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1. |
Speculations on continental crustal evolution |
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Eos, Transactions American Geophysical Union,
Volume 72,
Issue 52,
1991,
Page 585-590
Rolf Meissner,
Walter D. Mooney,
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摘要:
The evolution of the continental crust is a topic that has challenged Earth scientists since the earliest hypotheses of crustal evolution were put forth by such luminaries as Hutton, the 18th century Scottish scientist, and later by Stille (Germany), Argand (France), and Dana (United States). Recent geophysical observations provide important constraints on hypotheses of crustal evolution, and the most important of these observations are reviewed in a companion paper [Mooney and Meissner, 1991], henceforth referred to as Paper 1. In this article we briefly speculate on crustal evolution using both geological and geophysical data as guidelines.For the past 25 years, the basic framework for models of the evolution of the Earth's crust and lithosphere has been plate tectonics. This framework has been particularly successful in explaining the processes that form and modify the oceanic crust but has had somewhat more limited success in its application to the continental crust. Some of the basic tenets of plate tectonics, as applied to the continental crust, are listed below. Continental masses coalesce and disperse as ocean basins open and close in the Wilson cycle.
ISSN:0002-8606
DOI:10.1029/90EO00405
年代:1991
数据来源: WILEY
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2. |
Federal “Pork” at record high in 1991 |
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Eos, Transactions American Geophysical Union,
Volume 72,
Issue 52,
1991,
Page 586-586
Audrey T. Leath,
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摘要:
At approximately $500 million, the total of earmarked funds going to universities and colleges in the fiscal year 1991 federal budget was at an all‐time high. Although the full tally of “pork” in the new 1992 budget is not yet available, the total is not expected to meet or surpass that of 1991, due to the caps on discretionary funding required by the budget agreement.The following data were taken from a memo prepared by staff of the House Committee on Science, Space and Technology for its chairman, George E. Brown, Jr. (D‐Calif.). The top 10 states receiving earmarked funds in 1991 were Pennsylvania ($54.3 million), Iowa ($38.7), Alaska ($35.0), Massachusetts ($32.6), Louisiana ($24.4), Washington, D.C. ($21.0, includes appropriations to Howard University, Gallaudet University, and the University of the District of Columbia, which receive their basic operating budgets through federal appropriations), West Virginia ($19.9), Oregon ($18.9), New Jersey ($18.1), and Hawaii
ISSN:0002-8606
DOI:10.1029/90EO00404
年代:1991
数据来源: WILEY
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3. |
Yugoslav seismological research threatened |
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Eos, Transactions American Geophysical Union,
Volume 72,
Issue 52,
1991,
Page 587-587
Ivo Allegretti,
Michael Hamburger,
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摘要:
We in the Western scientific community have had the luxury, throughout most of our careers, of working in an environment insulated from the terrors of war and political violence. Well distanced from these horrors, we are often numbed by headlines reporting political turmoil elsewhere in the world—whether in Afghanistan, South Africa, or Yugoslavia. There are times, however, when personal contact with a colleague caught within one of these political wildfires reminds us of the very human tragedy that underlies these headlines.In studying a number of large earthquakes that took place in Central Asia in the 1930s and 1940s, we have been collecting seismograms from the well established European seismic observatories that recorded the events. Among them was the Zagreb Observatory, operated by the Mohorovicic Geophysical Institute of the University of Zagreb. The city of Zagreb—along with its scientific and cultural institutions—is now under siege, a result of the violent military conflict between the Yugoslav federal government and the Republic of Croatia. The following letter, which accompanied the Zagreb seismograms, provides a vivid picture of the daily hardships that our colleagues in Yugoslavia must be facing and a call to members of the international scientific community to help put an end to the rapidly escalating violence in Yugos
ISSN:0002-8606
DOI:10.1029/90EO00408
年代:1991
数据来源: WILEY
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4. |
Melt segregation and migration |
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Eos, Transactions American Geophysical Union,
Volume 72,
Issue 52,
1991,
Page 588-588
Ed. W. Sawyer,
Paul L. Bedard,
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PDF (174KB)
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摘要:
The processes by which melt separates from its associated solids are relevant to a wide range of geological problems. How is melt extracted during anatexis to form migmatites or granites? What drives melt segregation, especially at low melt fractions? What volume fraction of melt can be extracted? How do residual liquids percolate through accumulating crystal piles? How does melt reach high‐level plutons? These and related problems were discussed in a special session, “Melt Segregation and Migration in Partially Molten Rocks,” of the Geological Association of Canada‐Mineralogical Association of Canada (GAC‐MAC) annual meeting in Toronto, May 27–29. This session, sponsored by the MAC, attracted contributions on a wide range of field, structural, geochemical, theoretical, and geophysical studies.All of the field‐based studies brought out the close temporal and spatial association between shear zones and melt segregation. Sally Goodman of the University of Aberdeen showed that migmatization in the Crinan subgroup of the Scottish Dalradian began with metamorphic differentiation and progressed to extensive melting in shear zones associated with the influx of fluids. Although some melt pockets remained, rocks in the shear zone now consist largely of recrystallized restite material. Shearing at the time of melting apparently drove melt segregation, and the possibility that the expelled melt formed the nearby granite bodies is being
ISSN:0002-8606
DOI:10.1029/90EO00407
年代:1991
数据来源: WILEY
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