Document Type : Original Research Paper
Authors
1 M.Sc., Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran
2 Assistant Professor, Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran
3 Ph. D., Geochemical Exploration Group, Geological Survey of Iran, Tehran, Iran
4 M.Sc., Geochemical Exploration Group, Geological Survey of Iran, Tehran, Iran
Abstract
BLEGmethod is one ofmodern methodsusedfor goldgeochemicalexplorationstudies.Themethod has helped to locate many low grade gold deposits. The significant change of the method compared to common geochemical exploration methods is to use of large volumes ofsamples regardless of their sizeandlow densityof sampling.In order to evaluate the efficiency of the BLEG geochemical method with stream sediment method, 1:100000 SiahRud sheet was chosen in geological region of Azarbaijan in a district that geological map and geochemical exploration has already been carried out.The study area is 1850 km2, located in a mountainous area of northwest Iran in the Eastern-Azarbaijan province (NW of Ahar city).The rock units of the area consist mainly of the Upper Cretaceous limestone and flysch complex, Oligocene intrusive bodies and Eocene volcanic-sedimentary rocks. The Oligocene intrusive bodies are the most important igneous unit in the area.In this project, 168 BLEG samples and 103 stream sediment samples (silt samples) were prepared and studied. The range gold values in BLEG samples are from 0.1 to20 ppb, and in the stream sediment samples from 3 to459 ppb.The results ofsampling and analysis present four districts with high anomalous degrees: 1) Anigh-GharehChilar district, 2) Namnegh district, 3) Eshtobin district, and 4) Andrian or MiveRud district. Analysis ofthe stream sedimentsamplesrepresentshigh value of Cu andAu. Correlation of the elements in stream sediments taken from the Anigh-GharehChilar district represents high correlation of gold with arsenic, copper and leads elements. Copper also shows a high correlation with molybdenum, which is in accordance with mineralization of this area.
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