GEOLOGY OF GOLD MINERALIZATION IN QEISSAN COUNTY, BLUE NILE STATE, SOUTH EASTERN SUDAN.

Abstract

Abstract High-grade gneisses and low grade volcano-sedimentary rocks underlain the Queissan area. They have been sheared, folded and faulted extensively. Orogenic plutons and anorogenic ring complexes have intruded these successions. A mylonitic quartz feldspathic gneiss (politic), trending northeast to southwest and highly sheared meta-volcanic rocks hosting the auriferous quartz veins. Detailed geochemical study (grid soil sampling, rock chip sampling) has been carried out to determine the anomalous area. Also a few alluvial samples have been taken to trace alluvial gold mineralization. All samples, (soil & rock) are prepared, analyzed and the results are interpreted using different sofiware’s (Minpet, Statistica7, and Surferl0). * "Lllv - aw The gold concentration in soil is rather low grade ranging from .001 to 0.92ppm comparing with those of quartz vein ranging from 0.01 to 4.27ppm (Appendexl &2).The mean calculated for Au in soil was 0.l5ppm, while for rock was 0.0357ppm. The background and threshold values for gold in soil were 0.15 and 0.609ppm, while for rock were 0.0357 and 0.139ppm respectively. Statistical and geochemical analysis (correlation coefficient, factor analysis and cluster analysis) has been used for evaluating the soil and rock data, fiom the evaluation, the following are obtained: >Ni, Co, Cu, are forming one phase as they show correlations patterns extremely similar to each other (Fig.5.36).

>The relation between Au and Ag is positive in rock samples while the it is negative in the soil samples, this may be due to high solubility of silver or silver is amenable to mobilization by weathering. >Au path finder's in rock samples are Ni, Pb, Ag, and Co as they slightly positively correlated (the same cluster; Fig.5.3 6). Au correlations with the other trace elements is negative; Zn, and Cu. That means Au grew at their expense.