GEOCHEMISTRY
Year:2016 | Volume:5 | Issue:2|Papers Count:7

The Shahr-e-Babak porphyry copper deposit is located northwest of Kerman Cenozoic magmatic arc. Combining microthermometry, Raman Spectroscopy and laser ablation ICP-MS, fluid inclusions geochemistry studied in three mineralized (Group 1: Meiduk, Chah-Firouzeh and Iju) and three barren (Group 2: Kader, Abdar and Parkam) porphyries in the Shahr-e-Babak copper complex. Hydrothermal alteration has resulted in three stages of mineralization (quartz±sulfide) characterized by vein systems in both groups. These veins are divided into: (1) A and M vein-types (potassic alteration); (2) B vein-type (potassic-sericitic alteration); and (3) D vein-type (propylitic alteration). The main mineralization phase occurred during stages 1 and 2. Mineralization is related to aqueous-carbonic fluids (XCO2>9.6) in group 1 with salinity of 31-44 wt.% NaCl equivalent at temperatures ranging between 374 and 420oC, at pressure>751 bar during fluid unmixing process. In contrast, mineralization is related to homogeneous aqueous fluids (XCO2<7.1) in group 2 and characterized by high salinity (57-76 wt.% NaCl equivalent) at high temperature (570-660oC) and low pressure (<572 bar). Various redox conditions (log fO2) and sharp vapour/brine partition coefficient (DEV/B) of ore-forming metals in the mineralized (log fO2<-29.5; DEV/B=3.8) and barren (log fO2>-32.4; DEV/B=0.32) systems indicate that the majority of metals with the exception of Cu and S, preferentially fractionated into the vapor phase.

The Mio-Pliocene volcanic rocks are exposed in the Southwest of Bostanabad (Arvanehkuh, Biukdagh and Ghapandagh masses) East-Azerbijan province. These rocks formed a part of Uromieh-Dokhtar magmatic belt and consist of andesites and dacites. The rocks studied have porphyritic texture and Phenocrysts wiht plagioclase, sanidine, amphibole, biotite and quartz. Based on geochemical data and multielements pattern, these rocks are medium to high K calc-alkaline suite and show LILE and LREE enriched normalized multi-element patterns, and Nb and Ti deplated. Chondrite normalized REE patterns of the studied volcanic rocks display a decrease from LREE to HREE without any Eu anomaly and formed in subduction zone in an active continental margin. They have higher SiO2, Sr content, Sr/Y and La/Yb ratios and lower MgO, Y and Yb contents in compare to those of normal calc-alkaline volcanic rocks and show characteristics of HSA (high SiO2 adakites). HREE and Y depleted patterns suggest the existence of garnet and amphibole as a residue in the source. The source of these rocks was probably garnet-amphibolite possibly generated during subduction of the Neo-Tethyan oceanic slab beneath the Central Iran zone and in fact are Classic adakite.

The purpose of this study is to investigate the hydrogeochemical processes influencing the quality of ground waters in Rayen plain (northeast Kerman province). So, 23 groundwater samples were taken across the plain and the contents of pH, TDS, EC and alkalinity as well as the concentration of Ca2+, Mg2+, Na+, K+, Cl-, SO42- and HCO3- were determined. In order to study the geochemistry of aquifer and governing hydro geochemical processes, graphical plotting and statistical analyses (PCA, HCA and correlation coefficients) were applied. Plotting chemical data on Gibbs diagram indicates that weathering and evaporation are the main processes controlling water chemistry. Based on hydro geochemical and statistical analyses, the main factor affecting the groundwater quality of studying area is interaction between water and aquifer material (evaporate deposits and marl). Hydro geochemical processes affecting the chemical composition of groundwater include: dissolution of evaporate minerals such as gypsum and halite, dissolution of carbonate minerals, hydrolysis of silicates and ion exchange. Plotting chemical data on Gibss diagram indicates weathering of carbonates and silicates as well as dissolution of evaporate minerals are the main agents controlling groundwater chemistry in this area. According tothis investigation, ion exchange plays an important role on groundwater quality of the studied area. Statistical analyses attest the above-mentioned conclusions.

Darreh-Zanjir deposit is located 30 km southwest of Yazd city at the central Iran structural zone. The Cretaceous limestone is hosting Zn-Pb deposit that generally affected by dolomitization. Mineralization is mainly controlled by fault-fracturing, brecciated zones and dissolution cavities. Mineral assemblage is simple and includes sphalerite, galena, cerussite, smithsonite, hemimorphite, calcite and dolomite. Mineralization occurred mainly in the dolomitized carbonate rocks. Dolomitization took place early in the course of mineralization and is followed by late stage sulfide deposition. Geochemical investigation indicates that the host dolomitic rock is stoichiometric and formed in a reducing environment during burial diagenesis in an open system. Based on geochemical data of dolomitized host rock, the Sr content increased in dolomite relative to mineral deposit, and Sr reduce with increasing distance from deposit. Fluid inclusion petrography on sphalerite displays that almost fluid inclusions are two phases (L>V). Micro thermometry results show that homogenization temperature varies from 80 to 187oC and the salinity ranges between 7 to 20wt% eq. NaCl. Moderate salinity (average 16% NaCl), low temperature (133oC) and absent of clathrate phase is indicator of basinal fluids. The diversity of fluid inclusion results reflects two or more involved fluids with different chemical composition which control mineralization. Based on the results of this research, the Darreh-Zanjir Zn-Pb deposit is comparable to Mississippi Valley Type (MVT) Zn-Pb deposits.

The studied region is Kalghan dam in Bostanabad city of East Azarbaijan province. This research studies entering rivers sediments to Kalghan dam reservoir and rock unites surrounding dam reservoir. For this purpose, 3 sediment samples of ending rivers to dam reservoir and also 15 samples of rock units of dam reservoirs were adopted in 2012. In order to determine heavy metals in sediments, five-step chemical separation approach was used. Obtained results by evaluating enrichment factor (EF) showed that enrichment for arsenic is 3.88 that are in medium level of pollution. In addition, nickel, chromium and molybdenum pollution are in non-polluted range according to EF index, newly developedpollution index (Ipoll), and geo-accumulation index (Igeo). Petrography evaluation of rock units of Kalghan dam reservoir shows Sahand volcanism effect in dominant stone forming and reservoir surrounding in acidic environment. Moreover, various alterations are observed such as phyllic and propylitic in this region. In order to evaluate heavy metal concentrations in rock units of dam reservoir, the adopted samples were sent to laboratory of Alborz Geological Applied Researches Organization for ICP-OED analysis. Investigations have shown that heavy metals concentrations are more than their average value on earth crust. In order to investigate releasing amount of heavy metals from rock units by effect of dewatering the reservoirand transfer it to water resources, 7 samples from rock units were put in polyethylene bottles and simulated. Among the mentioned samples, just sample A7 is able to release heavy and toxic metals such as Mn, Zn, As, Cr, Cu, Pb to water and 4 samples of A2, A3, A5, A7 made fully acidic pH (3-4.5) in simulated water. Obtained results from full analysis of A8 sample shows high level of heavy and toxic metals concentrations in this sample. In addition, ICP-Mass analysis of acidic fountain which was made behind dam spillway and in middle of sample A8 shows that this water is rich of toxic and dangerous metals for human and environment.

The Nehbandan ophiolite complex (NOC) crops out in the Sistan suture zone, which marks the boundary between the Lut and Afghan continental blocks in the east Iran. After field studies in this area, 21 thin sections plus 32 polished sections were prepared for petrological and mineralogical studies, respectively. Furthermore, 6 least-altered and fractured samples were selected for geochemical studies. Major oxides were determined using XRF analyses.9 samples were selected for ICP-OES and Fire Assay analysis.Three different sequences of ophiolitic rocks can be recognized in the NOC: 1) mantle derived peridotites consisting of clinopyroxene- (Cpx-) rich harzburgites and depleted harzburgites; 2) olivine websterite-pyroxenite-gabbronorite sequence; 3) wehrlite-troctolite-cumulate gabbro-basalt sequence. Clinopyroxene bearing harzburgite and harzburgite are common rock types in the area. These rocks underwent strong serpentinization, during sea floor hydrothermal alteration. Listvenite occurs as dykes or pods in the peridotites. In the study area, more sulfide mineralization (chalcopyrite, chalcocite, covellite, digenite and bornite) occurred in the Cpx-rich harzburgite rocks. In addition of sulfide minerals, native copper, oxides minerals such as cuprite-tenorite and carbonate of copper was observed. Petrographic investigation of sulfides in host ultramafics indicated two sulfide generations. In the first generation, primary magmatic sulfide minerals occurred as interstitial disseminations, generally as anhedral grains. In the second generation, sulfide minerals formed as veinlets along host rock fractures. Grade of gold in mineralized samples is high and shows good correlation with copper and iron elements, whereas free mineral of Au wasn't recognized. Considering the extensive outcrops of serpentinized ultramafic rocks and listvenite in the region can be considered the source of Cu, Au and Fe in related to serpentinized ultramafic rocks.

Tikmeh-dash area is located 61 km SE of Tabriz in East Azarbaidjan province, within Alborz-Azarbaidjan structural zone. The main lithologies outcropped in the area are granitic, granodioritic and gabbro-dioritic intrusions of Oligocene age. The occurrence of relatively intense alterations within the granitic rocks at the north of Qezel Ahmad village in the south of Tikmeh-dash led us to investigate on the potential metal anomalies in the context of geochemical exploration. The purpose of this paper is to introduce anomaly zones of Cu and Au, as well as As and Sb as indicators of gold mineralization and to study these geochemical anomalies by filed survey and mineralized samples. For this purpose, 180 samples of -80 mesh portion of stream sediments were collected and sent to AMDEL lab for multi-element analysis. Gold content of the samples was measured by Fire Assay method, while other elements were analyzed by ICP-OES and ICP-MS methods. After determining the initial anomalies, filed survey and altered-mineralized samples were used for controlling study. In the result of interpretation and processing of the obtained data, 4 anomalous zones were identified, including Cu-Au-As-Sb anomalies in the northeastern part of the study area, Cu-Au-Sb anomalies in the northwestern section, As-Au anomalies in southwestern part and Sb anomaly in southeastern section of the Tikmeh-dash sheet. By putting together the obtained results, it was revealed that the main Au and Cu anomalies are related to the felsic-intermediate intrusions of Oligocene age and the fractured and hydrothermally altered zones.