نشریه علوم زمین
پیاپی 96 (تابستان 1394)

Qamsar cobalt deposit is located 26 km south of Kashan, in the middle part of Urumieh-Dokhtar magmatic arc. Exposed rock units in the area include Eocene volcanics, Qom Formation marine sediments and plutonic bodies. The intrusive bodies have quartz-diorite to granodiorite composition as well as porphyry microdiorite. Intruding bodies into the Eocene volcanics and Qom Formation units caused recrystallization and metamorphism and formed assemblages of skarn minerals such as garnet, pyroxene, epidote, tremolite and actinolite. Mineralization occurred as endo-skarn and exo-skarn in massive, vein, brecciated, open space filling and diffusion forms. Magnetite is the main ore mineral and is accompanied by cobaltite, chalcopyrite and pyrite. Fluid inclusion microthermometry studies were performed on prograde stage garnet and pyroxene and retrograde stage quartz. Microthermometry studies show homogenization temperatures 400 to more than 600°C and 180 to 200°C as well as salinities between 12 and 20% and between 5.8 and 11.9% wt NaCl equiv. for prograde and retrograde phases, respectively. Isotopic thermometry on pyrite-chalcopyrite pair minerals gives 241 to 528°C and that for quartz-magnetite pair minerals gives 441 to 549 °C. Sulfur and oxygen isotopic ratios offer magmatic origin which mixed with basinal fluid for this mineralization.

Astarghan area is located in ~ 50 km of north of Tabriz, southeast of Kharvana, East-Azarbaidjn. The area is a part of Gharadagh- Arasbaran metallogenic belt. The most important units in the area is a hypabyssal prophyritic to granular granodioritic intrusive body of Oligo-Miocene and flysch- type sedimentry sequence of limestone, limy sandstone and marl (Paleocene-Eocene). Intrusion of the stock into the sedimentary rocks caused them to convert into a series of metasomatites and contact metamorphic rocks. Geostatistic studies on stream sediments and heavy mineral were done and include data processing, (i.e. normalization, univariate and multivariate analysis), and ultimately preparation of anomaly maps. The correlation coefficients among elements were determined. Elements that show positive correlations with gold are Cu, Hg, Pb, As, Sb, Ag, Bi and Mo. The results of preliminary regional geochemical explorations have led to discovery of two anomalous zones for gold; grade 1 and grade 2. The anomalies were verified by studies on heavy minerals in stream sediments and mineralized and altered samples taken gold anomalous zones. The most important indentified heavy minerals include magnetite, malachite, gold, micaseous hematite, pyrite, galena, cerussite, pyrite- limonite, goethite, limonite, barite, hematite, pyrite- oxide which are affiliated with alteration and mineralzation zones. The major alterations in the area are argillic, sericitic and propylitic developed along the vein’s walls. Field and analytic studies done on samples taken the gold anomalous zones led to identification of epithermal gold veins having over 4.5 ppm gold grade. The concordance of anomaly map with tectonic map and altered zones indicate that the faulted and fractured zones have played a crucial role in creation of gold anomalous zones. The incorporation of these data in the area led to introduction of several anomalous zones belonging to Au, Ag, Cu, As and Pb that can be used as passfinders for epithermal gold.

The purpose of this research is to study active faulting in western part of the Middle East, between Caspian Sea to the east and Mediterranean Sea to the west. This region covers several countries and thus geological maps have different scale and errors in locations. The mismatch between fault traces in geological maps with their actual position on the ground is sometimes up to several hundred meters. The main goal of this study was to prepare continues map of active faults together with seismicity for the entire region of interest. This map also shows the slip rate of the active faults, estimated based on available geodetic measurements (GPS) or other published data. All available information including geological maps, satellite images, topographic data, GPS measurements, and earthquake data were imported into Arc GIS system. The Landsat 7 satellite images were used to correct location of active faults and measuring young offsets along the faults. Most of active faults bound the mountains implying that they control current topography of the region. The earthquakes are more frequent in the Zagros, especially in western part, around junction of the North and East Anatolian faults. This is in contrast with the Dead Sea region lower seismic activity observed. However larger earthquakes are distributed over entire region, though we have more record of historical earthquakes in NW Iran, Eastern Turkey and the Dead Sea region probably related to documentation of historical data rather than occurence of earthquakes. In the eastern Zagros (NW of Iran) total shortening is partitioned into pure strike-slip and thrusting. In the middle part (eastern Turkey) the Zagros trends east-west and most of shortening is taken up by pure thrusting. The Central and Eastern Turkey is dominated by strike-slip faults and rotation of blocks. Shortening across left-lateral and right-lateral systems in eastern Turkey cause the Turkish block to move to the west and subduct in Hellenic trench. Comparing rate of shortening with moment released by earthquakes in Zagros and Caucuses suggest that part of shortening is taking up by creep.