Variations in the crustal structure beneath western Turkey   总被引：6，自引：0，他引：6  

Paul Saunders  Keith Priestley  & Tuncay Taymaz 《Geophysical Journal International》1998,134(2):373-389

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The kinematics of the ionized gas in the Circinus galaxy     

Marc Elmouttie  Bärbel Koribalski  Scott Gordon  Keith Taylor  Sally Houghton  Tracy Lavezzi  Raymond Haynes  & Keith Jones 《Monthly notices of the Royal Astronomical Society》1998,297(1):49-68

The TAURUS-2 Fabry–Perot interferometer, mounted on the 3.9-m Anglo-Australian Telescope, has been used to observe the Circinus galaxy. We have mapped the intensity and velocity distribution of the ionized hydrogen in the galaxy using the Balmer series Hα spectral line.
The semiresolved core (observed with a seeing disc of 30 pc) appears amorphous in shape, which is commonly observed in Seyfert 2 galaxies. Its peak coincides with the core position measured in the radio continuum, suggesting that ionized gas surrounds a non-thermal source.
A circumnuclear ring or spiral of radius 220 pc and a rotational velocity of 350 km s⁻¹ (assuming circular motions) surrounds the core. The inclination angle of this feature, i =40°±10°, is less than that of the previously observed radio continuum disc. The velocity channel maps obtained for the Hα ring show that the kinematics resemble those of a rotating ring and the intensity displays a complex structure indicative of several, unresolved, H II regions. We believe the ring to represent a circumnuclear starburst.
Our Hα data also show the presence of the previously detected [O III ] ionization cone to the north-west of the core, measuring more than 400 pc in length. We suggest that the ionization cone lies in a different plane from that of the starburst ring and is directed away from us. Several kinematic components of the core are derived and we calculate an outflow velocity in excess of 150–200 km s⁻¹ for gas above the core of Circinus. We also present evidence for inflowing ionized gas at the centre of Circinus.
The correlation of the Hα and radio continuum features is discussed, as well as the possible presence of a starburst-driven superwind in the Circinus galaxy.  相似文献   

The 1996 outburst of GRO J1655–40: the challenge of interpreting the multiwavelength spectra     

R. I. Hynes  C. A. Haswell  C. R. Shrader  W. Chen  Keith Horne  E. T. Harlaftis  K. O'Brien  C. Hellier  & R. P. Fender 《Monthly notices of the Royal Astronomical Society》1998,300(1):64-82

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AN ALL-TEFLON BAILER AND AN AIR-DRIVEN PUMP FOR EVACUATING SMALL-DIAMETER GROUND-WATER WELLS     

Daniel F. Buss  Keith E. Bandt 《Ground water》1981,19(4):429-431

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Minerals produced during cooling and hydrothermal alteration of ash flow tuff from Yellowstone drill hole Y-5     

Terry E.C. Keith  L.J.P. Muffler 《Journal of Volcanology and Geothermal Research》1978,3(3-4)

A rhyolitic ash-flow tuff in a hydrothermally active area within the Yellowstone caldera was drilled in 1967, and cores were studied to determine the nature and distribution of primary and secondary mineral phases. The rocks have undergone a complex history of crystallization and hydrothermal alteration since their emplacement 600,000 years ago. During cooling from magmatic temperatures, the glassy groundmass underwent either devitrification to alkali feldspar + α-cristobalite ± tridymite or granophyric crystallization to alkali feldspar + quartz. Associated with the zones of granophyric crystallization are prismatic quartz crystals in cavities similar to those termed miarolitic in plutonic rocks. Vapor-phase alkali feldspar, tridymite, magnetite, and sporadic α-cristobalite were deposited in cavities and in void spaces of pumice fragments. Subsequently, some of the vapor-phase alkali feldspar crystals were replaced by microcrystalline quartz, and the vapor-phase minerals were frosted by a coating of saccharoidal quartz.Hydrothermal minerals occur primarily as linings and fillings of cavities and fractures and as altered mafic phenocrysts. Chalcedony is the dominant mineral related to the present hydrothermal regime and occurs as microcrystalline material mixed with various amounts of hematite and goethite. The chalcedony displays intricate layering and was apparently deposited as opal from silica-rich water. Hematite and goethite also replace both mafic phenocrysts and vapor-phase magnetite. Other conspicuous hydrothermal minerals include montmorillonite, pyrite, mordenite, calcite, and fluorite. Clinoptilolite, erionite, illite, kaolinite, and manganese oxides are sporadic. The hydrothermal minerals show little correlation with temperature, but bladed calcite is restricted to a zone of boiling in the tuff and clearly was deposited when CO₂ was lost during boiling.Fractures and breccias filled with chalcedony are common throughout Y-5 and may have been produced by rapid disruption of rock caused by sudden decrease of fluid pressure in fractures, most likely a result of fracturing during resurgent doming in this part of the Yellowstone caldera. The chalcedony probably was deposited as opal or β-cristobalite from a pre-existing silica floc that moved rapidly into the fractures and breccias immediately after the sudden pressure drop.  相似文献   

Long base line tilt and strain measurement     

Paul Davis  Keith Evans  John Hosfall  Geoffrey King 《Tectonophysics》1979,52(1-4)

Two types of noise afflict strain and tilt measurement. They may be categorized as “active” noise, which is due to atmospheric pressure variations, temperature variations, water-table variations and so forth; and “passive” or signal-generated noise which is a consequence of the interaction of the strain field of interest with inhomogeneities of material properties local to the measurement site.The reason why both types of noise are normally reduced by the use of long base line instruments is explained and a simple, practical long base line tiltmeter is described.  相似文献   

Amino-acid racemizarion in Quaternary shell deposits at Willapa Bay,Washington     

Keith A. Kvenvolden  David J. Blunt  H.Edward Clifton 《Geochimica et cosmochimica acta》1979,43(9):1505-1520

Extents of racemization ($\text{d}\text{l}$ ratios) of amino acids in fossil Saxidomus giganteus (Deshayes) and Ostrea lurida Carpenter were measured on shell deposits exposed at 21 sites on the east side of Willapa Bay, Washington. Amino acids from Saxidomus show less variability in $\text{d}\text{Spl}$ ratios and, therefore, are of greater use in correlation and age estimation than are amino acids from Ostrea. Shells of two different ages, about 120,000 ± 40,000 yr old and about 190,000 ± 40,000 yr old, are present. These ages correspond to Stages 5 and 7 of the marine isotope record defined by Shackleton and Opdyke in 1973 and hence the shell deposits likely formed during two different high stands of sea level. The stratigraphic record at Willapa Bay is consistent with this interpretation.  相似文献   

Amino acid racemization dating of fossil bones,I. inter-laboratory comparison of racemization measurements     

Jeffrey L. Bada  E. Hoopes  D. Darling  Graham Dungworth  Henk J. Kessels  Keith A. Kvenvolden  David J. Blunt 《Earth and Planetary Science Letters》1979,43(2):265-268

Enantiomeric measurements for aspartic acid, glutamic acid, and alanine in twenty-one different fossil bone samples have been carried out by three different laboratories using different analytical methods. These inter-laboratory comparisons demonstrate that D/L aspartic acid measurements are highly reproducible, whereas the enantiomeric measurements for the other amino acids show a wide variation between the three laboratories. At present, aspartic acid measurements are the most suitable for racemization dating of bone because of their superior analytical precision.  相似文献   

A novel charge-transfer polymer for separating hydrocarbon fractions of crude oils     

Keith C.C. Bancroft  Susan B. Kendall  Michael M. Rhead  Gerard Hentic 《Marine pollution bulletin》1979,10(8):238-239

Hydrocarbon fractions in crude oil were separated by a new charge-transfer polymer in place of silver ions in Argentation TLC. The charge-transfer plates are cheaper than their silver nitrate equivalents, do not discolour, and store well. The polymer/silica gel mix can be re-used.  相似文献   

Fore-arc evolution and continental growth: a general model     

Keith A.W Crook 《Journal of Structural Geology》1980,2(3):289-303

The extended evolution of fore-arc regions which leads to their eventual incorporation into stable kratonic continental crust is elucidated by a general model based upon observations from the modern circum-Pacific and the Palaeozoic Tasman Geosyncline.Fore-arc regions widen during subduction in the manner described by Karig & Sharman (1975). Their history, after subduction has ceased, depends upon the thickness of the accretionary prism formed during subduction. Where the prism is thick (ca. 20 km) kratonization is a single-step process. The fore-arc region remains above sea-level; post-arc silicic volcanics accumulate due to granitoid plutonism, the magmas being derived by melting of the subduction complex and from the oceanic lithosphere trapped beneath it. The volcanic arc subsides, becoming the site of a fore-deep.Intermediate-thickness accretionary prisms (ca. 16 km) are kratonized in a two-step process. They remain at shelf depths, while their associated volcanic arcs sink to comparable depths. Both acquire a post-arc shallow marine sequence of typical platform-cover facies. They are then deformed and intruded by granitoids when the crust attains critical thickness (ca. 20 km).Thin accretionary prisms (≤ 12 km) require a three-step process for kratonization. They and their associated arcs sink to bathyal depths. They are overwhelmed by prograding post-arc flysch deposits of continental origin. Deformation of the post-arc flysch and plutonism occur when critical crustal thickness (ca. 20 km) is attained. A transitional tectonic regime ensues, with molasse-like transitional basins preferentially sited over the extinct volcanic arcs and the thinner parts of buried accretionary prisms.The model satisfactorily explains the Late Proterozoic-Palaeozoic evolution of southeast Australia, where a 1000 km wide tract of continental crust was accreted to the Australian Kraton in 250–300 Ma, beginning as a S.W. Pacific-type oceanic terrain. It has been found useful for interpreting geosynclinal terrains in other continents.According to the model, the dynamic processes that contribute to kratonization are systematically causally connected. Kratonization is a unified, internally deterministic and self-sustaining phenomenon. The model has implications for the origin, ‘stratigraphy’ and composition of upper and lower continental crust; the origins and tectonic settings of ophiolites, granitoids, paired metamorphic belts and transitional basins; and for the nature and causes of orogenesis.  相似文献