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91.
I. C. W. FITZSIMONS P. D. KINNY S. WETHERLEY D. A. HOLLINGSWORTH 《Journal of Metamorphic Geology》2005,23(4):261-277
Several petrographic studies have linked accessory monazite growth in pelitic schist to metamorphic reactions involving major rock‐forming minerals, but little attention has been paid to the control that bulk composition might have on these reactions. In this study we use chemographic projections and pseudosections to argue that discrepant monazite ages from the Mount Barren Group of the Albany–Fraser Orogen, Western Australia, reflect differing bulk compositions. A new Sensitive High‐mass Resolution Ion Microprobe (SHRIMP) U–Pb monazite age of 1027 ± 8 Ma for pelitic schist from the Mount Barren Group contrasts markedly with previously published SHRIMP U–Pb monazite and xenotime ages of c. 1200 Ma for the same area. All dated samples experienced identical metamorphic conditions, but preserve different mineral assemblages due to variable bulk composition. Monazite grains dated at c. 1200 Ma are from relatively magnesian rocks dominated by biotite, kyanite and/or staurolite, whilst c. 1027 Ma grains are from a ferroan rock dominated by garnet and staurolite. The latter monazite population is likely to have grown when staurolite was produced at the expense of garnet and chlorite, but this reaction was not intersected by more magnesian compositions, which are instead dominated by monazite that grew during an earlier, greenschist facies metamorphic event. These results imply that monazite ages from pelitic schist can vary depending on the bulk composition of the host rock. Samples containing both garnet and staurolite are the most likely to yield monazite ages that approximate the timing of peak metamorphism in amphibolite facies terranes. Samples too magnesian to ever grow garnet, or too iron‐rich to undergo garnet breakdown, are likely to yield older monazite, and the age difference can be significant in terranes with a polymetamorphic history. 相似文献
92.
Episodic, large‐volume pulses of volcaniclastic sediment and coseismic subsidence of the coast have influenced the development of a late Holocene delta at southern Puget Sound. Multibeam bathymetry, ground‐penetrating radar (GPR) and vibracores were used to investigate the morphologic and stratigraphic evolution of the Nisqually River delta. Two fluvial–deltaic facies are recognized on the basis of GPR data and sedimentary characteristics in cores, which suggest partial emplacement from sediment‐rich floods that originated on Mount Rainier. Facies S consists of stacked, sheet‐like deposits of andesitic sand up to 4 m thick that are continuous across the entire width of the delta. Flat‐lying, highly reflective surfaces separate the sand sheets and comprise important facies boundaries. Beds of massive, pumice‐ and charcoal‐rich sand overlie one of the buried surfaces. Organic‐rich material from that surface, beneath the massive sand, yielded a radiocarbon age that is time‐correlative with a series of known eruptive events that generated lahars in the upper Nisqually River valley. Facies CF consists of linear sandbodies or palaeochannels incised into facies S on the lower delta plain. Radiocarbon ages of wood fragments in the sandy channel‐fill deposits also correlate in time to lahar deposits in upstream areas. Intrusive, sand‐filled dikes and sills indicate liquefaction caused by post‐depositional ground shaking related to earthquakes. Continued progradation of the delta into Puget Sound is currently balanced by tidal‐current reworking, which redistributes sediment into large fields of ebb‐ and flood‐oriented bedforms. 相似文献
93.
《The Professional geographer》2013,65(4):488-489
Book Reviewed in this article: Main Street: Northeastern Oregon: The Founding and Development of Small Towns. Barbara Ruth Bailey. Food Politics: The Regional Conflict. David N. Balaam and Michael J. Carey, eds. The International Economy and Industrial Development: Trade and Investment in the Third World. R. Ballance, J. Ansari and H. Singer. Neighborhoods in Urban America. Ronald H. Bayor, ed. The English Heartland. By Robert Beckinsale and Monica Beckinsale. Regional Dimensions of Industrial Policy. Michael E. Bell and Paul S. Lande, eds. Tension Areas of the World. D. Gordon Bennett, ed. Latin America: an Introductory Survey. B. W. Blouet and O. M. Blouet, eds. Integration and Division: Geographical Perspectives on the Northern Ireland Problem. Frederick W. Boal and J. Neville H. Douglas, eds. Energy and Land Use. Robert W. Burchell and David Listokin, eds. Slopes and Weathering. Michael Clarke and John Small. Alaska's Rural Development. Peter G. Cornwall and Gerald McBeath, eds. The Politics of Park Design: A History of Urban Parks in America. Galen Cranz. World Congress on Land Policy, 1980, Proceedings. Matthew Cullen and Sharon Woolery, eds. Oregon Divided: A Regional Geography. Samuel N. Dicken and Emily F. Dicken. Urban Food Marketing and Third World Rural Development. T. Scarlett Epstein. South Africa: Spatial Frameworks for Development. T. J. D. Fair. Institutions and Geographical Patterns. Robin Flowerdew, ed. Industrialization of U.S. Agriculture, An Interpretive Atlas. Howard F. Gregor. Planning Theory: Prospects for the 1980s. Patsy Healy, Glen McDougall and Michael J. Thomas, eds. Neighborhood Mobilization: Redevelopment and Response. Jeffrey R. Henig. The American Urban System: A Geographical Perspective. R. J. Johnston. Climate, History and the Modern World. Hubert H. Lamb. Climate and History: Studies in Past Climates and Their Impact on Man. T. M. L. Wigley, M. J. Ingram and G. Farmer. China: Railways and Agricultural Development, 1875–1935. Ernest P. Liang. A Desirable Energy Future—A National Perspective. Robert S. Livingston, T. D. Anderson, T. M. Besmann, M. Olszewski, A. M. Perry, and C. D. West. Topothesia: Essays Presented to T. S. Ó Máille. B. S. Mac Aodha, ed. Transportation for the Poor: Research in Rural Mobility. Hal S. Maggied. Land Uses in American Cities. Harold M. Mayer and Charles R. Haves. Industrial Organisation and Location. Philip McDermott and Michael Taylor. Human Adaptability: an Introduction to Ecological Anthropology. Emilio F. Moran. Regional Analysis and the New International Division of Labor. Frank Moulaert and Patricia W. Salinas, eds. The Nuclear War Atlas. Victoriaville, Quebec, Canada: Urbanization and Environmental Quality. Isao Orishimo. The Garden of Eden: The Botanic Garden and the Re-Creation of Paradise. John Prest. Earthfire, The Eruption of Mount St. Helens. Charles Rosenfeld and Robert Cooke. Contest for the South China Sea. Marwyn S. Samuels. The Future of the Wetlands: Assessing Visual-Cultural Values. Richard C. Smardon, ed. Tucson: the Life and Times of An American City. C. L. Sonnichsen. The Geography of Multinationals. Michael Taylor and Nigel Thrift, eds. Impact of Marine Pollution on Society. Virginia Tippie and Dana Kester. Reviving the Industrial City: the Politics of Urban Renewal in Lyon and Birmingham. Jerry A. Webman. Andean Reflections: Letters from Carl O. Sauer While on a South American Trip under a Grant from the Rockefeller Foundation, 1942. Robert C. West, ed. Cartographic Drawing with Computers. P. Yoeli. 相似文献
94.
《第四纪科学杂志》2017,32(4):457-462
95.
96.
Recent seismological studies of the Cameroon Volcanic Line show that Mt. Cameroon is the most active centre, so a permanent seismic network of six seismographs was set up in its region between 1984 and 1986. The network was reinforced with temporary stations up till 1987, and the local seismicity was studied. Here we emphasise a statistical analysis of seismic events recorded by the permanent seismic stations. Four swarms lasting 9 to 14 months are identified at intervals of 2–3 years. Most earthquakes are felt (intensity and magnitude, respectively, less than VI MM and 5) during the first three swarms and a few during repose periods. The main focal regions are the northwest and southeast flanks, the Bimbia and Bioko regions in the South of the volcano. Hypocentres are distributed from the surface to 60 km depth indicating crustal and subcrustal activities. The subcrustal events are observed only in the southeast flank, they are the most regular earthquakes with a monthly frequency of 9 to 15 events. They are characteristic earthquakes with magnitude 2.8 ± 0.1. Between 1984 and 1992, their yearly mean time interval between successive events range from 50 to 86 hours. For that period their occurrence can be modelled as a stationary renewal process with a 3-day period. But the analysis of variance shows possible significant differences among yearly means. A Weibull's distribution confirms that the time intervals between successive deep events are not independent, and in 1993 a swarm of deep earthquakes is recorded, hence a non-loglinear magnitude/frequency relation. The deep seismicity is thought to be associated with a zone of weakness (perhaps a magmatic conduit) and may have some close relationship with the magmatic activity. 相似文献
97.
K. Gessner M. Kühn V. Rath C. Kosack M. Blumenthal C. Clauser 《Surveys in Geophysics》2009,30(3):133-162
Hydrothermal systems are characterised by complex interactions between heat transfer, fluid flow, deformation, species transport and chemical reactions. Numerical models can provide quantitatively constrained information in regions where acquisition of new data is difficult or expensive thus providing a means for reducing risks, costs, and effort during targeting, production, and management of resources linked to hydrothermal systems. Here we show how numerical simulations of hydrothermal processes can be used to better understand coupled reactive transport in modern geothermal systems and in ancient hydrothermal ore deposits. We give examples based on the Enhanced Geothermal System at Soultz-sous-Forêts in France, hydrothermal mineralisation at Mount Isa in Australia, and the geothermal resource at Hamburg-Allermöhe in Germany. 相似文献
98.
99.
《The Professional geographer》1983,35(4):488-524
Book Reviewed in this article: Main Street: Northeastern Oregon: The Founding and Development of Small Towns . Barbara Ruth Bailey . Food Politics: The Regional Conflict . David N. Balaam and Michael J. Carey , eds. The International Economy and Industrial Development: Trade and Investment in the Third World . R. Ballance , J. Ansari and H. Singer . Neighborhoods in Urban America . Ronald H. Bayor , ed. The English Heartland . By Robert Beckinsale and Monica Beckinsale . Regional Dimensions of Industrial Policy . Michael E. Bell and Paul S. Lande , eds. Tension Areas of the World . D. Gordon Bennett , ed. Latin America: an Introductory Survey . B. W. Blouet and O. M. Blouet , eds. Integration and Division: Geographical Perspectives on the Northern Ireland Problem . Frederick W. Boal and J. Neville H. Douglas , eds. Energy and Land Use . Robert W. Burchell and David Listokin , eds. Slopes and Weathering . Michael Clarke and John Small . Alaska's Rural Development . Peter G. Cornwall and Gerald Mc Beath , eds. The Politics of Park Design: A History of Urban Parks in America . Galen Cranz . World Congress on Land Policy, 1980, Proceedings . Matthew Cullen and Sharon Woolery , eds. Oregon Divided: A Regional Geography . Samuel N. Dicken and Emily F. Dicken . Urban Food Marketing and Third World Rural Development . T. Scarlett Epstein . South Africa: Spatial Frameworks for Development . T. J. D. Fair . Institutions and Geographical Patterns . Robin Flowerdew , ed. Industrialization of U.S. Agriculture, An Interpretive Atlas . Howard F. Gregor . Planning Theory: Prospects for the 1980s . Patsy Healy , Glen Mc Dougall and Michael J. Thomas , eds. Neighborhood Mobilization: Redevelopment and Response . Jeffrey R. Henig . The American Urban System: A Geographical Perspective . R. J. Johnston . Climate, History and the Modern World . Hubert H. Lamb . Climate and History: Studies in Past Climates and Their Impact on Man . T. M. L. Wigley , M. J. Ingram and G. Farmer . China: Railways and Agricultural Development, 1875–1935 . Ernest P. Liang . A Desirable Energy Future—A National Perspective . Robert S. Livingston , T. D. Anderson , T. M. Besmann , M. Olszewski , A. M. Perry , and C. D. West . Topothesia: Essays Presented to T. S. Ó Máille . B. S. Mac Aodha , ed. Transportation for the Poor: Research in Rural Mobility . Hal S. Maggied . Land Uses in American Cities . Harold M. Mayer and Charles R. Haves . Industrial Organisation and Location . Philip Mc Dermott and Michael Taylor . Human Adaptability: an Introduction to Ecological Anthropology . Emilio F. Moran . Regional Analysis and the New International Division of Labor . Frank Moulaert and Patricia W. Salinas , eds. The Nuclear War Atlas. Victoriaville, Quebec, Canada : Urbanization and Environmental Quality . Isao Orishimo . The Garden of Eden: The Botanic Garden and the Re-Creation of Paradise . John Prest . Earthfire, The Eruption of Mount St. Helens . Charles Rosenfeld and Robert Cooke . Contest for the South China Sea . Marwyn S. Samuels . The Future of the Wetlands: Assessing Visual-Cultural Values . Richard C. Smardon , ed. Tucson: the Life and Times of An American City. C. L. Sonnichsen . The Geography of Multinationals . Michael Taylor and Nigel Thrift , eds. Impact of Marine Pollution on Society . Virginia Tippie and Dana Kester . Reviving the Industrial City: the Politics of Urban Renewal in Lyon and Birmingham . Jerry A. Webman . Andean Reflections: Letters from Carl O. Sauer While on a South American Trip under a Grant from the Rockefeller Foundation, 1942 . Robert C. West , ed. Cartographic Drawing with Computers . P. Yoeli . 相似文献
100.
近十余年环珠江口地区5000 ̄6000年前的新石器时代遗址已发掘20多处,其中11个遗址是位于9个岛屿之上。这些考古学资料表明,6000年前左右沿海居民海洋蛋白资源开拓的重要证据。 相似文献