A Note on Robust Estimates     

Brian LISTER 《Geostandards and Geoanalytical Research》1984,8(2):171-172

It is well known that the mean can be an unsatisfactory estimator of a true value if data are a poor approximation to a normal distribution or are too few in number for a normal distribution to be adequately delineated. Unfortunately, this knowledge is not always implemented in the evaluation of analytical data. The median may be used occasionally because it is recognised to be less affected by discrepent data. However, there are other 'robust' estimators which can be better than the simple median. This note complements a previous paper by the writer (1).  相似文献   

Assessment of massive sulphide base metal targets using lead isotopes in soils     

Brian L. Gulson 《Journal of Geochemical Exploration》1984,22(1-3)

An assessment is made of the use of lead isotopes in soils as an exploration tool for concealed lead-rich base metal massive sulphide deposits, using four case histories in southeast Australia as examples. Case history 1 covers soil profiles (< 1 m depth) unrelated to mineralization in which the lead isotope ratios exhibit variation with depth and are different from those for massive sulphide deposits. Case history 2 covers six shallow (< 0.4 m depth) profiles from two traverses over the concealed Elura Zn-Pb-Ag deposit in central western New South Wales. For one traverse over completely concealed (blind) sulphides, no isotopic or geochemical signature of the orebody could be detected. In two profiles from the other traverse, for depths of 0.15 m and 0.3–0.45 m, the lead isotopic ratios in the soils are identical with those in the ore (the target isotope ratios). Case history 3 covers two occurrences of Silurian volcanogenic Cu-Zn-Pb mineralization at the Benambra prospect in northeast Victoria. The isotopic ratios for the soils are identical with those in the sulphides and the isotopic signature of the sulphides is also detectable in traverses where no obvious surface anomaly is developed. Case history 4 is an undrilled anomaly in Silurian shales and felsic volcanics where the isotope ratios in B horizon soils are consistent with those of the target isotopic signature.The information from these case histories suggests that the lead isotopic analysis of soils will be a useful exploration tool for concealed mineralization, although at the present stage of research it appears that its application may be limited to shallowly buried (< 100 m) targets or deeply buried targets with an extensive oxidation profile. Its main advantage over conventional geochemical techniques is its ability to discriminate between similar geochemical anomalies arising from different styles of mineralization, as illustrated by an example from Benambra.  相似文献   

Contemporary and palaeo channel patterns and the late quaternary stratigraphy of Cooper Creek,Southwest Queensland,Australia     

Brian R. Rust  Gerald C. Nanson 《地球表面变化过程与地形》1986,11(6):581-590

Braided and anastomosing channels make up two major coexistent networks in the mud-dominated fluvial system of Cooper Creek, Southwest Queensland. The floodplain is characterized by a system of mud braids operative when floods inundate the whole alluvial surface. Anastomosing channels are inset deeper into the floodplain, operate at modern flows, and transport a traction load of sand. Shallow stratigraphic data show that an underlying sand sheet is unrelated to surface channel patterns and was formed by a system of meandering streams. According to preliminary dates based on thermoluminescence, the change from a sand- to mud-dominated fluvial regime took place between 50 000 and 200 000 years B.P., and probably reflects increasing aridity.  相似文献   

Transport and economic development in the less-developed countries: Some reflections on the seaports of Kenya and Tanzania     

Brian Stewart Hoyle Dr. 《GeoJournal》1986,12(3):233-242

The significant role of transport in the development of less-developed countries is widely accepted, but the critical importance of seaports is often under-appreciated. Evidence from the Indian Ocean ports of Kenya and Tanzania is used in this paper to illustrate and support the argument that efficient port operation is an essential contributory factor in the development process.  相似文献   

Re-evaluation of Reference Materials, IGS 21-39     

Brian LISTER 《Geostandards and Geoanalytical Research》1986,10(2):177-181

The 20 ore and concentrate reference materials originally issued by the Institute of Geological Sciences (as it then was) in 1977 have been reevaluated using robust as opposed to classical statistical techniques. The opportunity has also been taken to correct minor errors and to incorporate any new data. One material, the nickel concentrate, IGS 20, has been withdrawn due to incipient oxidation. A total of 24 elemental concentrations in the remaining 19 samples have received revised values.  相似文献   

A Comparison of Methods to Determine K in a Shallow Coastal Aquifer   总被引：5，自引：0，他引：5  

Newton P. Millham  Brian L. Howes 《Ground water》1995,33(1):49-57

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Estimation of meiobenthic nematode diversity by non-specialists     

Colin G. Moore  Scot Mathieson  David J. L. Mills  Brian J. Bett 《Marine pollution bulletin》1987,18(12):646-649

A methodology is presented for the estimation of nematode diversity using Cairns' technique of sequential comparisons. The accuracy and precision of the method are examined and a test presented for the comparison of diversity estimates.  相似文献   

Book review     

Brian F. Farell 《Pure and Applied Geophysics》1987,125(1):183-189

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Book review     

William D. Stuart  Kacper Rybicki  Brian J. Mitchell  Daniel Moos  Jeanne Sauber  Bernard Vonnegut  Ross J. Salawitch  David S. Gutzler 《Pure and Applied Geophysics》1987,125(5):853-855

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A study of intergranular and fissure permeability in Chalk and Permian aquifers,using double-packer injection testing     

Michael Price  Brian Morris  Anne Robertson 《Journal of Hydrology》1982,54(4):401-423

Double-packer injection tests have been carried out in a borehole in the Chalk of Hampshire and a borehole in the Permian Penrith Sandstone of Cumbria, England. The tests have been supplemented by borehole logging and television inspections and by laboratory measurements on cores. A new mathematical treatment has enabled results to be calculated for injection test intervals containing fissures. In both formations, transmissivity immediately around the borehole is dominated by a few major fissures. In the Penrith Sandstone there is good agreement between intergranular hydraulic conductivity measurements and packer-test results in the portions of the borehole which do not contain major fissures. In the Chalk, the packer-test values are always higher than the intergranular measurements, suggesting that some degree of fissuring is present throughout.  相似文献