Mineral adequacy, exploration success, and mineral policy in the United States

Data on copper reserves, recent discovery rates, and historical tonnage-grade relations indicate that the U.S. can be approximately self-sufficient in copper to the year 2000 by mining grades similar to those presently being mined, and given reasonable exploration efforts, the U.S. can supply its demand for about 100 years by mining inferred tonnages above 0.1% Cu. However, recent price trends and the increased cost of mining lower grade ore will increase the price of copper at a rate faster than the general inflation rate, and may lead to significant imports because of their cheaper price.Compilation of the discovery history for copper shows that the Hubbert Gaussian curve is not applicable to predict copper reserves, and may not be applicable for other commodities.A compilation of the value of base and precious metal deposits discovered since 1940, along with meager data on cost and manpower used in exploration, indicates very little decrease in exploration effectiveness over the 40-year interval, in contrast to oil and uranium. Collection of better data on expenditures for metallic mineral exploration is recommended.     

CDP seismic sections of the western Beaufort continental margin

The continental rise, slope, and shelf in the Beaufort Sea off northern Alaska were surveyed with 5600 km of common-depth-point (CDP) seismic data by the U.S. Geological Survey in 1977. The lower continental rise consists of a wedge of at least 4.5 km of low-velocity, generally flat-lying, parallel-bedded sediments. Slump-related diapiric folds, probably cored by shale, occur on the upper rise and lower slope. The observed minimum depth to oceanic basement in the Canada Basin requires an age for this basin of at least 120 m.y., assuming it to be floored by oceanic crust with a subsidence history similar to that of the Atlantic and Pacific oceans.     

Overturning effects in stiffened building frames

In this paper seismically induced overturning effects in stiffened building frames are studied by examining the response of two structures: a 20-storey ‘core wall’ reinforced concrete frame and a 10-storey steel braced frame. The excitations utilized in the study are the 1971 Pacoima Dam S16E Record and the 1940 El Centro N-S Record magnified by a factor of two. Non-linear effects of the following types are considered: plastic hinging of beams and columns, yielding and/or buckling of bracing members and transient uplift of portions of the structures from the foundation. In particular, comparisions are made between response with unlimited base overturning capacity assumed and response with dead-weight overturning resistance only. Providing dead-weight overturning resistance only is shown to significantly reduce seismic load levels, with relatively little or no loss in drift control. Ductility demand in these stiffened frames is shown to be limited, when transient uplift is allowed, to the link beams connecting stiffened and unstiffened portions of the structures.     

The geochemistry of mercury in sedimentary rocks and soils in Pennsylvania

The mercury contents of 11 sandstone, 11 shale and 6 limestone samples from Pennsylvania average 7, 23 and 9 ppb Hg, respectively, which is lower than the values for sedimentary rocks reported in the literature. The differences may arise because many of the reported high values are from regions characterized by more mineralization and volcanism than is present in central Pennsylvania. The lowest values found for shale and sandstone in Pennsylvania (0.4 and 0.5 ppb Hg, respectively) are lower by an order of magnitude than the lowest previously reported values. The mercury content of sedimentary rocks varies markedly due to the effects of volcanism, organic material and sulfur in reducing environments, iron and manganese oxides in oxidizing environments, diagenesis, hydrothermal processes, and the thermal history of the rock.Soils in Pennsylvania have much greater amounts of mercury than their parent rocks even after taking into account possible residual concentration, suggesting that mercury is added to the soils from an outside source. Rain is the major source of mercury absorbed by the soil. A portion of the absorbed mercury returns to the atmosphere, establishing a rain-soil-atmosphere mercury cycle. The general enrichment of mercury in soils and sediments compared to rocks is supported by the observation that the mercury content of rain is greater than freshwater. The much higher values of mercury in unconsolidated sediments compared to sedimentary rocks suggest that mercury is lost during diagenesis.Man's contribution of mercury to the surface environment is nearly equal to the natural contribution. Industrial loss contributes more than 65 per cent of man's total, and the contribution of fossil fuel consumption is small, although it may be locally important. The implications of mercury loss and absorption by soils may be an important factor in concentrating mercury in crops and other living matter, especially near industrialized areas.     

Paleoclimatological records of the Great Ghost Lake in Taiwan

Distinctive white laminations appear in the black sediments of the Great Ghost Lake in Taiwan. Compared with the black sediments, these white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S and N/S ratios, and with organic matter characterized by the phytoplanktons. It suggests that they may be deposited in cooler and drier periods. The organic matter of the black sediments was mainly from land plants, suggesting deposition under warmer and wetter climates. Major white laminations appear in 0 AD, 500 AD, 700 AD, 900 AD, 1 350 AD, 1 500 AD, etc., and correspond to the periods of cold/dry and frequent dust storms from the historical and natural records of China or Peru. These seem to reflect large-scale climatic changes.     

Spatial redistribution of the Torres Strait Islander population: a preliminary analysis

Until World War II, Torres Strait Islanders were restricted in their distribution to the Torres Strait itself. Since that time, migration to the Australian mainland has contributed to a significant redistribution with the majority of Torres Strait Islanders now resident in the major cities of eastern Australia. Despite the importance of migration in determining Torres Strait Islander involvement in the labour market, study of their population movement has been limited and such analysis as does exist is unsystematic, spatially restricted and generally dated. This paper is therefore an attempt to draw from the literature what is known about the redistribution of Torres Strait Islanders and to supplement this with an analysis of the most recently available internal migration data from the 1986 and 1991 censuses. While it appears that the search for employment was an important stimulant for migration in the past, this is probably less so now, not least because Torres Strait Islanders now find themselves located in places where labour markets exist. No evidence is found from the 1986 Census to support the idea of sustained redistribution away from areas of long standing settlement in northern Queensland. This contrasts intuitively with distribution patterns revealed by the 1991 Census, and the extent to which this discrepancy is due to migration or census error raises a critical issue in the analysis of Islander population change.     

Entry of pollutants from seawater into the spermatophore and spermatozoa of the giant octopus of the North Pacific

Copulation in the giant octopus of the North Pacific, Octopus dofleini martini, takes place in seawater and lasts 2 h. During that time the spermatophore undergoes the spermatophoric reaction resulting in the transfer of spermatozoa to the female. Methylmercuric chloride and several organochlorine pollutants enter readily the spermatophore during the sphermatophoric reaction and accumulate in the spermatozoa at surprisingly high concentrations, in some instances exceeding many fold the levels in the seawater.     

Horizontal cleavage in southeastern Sinai: the case for a coaxial strain history

A horizontal cleavage and associated lineation are developed in a low-pressure igneous-related metamorphic terrain in southestern Sinai. The cleavage is axial planar to recumbent folds, which are never large, and varies from a smooth slaty cleavage to a discrete crenulation cleavage. Structural evidence on the macro, meso and microscales suggests that cleavage and lineation were formed during irrotational extension and not by simple shear. Estimates of strain using the March method indicate 50–70% vertical shortening. This structural evidence when combined with metamorphic and age data strongly suggests that the cleavage was formed by the forceful emplacement of a pluton at depth.