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D. S. Ormerod N. W. Rogers C. J. Hawkesworth 《Contributions to Mineralogy and Petrology》1991,108(3):305-317
The variations in trace element abundances of a suite of alkali-olivine basalts from the Big Pine volcanic field, California,
have been ‘inverted’ following the method of Hofmann and co-workers to obtain source concentration and distribution coefficient
data. The high Mg-numbers and ne-normative mineralogy of these lavas allow a simple correction to be made for fractional crystallisation,
and together with a limited range in 87Sr/86Sr (0.7056–0.7064), suggest derivation from a relatively homogeneous source region. Negative correlations between SiO2 and P2O5, and SiO2 and Rb in the calculated primary magmas imply that both major and trace elements vary in a coherent fashion as a function
of the degree of partial melting. The Big Pine lavas are characterised by high ratios of large-ion lithophile to high-field
strength elements (Ba/Nb>60), and the inverse procedure demonstrates that this reflects source concentrations, as opposed
to a mineralogical control. The calculated mantle source is further characterised by generally high abundances of Sr, Ba,
K, and Th relative to Nb and Ta which imply that incompatible element enrichment of the source occurred above a subduction
zone. A model Sm/Nd age of 1.8 Ga for this enrichment coincides with the regional crustal formation age. Such features imply
that both the major and trace element components of the Big Pine lavas are derived from within lithospheric mantle, perhaps
mobilised by the high geothermal gradients which characterise the extensional environment of the Basin and Range Province.
A comparison with other Cenozoic mafic lavas throughout the western United States suggests that a substantial proportion of
the mantle lithosphere in this area has similar chemical characteristics to the source of the Big Pine lavas. If this is the
case, then it implies that convergent margins represent an important tectonic environment for the formation of lithospheric
mantle. 相似文献
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L. M. Ormerod 《水文研究》1998,12(7):1009-1020
While there has been increased interest in determining sedimentation rates and sources in agricultural and forested catchments in recent years, there have been few studies dealing with urbanized catchments. A study of sedimentation rates and sources within channel and floodplain deposits of a partially urbanized catchment has been undertaken using the 137Cs technique. Results for sedimentation rates showed no particular downstream pattern. This may be partially explained by underestimation of sedimentation rates at some sites by failure to sample the full 137Cs profile, floodplain erosion and deliberate removal of sediment. Evidence of lateral increases in net sedimentation rates with distance from the channel may be explained by increased floodplain erosion at sites closer to the channel and floodplain formation by lateral deposition. Potential sediment sources for the catchment were considered to be forest topsoil, subsurface material and sediments derived from urban areas, which were found to be predominantly subsurface material. Tracing techniques showed an increase in subsurface material for downstream sites, confirming expectations that subsurface material would increase in the downstream direction in response to the direct and indirect effects of urbanization. © 1998 John Wiley & Sons, Ltd. 相似文献
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Timothy Andrew Stojanovic Hugh D. Ormerod Smith Christopher F. Wooldridge 《GeoJournal》2006,65(3):165-176
Thirteen years since the EU Habitats Directive (1992/43/EEC) became a binding legal agreement, this paper considers the implementation
of this important European environmental legislation as it applies to the coastal activities of seaports and harbours. The
paper examines the relationship between environmental legislation and ports policy, and seeks to provide a comprehensive assessment
of the policy and science that has been developed in relation to protected areas and port management. The paper reports the
results of a survey of European port professionals, and their perception of the successes and challenges of the management
regimes that have been established, as well as their opinions on how these have influenced the management within ports. The
paper also provides a detailed examination of the scientific and technical developments with particular regard to dredging
and habitat management in European ports. Key research gaps are identified, including: practical approaches to licensing procedures;
lack of baseline information, especially with regard to in-combination effects; the efficacy of techniques for mitigating
the impacts of dredging; and greater understanding on how more resilient models for collaborative action can be developed.
The paper will be of use to environmental planners, scientists, regulators, conservationists, and port managers, as they consider
how to apply science and management to the sustainable development and environmental protection of coastal areas. 相似文献
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Hard Mode Infrared Spectroscopy (HMIS) is used to correlate the line shifts Δω, the intensity changes ΔA and the variations of spectral line widths Γ of infrared absorption bands with the degree of Al, Si ordering, Q od, in kinetically disordered Na-feldspar. A simple relationship Δω∝ΔA∝ΔΓ∝Q od 2 was found with the phonon band around 650 cm?1 being particularly sensitive to small changes of the degree of Al, Si ordering. It is shown that the average degree of Al, Si order can be determined from HMIS with an accuracy of ca. 8 percent using 50 mg of Na-feldspar. The experimental results agree well with recent X-ray determinations using identical samples. The significance of HMIS for the study of kinetic processes in minerals is explained. 相似文献
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