Re-evaluation of Reference Materials, IGS 21-39

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 One material, the nickel concentrate, IGS 20, has been withdrawn due to incipient oxidation.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.     

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

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.     

Sulphur uptake by salt grasses,mangroves, and seagrasses in anaerobic sediments

Stable sulfur isotope analyses show that rooted estuarine plants growing in anoxic sediments incorporate substantial amounts of ³⁴S-depleted sulfides, or oxidation products thereof. In roots, this incorporation predominates over sulfate uptake from interstitial porewater. Either the plants incorporate normally toxic sulfides, or they are creating and using a specialized nutrient pool of oxidized sulfides at the root-sediment interface.     

Spontaneous potential corrections for groundwater salinity calculations — Carter County,Oklahoma, U.S.A.

The spontaneous potential log was used to compute the thickness and distribution of groundwater with a total dissolved solids (TDS) of less than 1000 mg l^?1 for Carter County, Oklahoma. To compute accurate salinities from the spontaneous potential in high-resistivity zones, empirical correction factors had to be developed and applied. For the formations present equivalent water resistivity vs. water resistivity curves were developed from chemical analyses and digitized. Water resistivity vs. TDS curves were also developed and digitized. The existing empirical thin-bed corrections were curve-fit with equations and applied to each zone. Except in beds less than 3.65 m thick they had little effect.It was found that after applying the thin-bed corrections used by logging companies, the computed TDS was a function of resistivity of the mud filtrate at 24°C. An empirical relationship was developed between spontaneous potential and resistivity of the mud filtrate at 24°C, using well logs of beds with known water chemistry. This relationship was entered as a correction equation into a computer program developed by the author. The correction is necessary since the voltage drop in a freshwater formation is greater than predicted by earlier electric analog modeling, and the spontaneous potential is less than the static spontaneous potential. Testing of the correction factors shows that in a formation with TDS of ～750 mg l^?1 the average error decreases from ～37% to 10%.A data set of 704 well logs was built with data from each freshwater zone from the base of the regolith to a depth where the TDS was greater than 10,000 mg l^?1. The TDS was computed for each zone. Two maps were prepared from the results; an isopach of the formations with TDS of less than 1000 mg l^?1, and a depth to the base of the water with TDS of 1000 mg l^?1.     

Water pollution: A view from ecology

The results of various methods typically used by governments to assess the environmental impact of potential pollutants do not give comparable results. It is argued that the cause is not the assessment techniques themselves but rather the paradigm of ecology from which they spring.     

Banded iron formations in Proterozoic greenstone belts: Call for further studies

Banded iron formations occur in greenstone belts in which volcanic rocks are predominant. Greenstone belts are not restricted to the Archaean (>2500 Ma), as is commonly perceived, but they continued to form, albeit in lesser abundance, in the Proterozoic. Thus, banded iron formations which are closely associated with volcanic sequences occur in several well-documented early-mid Proterozoic greenstone belts. Examples are the Yavapai belts at Jerome in Arizona, the Trans-Amazonian belts in Guiana, and the Dalma belts of the Singhbhum region of NE India. Stratigraphic and sedimentological studies are needed to establish the similarities and differences of these iron formations with those in Archaean greenstone belts, and with the banded iron formations which were common in cratonic-shelf environments in the early-mid Proterozoic.