Nuclear ''Metalog'' grade logging in mineral deposits

A technique, termed the Metalog, using prompt gamma emissions from neutron capture processes has been developed and successfully employed for nuclear grade logging in lateritic nickel, porphyry copper and coal deposits. Based on field results, the following conclusions are drawn. (i) In nickel laterites, (a) the constituents nickel, iron and silica can be determined simultaneously with average relative standard errors of: <5% of the nickel grade for >1%Ni, <4% of the iron grade for >10%Fe, and <4% of the silica grade for >15%SiO2. The correlation of the Metalog versus bulk (chemical) analyses is significantly better than that for Metalog versus core (chemical) analyses. These results demonstrate the capability of this nuclear technique for bulk assaying. (b) Logging over one-metre sections, approximately 45m of borehole can be logged in one 10-h shift. (ii) In porphyry copper deposits, copper can be determined at levels above 0.2% using a logging speed of 37m/h and averaging over 3-m sections of the borehole. The error is <10% of the copper content. (iii) In coal deposits, averaging over 0.5m sections at a speed of 7m/h, sulphur can be determined with an error of <8% of the sulphur grade for >1%S. Delineation of coal seams at speeds up to 9m/h can be achieved. (author)