic rocks, consists of 40 to 90 percent orthoclase in laths up to several cm long, and of up to 60 percent mafic minerals now mostly altered to biotite. Rare earth element values of syenite, when normalized to chondritic values, have a crustal pattern with magnitude slightly higher than that of crustal rocks. Dikes, believed to be cogenetic with syenite, intrude sedimentary rocks within and inear the contact metamorphic aureole. These dikes are dark-coloured and originally contained up to 25 percent zircon (now partly altered to secondary minerals). Zircon is enriched in total REE and relatively enriched in light REE compared to syenite, probably due to selective partitioning of REE. REE patterns in skarn and sedimentary rocks suggest that fluids circulated through syenite and carried trace amounts of REE from it into the skarn. There was no significant movement of REE from dikes into skarn or sedimentary rocks. Contact metamorphic rocks can be divided into three units: quartz-muscovite hornfels, dark green diopsade-calcite-phlogopite-tremdlite-sphene skarn, and light green diopside-calcite-phlogopite skarn. Depth at time of intrusion of syenite, as estimated from regional geologic contraints, was around 1 to 2 km (circa 500 bars). Parageneses and textures observed in thin section in contact metamorphic rocks indicate that prograde metamorphism at this pressure reached a maximum temperature of 450 to 540 degrees C, with heat being transferred from the intrusive dominantly by fluids. The mole fraction of CO₂ in metamorphic fluids, increased By the liberation of CO₂ during prograde metamorphic reactions, was moderate. Large amounts of Fe, Mg, and possibly Si0₂, were added to the skarn. Retrograde metamorphism involved significant addition of water to the system, proven by the appearance of secondary epidote, chlorite, and, later, serpentine. Extensive retrograde metamorphism accompanied by large-scale migration of elements through syenite ended 206 ±15 Ma ago (syenite whole-rock isochron) and the last resetting event took place between 156 ± 5 Ma (K-Ar date on biotite-altered arfvedsonite) and 128 ± 25 Ma (syenite mineral isochron). Petrology, geochronometry, and rare earth element studies presented here have contributed to an understanding of the genesis of syenite, skarn, and mineralized dikes within the Guano-Guayes area. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Unknown

An ecological classification of high elevation range provides a framework for proper resource management. Alpine and subalpine vegetation in the Southern Chilcotin Mountains was studied to characterize the plant communities of the high elevation rangelands in the southern interior of British Columbia. The impacts of grazing on the structure and composition of the vegetation were evaluated. Two hundred and thirty-nine sites were sampled in a 10,000 ha area. Plots were selected randomly within homogeneous units delineated on 1:30,000 (40 chain) air photos prior to the field season. These were classified on the basis of physiognomy, dominant species and environmental conditions. The following nineteen community types were described: Picea engelmanii-Abies lasiocarpa forest, Pinus albicaulis-Juniperus communis forest, Salix bare layi-Carex aquatilis shrub wetland, Salix barrattiana alpine shrub wetland, Salix brachycarpa-Salix barclayi shrubland, Salix brachycarpa-Festuca spp. shrubfieId, Salix brachycarpa-Phleum alpinum shrubfieId, Arctostaphylos uva-ursi-Amelanchier alnifolia dry shrubland, Salix cascadensis dwarf willow shrubland, Dryas octopetala fellfield, Dryas octopetala-Festuca altaica alpine grassland, Carex aquatilis/rostrata wetland, Carex nigricans late snowbed meadow, Festuca altaica-Festuca brachyphylla meadow, Festuca brachyphylla meadow, Festuca brachyphylla-Phleum alpinum meadow, Phleum alpinum-Carex phaeocephala meadow, Koeleria cristata dry meadow, and crustose lichen rock-land or talus terrain unit. Changes in the structure and composition of plant communities in response to grazing pressure were evident on the more heavily used valley bottom meadow community types. After many years of use, Festuca altaica appears to have, been eliminated from heavily grazed meadows, there is a decrease in the height of the vegetation, an increase in the exposed bare ground, and an increase in the abundance of weedy species in all community types. Many of the community types described from this region are floristically and/or ecologically comparable with plant communities described from other high elevation areas in British Columbia, the southern Yukon, and the Pacific Northwest of the United States. / Land and Food Systems, Faculty of / Graduate

No description available.

No description available.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1981. / Microfiche copy available in Archives and Science / Includes bibliographies. / by Jon Eric Spencer. / Ph.D.

No description available.

It was to provide some detailed information about the alpine flora , particularly as it relates to successional aspects , that the present study was undertaken . The environmental conditions of weather and soil , as they effect floral composition , are important factors in the plant succession or alpine communities . The investigation was designed to uncover such information about the alpine flora and environment necessary to establish the pattern of succession .

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1982. / Microfiche copy available in Archives and Science / Vita. / Includes bibliographies. / by Leigh Handy Royden. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 207-215. / by John Sharry. / Ph.D.

Thesis. 1976. M.S.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography: leaves 51-56. / by Waris E.K. Warsi. / M.S.