Magmagenesis in a subduction-related post-collisional volcanic arc segment: the Ukrainian Carpathians   总被引：6，自引：0，他引：6  

Ioan Seghedi  Hilary Downes  Zolt  n P  cskay  Matthew F. Thirlwall  Alexandru Szak  cs  Michail Prychodko  David Mattey 《Lithos》2001,57(4):237-262

Calc-alkaline magmatism in the south-west Ukraine occurred between 13.8 and 9.1 Ma and formed an integral part of the Neogene subduction-related post-collisional Carpathian volcanic arc. Eruptions occurred contemporaneously in two parallel arcs (here termed Outer Arc and Inner Arc) in the Ukrainian part of the Carpathians. Outer Arc rocks, mainly andesites, are characterized by LILE enrichment (e.g. K and Pb), Nb depletion, low compatible trace element abundances, high ⁸⁷Sr/⁸⁶Sr, high δ¹⁸O and low ¹⁴³Nd/¹⁴⁴Nd isotopic ratios (0.7085–0.7095, 7.01–8.53, 0.51230–0.51245, respectively). Inner Arc rocks are mostly dacites and rhyolites with some basaltic and andesitic lavas. They also show low compatible element abundances but have lower ⁸⁷Sr/⁸⁶Sr, δ¹⁸O and higher ¹⁴³Nd/¹⁴⁴Nd ratios (0.7060–0.7085, 6.15–6.64, 0.5125–0.5126, respectively) than Outer Arc rocks. Both high-Nb and low-Nb lithologies are present in the Inner Arc. Based on the LILE enrichment (especially Pb), a higher fluid flux is suggested for the Outer Arc magmas compared with those of the Inner Arc.

Combined trace element and Sr–Nd–O isotopic modelling suggests that the factors which controlled the generation and evolution of magmas were complex. Compositional differences between the Inner and Outer Arcs were produced by introduction of variable proportions of slab-derived sediments and fluids into a heterogeneous mantle wedge, and by different extents of upper crustal contamination. Degrees of magmatic fractionation also differed between the two arcs. The most primitive magmas belong to the Inner Arc. Isotopic modelling shows that they can be produced by adding 3–8% subducted terrigenous flysch sediments to the local mantle wedge source. Up to 5% upper crustal contamination has been modelled for fractionated products of the Inner Arc. The geochemical features of Outer Arc rocks suggest that they were generated from mantle wedge melts similar to the Inner Arc primitive magmas, but were strongly affected by both source enrichment and upper crustal contamination. Assimilation of 10–20% bulk upper crust is required in the AFC modelling, assuming an Inner Arc parental magma. We suggest that magmagenesis is closely related to the complex geotectonic evolution of the Carpathian area. Several tectonic and kinematic factors are significant: (1) hydration of the asthenosphere during subduction and plate rollback directly related to collisional processes; (2) thermal disturbance caused by ascent of hot asthenospheric mantle during the back-arc opening of the Pannonian Basin; (3) clockwise translational movements of the Intracarpathian terranes, which facilitated eruption of the magmas.  相似文献   

The Value of Ground Water Monitoring   总被引：1，自引：0，他引：1  

A. Roger Anzzolin  Mary T. Siedlecki 《Ground Water Monitoring & Remediation》2001,21(1):36-40

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Field Measurement of Dissolved Oxygen: A Comparison of Methods     

Richard T. Wilkin  Mary S. McNeil  Cherri. J. Adair.  John T. Wilson 《Ground Water Monitoring & Remediation》2001,21(4):124-132

The ability to confidently measure the concentration of dissolved oxygen (D.O.) in ground water is a key aspect of remedy selection and assessment. Presented here is a comparison of the commonly practiced methods for determining D.O. concentrations in ground water, including colorimetric, membrane-covered electrode, and modified Winkler techniques. The Winkler titration (azide and permanganate modifications) is the most accurate and precise technique for determining D.O. and is appropriate for applications with stringent data quality objectives. In addition, excellent correlation over a wide range of D.O. concentrations was found between Winkler titrations and colorimetric tests using the rhodazine D (below 1 part per million [ppm]) and indigo carmine reagents (above 1 ppm). Electrode measurements represent the simplest method for determining D.O. concentrations on a continuous basis and electrode determinations positively correlate with Winkler results above 1 ppm. Below 1 ppm, electrodes provide only a qualitative measure of low D.O. level, apparently due to slow electrode response.  相似文献   

Molecular gas distribution and dynamics in the luminous merger NGC 6240     

L.J. Tacconi  R. Genzel  M. Tecza  J.F. Gallimore  D. Downes  N.Z. Scoville 《Astrophysics and Space Science》1999,266(1-2):157-162

We present the results of our subarcsecond resolution interferometricobservations of the 1.3 mm CO J = 21 line in the luminous merger NGC6240. Roughly half of the CO flux is contained in a rotating and highlyturbulent thick disk centered between the two radio and near-infrarednuclei. In this disk the molecular gas has velocity widths which reachFWZP line widths of up to 1000 km s^-1. The mass of this gasconcentration makes up between 30%–70% of the dynamical mass in thisregion. NGC 6240 may be in an earlier merging stage than typical ULIRGssuch as Arp 220. We compare these results from NGC 6240 with thoseof other luminous, gas-rich interacting galaxies and mergers.  相似文献   

A close-interval sampler for collection of sediment pore waters for nutrient analyses     

John R. Montgomery  Mary T. Price  John Holt  Carl Zimmermann 《Estuaries and Coasts》1981,4(1):75-77

An in situ sediment pore water sampler is described. It can simultaneously and continuously sample at four discrete 1 cm levels at one location without disturbing the sediment or the sample. The sampler can maintain an anaerobic environment, and can be used over extended periods of time. Laboratory tests indicate 98 to 100 percent recoveries for ammonium, silicate, reactive phosphate, nitrate and nitrite. Vertical profiles for ammonium, reactive phosphate and silicate are shown from field studies.  相似文献   

Metal ion complex formation constants of some sedimentary humic acids with Zn(II), Cu(II) and Cd(II)     

Mary L Sohn  Michael C Hughes 《Geochimica et cosmochimica acta》1981,45(12):2393-2399

Metal ion complex formation constants were determined for several sedimentary humic acids (SHA) derived from a fresh water lake and several coastal marine environments, using a method based on size exclusion chromatography. Only one type of binding site was observed in all cases, and conditional log K_f values of between 5 and 7 (at pH 8, I = 0.01 M) were found. Elemental composition of the SHA was similar to soil HA, except that nitrogen content was significantly higher in the SHA. Other chemical properties of the SHA were consistent with those reported by other workers. While spectroscopic measurements indicated that the SHA may have contained significant amounts of polysaccharide compounds which were not removed by conventional separation and purification procedures, analysis indicated only very low levels of polysaccharides were present in the SHA.  相似文献   

The Use of Ground-Water Flow Models for Estimating Lake Seepage Rates     

James A. Munter  Mary P. Anderson 《Ground water》1981,19(6):608-616

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Geomagnetic field variations in southeastern Europe between 6500 and 100 years B.C.     

Mary Kovacheva  Dushan Veljovich 《Earth and Planetary Science Letters》1977,37(1):131-138

Results from joint work between the Geophysical Institute (Sofia, Bulgaria), and the Geomagnetic Institute (Grocka, Yugoslavia) on the geomagnetic field variation in the prehistoric past are presented. Preliminary curves of variation of the three geomagnetic elements: declination, inclination and intensity are presented. The movement of the virtual pole position for the 6500 years time period B.C. is derived. The curves and the virtual pole positions provide a dating tool for archaeological purposes and determination of the periodicities in the geomagnetic secular variations in southeastern Europe.  相似文献   

Silica Springs,Tongariro National Park,New Zealand—analyses of the spring water and characterisation of the alumino-silicate deposit     

N. Wells  C.W. Childs  C.J. Downes 《Geochimica et cosmochimica acta》1977,41(10):1497-1506

The creamy-white deposit in the stream bed below Silica Springs outlet on Mount Ruapehu, Tongariro National Park, New Zealand, has been identified as a hydrous, X-ray-amorphous, aluminosilicate (allophane). The SiO₂/Al₂O₃ mole ratio varies from close to one, to close to two. The elements K, Ca, Mn and Fe are present in low concentrations relative to those in allophanic soil clays, and tend to increase in concentration downstream from where the deposit first occurs. The concentration of S decreases downstream from 0.5% to 0.1%. Surface areas of samples, measured by the ethylene glycol desorption method, are about 200–300 m²/g. The outlet water at Silica Springs contains low dissolved solids and is undersaturated with respect to amorphous silica, but is supersaturated with respect to several alumino-silicate minerals (of which allophane may be considered the precursor) and with respect to CO₂. Gas bubbling at the outlet contains about 10% CO₂ which has a δC¹³_PDB value of ?7.5%..Silica Springs water is derived from the addition of geothermal CO₂ (and possibly H₂S) to near-surface meteoric water from the lava flow above the outlet, and the chemical attack of this water on the andesitic rocks and soil through which it passes. The pH of water at Silica Springs increases from 5.45 at the outlet, to 5.90 where deposition first occurs, to 6.80 below the region of maximum deposition. This rise in pH correlates with loss of excess CO₂ in turbulent regions of the stream, and, through surface charge effects, is probably an important influence on the site of deposition, which begins approx. 100m downstream from the outlet.  相似文献   

Nonlinear Plasma Phenomena in the Ionosphere: A.V. Gurevich. Springer-Verlag,New York-Heidelberg-Berlin, 1978 370 pp., US $ 49.00, ISBN 3-540-08605-6     

Mary K. Hudson 《Physics of the Earth and Planetary Interiors》1980,23(1):79

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