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511.
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513.
Du Zongjun Li Yun Yu Dehua Wang Xianghong Chen Jixiang P. A. W. Robertson B. Austin Xu Huaishu 《中国海洋大学学报(英文版)》2002,1(1):59-62
From Oct. 1999 to Oct. 2000, the heterotrophic bacterial floras in the industrial marine environment around the Qingdao Power
Plant (QPP) and in the unpolluted marine environments were investigated. The results showed that the numbers of the heterotrophic
bacteria around QPP were much higher than those in unpolluted environments, and the average numbers in QPP Seawater, QPP Sediment,
Unpolluted Seawater and Unpolluted Sediment were 5.4×104cfu(mL)−1, 5.0×105cfug−1, 3.0×102cfu(mL)−1 and 1.3×105cfug−1 respectively. Totally, 118 strains were isolated from QPP and 99 of them were Gram-negative. One hundred and twenty one strains
were isolated from the unpolluted environments and 104 of them were Gram-negative. All the Gram-negative bacteria belonged
to 13 genera. The distribution of the bacteria was varied in different marine environments. The results showed that the unpolluted
marine environments contained much more Vibrio than seawater and sediment around QPP. 相似文献
514.
N. Tamura G. J. Murray P. Luke C. Blackburn D. J. Robertson N. A. Dipper R. M. Sharples J. R. Allington-Smith 《Experimental Astronomy》2003,15(1):1-12
We present results from cryogenic tests of a Volume-Phase Holographic(VPH) grating at 200 K measured at near-infrared wavelengths.
The aims of these tests were to see whether the diffraction efficiency and angular dispersion of a VPH grating are significantly
different at a low temperature from those at a room temperature, and to see how many cooling and heating cycles the grating
can withstand. We have completed 5 cycles between room temperature and 200 K, and find that the performance is nearly independent
of temperature, at least over the temperature range which we are investigating. In future, we will not only try more cycles
between these temperatures but also perform measurements at a much lower temperature (e.g., ∼80 K). 相似文献
515.
P. Blyth Robertson 《Meteoritics & planetary science》1988,23(3):181-184
Abstract— Although mapped initially as a piercement dome, subsequent discovery of shock metamorphism in clasts of an impact breccia, shatter cones in outcrops of uplifted target rocks and morphological and geophysical characteristics consistent with a complex crater, confirmed a meteorite impact origin for the Haughton structure, Devon Island. Results of three field investigations carried out prior to 1984 defined a complex crater, 20 km in diameter, formed in a lower Paleozoic sedimentary sequence overlying gneisses of the Precambrian basement. The distribution of allochthonous breccia overlying the disturbed target rocks and of the sediments deposited in the crater-filling lake were mapped. A Miocene or possibly Holocene age for the crater was based on paleo-flora and fauna assemblages from the lake sediments. Gravity and magnetic surveys revealed anomalies coincident with the crater, but not interpretable from surface lithologies. Some of the early investigations were of a reconnaissance nature and results and interpretation can only be considered preliminary. Other studies that were carried out in some detail, petrographic investigations in particular, require complementary work for a fuller understanding of their significance. As a result, in 1984 the HISS (Haughton Impact Structure Studies) group carried out a program of detailed geological mapping and sampling, and seismic, gravity, and magnetic surveys in an attempt to improve the definition of the surface and subsurface nature of Haughton, and to formulate a more complete understanding of its formation and subsequent history. Results of these various studies are presented in the eight succeeding papers of this volume. 相似文献
516.
517.
Stephen F. Foley Wayne R. Taylor David H. Green 《Contributions to Mineralogy and Petrology》1986,94(2):183-192
The effects of H2O, CO2, CH4 and HF on partial melting of a model phlogopite harzburgite mantle are considered with regard to the production of ultrapotassic magmas. Fluorine has a polymerising effect in H2O-poor conditions, but in the presence of abundant H2O where HF rather than F is dominant, the overall effect is depolymerisation. Methane also dissolves by forming (OH)– groups, and so has a depolymerising effect. Group I ultrapotassic rocks (lamproites) probably originate from primary magmas with SiO2 contents ranging from around 40 wt% to at least 52 wt%. This range can be explained by differing depths of origin from a similar source with a similar reduced H2O-CH4-HF volatile mixture. The formation of silica-rich initial melts from a model phlogopite harzburgite is assisted by the presence of CH4 and HF. Dissociation of less than 0.1 wt% H2O, driven by H2 loss, is sufficient to cause oxidation during emplacement to observed oxidation states. Silica-poor ultrapotassic rocks could be produced at higher pressures in a reduced environment, or in an oxidised environment with high CO2/(CO2 + H2O) ratios.Group II (African Rift) potassic rocks may originate in H2O-poor conditions in which fluorine will maintain a large phlogopite phase field, so that initial melts will be magnesian and silica-undersaturated. 相似文献
518.
Stephen F. Foley Wayne R. Taylor David H. Green 《Contributions to Mineralogy and Petrology》1986,93(1):46-55
Phase relationships in the system kalsilite-forsterite-quartz with fluorine added by direct substitution for oxygen were examined at 28 kb. A large liquidus field for fluorphlogopite exists with approx. 4 wt% F added to the system and the thermal stability of phlogopite is increased by 300° C relative to the water saturated system. Fluorine expands the phase volume of enstatite relative to forsterite so that the peritectic point PHL+EN+FO+L, a model for melting of a phlogopite harzburgite, lies in the silica-undersaturated field. Experimental phlogopites have excess Si which correlates with F content and are Al-deficient. The high Si contents indicate solid solution with an end member intermediate between tri- and di-octahedral micas. Glasses with compositions analogous to partial melts from phlogopite harzburgite were examined by infrared spectroscopy in the mid- and far-IR regions. Results show that fluorine polymerises the melt by bonding with all the network modifying cations K, Mg and Al. At higher F contents, but still less than 1 wt%, tetrahedral KAlO2-groups are complexed by fluorine and removed from the aluminosilicate network simultaneously polymerising and increasing the Si/(Si+Al) ratio of the network. However, when HF rather than F is present, the overall effect will be to depolymerise melts due to the effect of OH released by dissolution of HF. The presence of abundant Si-F bonds is considered unlikely even in silica-rich magmas: the viscosity decrease characteristic of fluorine-bearing melts can be attributed to the formation of fluoride complexes. 相似文献
519.
The vein-type gold deposits of middle to late Archean age constitute one of the major sources of gold production in the world. These deposits are highly diverse in character, but are invariably found in proximity to mafic and ultramafic volcanic rocks, and closely associated with tectonically disturbed zones, or breaks, in the ancient crust. Using the Larder Lake break of northern Ontario and Quebec as a model, a general theory of genesis for such deposits is proposed.The Larder Lake break is of linear configuration, up to four miles wide, and extending over a distance of approximately 150 miles. Many rich and extensive vein-type gold deposits are associated with it. This break is recognized as a highly folded and faulted, dominantly sedimentary stratigraphic unit, formed as part of the development of the Blake River geosyncline of the Abitibi greenstone belt. Faulting is pervasive within the break but it is non-continuous.Under an oxygen-poor, somewhat acidic weathering regime believed extant in Archean time, gold and associated constituents, derived as weathering products from mafic and ultramafic volcanics, appear to have been concentrated as solutions and sols in muddy surficial accumulations along a paleo-continental margin. On transfer to a shallow marine environment, the gold-bearing solutions became concentrated mainly as cherty and pyritic evaporitic residues. These residues, infolded and variably metamorphosed and remobilized during ensuing geosynclinal development, formed the numerous and apparently heterogeneous gold deposits of the Larder Lake break.Mode of redistribution of gold-bearing residues and metamorphism of their host rocks varies widely. In mild form, little vein development is present and original sedimentary features of the host rock are often preserved. In more extreme cases, true hydrothermal veining is evident and complete recrystallization of the host rock has taken place, sometimes to the extent of formation of a melt with intrusive capabilities. In any case, the gold and related vein constituents remain closely associated with the primary host material and alteration effects are largely derived from the recrystallization of original host rock constituents.The suggested mode of genesis clarifies the relationship between various types of break-related, vein-type gold deposits and offers an explanation of the complex stratigraphy and structure of the break environment. It also suggests a penecontemporaneous relationship between the Larder Lake break and other auriferous breaks, of varying configuration, within the Superior Province of the Canadian Shield. The concept can be used advantageously in exploration for new breaks and new deposits. 相似文献
520.
The Troodos ophiolite formed during the Late Cretaceous (Turonian) in a spreading setting above a northerly-dipping subduction zone. Palaeomagnetic data establish that the ophiolite experienced a 90° anticlockwise palaeorotation that occurred during the Late Cretaceous-Early Eocene interval During this period, the ophiolite was stranded adjacent to a generally south-facing continental margin, the remnants of which are preserved in south-west Cyprus (Mamonia Complex), southern Cyprus (Moni melange) and in northern Cyprus (Kyrenia Range). A review of field evidence from these Mesozoic basin margin units shows that strike-slip played a critical role in their Late Cretaceous-Early Tertiary deformation while magnetic and gravity surveys support the existence of major lineaments preserved at depth beneath these areas. Thus, in agreement with available palaeomagnetic data from mainland Turkey and Africa, the rotated crustal unit is believed to be relatively small with its boundaries probably located in the vicinity of Cyprus. In the favoured palaeorotation model, a small supra-subduction zone oceanic crustal unit was rotated about a pole located close to the exposed ophiolite complex. Fragments of the northern continental margin became attached to the rotating microplate along strike-slip lineaments and were then carried southward to their present position. In the light of the regional tectonic setting, it was probably the oblique consumption of crust beneath the ophiolite and/or a collision outside the present area of Cyprus that provided the necessary driving force for the palaeorotation. 相似文献