Preliminary Au-W exploration in the southeast of Davijan and West of Samen, 1:100000 sheet of Malayer, Hamedan
The Samen exploration area is located between 48 30' to 48 34' eastern longitudes and 34 11' and 34 15' northern latitudes. The exploration study has done by heavy mineral method in a 56 Km2 wide zone. Geology map was produced for a 77 Km2 wide zone on the scale 1:20000. Four trenches were excavated that totally are 141m long. 47 samples were taken from trenches and 57 samples from rock exposures.
Most of data achieved from 100 heavy mineral samples of which 21 samples contained gold (1 to 7 particles) and 74 samples contained scheelite (0.01 to 153 ppm). Gold didnít correlate with scheelite and pyrite and has negative correlation with pyrite oxide. However, gold had maximum correlation with lead-zinc minerals. Gold particle size ranges between 100 to 1700 microns with an average of 298 microns. North-central portion of Samen has priority for gold and tungsten exploration. One fourth of this area consists of igneous rocks and the other parts include hornfels, schist, marble and little skarn.
Samples taken from the excavated trenches in the skarn of Anjire, show a relatively concentrating of Au, Cu, Zn, Pb, As, Sb, Sn, W and Mo. Maximum and average gold grades are 149 and 19 ppb. For tungsten these values are 399 and 52 ppm. Several rocks samples were analyzed for controlling the anomalies, of which 27 samples were related to the silica veins and skarn that showed distinct enrichment. The high gold samples (523 and 546 ppb) were from silica veins in the east of the area. In zones with greatest data including heavy mineral, mineralized sample and thin section that classified into six zones, there is discorrelation between the grades of copper, lead and zinc. Polished section show evidence of mineralization, but they had not yield gold evidence. It is confirmed that gold and tungsten mineralization is in relation to intrusion of igneous bodies in the carbonate and sandstone rocks. Extensive fracture system as a ring structure and radial faults influence the area and provide a channel for flow of hydrothermal fluids. ICP-Mass analysis data of 17 no altered samples were used for determination of degree of magma oxidation, differentiation, tectonic setting and formation of parent igneous body.
The Samen igneous body has suffered low differentiation. It is magnetic-series granite that can be a moderate producer of Au-Bi mineralization (Bi up to 2130 ppm and Au more than 0.5 ppm). Au/Ag ration in Anjire skarn is 0.02 that reached to 1 in similar deposits in the world. Samen granitoid is an intracontinental (WPG) granite. Skarn and silica veins are favorable mineralized zones. The deposit type can be proximal skarn is low depth. It is suggested to continue the exploration on the scale 1:5000.