Multivariate statistical techniques applied to pisolitic laterite geochemistry at Golden Grove, Western Australia     

Raymond E. Smith  N.A. Campbell  R. Litchfield 《Journal of Geochemical Exploration》1984,22(1-3)

Multivariate statistical procedures are applied to pisolitic laterite geochemistry in a study of the Golden Grove massive sulphide district. The objective is to optimize identification of geochemical anomalies caused by base metal mineral deposits.The statistical approach used in this paper depends upon geochemical data for appropriate reference groups (or training sets) being available. The target group consists of orientation data from pisolitic laterite about the Gossan Hill Cu-Zn massive sulphide deposit. A group representing background sequence was selected by combining three subareas in a geochemically quiet part of the prospective acid volcano-sedimentary sequence.A multi-element allocation procedure was set up using data from the reference groups. The exploration samples are then allocated, one sample at a time, to either one of the reference group categories, using the probability of group membership. A map showing the relative probability values for each sample site is the final product for interpretation, aided by ancillary use of an index of typicality.The allocation procedures were carried out using different element combinations, these being based on a procedure for subset selection to give maximum separation of reference groups, and on geochemical insight. Whilst many versions of the allocation procedure gave positive identification of the anomaly related to the blind Scuddles Cu-Zn deposit, allocation using only Cu, Pb, Zn and Ag did not. The results emphasize the importance of pathfinder elements in geochemical studies in weathered terrain.The allocation procedure using the most appropriate element combinations provided more positive identification of the main areas of known mineralization than had the previously used empirically derived methods of Smith and Perdrix (1983). The formal allocation procedure has the following additional advantages: results are not markedly affected by a very high value for any single element since robust procedures are incorporated into the analysis; better discrimination appears to be possible for weaker anomalies; separation of target from background can be optimized by formal calculations instead of by trial and error; and better suppression of background variation results.  相似文献   

Rates of sulfur dioxide and particle emissions from White Island volcano,New Zealand,and an estimate of the total flux of major gaseous species     

William I. Rose  Raymond L. Chuan  Werner F. Giggenbach  Philip R. Kyle  Robert B. Symonds 《Bulletin of Volcanology》1986,48(4):181-188

Airborne correlation spectrometry (COSPEC) was used to measure the rate of SO₂ emission at White Island on three dates, i.e., November 1983, 1230 ± 300 t/d; November 1984, 320 ± 120 t/d; and January 1985, 350 ± 150 t/d (t = metric tons). The lower emission rates are likely to reflect the long-term emission rates, whereas the November 1983 rate probably reflects conditions prior to the eruption of December 1983. The particle flux in the White Island plume, as determined with a quartz crystal microbalance/cascade in November 1983, was 1.3 t/d, unusually low for volcanic plumes. The observed plume particles, as shown from scanning electron microscopy, include halite, native sulfur, and silicates and are broadly similar to other volcanic plumes.Gas analyses from high-temperature volcanic fumaroles collected from June 1982 through November 1984 werde used together with the COSPEC data to estimate the flux of other gas species from White Island. The rates estimated are indicative of the long-term volcanic emission, i.e., 8000–9000 t/d H₂O, 900–1000 t/d CO₂, 70–80 t/d HCl, 1.5–2 t/d HF, and about 0.2 t/d NH₃. The long-term thermal power output at White Island is estimated at about 400 MW.  相似文献   

Infrared vibrational spectra of Beta-Phase Mg2SiO4 and Co2SiO4 to Pressures of 27 GPa     

Quentin Williams  Raymond Jeanloz  M. Akaogi 《Physics and Chemistry of Minerals》1986,13(3):141-145

Infrared absorption spectra of the high-pressure polymorphs β-Mg₂SiO₄ and β-Co₂SiO₄ have been measured between 0 and 27 GPa at room temperature. Grüneisen parameters determined for 11 modes of β-Mg₂SiO₄ (frequencies of 300 to 1,050 cm^?1) and 5 modes of β-Co₂SiO₄ (490 to 1,050 cm^?1) range between 0.8 and 1.9. Averaging the mid-infrared spectroscopic data for β-Mg₂SiO₄ yields an average Grüneisen parameter of 1.3 (±0.1), in good agreement with the high-temperature thermodynamic value of 1.35. Similarly, we find a value of 1.05 (±0.2) for the average spectroscopic Grüneisen parameter of β-Co₂SiO₄.  相似文献   

A 140 Ma K/Ar age for the Msissi norite (Morocco): new geochemical and paleomagnetic data     

E. Salmon  R. Montigny  J.B. Edel  A. Pique  R. Thuizat  M. Westphal 《Earth and Planetary Science Letters》1987,81(2-3)

The plutonic intrusion known as the Msissi norite (southern Morocco), which represents the single paleomagnetic reference pole for Africa in Devonian times, has been investigated. This Msissi intrusion is in fact an alkaline gabbro, a teschenite. K/Ar dating on separate biotites yields a 140 Ma age. Paleomagnetic results reveal a large scatter of isolated directions that precludes the computation of any Late Jurassic/Early Cretaceous paleopole. All these data lead us to reject this intrusion as a reference pole for the Devonian in Africa. The paleoposition of Africa in Devonian times remains, therefore, largely unknown.  相似文献   

Reviews in mineralogy,volume 10, characterization of metamorphism through mineral equilibria: edited by John M. Ferry,Mineralogical Society of America, 1982, 397 pp. $8.00     

Raymond Joesten 《Geochimica et cosmochimica acta》1983,47(7):1335-1336

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Impacts of Present and Future Climate Change and Climate Variability on Agriculture in the Temperate Regions: North America   总被引：2，自引：0，他引：2  

Raymond P. Motha  Wolfgang Baier 《Climatic change》2005,70(1-2):137-164

The potential impact of climate variability and climate change on agricultural production in the United States and Canada varies generally by latitude. Largest reductions are projected in southern crop areas due to increased temperatures and reduced water availability. A longer growing season and projected increases in CO₂ may enhance crop yields in northern growing areas. Major factors in these scenarios analyzes are increased drought tendencies and more extreme weather events, both of which are detrimental to agriculture. Increasing competition for water between agriculture and non-agricultural users also focuses attention on water management issues. Agriculture also has impact on the greenhouse gas balance. Forests and soils are natural sinks for CO₂. Removal of forests and changes in land use, associated with the conversion from rural to urban domains, alters these natural sinks. Agricultural livestock and rice cultivation are leading contributors to methane emission into the atmosphere. The application of fertilizers is also a significant contributor to nitrous oxide emission into the atmosphere. Thus, efficient management strategies in agriculture can play an important role in managing the sources and sinks of greenhouse gases. Forest and land management can be effective tools in mitigating the greenhouse effect.  相似文献   

Gas exchange in rivers and estuaries: Choosing a gas transfer velocity   总被引：12，自引：0，他引：12  

Peter A. Raymond  Jonathan J. Cole 《Estuaries and Coasts》2001,24(2):312-317

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Mapping of benthic enrichment patterns in Narragansett Bay,Rhode Island     

Raymond M. Valente  Donald C. Rhoads  Joseph D. Germano  Victor J. Cabelli 《Estuaries and Coasts》1992,15(1):1-17

A synoptic reconnaissance survey was performed over a five-day period in August 1988 to assess benthic habitat quality throughout Narragansett Bay, Rhode Island, using REMOTS^® sediment-profile photography and analysis in combination with measurements of the levels ofClostridium perfringens spores (a fecal indicator) in sediments. Three main areas of degraded benthic habitat quality related to either excessive organic enrichment or physical disturbance were identified based solely on the REMOTS^® analysis: the Providence River Reach, Greenwich Bay and its associated coves and harbors, and an area located along the southwest side of Prudence Island. Sediments at many stations in these areas exhibited shallow apparent redox-potential discontinuity (RPD) depths, high apparent oxygen demand, and low-order benthic successional stages. ElevatedClostridium perfringens spore counts in surface sediments were attributed to inputs from wastewater treatment facilities. The highest spore counts occurred at the head of the bay, where wastewater treatment discharges and associated combined sewer overflows are numerous. Using data from the REMOTS^® analysis and the sediment inventory ofC. perfringens spores, a distinction was made between organic enrichment of the bottom from sewage, versus nonsewage enrichment or physical disturbance. The combination of techniques employed in this investigation could be used to design more efficient monitoring programs to assess eutrophication effects in estuaries and determine the effectiveness of regulatory or management initiatives to reduce organic overenrichment of benthic habitats.  相似文献   

Computation of 5-day temperature normals in western Europe and the Mediterranean area     

Kurt Bender  Ulrich Chorus  Raymond Nybro  Robert Sanderson  Ingrid Weiss 《Pure and Applied Geophysics》1957,38(1):265-285

Summary UsingCraddock's method of representing the annual temperature variation by a two-term harmonic form fitted to monthly means, the harmonic coefficients of 63 stations in western Europe and around the Mediterranean Sea, as well as the 5-day normals for 24 Mediterranean stations, were computed and tabulated. In addition, some of the harmonic coefficients were charted and isoplethed, showing very distinctly the influence of continentality and topography. These charts, together withCraddock's charts for northern and northwestern Europe, provide fairly complete coverage of Europe and the Mediterranean area.This paper was prepared in the offices of the Technical Support Division of the 2d Weather Wing, United States Air Force, as a matter of routine business. The information contained herein was presented at the 5th Meeting of the Italian Society of Geophysics and Meteorology by Dr.Ingrid Weiss (Genoa: 23–25 April 1957). Since the paper is of general interest to all meteorologists of the Mediterranean area, it is published here with the permission of the originating agency as «Mémoire No. 3 du Centre International de Recherches sur la Météorologie de la Méditerranée (CIRMM)».  相似文献   

Trace element geochemistry and genesis of the Pindos ophiolite suite     

R. Montigny  H. Bougault  Y. Bottinga  C.J. Allegre 《Geochimica et cosmochimica acta》1973,37(9):2135-2147

Abundances of major elements, rare earth elements, transition metals, alkali metals and alkaline earth metals have been measured in a representative suite of samples from the Pindos (Greece) ophiolitic complex. Our data indicate that the igneous members of the complex are genetically related. An ocean floor origin of the complex is suggested.  相似文献