OPTIMIZATION OF SELECTIVE EXTRACTION FOR PROSPECTING IN CONCEALED ORE MINERALIZATION: A CASE STUDY IN THE MOROKWENG IMPACT STRUCTURE, SOUTH AFRICA

Selective extraction can be very useful in exploration geochemistry for investigating the distribution of elements in various mineral phases in regolith. Hydroxylamine hydrochloride leaching as a selective extraction was employed in the Morokweng Impact Structure (MIS) because the Fe-Mn oxides are the major components in aeolian sand and control the distribution patterns of mobile metal ions. This study was aimed at optimizing the hydroxylamine hydrochloride as a selective extraction technique which involves the effects of variable sample weight, grain size fraction, agitation time and concentrations. An attempt will be made to present a summary of analytical data, describe associated element patterns and highlight existing element assemblages that show the strongest reflection of geology / mineralization.

70 Regolith samples were collected and air dried, from the MIS in a range of 90 square kilometers. Each Sample was sieved into three fractions (<75µm, 75-125µm, >125µm) and extracted under the optimized condition with both cold and hot hydroxylamine leach. The inductively coupled plasma mass spectrometry (ICP–MS) is required to measure accurately and precisely for 24 elements e.g. Au, Ni and Platinum Group Elements (PGE) etc. The concentration of hydroxylamine hydrochloride ranges from 0.1M to 0.25M, increasing by 0.05M at a time.

Optimum extraction for aeolian sand in the MIS, 1g fraction of less than 75µm was used for 0.1M hydroxylamine hydrochloride extraction due to the coincidence of bedrock setting and possible mineralization.