Geology

Zarin-Kamar region is located north east of Shahrood (36o37’-36o42’N, 55007’-55012’E). Plutonic rocks in this area belongs to syenite group and their texture is intergranular hypidiomorphic. Volcanic rocks in the area have porphyritic, amygdale intersertal texture. which quartz is also seen among their cavities and porosities. Total concentration of REEs (ΣREE) in the study igneous rocks varies between 450 and 683 ppm. Diagram of Eu/Eu* versus Sr and Eu/Eu* versus Ba show negative anomalies of Eu. This phenomenon as well as Ba and Sr trends show that plagioclase removal has happened during the magma evolution. These rocks have rock has originated from an enriched mantle source. The rate of Dy/Yb in the igneous rocks of the region varies between 1.32 and 2.62. it shows that it stemmed from a garnet lherzolitic source. The rate of (Tb /Yb )N was between 0.97 to 2.25 showing a garnet source. Also other related figures showed that the samples belonged to OIB (Oceanic Island Basalt). The...

Soltan-Meydan basaltic suite (SMBS) with more than 100 km long and about 1000 meter thickness is the most volcanic activity of the early Paleozoic in the eastern Albours’ mountain which was named as one of the Paleozoic formation in the geology of Iran. SMBS is overlaid disconformably by Padeha sandstone (lower Devonian) and is also underlaid disconformably by sandstone of Shir-Gesht formation (Ordovician) therefore its stratigraphy position indicates the Silurian age. Post magmatism processes such as hydrothermal alteration and metasomatism affect the major and mobile trace element concentration hence they overlap with magmatism processes which result in a complicated geochemistry of SMBS.

Geology of Iran shows an ophiolitic belt around the central Iran micro-continent. One of the main ophiolite suites, with ca. 100km long and 15km wide, located northeastern Iran as Sabzevar ophiolite suite. Ultramafic rocks of this ophiolite suite, display a high concentration of chromium (1000-3000 ppm) as a compatible element, especially in pyroxene group minerals. Average Chromium content of this ophiolite suite in peridotites is 2558 ppm , with maximum 4525 ppm (in pyroxenite) and minimum 832 ppm (in dunite). Dunite layers lie underneath of these ultramafic rocks, containing chromite lenses (FeCr 2 O 4) with 20.56wt% Cr 2 O 3. Today, about 10 active mining sites excavate ultramafic rocks for chromite ore mineral and altered ultramafic rocks, serpentinite, dump as unconsolidated gangue materials along stream pathways. There is an unconfined aquifer just southern of this ophiolite range containing detrital altered ultramafic rocks with the high concentration of chromium minerals. In this study 23 groundwater samples, collected from unconfined serpentinite alluvium aquifer that shows cumulative increasing Cr towards south because of increasing residence time, and much more water-rock interactions. Total Cr concentrations in this aquifer are from 12 to 61µg/l, higher than normal level of Cr mentioned by WHO (2µg/l). On the other hand, discharging of chromite mine and mineral processing site, contaminate one of drinking well at Forumad village up to 61µg/l of total chromium. Although trivalent Cr is an essential nutrient, in oxidation conditions with increasing Eh and pH, it changes to chromate (CrO 4 −2) and dichromate (Cr 2 O 7 2-) as dissolved anions which will be toxic and carcinogenic in groundwater. Based on California EPA Office of Environmental Health Hazard Assessment (OEHHA), 7.2% of total Cr is hexavalent. Recent information indicates that hexavalent chromium varies from 50% to 90% of the total chromium in many water supplies.