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361.
David Gubbins Peter Molnar J. G. Olliver Petr Vanīček Kenji Satake Allan M. Rubin Waclaw M. Zuberek Janusz Niewiadomski Leszek Czechowski David J. Steveson Jacek Leliwa-Kopystyński Yu. N. Korenkov Fred Lipschultz Marek Jerczyński Krzysztof E. Haman Jerzy Radziwill Maciej Sadowski Maciej Sadowski 《Pure and Applied Geophysics》1990,132(3):599-637
362.
363.
Fred B. Wood 《Climatic change》1988,12(3):297-312
The Jones et al. hemispheric and global temperature trends and the methodology used to detect and correct for urban heat island effects are examined in detail. The results of this review suggest that there is still the possibility of significant urban warming bias remaining in the hemispheric and global averages. The actual extent of any such bias is unknown but warrants full investigation, since undetected and/or uncorrected urban warming could account for some of the hemispheric and global warming reported by Jones et al. Several research activities are suggested for resolving this uncertainty, including the rigorous application of urban warming correction factors to the data set used by Jones et al. and the development of geographically representative rural temperature series.Office of Technology Assessment, United States Congress, Washington, D.C. 20510, U.S.A. The views expressed are those of the author and not necessarily those of the OTA, Technology Assessment Board, or U.S. Congress. The article is based on independent research of the author and not on work conducted for the OTA. 相似文献
364.
Pradeep K. Aggarwal Fred J. Longstaffe 《Contributions to Mineralogy and Petrology》1987,96(3):314-325
Oxygen-isotope compositions have been measured for whole-rock and mineral samples of host and hydrothermally altered rocks from three massive sulfide deposits, Centennial (CL), Spruce Point (SP), and Anderson Lake (AL), in the Flin Flon — Snow Lake belt, Manitoba. Wholerock
18O values of felsic metavolcanic, host rocks (+8.5 to +16.1) are higher than those of altered rocks from the three deposits. The
18O values of altered rocks are lower in the chlorite zone and muscovite zone-I (CL=+ 5.3; SP=+5.4 to +8.3; AL= +3.7 to +5.9) than in the gradational zone (CL= +9.9 to +11.7; SP= +8.4 to +9.8; AL= + 6.6 to +7.7). Muscovite schist (Muscovite Zone-II) enveloping the Anderson Lake ore body has
18O values of +7.2 to +8.3. Quartz, biotite, muscovite, and chlorite separated from the altered rocks have lower
18O values compared to the same minerals separated from the host rocks. However, isotopic fractionation between mineral-pairs is generally similar in both host and altered rocks.It is interpreted that differences in the oxygen-isotope compositions of the altered and host rocks were produced prior to metamorphism, during hydrothermal alteration related to ore-deposition. Isotopic homogenization during metamorphism occurred on a grain-to-grain scale, over no more than a few meters. The whole-rock
18O values did not change significantly during metamorphism. The generally lower
18O values of altered rocks, the Cu-rich nature of the ore and the occurrence of the muscovite zone-II at Anderson Lake are consistent with the presence of higher temperature hydrothermal fluids at Anderson Lake than at the Centennial and Spruce Point deposits. 相似文献
365.
Yo-ichiro Otofuji Sadao Sasajima Susumu Nishimura Agus Dharma Fred Hehuwat 《Earth and Planetary Science Letters》1981,54(2):272-280
Paleomagnetic results from the northern arm of Sulawesi show that the arm has been subjected to a clockwise rotation of more than 90° and that its rotational motion began no later than the middle Miocene. The mean direction showing a normal polarity at the Eocene to the early Miocene isD = 98.0° andI = 6.9°. A declination value ofD = 50.1° obtained from Miocene rocks indicates a transition stage of the rotational motion. The datum from Plio-Pleistocene volcanics isD = ?4.6° andI = ?9.3°. This suggests that the rotational motion terminated before the initiation of volcanic activity during the Plio-Pleistocene. 相似文献
366.
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368.
Mary K. Roden Stanley R. Hart Fred A. Frey William G. Melson 《Contributions to Mineralogy and Petrology》1984,85(4):376-390
Surface samples of peridotites and hornblendite mylonites from St. Paul's Rocks, and dredge samples from the flanks of the massif, have been analyzed for Sr, Nd and Pb isotopic ratios and Rb, Sr, and REE concentrations. This data, coupled with previous K and REE data, are used to develop a self-consistent model for the genesis of these ultramafic rocks. This model involves metasomatism of an ocean island-type mantle about 155 m.y. ago by a strongly light-REE-enriched metasomatic fluid, probably derived from the same mantle. This metasomatism produced light-REE-enriched materials which were isotopically homogeneous on a small scale (100 m), and isotopically heterogeneous on a large (km) scale. The geochemical relationships between the peridotites and the hornblendites were established by metamorphic equilibration on a relatively small scale (<10 m). The average mantle produced by these events is characterized by87Sr/86Sr=0.7034,143Nd/144Nd=0.51291,206Pb/204Pb=19.33 and 207/204=15.63. An alkali basalt which postdates the mylon-itization of the ultramafic massif has an isotopic character which is identical to the average ultramafic massif; it also lies on the five-dimensional isotopic mantle plane of Zindler et al. (1982). With respect to major elements, trace elements, and Sr, Nd and Pb isotopes, the average ultramafic rock of the St. Paul's massif is an ideal candidate for a mantle source from which alkali basalts can be derived by partial melting; the St. Paul's massif is in fact the first such example of an ultramafic rock which meets all the requirements to be an alkali basalt source. 相似文献
369.
370.
Chemical analyses of pore waters from recent marine carbonate sediments, Devil's Hole, Harrington Sound, Bermuda, have been obtained at intervals over a four year period. Interstitial waters were systematically analyzed for pH, titration alkalinity, dissolved sulfides, NH4+, Ca2+, Mg2+ and Na+ or Cl?. Additional analyses on some cores included SO42?, PO43?, dissolved CH4 and N2, and C:N:H ratios in the detrital organic material. The following general trends with depth (to ~ 1 m) are observed: (1) major cations show little or no change; (2) pH decreases; (3) alkalinity, sulfides, NH4+ and PO43? increase; (4) dissolved CH4 is consistently low. The chemical changes with depth can be modelled theoretically and are consistent with experimental data.Significant seasonal changes in pore water chemistry are observed. The data suggest an annual exchange between the pore waters (to a depth of ~ 1 m) and the overlying water of Harrington Sound; the exchange occurs between August and January. The nutrient flux out of the sediments during this process may be a major factor in the plankton ecology of Harrington Sound. 相似文献