Mineral resource assessment using the unit regional value concept

The resources produced in some specific region may be measured in terms of the amount of resource produced and its value: if these measures are cumulated over the period of production and prorated over the area of a region. say in km², they yield the unit regional weight (u.r.w.) and unit regional value (u.r.v.) of resources produced in the region. Frequency distributions of u.r.w. and u.r.v. may be constructed by measuring them on a number of regions; for the 50 states in the U.S.A. the logarithm of u.r.v. is normally distributed and hence different regions may be ranked on this scale using the mean and standard deviation intervals as calibration levels. The u.r.w. and u.r.v. of the 50 states in the U.S.A., may be used as a reference background for such comparisons. The average u.r.v. for all resources produced over the period 1905 to 1972 for the 48 coterminous states is 54.954 (1967) U.S. (S). Alaska, over the same period, possess a u.r.v. of 2738 (1967) U.S. (S) and so its u.r.v. is some 20 times less: this yeilds a conservative measure of the future potential for development of the mineral resources of Alaska. This unconditional estimate of the u.r.v. of Alaska is based solely on its area and one way of refining this estimate is to introduce geology as a conditioning variable. The geological composition of each state in the U.S.A. was point counted from available geological maps of the states and the proportions of different rock units were expressed in terms of 65 standardized time-petrographic units. The accumulated data for ail 50 states yields a diversity (or richness=s−1) of 51 rocktypes: the range in value for the individual states extends from an s−1=1 in Louisiana to s−1=25 in California. Alaska is about seventh among the states in geological diversity and groups with Arizona, Montana. Utah. Nevada, and Washington. However, the dominant rocktype in Alaska is the detrital high-rank graywacke and this characteristic eliminates all but Nevada as a geologically comparable state. New Zealand also possesses similar geological characteristics. The diversity of mineral resources produced in each region may also be standardized and measured in a similar manner as richness=s−1. It has been found that there is a linear association between mineral resource diversity (Y) and the variety of geological roccktypes (X): the degree of common association between these two variables isr ²=80%. This relationship may now be used as predictor equation and we can calculate the expected value for Alaska as s−1=45 against an observed mincral resource variety of s−1=27. Since Nevada (s−1=49) and New Zealand (s−1=36) both possess much higher resource diversity than Alaska it is likely that the extra resources produced in these two regions should be present in Alaska. This permits us to pinpoint, first. the mineral resource sectors, such as constructional materials. fuels. metals. precious metals, and nonmetals, which are underproduced. By returning to the frequency distributions of u.r.v. (and u.r.w.) of the individual commodities which are likely to occur in Alaska, it is possible to estimate both what new resources may be expected and. very approximately. how much more of the resources already produced may be obtained in the future in Alaska. The annual value of the resources of Alaska from 1880 to 1972 may be treated as a time series and projections of future value may be made under different scenarios. This past history clearly emphasizes that the annual value of the mineral resources produced in Alaska is essentially determined by the “degree of commitment” given to investment in their development. This paper was presented at the International Geological Correlation Program (IGCP) Project 98: “Standards for Computer Applications ia Resource Studies” held at Taita Hills, Kenya, November 8–15, 1977. Par variable régionalisée. nous entendons une fonction d'espace, dont valeur varie d'un lieu à l'autre avec une certaine apparance de continuité, sans qu'il soit en général possible d'en représenter la variation par une loi mathèmatique extrapolable… Une teneur, dans un gisement minier, est une variable régionalisée.