GEOCHEMISTRY
Year:2016 | Volume:5 | Issue:3|Papers Count:7

Vorazgh copper deposit is located 22km southeast of Qaen in the East Iran tectonic zone. Volcanic rocks of the Vorazgh area with an age of Paleocene-Eocene are mainly composed of lava flows (andesite, trachy-andesite and basaltic trachy-andesite) and pyroclastic rocks (various types of tuffs and agglomerate). Based on major and trace elements geochemical data, these rocks have calc-alkaline affinity. They contain high Al2O3 and low Mg contents. All samples are metaluminous with medium to high K-calc-alkaline nature. High values of Rb, Sr, K, U, Th, Zr and Ba and high ratios of K2O/Rb and FeO/Mg indicate the similarity of these rocks to the rocks of active continental margin magmatic arcs. Depletion of high field strength elements (HFSE) such as Ti, Y and Nb, enrichment of rare earth elements (including La and Ce) and large-ion lithophile elements (LILE) are observed, which are subduction-related characteristics. Depletion of HFSEs like Zr, Ti, Y, Nb and enrichment of Ba, Sr and K show crustal contamination at later stage of magmatic process. Copper sulfide mineralization is the result of hydrothermal fluid percolation through the faults. Mineralization occurs as disseminations and veinlets and is restricted to the upper part of the volcanic assemblage. The deposit characterized by simple paragenesis dominated by chalcocite as the main ore mineral. The mineral association is chalcocite, digenite, covellite, bornite and chalcopyrite. In addition to sulfide minerals, native copper, oxide minerals such as cuprite-tenorite and Cu-carbonate were also found.

In this research, we try to evaluate the heavy metals concentrations in water resources and soil in Sang-Bast area which is located about 40 Km southeast of Mashhad. In this study, 17 sediments and 10 water samples were collected. The Ph of sediments in the study area is alkali. This could be due to the presents of sulfide mineral, such as arsenopyrite, in the sediments. In the study area, soil is very rich in chrome. The presence of this element can be related to ultramafic units (Binalud zone) as well as chromite mines in northern parts of the study area. Pollutant elements in this area is from outside and is not related to Sang-Bast granitoid. Pollution in this area is supported by landfills index and pollution coefficient. Finally, evaluation of water qualify index (WQI) indicates that the quality of water resources in the study area is low; however in the Sang-Bast village is acceptable.

Urmieh-Dokhtar magmatic belt is one of the most important metallogenic substrates in Iran. Several exploratory investigations have been conducted across this belt to explore metals such as copper. Southern part of the belt, in the range of geological Jebal Barez, has been less investigated because of the mountainous and rough topography and also some security confrontation. In this study, a systematic lithogeochemical sampling of rock units of the region in a selected range with an area of 140.28 square kilometers was carried out. 368 samples among the obtained samples were put under ICP chemical analysis. The data obtained were analyzed by geochemical methods in two levels of classical and fractal statistics to produce copper anomaly maps. According to results of the analysis carried out, the highest concentration of copper was 85196 ppm. Based on fractal statistics, the estimated threshold level was 11481 ppm which is indicative of the intensity of the anomalies and hypogene and supergene phases of mineralization in fractal method. Also by manifestation of copper annular abnormality range with being enriched toward the center in the final contour map of copper grade, the estimated anomaly porphyry genesis in the region would be possible.

A number of dark color sills, olivine gabbro-tructolite, olivinegabbro to gabbro-diorite in composition, have intruded into the Rizu formation including alternation of carbonate and volcanic rocks in related to a rift zone, in Central Iran. This area is a part of central Iran micrcontinent and north of Bafq. Petrography and mineralogy study reveal that the sills are change of ultramafic to mafic component and mineralogical data reveal that the olivine+pyroxene+amphibole (brown amphibole) +calcic plagioclase+opaqiue, and intermediate (or sodic) plagioclase+pyroxene and amphibole+opaqiue minerals have formed the olivinegabbro-tructolite to gabbro-diorite rocks, respectively. Petrographic evidence and geochimical data indicate that the mafic sills have alkaline nature. In the related spidergrams reveal LREE elements have positive anomaly and pattern REE is same of Afriqa alkaline rift. The mafic sills have originated of enriched lerzolite with 12% to 14% partial melting.

The Naein ophiolite is located at western part of central Iran micro continent, along Doruneh-Baft fault zone. The frist study area is situated in southern part of Naein ophiolite. The main lithological unit of this colored melange is composed of metamorphosed peridotited of mantle. Harzburgites with various range of serpentinitization are most predominant unit. Serpentinites are found as massive and brecciated bodies in south of the Naein ophiolite. The second study area is located at Khoy-Chalderan ophiolite in north-western Iran, know as the Khangoly area. Metamorphosed mantle peridotites composed of harzburgites are also outstanding in the area and serpentinization is mainly occurred as brecciated type. Serpentinization of peridotites led to formation of light and porous rock which is favered by circulation of later fluids. Hydrothermal fluids rich of CO2-H2O and Mg+2-Ca+2 Ions and ore forming elements could faciliated the formation of listwaenites during the carbonatization of serpentinites. According to field and microscopic observations carbonate-silica mineral aboundances both studied listwaenites can be grouped in three group: carbonate-silica listwaenite and silicic listwaenites. From economic point of view there is anomalous content Hg, Au, Sn, Sb, As, Co, Ni and Cr in the studied listwaenites too. According to petrographic evidences there are noticable amounts of native Au in Naein and Hg in Khangoli ophiolites are most enriched by those elements. It could be deduced that the silicification phase is the main mineralization phase in listwaenites Au and Hg are found as valuable amounts in silicic listwaenites but there is not any economic factor for their extraction now.

Abarkooh playa in center of Iran is considered as part of the Sanandaj-Sirjan structural zone and is located in the north-eastern edge of this zone. The geological features of this area is the variety of lithological parts in these areas and led to the diversity of evaporate deposits in these area. Study of brines in these regions, shows high abnormalities of Potassium at southern part of Playa. XRD study of the southern part of the dried residual brine suggested the existence of mineral such as halite, gypsum, carnallite, tachyhidrite, korshunoviskite. carnallite is one of the most important economic minerals that contain potassium. According to the comparative study of brines in the country, potassium salts in the southern part of Iran was 9 g/lit that is beneficial for exploitation from economically aspect. However, magnesium and iodine salts in these brines are highly enriched.

The Tang-e-Gorak copper deposit, located on the eastern edge of the Sanandaj-Sirjan structural zone, southwestern Iran (45 km northwest of Dehbid) is hosted by the Upper Triassic-Lower Jurassic Koli-Kosh metamorphic complex. Occurrence of two distinct metamorphic-hydrothermal phases resulted in the formation of barren (early stage) and ore-bearing quartz (late stage) veins. The early stage veins are characterized by the occurrence of coarse grain quartz and lack of sulfide minerals. In contrast, the late stage veins mainly consist of microcrystalline quartz and comprise chalcopyrite, pyrite, sphalerite, and galena. Two types of fluid inclusions (FIs), including aqueous (I-type) and carbonic-aqueous (II-type) have been identified in the ore-bearing quartz veins. These FIs is mainly homogenized attemperatures of 174−394oC, with salinities of 1.6−15.2 wt.% NaCl equivalent, and pressures below 4344bar. Physico-chemical changes caused by the interaction of hydrothermal fluids and the metamorphic host rocks indicate that the ore mineralization resulted from a decrease in copper solubility during the fluid immiscibility, cooling, formation of II-types of FIs, break the ligands, decreasing of H2O dielectric constant and an increase in pH. The estimated log f O2 values (-41.77 to -32.73 bar) also fall within the pyrite field (along QFM buffer line), which is consistent with a relatively reduced state of ore-forming fluid during mineralization in the Tang-e-Gorak deposit.