Apatite/liquid partition coefficients for the rare earth elements and strontium     

E. Bruce Watson  Trevor H. Green 《Earth and Planetary Science Letters》1981

Sixteen sets of apatite/liquid partition coefficients (D^ap/liq) for the rare earth elements (REE; La, Sm, Dy, Lu) and six values for Sr were experimentally determined in natural systems ranging from basanite to granite. The apatite + melt (glass) assemblages were obtained from starting glasses artificially enriched in REE, Sr and fluorapatite components; these were run under dry and hydrous conditions of 7.5–20 kbar and 950–1120°C in a solid-media, piston-cylinder apparatus. An SEM-equipped electron microprobe was used for subsequent measurement of REE and Sr concentrations in coexisting apatites and quenched glasses. The resulting partition coefficient patterns resemble previously determined apatite phenocryst/groundmass concentration ratios in the following respects: (1) the rare earth patterns are uniformly concave downward (i.e., the middle REE are more compatible in apatite than the light and heavy REE); (2) D_REE^ap/liq is much higher for silicic melts than for basic ones; and (3) strontium (and therefore Eu²⁺) is less concentrated by apatite than are the trivalent REE. The effects of both temperature and melt composition on D_REE^ap/liq are systematic and pronounced. At 950°C, for example, a change in melt SiO₂ content from 50 to 68 wt.% causes the average REE partition coefficient to increase from ～7 to ～30. A 130°C increase in temperature, on the other hand, results in a two-fold decrease in D_REE^ap/liq. Partitioning of Sr is insenstitive to changes in melt composition and temperature, and neither the Sr nor the REE partition coefficients appear to be affected by variations in pressure or H₂O content of the melt.The experimentally determined partition coefficients can be used not only in trace element modelling, but also to distinguish apatite phenocrysts from xenocrysts in rocks. Reported apatite megacryst/host basalt REE concentration ratios [12], for example, are considerably higher than the equilibrium partition coefficients, which suggest that in this particular case the apatite is actually xenocrystic.A reversal experiment incorporated in our study yielded diffusion profiles of REE in apatite, from which we extracted a REEαCa interdiffusion coefficient of 2–4×10^?14 cm²/s at 1120°C. Extrapolated downward to crustal temperatures, this low value suggests that complete REE equilibrium between felsic partial melts and residual apatite is rarely established.  相似文献   

Effects of pollution on the benthos of the Firth of Forth     

P.A. Read  K.J. Anderson  J.E. Matthews  P.G. Watson  M.C. Halliday  G.M. Shiells 《Marine pollution bulletin》1983,14(1):12-16

A long-term benthic study has been undertaken in the Firth of Forth to assess the environmental impact of a new sewage treatment scheme for the city of Edinburgh. The Sewage Scheme reduces the suspended solids content of the liquid effluent by approximately 60% and achieves a lowering of the concentration of materials in solution through more efficient dilution and dispersion. Marked changes in the intertidal benthic flora and fauna have been recorded along the Edinburgh coastal zone. These changes have been apparent as the decline and disappearance of populations of certain pollution indicator species and the appearance and establishment of several species previously unrecorded along the more polluted parts of the Edinburgh shoreline. Study of the sublittoral benthos has shown no deleterious effect arising from the new effluent outfall, although there does appear to be some enhancement of the fauna in the area.  相似文献   

Apatite and phosphorus in mantle source regions: An experimental study of apatite/melt equilibria at pressures to 25 kbar   总被引：1，自引：0，他引：1  

E. Bruce Watson 《Earth and Planetary Science Letters》1980,51(2):322-335

The solubility of fluorapatite in a wide variety of basic magmatic liquids was experimentally determined over a range of upper mantle P-T conditions (8–25 kbar, 1275–1350°C). Fluorapatite is stable over the entire range of conditions investigated, but its solubility in melts is variable, depending negatively on SiO₂ content of the melt and positively upon temperature, with relatively little sensitivity to pressure above 8 kbar. At upper mantle pressures and a temperature of 1250°C, molten basalt (50% SiO₂) will dissolve 3–4 wt.% P₂O₅ before saturation in apatite is reached. For a magma 100°C cooler or containing 10 wt.% more SiO₂, apatite saturation occurs at less than 2 wt.% dissolved P₂O₅. The observed high solubility of apatite in basic magmas at their normal near-liquidus temperatures virtually precludes the occurrence of residual apatite in mantle source regions. If relatively low-temperature melting conditions prevail (e.g., 1100°C), as might be possible in H₂O-bearing regions of the upper mantle, apatite could remain in the residue, but only in amounts too small to have significant effects on the rare earth patterns of the liquids.Because of the high solubility of apatite in basic magmas, phosphorus can be confidently treated as an incompatible element in peridotite melting models. Such models, in combination with observed characteristics of basic lavas, indicate that the upper mantle contains ～200 ppm of phosphorus, much less than the chondritic abundance of ～900 ppm.  相似文献   

The tectonic evolution of the Lewisian complex in northern Lewis,Outer Hebrides     

F.B. Davies  R.J. Lisle  J. Watson 《Proceedings of the Geologists' Association. Geologists' Association》1975,86(1):45-IN2

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Ein neuer Windschreiber für kleine Windgeschwindigkeiten     

Reg. Rat Dr. Eduard Huss 《Pure and Applied Geophysics》1953,25(1):83-91

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Review of Short Course in Granitic Pegmatites in Science and Industry: (ed. P. Cerny), Mineralogical Association of Canada, 1982, 555 p., $15.55 Cdn.     

E.Bruce Watson 《Geochimica et cosmochimica acta》1983,47(1):145

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Water quality in the firth of forth     

P. A. Read  K. J. Anderson  J. E. Matthews  P. G. Watson  M. C. Halliday  G. M. Shiells 《Marine pollution bulletin》1982,13(12):421-425

A long-term programme of water quality monitoring has been undertaken in the Firth of Forth to assess the environmental impact of a new sewage treatment scheme for the City of Edinburgh. The sewage scheme reduces the suspended solids content of the liquid effluent by approximately 60% and achieves a lowering of the concentration of materials in solution through more efficient dilution and dispersion. The application of a sea water quality index to water quality data has demonstrated a significant improvement along the Edinburgh coastal zone, resulting mainly from a reduction in suspended solids, biochemical oxygen demand, primary nutrients and faecal contamination. There has been no apparent change in the levels of trace metals.  相似文献   

Interdiffusion of H₂O and CO₂ in metamorphic fluids at ∼490 to 690°C and 1 GPa     

David A. Wark  E.Bruce Watson 《Geochimica et cosmochimica acta》2004,68(12):2693-2698

Interdiffusion coefficients have been determined for H₂O-CO₂ mixtures by quantifying the flux of CO₂ between two fluid-filled chambers in a specially designed piston-cylinder cell. The two chambers, which are maintained at 1.0 GPa and at temperatures differing by ∼100°C, each contain the X_CO2-buffering assemblage calcite + quartz + wollastonite, in H₂O. The positive dependence of X_CO2 on temperature results in a down-temperature, steady-state flux of CO₂ through a capillary tube that connects the two chambers. This flux drives the wollastonite = calcite + quartz equilibrium to the right in the cooler chamber, producing a measurable amount of calcite that is directly related to CO₂-H₂O interdiffusion rates. Diffusivities calculated from seven experiments range from 1.0 × 10⁻⁸ to 6.1 × 10⁻⁸ m²/s for mean capillary temperatures between ∼490 and 690°C. The data set can be approximated by an Arrhenius-type relation: