Grade-Tonnage Models of Copper Deposits in China

Abstract

Copper-bearing deposits of China are statistically analyzed in terms of ore grade, metal amount and ore tonnage. Ore grade correlates to neither metal amount nor tonnage, while metal amount depends largely on tonnage. Each of grade, metal amount and tonnage shows more or less a lognormal distribution. Based on the ratio of copper in ore value (RCu), Chinese copper deposits are classified into two groups: mainly copper-producing deposits (MC : RCu ≥ 0.5) and accessorily copper-producing deposits (AC : RCu < 0.5). The grade-tonnage relation of MC deposits can be combined by two exponential functions approximating high grade (> 3.0%) and low grade (< 2.0%) parts. The critical copper grade, which is obtained from the low grade part of the relation, is 0.34%. Since less metal amounts are expected with decreasing ore grade below the critical grade, Chinese copper resources are concluded to become pessimistic, because some mines are working with grades close to this critical value. Taking account of the fact that many copper deposits are actually polymetallic, Cu-equivalent grades, which are converted from ratios of metal prices to the copper price, are also introduced. The critical Cu-equivalent grade of MC deposits (0.43%) is also suggesting that Chinese copper resources are pessimistic.