مصطفی اسماعیلی وردنجانی

Gonharan district is located 26 km east of Daran city in the Sanandaj-Sirjan area and in the Melair-Isfahan metallurgical belt.From the structural point of view, the main fold consists of an anticline with a WNW-ESE trend and an axial inclination towards the ESE and close to its plunge location. A secondary fault with a northwest-southeast trend is also located in the south of the range. The slope of low layers and layering levels in the Lower Cretaceous rock-layer units shows the main concentration with a slight slope towards the ESE (105/16) approximately parallel to the Chinese axis. The faults collected in the study area are divided into four categories according to the direction and mechanism of movement, the category of reverse to transpressional faults with a WNW-ESE direction and a slope towards the NNE with a maximum concentration of ten percent in 50.020 is statistically the most abundant category of the faults are limited. The rock units in the area include limestone and lower Cretaceous marl in the Aptian-Albian scub and Quaternary sediments.Gray limestone with orbitulin in the lower part hosts most of the mineral matter, and marl and clay limestone are placed on it in a continuous and even slope.The mineralized dolomitized sections are mostly related to the reverse fault zones and have a tendency to be approximately parallel to the reverse faults and fracture faces.The dolomitized parts are brittle and brittle, and most of their mineral veins are approximately parallel to the tensile sheets and normal faults.

Gilsonite mineralization in Shak Meydan zone as the most prone zone of Iranian gilsonite mineralization was predominantly hosted by the anidrite part of Asmari Formation (Kalhor member) and Gachsaran Formation. To find the prospect areas of gilsonite mineralization in ShakMeydan zone, the zone was divided into three sub zones in which exploration studies were conducted. We first tried to determine lithologic units using remote sensing processing and to separate rock units using image processing technology. Next, we plotted a 3D structural modeling of the study zone in order to increase the depth precision and to determine the stratigraphic sequence and stratigraphy-structural adaptation. Finally, we detected structural controllers including faults and existing breaks in each sub zone and circular structures prone to translocate minerals. In the sequel, we assigned appropriate weights to applied information layers including geological, tectonic, mineral information and the results of remote sensing studies using analytical hierarchy process (AHP) based on Knowledgeable information and field studies to synthesized the exploratory data in order to introduce the prospect areas with exploration priority.

In hydrogeochemical exploration, the association of elements usually are studied in parallel and prepared their distribution map in order to identify probable anomalies. To do this in Kadkan region, 110 underground water samples are analyzed and R-factor method is applied to identify element distribution. Finally, after statistical processing and determining the number of different factors, 6-factor model was selected, constituting 69.72% total of data variance and reflecting most coincidence with lithological, hydrochemical unites and potential parts of probable mineralization of uranium in region. For determination of anomalies, Factor scores of all data related to region were calculated. Based on this calculation, mineralization factor (4) has strong positive loadings for the uranium, sulfur, molybdenum, selenium elements and fluoride, phosphate, sulphate ion. These elements are the traces elements of uranium deposits, so, can indicate the possible zones of uranium mineralization.

Copper mineralization in the Kadkan sedimentary basin occurs as stratiform and lenticular shape and it seems to be redbed type sediment-hosted copper deposits. Mineralization is mainly dispersed and confined to the red sandstone- marl units with thick interbeds of Eocene-Oligocene conglomerate and includes primary ore minerals: chalcopyrite¡ pyrite and chalcocite and secondary ore minerals: covellite¡ malachite and azurite. By considering the obtained results¡ control of mineralization in these sandstones is in relation with alteration of feldspars¡ concentration of clays and organic matter. Sandstones are medium to thick in thickness¡ bright red to dark gray in color and are classified as arkose¡ lithic arkose and iron bearing fine-grained submature feldspatic litharenite that were deposited in a river-dominated deltaic environment and active margin. The potential of sediment-hosted copper mineralization decreases in the redbeds from east to west (Kadkan) of the region. The results indicate that the copper mineralization in the study area is redbed type sediment-hosted copper.

Uranium becomes soluble and mobile under oxidizing conditions in aqueous environment, and presence of complexing agents with uranium increase this mobility. Existence of such conditions in groundwaters of Ayrakan and Cheshmeh Shotori areas has led to oxidation, solubility and mobility of uranium minerals. Hydrogeochemical study of uranium in the study areas reveals the presence of bicarbonate ion, as the complexing agent with uranium (UO2 (CO3)22-) and icreasing factor of uranium mobility in groundwaters. Calculating the uranium mineral’s saturation index also indicates the super saturation of water samples in pitchblende. The positive saturation index of pitchblende expresses the proper water flow rate to steady-state equilibrium with probable uranium mineralization in depth and indicates that the permeability of groundwaters by porous flow has provided the enough time for their contact with hidden uranium mineralization (uranium ore deposit). As a result of this contact and because of the presence of carbonate complexes, solubility and mobility of uranium has increased. Hydrogeochemical studies, high activity of water and soil samples and all the above evidences indicate the possibility of existence of hidden uranium mineralization in depth and the distance between Ayrakan and the Cheshmeh Shotori areas.

Groundwaters hydrochemistry of Ayrakan and Cheshmeh Shotori areas and geochemistry of rare earth elements، indicate Ayrakan alkali granite as the origin of uranium and other dissolved elements in groundwaters of these areas. Geochemical and hydrogeochemical studies as well as the trend of uranium and thorium transition and mobility in aqueous environments of these areas indicate uranium adsorption by iron hydroxide (goethite) as the deterrent agent against uranium transition and mobility from depth to surface. Gamma-ray spectroscopic study of sediments from Cheshmeh Shotori area by HPGe detector indicates the presence of 226Ra in high contents and as the radioactive nuclide that is the reason for high activity of these sediments. Production of 226Ra from 238U decay، shorter half-life of 226Ra compared to 238U، radium transition by groundwaters from depth to surface as well as hydrogeochemical evidences، all suggest the possibility of existence of hidden uranium deposit and uranium mineralization in depth and the distance between Ayrakan and Cheshmeh Shotori areas.