Studies on the flotation of sulphides. I. The effect of Cu(II) ions on the flotation of zinc sulphide     

D.A. Baldwin  M.R. Manton  J.M. Pratt  M.J. Storey 《International Journal of Mineral Processing》1979,6(3):173-192

The effect of Cu(II) ions on the froth flotation of ZnS in the absence of any collector has been studied in a Fuerstenau microflotation cell. The flotation of pure synthetic ZnS, in both cubic and hexagonal modifications, can be greatly enhanced by the adsorption of traces of Cu(II) ions. In the case of cubic ZnS, the “activating” effect of Cu(II): (a) involves the stoichiometric replacement of one Zn(II) ion in the lattice by one Cu(II) ion from solution at a rate which is independent of pH (1–5); (b) is noticeable at coverages corresponding to as little as 0.1% of a monolayer, reaches a maximum at coverages of 2–100% of a monolayer, and decreases again at higher coverages; (c) is unaffected by the presence or absence of O₂, by variation of the pH of flotation (6–10), by heating in vacuum at 250°C for two hours or by storing in the dry state for over one year; and (d) does not appear to involve any significant change in surface area or in the state of aggregation of the particles.  相似文献   

Geochemical studies on the Feshcha Springs,Dead Sea basin     

Emanuel Mazor  Magda Molcho 《Journal of Hydrology》1972

The Feshcha springs issue in a 4 km long strip on the Dead Sea shores. They constitute two separate groups: a) T-N waters, similar in their salt composition, temperature and radon content to the many other members of the Rift Valley “Tiberias-Noit water association”. The hydrologic, radon, tritium and carbon-14 indicate they are mixtures of recent meteoric waters with ancient (trapped) T-N waters of an age of at least 18000 years. b) Z-Y waters which, like other members of the Dead Sea basin “Zohar-Yesha water group”, originate by a mixing of T-N waters with Dead Sea waters. This is seen in the chemical compositions and is confirmed by the oxygen-18 and deuterium data.  相似文献   

The volatile component of some pumice-forming alkaline magmas from the Azores and Canary Islands     

J. A. Wolff  M. Storey 《Contributions to Mineralogy and Petrology》1983,82(1):66-74

The abundances of pre-eruptive magmatic volatile species in the system H-O-S may be determined by application of thermodynamic methods to phenocryst assemblages commonly found in volcanic rocks, as demonstrated by Rutherford and Heming (1978). These methods are applied to alkaline pumice deposits, of airfall and ignimbrite type, from Tenerife (Canary Islands), Sao Miguel and Faial (Azores). It is argued that reliable temperature and fO₂ buffering mechanisms found in rhyolitic magmas appear not to operate in more alkaline liquids. fH₂O is estimated using biotite; the high values found are shown to be compatible with the violently explosive nature of the magmas concerned. fS₂ is estimated from pyrrhotite composition. fH₂, fH₂S, fSO₂, fSO₃ are calculated from gas equilibria. Water fugacity may be very roughly estimated for non-biotite bearing samples from data on the sulphur species. Abundances of these species are similar in alkaline and calc-alkaline salic magmas. Volcanological implications, relating to the release of volatiles during explosive eruptions, are considered.  相似文献   

Gondwana 11: Correlations and Connections - Introduction     

Bryan C. Storey  N. Hiller  N. Mortimer  H.J. Campbell  T.A. Moore 《Gondwana Research》2004,7(1):3-5

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Helium isotope composition of the early Iceland mantle plume inferred from the Tertiary picrites of West Greenland     

D.W. Graham  L.M. Larsen  B.B. Hanan  M. Storey  A.K. Pedersen  J.E. Lupton 《Earth and Planetary Science Letters》1998,160(3-4):241-255

Picrites from the 61 million year old Vaigat Formation of the Nuussuaq Peninsula in West Greenland have ³He/⁴He ratios trapped in olivine phenocrysts which range up to 30 times the atmospheric ratio. These high values, measured during gas extraction by crushing in vacuum, are similar to the highest magmatic ³He/⁴He ratios found in young terrestrial volcanic rocks. By analogy with young basalts, in which crushing selectively extracts magmatic helium, any significant cosmogenic ³He appears to be absent in these picrites. Additional evidence for the absence of cosmogenic helium is provided by fusion results on the crushed olivine powders and by a single stepwise crushing experiment, in which only magmatic and radiogenic helium components are resolvable. The West Greenland picrites have Pb, Nd and Sr isotope compositions which overlap those found in picrites from Iceland and in basalts from Loihi Seamount, localities which today also have high ³He/⁴He ratios. Isotopic variations in He, Pb, Nd and Sr for the West Greenland picrites are interpreted to largely result from interaction of the early Iceland mantle plume with the upper mantle during plume ascent and dispersion beneath the continental lithosphere. The presence of high ³He/⁴He ratios in West Greenland, and the onset of magmatism across the North Atlantic Volcanic Province near 62 Ma, supports the hypothesis for very rapid dispersion (>1 m/year) of mantle plume head material during the earliest stages of plume impact, as predicted in recent numerical simulations of plume behavior during thermal mantle convection with non-Newtonian rheology.  相似文献   

Revision of the basic equations of wave distribution function analysis     

L. R. O. Storey 《Annales Geophysicae》1998,16(5):651-653

The basic equations of wave distribution function analysis are rewritten in forms that treat the electric and magnetic fields of the waves in a more symmetrical way than the original equations do, and are slightly better for computing.  相似文献   

Recombination of helium-like ions – I. Photoionization cross-sections and total recombination and cooling coefficients for atomic helium     

D. G. Hummer  & P. J. Storey 《Monthly notices of the Royal Astronomical Society》1998,297(4):1073-1078

A new calculation of photoionization cross-sections is described for the ground and excited states of atomic helium up to principal quantum number n =25 and angular momentum quantum number l =5. These cross-sections are used to calculate total recombination and cooling coefficients for atomic helium for electron temperatures given by log( T )=1(0.2)4.4. A comparison of the threshold photoionization cross-sections obtained here with extrapolations of the highly accurate bound–bound oscillator strength calculations by Drake shows that the new calculations are in error by no more than 1 per cent. The accuracy of the photoionization cross-sections used by previous workers to derive recombination coefficients is also discussed.  相似文献   

Nucleation and growth of strike-slip faults in limestones from Somerset, U.K.     

Emanuel J.M. Willemse  David C.P. Peacock  Atilla Aydin 《Journal of Structural Geology》1997,19(12):1461-1477

Small-scale structures along strike-slip fault zones in limestones exposed around the Bristol Channel, U.K., suggest that pressure solution plays a key role during fault nucleation and growth. Incipient shear zones consist of enéchelon veins. The first generation of solution seams form due to bending of the intact rock (bridge) between overlapping veins. As the bridge rotates, slip occurs along the seams, linking the veins, causing cm-scale calcite-filled pull-apart structures to form and allowing fault displacement to increase. A second generation of solution seams forms at the tip of the sliding seams. As displacement increases further, causing larger rotation, slip also can occur along these second-generation solution seams, producing the third generation of solution seams as well as tail cracks (pinnate veins) at their tips. These three generations of solution seams all contribute to the formation of individual fault segments. Fourth and fifth generations of solution seams occur within larger-scale contractional oversteps between side-stepping fault segments. The oversteps are breached by slip along these localized solution seams, eventually leading to the formation of a distinct through-going fault with several metres of displacement.The initial enéchelon veins, solution seams of various generations and tail cracks progressively fragment the fault-zone material as fault slip accumulates. Slip planes nucleate on these pre-existing discontinuities, principally along the clay-enriched, weaker solution seams. This can be observed at a variety of scales and suggests that Mode II shear fracturing does not occur as a primary fracture mechanism, but only as a macroscopic phenomenon following Mode I (veins and tail cracks) and anti-mode I (solution seams) deformation. It appears that solution seams can play a similar role to microcracks in localizing a through-going slip plane. This micromechanical model of faulting may be applicable to some other faults and shear zones in host rocks which are prone to pressure solution.  相似文献   

Response to comment: Climatic change and the broad-scale distribution of terrestrial ecosystem complexes     

William R. Emanuel  Herman H. Shugart  Mary Stevenson 《Climatic change》1985,7(4):457-460

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The Late Cenozoic uplift – climate change paradox   总被引：3，自引：0，他引：3  

William W. Hay  Emanuel Soeding  Robert M. DeConto  Christopher N. Wold 《International Journal of Earth Sciences》2002,91(5):746-774

The geologic evidence for worldwide uplift of mountain ranges in the Neogene is ambiguous. Estimates of paleoelevation vary, according to whether they are based on the characteristics of fossil floras, on the masses and grain sizes of eroded sediments, or on calculations of increased thickness of the lithosphere as a result of faulting. Detrital erosion rates can be increased both by increased relief in the drainage basin and by a change to more seasonal rainfall patterns. The geologic record provides no clear answer to the question whether uplift caused the climatic deterioration of the Neogene or whether the changing climate affected the erosion system in such a way as to create an illusion of uplift. We suggest that the spread of C₄ plants in the Late Miocene may have altered both the erosion and climate systems. These changes are responsible for the apparent contradictions between data supporting uplift and those supporting high elevations in the past.  相似文献