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991.
E. Juvigné 《Quaternary Research》1975,5(1):121-123
The following note on a new method for extracting pollen from fossil pollen grains summarizes two articles in French, published in Annales de la Société Géologique de Belgique (Juvigné, 1973a; 1973b).The new method proposed has three important parts: (1) Elutriation of the sediment in water; (2) the specific gravity of the heavy liquid must be between 2.25 and 2.5; and (3) the dispersion of the sediment in the heavy liquid is made with a high-speed mixer. 相似文献
992.
P. J. Patchett O. van Breemen R. F. Martin 《Contributions to Mineralogy and Petrology》1979,69(1):65-73
Late-crystallised interstitial alkali feldspars and a single epidote from selected Proterozoic dolerites in Sweden have higher initital 87Sr/86Sr ratios, (e.g., 0.709) than the early-crystallised minerals of the same rocks ( 0.704); anomalies in Rb and Sr concentrations are also noted. This radiogenically-enriched Sr must originate in the older host rocks of the intrusions. As the contaminated phases often occupy <1 % of the dolerite, only an aqueous fluid would have been capable of transporting the contamination through the 99% solid intrusions. Textural association of late feldspars with hydrous alteration products supports this interpretation. Feldspar structural data suggest that most dolerites have been affected by subsolidus aqueous fluids, causing extensive structural re-equilibration in interstitial K-feldspars, as well as occasional metasomatic effects. Anomalies in 87Sr developed only where the fluids interacted with host rocks. 相似文献
993.
Martin I. Hoffert Yeong-Cherng Wey Andrew J. Callegari Wallace S. Broecker 《Climatic change》1979,2(1):53-68
The possibility of controlling atmospheric carbon dioxide accumulation and attendant climatic effects from fossil-fuel burning by diverting a fraction of the combustion product and injecting it into the deep-ocean, as proposed by Marchetti, is analyzed using an atmosphere/mixed layer/diffusive deep-ocean model for the carbon cycle. The model includes the nonlinear buffering of CO2 at the air/sea interface, and considers the long term trends associated with consuming an assumed fossil-fuel reserve equivalent to 7.09 × 1015 kg carbon as a logistic function of time as in the projections of Siegenthaler and Oeschger, except that atmospheric carbon dioxide levels are computed for five alternate strategies: (a) 100% injected into atmosphere, (b) 50% injected at oceanic depth of 1500 m and 50% into atmosphere, (c) 50% injected at sea floor (4000 m) and 50% into atmosphere, (d) 100% at 1500 m depth and (e) 100% at sea floor. Since no carbon leaves the system, all runs approached the same post-fossil fuel equilibrium after several thousand years, C
a
- 1150 ppm, almost four times the pre-fossil fuel value (- 300 ppm). But the transient response of these cases showed a marked variation ranging from a peak overshoot value of 2800 ppm in the year 2130 for 100% atmospheric injection to a slight decrease to the pre-fossil fuel 300 ppm lasting till 2300 with a subsequent slow approach to equilibrium for the 100% deep-ocean injection. The implications of these results for an oceanic injection strategy to mitigate the climatic impact of fossil-fuel CO2 is discussed, as are the ingredients of a second generation carbon cycle model for carrying out such forecasts on an engineering design basis. 相似文献
994.
995.
P.Y. Gillot J. Labeyrie C. Laj G. Valladas G. Guérin G. Poupeau G. Delibrias 《Earth and Planetary Science Letters》1979,42(3):444-450
The reverse paleomagnetism of the lava flows of Laschamp and Olby, already discovered by Bonhommet and Babkine, is confirmed. The ages of these flows, measured by14C, thermoluminescence and K-Ar dating are respectively36,000 ± 4000 and42,000 ± 5000years. VGP's comparison of the “Laschamp event” with those of the 30,000-year Lake Mungo excursion does not show evidence of coincidence between these two events. 相似文献
996.
997.
Algal humic-like substances were oxidized with KMnO4. The oxidation products were analyzed by GC-MS. Normal and branched fatty acids, dicarboxylic and benzene carboxylic acids were identified. Aliphatic acids were by far the most prominent compounds. Similarities between humic and fulvic acids of both Fucus and Laminaria algae were apparent. Fucus humic acids, however, showed a more aromatic structure than their Laminaria counterpart. The contribution of algae to marine sedimentary humus is discussed. 相似文献
998.
Spherical aggregates of orthopyroxene are reported from some parts of the Bushveld Complex in a variety of host rocks.Detailed mapping has shown that these spherical aggregates, comprising pyroxenite spheroids in a quartz-norite matrix, are contact phenomena and not stratigraphic markers. Orthopyroxene, biotite and amphibole are enriched in spheroids relative to matrix; their mineral chemistry showing a fairly constant orthopyroxene and plagioclase composition through the spheroids and into the matrix, indicating in-situ formation.Bulk chemistry shows spheroid to matrix tie-lines orthogonal to those generally accepted for silicate liquid immiscibility, but other chemical information is consistent with the occurrence of immiscibility.The formation of the aggregates may be related to the industrial process of spherical agglomeration, by which spheroids are formed by the introduction of an immiscible “bridging liquid” to the melt — probably derived from the floor rocks in this case. The mechanism accounts for the field relationships, petrography and chemistry of the aggregate-matrix system. The petrology of the process equates with a special case of silicate liquid immiscibility induced by local contamination and ageing of the original magma.A similar “bridging liquid” mechanism could also account for the formation of the so-called “boulder bed” beneath the Merensky Reef. 相似文献
999.
Rainer Altherr Manfred Schliestedt Martin Okrusch Eberhard Seidel Hans Kreuzer Wilhelm Harre Heinz Lenz Immo Wendt Günther A. Wagner 《Contributions to Mineralogy and Petrology》1979,70(3):245-255
Polymetamorphic rocks of Sifnos (Greece) have been investigated by Rb-Sr, K-Ar, and fission track methods. Critical mineral assemblages from the northern and southernmost parts of Sifnos include jadeite+quartz+3T phengite, and omphacite+garnet +3T phengite, whereas the central part is characterized by the assemblage albite+chlorite+epidote+2M
1 phengite.K-Ar and Rb-Sr dates on phengites (predominantly 3T) of the best preserved high P/itTmetamorphic rocks from northern Sifnos gave concordant ages around 42 m.y., indicating a Late Lutetian age for the high P/T metamorphism. Phengites (2M
1+3T) of less preserved high P/T assemblages yielded K-Ar dates between 48 and 41 m.y. but generally lower Rb-Sr dates. The higher K-Ar dates are interpreted as being elevated by excess argon.K-Ar and Rb-Sr ages on 2M
1 phengites from central Sifnos vary between 24 and 21 m.y. These ages date a second, greenschist-facies metamorphism which overprinted the earlier high-pressure metamorphic rocks. 相似文献
1000.