Geochemical Survey in the 1:25000 sheet of Meshkinshahr-II
Executive: Naser Abedian
Technical executive: Ebrahim Shahin
Supervisor: Abbas Maqsoudi
Consultant: Kan-Azin Consulting Engineers
The study area is located in the Ardebil province, 12 Km away from the SW of Meshkinshahr and 1.5 Km away from SW of Agh-Boulagh. This area was a favorable anomaly that identified in the 1:100000 geochemical survey of the Meshkinshahr sheet. The aim of current project is to do a more detailed study on the anomaly.
From geological viewpoint, volcanic rocks such as andesite and trachy-andesite, intrusive rocks such as monzonite and quartz monzonite are dominant in the area.
Based on the previous studies and airborne geomagnetic data, a sampling network was designed. The sampling density was 6 and 2 samples per square kilometer for stream sediment and heavy mineral methods, respectively. 515 stream sediment samples and 184 heavy mineral samples were taken. The stream sediment samples were 120-mesh. The samples were analyzed in the Applied Geoscience Research Center of Iran by ES (for Au, Pb, Ag, Sn), AF (for Hg, As, Sb, Bi), POL (for W, Mo) and ICP-OES (for other elements and oxides) methods. Error estimation that took placed on the base of 26 duplicate samples and 39 analyzed elements. The result of error estimation shows that only As, Sb, W, Mo, Al2O3, MgO, Be, Co, P have less than 20% error. The error of Pb, Ag, Sn, Hg, Bi, Sc, Y, Yb is less than 50%, in grade range that is 10 times of censored limit. So their error is acceptable. Other elements and oxides such as Mn, S, Sr, Zr, Nb, Ba, La, Ce, Cr, Cu, Li, Au, Ni, Rb, Ti, V, Na2O has more than 20% error that is not good for assessment proposes.
Data processing and uni-variable and multi-variable analyses confirmed the association between As-Sb-Au; Ag-Mo-Pb and Cu-Ba that support the hydrothermal mineralization.
Anomaly maps were prepared. Heavy mineral data was processed and distribution map of various minerals was produced. Existence of gold, malachite, molybdenite and jarosite was favorable is this zone. Ultimately, after compilation of stream-sediment and heavy mineral data, 11 anomalies were identified.
In the filed checking step, 82 samples including 62 element analysis samples, 6 XRD samples, 5 thin polished section samples and 9 thin section samples were studied. Extensive alterations such as propylitic and argillic observed in the area. Silicic and carbonatic veins contain pyrite, chalcopyrite and malachite. In the samples taken from superficial malachite exposures in the south and southwest, 7 samples had more than 50 ppb gold and 18 samples had more than 200 ppm Cu. Two favorable zones were introduced that totally have 28.33 Sq Km areal extension. These zones should be studied in more detail.