Negative Geochemical Anomalies and Their Importance in Regional Exploration, Gharahchaman-Duzduzan

Gharahchaman is located inthe Urumieh Dokhtar zone in east Azerbaijan. The area is mostly comprises of intermediate to acidic intrusive and extrusive, Oligocene igneous rocks along with younger sedimentary units. The regional geochemical exploration program with the aim of delineating potential zones in the area were attempted by collecting 394 stream sediment samples, which analyzed for 44 elements. Most of the exploration programs are routinely based on the positive anomalies (+ve) detection and the negative halos (-ve) are rarely considered. The depletion of some pathfinder elements may be related to ore mineralization in the area. Therefore (-ve) halos also can be significant in regional exploration. Conventionally, negative anomalous threshold values have been calculated in the same way as positive one, which causes drawbacks and hinder their application. In this paper an attempt were made to construct integrated models of (-ve) and (+ve) potential maps for detecting optimized geochemical pattern. It can be deduced from this study that the detected significant (-ve) halos, mostly are influenced by syngenetic processes and some are also related to ore bearing solutions. Detecting (-ve) halos of elements such as Sc, Sr, and Na in a particular pattern and in vicinity of (+ve) halos like Au, Cu, Pb, U, Zn are related to base metal mineralization and other important elements in the region. On the basis of combined distribution pattern of elements three models of geochemical anomalies are accompanied each other;1) Overlapping of multi-element (-ve) and (+ve) anomalies like (Rb, Sr); 2) Peripheral regional multi element (-ve) anomalies that surround (+ve) anomalies like (-ve) halo of Sc around (+ve) halos of Ce, Rb/K and (–ve) halo of Sr with Ba/Sr ratio, felsic and chloritic zones in the area; 3) Discriminated Indices model of (-ve) and (+ve) halos of (Mo-Sr), (U-Sr), (Cu-Sr).This indicates that the combined study of (+ve) and (-ve) halos in regional geochemical exploration studies can be more significant in detecting hidden ore deposits. The distribution pattern of felsic and chloritic additive composite alteration zones match with Model2, which mutually correspond to (+ve) and (-ve) anomalies of Au and Sr respectively. Ultimately the results revealed deficiency in study of only positively concentration of elements along with faulted zones, whereas the present study emphasis that modeling corresponding of (-ve) and (+ve) halos along with results obtained from composite additive indices confirms NW-SE concentration of ore mineralization in the area.