فصلنامه زمین شناسی اقتصادی
سال هفتم شماره 1 (پیاپی 12، بهار و تابستان 1394)

The Shahrestanak Mn deposit is located in southern Qom province، 12 km southwest of the city of Kahak. Based on geological-structural divisions of Iran، the deposit belongs to central volcanic belt or Urumieh-Dokhtar zone. The Venarch deposit is one the most important known manganese deposits in Iran. The Sharestanak and Venarch deposits are spatially and temporally related to each other، and have similar geology، mineral texture and structure، host rocks، relationships with faults، and depositional environment. So، their magmatism and deposition conditions can be related to each other. Since no systematic study on the Shahrestanak deposit had been performed before discussing its geological and geochemical characteristics، here it is being attempted to study the geology، petrography، geochemistry of major، minor and trace elements، and Rare Earth Elements (REE) of ore، to distinguish the depositional environments and genesis of this deposit and to compare REE of ore in this deposit with other deposits. Sampling and method of study: Fourteen samples of manganese ore were selected for geochemical study and analyzing of major، minor، trace elements and REE by ICP-AES and ICP-MS and were sent to SGS Co.، Toronto. Detection limits for major elements and trace elements are 0. 01% and 0. 05ppm، respectively.

The deposit is characterized by various lithology and stratigraphy units، consist of: 1) Middle to -Upper Eocene volcano-sedimentary rocks، 2) Oligocene lower red conglomerate and sandstone، 3) Oligo-Miocene limestone and marl (Qom Formation)، and 4) Eocene and Lower Miocene basic to intermediate dykes. The most abundant minerals of the deposit are braunite، hausmannite، pyrolusite، and manganite. Evidences such as high Mn/Fe (11. 33) and Si/Al (4. 86) ratios، low contents of trace elements specially Co (11. 40 ppm)، Ni (24 ppm)، Cu (81. 85 ppm)، and Ce، with high amounts of SiO2، Mn، Fe، Ba، Zn، As and Sr، all represent hydrothermal processes. It seems that hydrogenous processes have not had significant role on the genesis of the Shahrestanak Mn deposit. During deposition of Fe and Mn from hydrothermal solution، they separated from each other and produced different Fe/Mn ratios in sedimentary exhalative deposit (SEDEX). The Fe/Mn ratios are 5. 7 to 40. 35 (ave.، 11. 33). Very high and very low ratios of Fe/Mn can be interpreted as fractionation and separation of these two elements from transportation during hydrothermal activities and mineralization. So، high Fe/Mn ratios here can be considered as in submarine hydrothermal deposits. Cann et al. (Cann et al.، 1977) suggested that Fe/Mn ratios in volcano-sedimentary and hydrothermal deposits are so variable and characteristic. Hydrothermal deposits are in close relationships with ferruginous silica gel which itself formed from submarine hydrothermal outpouring and discharging of metals in marine sediments. So، Si wt. % versus Al wt. % is high in exhalative activities. The average Si/Al ratio is 4. 86 in the Shahrestanak deposit which is in the range of hydrothermal deposits (SEDEX). Nicholson (Nicholson، 1992) suggested Na versus Mg content diagram for distinction between fresh water، shallow and deep marine environments. Bonatti et al. (Bonatti et al.، 1992) introduced Fe-Mn- (Co+Cu+Ni) *10 ternary diagram for distinction between marine sedimentary and hydrothermal Fe-Mn deposit. According to this diagram، hydrothermal oxides depleted in Ni، Cu، Co and zinc relative to sedimentary-marine deposits. Nicholson (Nicholson، 1992) suggested that hydrothermal Mn deposit distinguished with Zn، V، Mo، Cd، Li، Sr، Sb، Pb، Cu، Ba، and As and sedimentary deposit with enrichment in Ni، Cu، Co، Sr، Mg، Ca، Na and K. Hydrogenetic ferromanganese deposit has higher enrichment of Ni، Cu and Co relative to hydrothermal (exhalative) deposit. Low contents of Cu، Co and Ni indicate low input of these elements from hydrothermal activities and derivation of Zn from hydrothermal source. As (Co/Zn) - (Co+Cu+Ni) diagram، the samples from Shahrestanak deposit show close similarities with hydrothermal deposits which in turn show common genesis. Using Pb versus Zn diagram، dubhite (deposits derived from previous mineralized sequence) can be distinguished from other Mn oxide (hydrothermal or supergene) deposits. The dubhite deposits have high Pb/Zn ratios and more than 1 percent Pb and Zn contents. Meanwhile، other types of deposits like shallow marine deposit، hot springs، SEDEX، weathered deposits have lower contents of Pb and Zn. The Shahrestanak deposit has more similarities with SEDEX and shallow marine deposits.

Geological and geochemical evidences show that deposition of ore occurred by submarine hydrothermal activities in Neotethys oceanic basin during Middle to Upper Eocene in calcareous tuff with intercalation of micrite and calcareous limestone. For the genesis of the deposit، it can be stated that the pillow basalt and andesite lavas were leached by hydrothermal activities and Mn، Fe، Si، Ba، Sr and As entered in sedimentary basin by exhalative – volcanic activities through faults، then by regression of the sea and forming oxidizing condition، primary oxide-hydroxide Mn-minerals are deposited.

The Ferezneh prospect area is one of the eastern anomalies of Khaf’s Sangan iron mine. The Sangan mines complex is located within the Khaf-Kashmar-Bardeskan volcano-plutonic and metallogenic belt in northeastern Iran. The Sangan mine is the largest Fe skarn in western Asia، having a proven reserve of over 1000 Mt iron ore @ 53% Fe (Golmohammadi et al.، 2015) and consisting of three parts; western، central and eastern Sangan، each part including several anomalies. In this study، Ferezneh (North and West) prospect area which is an eastern anomaly of the Sangan iron ore is discussed. Ferezneh anomaly is located in 60°36''7 «- 60°34''27» E and 34°30''47 «- 34°29''46» N، 35 km south of the city of Taybad، 10 km southeast of Karat and 1. 5 km southwest of Ferezneh village. The purpose of this study was to prepare a geologic map for separation and identification of the intrusions، determining their relationships with mineralization، distinguishing the type of mineralization، mineralogy، petrology and geochemistry of the mineral deposits، and finally their relationship with other major Sangan’s deposits.

In order to achieve the objectives of the study: 1- 140 thin sections of the intrusive rocks، marble limestone and dolomite، as well as 40 polished sections of ore were taken in an area of 9. 5 km2. Mineralogy and mineralization studies were performed in the Economic Geology Laboratory of Ferdowsi University of Mashhad. 2- A few samples were selected for X-ray diffraction analysis in order to ensure accuracy of mineralogical studies and were sent to Binalood Laboratory in Tehran. 3- In addition to major and minor elements geochemistry study of the ores، 10 samples were sent to East Amitis Laboratory in Mashhad for XRF analysis and also to Canada S. G. S Laboratory for ICP-MS analysis. Discussion and

Mineralization in the Ferezneh prospect area was limited to iron and manganese oxides in the form of massive and stratabound in recrystallized limestone that followed the structure pattern. Iron oxides often include goethite and hematite; while manganese oxides are pyrolusite، psilomelane and lesser amounts of cryptomelane. Small spots of rutile are rarely seen. The gangue minerals are dolomite، calcite and cryptocrystalline quartz. XRD analysis shows that iron and manganese oxides are the only metallic minerals.

Heavy metals are the most toxic pollutants in aquatic ecosystems. This contamination can result from the release of heavy metal elements during alteration and weathering of ultramafic and mafic rocks (ophiolite zones). Among the important metals and pollutants in the ophiolite; chromium، cobalt، nickel، iron، magnesium، manganese، zinc and copper could be noted. Basically، a mass of serpentine consists of serpentine، amphibole، talc، chlorite، magnetite، and the remainder of olivine، pyroxene and spinel (Kil et al.، 2010). In such areas، the prevailing cold climate، during the serpentinization، chloritization and epidotiization، the activity of the solvent، such as chloride، fluoride، carbonates، sulfide، sulfosalt would be able to import the elements such as magnesium and iron، copper and zinc into the soil and groundwater. The study area is located in northwestern Iran. This area is located in the northwest of the city of Khoy. Because of the proximity to the north and northwest Khoy plains with ophiolite rocks، the soil of this region could possibly show the potential of contamination with heavy metals. Due to the toxicity and disease of unauthorized grades of these elements in groundwater in the study area، this study is focused on the more contaminated groundwater of the areas.

In this study، over a period of 5 days، sampling from 42 water sources، including fountains، aqueducts، wells، piezometers and wells in operation، was performed. The container was washed with acid and then rinsed 3 times with the water sample. The pH and temperature of the water in the samples was measured in the field. Then to each of the samples was taken from 2 to 5 ml of concentrated nitric acid (This causes that the metal elements would not adsorbed or precipitated by these particles) and pH of the samples was measured with litmus paper to reach level 2. This was done to ensure the consolidation of the water samples. Analysis of samples carried out in the chemistry laboratory of the University of Urmia. All water sampling procedures were performed based on standard protocols (SMEWW، 2010). The maximum concentration of heavy metal contamination of drinking water with EPA، WHO and national standards were compared. In this study، the chemical analysis of heavy metals، were used by graphite furnace atomic absorption spectrometry (at ppb) for the elements Cu، Mg، Fe and Zn. Concentration of the heavy metals in acidified water samples (pH value of 2)، using a flame atomic absorption spectrophotometer were analyzed.

There are enormous amounts of Fe and magnesium in groundwater from the north and northwest Khoy plain، and the amount of Cu and zinc are in the normal range in water resources. The source of iron and magnesium in the groundwater of the study area is ultramafic and mafic rocks of the Khoy ophiolite complex. Weathering of ultramafic and mafic igneous rocks such as peridotite، olivine basalt، gabbro and pillow lava and then soil formation، high concentrations of the elements Mg and Fe were transferred to soil. Ferromagnesian olivine is formed Mg2+ and Fe2+ ions and tetrahedral silicon. If sufficient amount of Mg2+ and Fe3+ ions combine with silicon and oxygen، silicon into the soil، forms silicic acid (H4SiO4)، or magnesium or iron smectite (clay minerals) (Alexander et al.، 2007). Several types of pyroxene are more stable than olivine. Orthopyroxene during weathering decompose into talc and smectite. Magnesite (MgCO3) is present in some serpentine soils. With respect to the empirical relationship (Kierczak et al.، 2007) and based on temperature and rainfall، the study area with a drought index of 12. 48 places in the category of semi-arid-cold climate between 10 and 19. 9. Temperature changes in the condition cause weathering and leaching of serpentine soils، and subsequently can remove large amounts of magnesium. Weathering and leaching serpentine soils، releases immediately magnesium and its concentration in soil decreases. As a result، the concentration of the element in the water increases.

Based on the charts and maps of iron، magnesium، zinc and copper contaminations، it is found that the concentrations of Fe and Mg in the north and northwest Khoy plain are higher than the permissible limit for drinking water. In some parts of the sample، the concentrations of Cu and Zn are exceeded WHO. However، based on EPA standard، the amount of copper is less than the limit. On the basis of three criteria: EPA، WHO and national standards، except for the village Ghez Ghaleh، zinc concentration is below the standard. According to the geological map of Khoy، the Khoy ophiolite complex containing mafic rocks and ultramafic is a source of iron and magnesium in groundwater. Acknowledgements: Editor of the Journal of Economic Geology، Professor Mohammad Hassan Karimpour and reviewers of this article are acknowledged for their unwavering assistance. Also، the authors thank Deputy of Research of the University of Urmia for the support required for this study.

Several valuable calcite deposits are located in Ghare-Gheshlagh، south basin of Urmia Lake، NW Iran. Ghare-Gheshlagh area is situated in the northern part of tectono-sedimentary unit، forming NW part of Tertiary Sanandaj-Sirjan geological belt (Stocklin and Nabavi، 1972). The predominant rock types of the area include light color limestones (Qom Formation) and Quaternary alluviums and underlined dolomite in depth (Eftekharnejhad، 1973). The thickness of these units varies between 10 cm and 6 meters and up to some hundred meters in length. In the present study، the effect of geochemical parameters responsible for precipitating calcite from the carbonate aqueous fluids is interpreted by the TOPSIS method to find the most preferable sampling sites and geochemical data.

A total of 20 samples were taken from a NE-SW trending profile including 15 calcites of fresh surface outcrops (5 samples per each colored calcite units) in order to determine the nature of the rocks. The mineral assemblages were analyzed by optical methods in combination with XRD powder diffraction analysis. Major elements were determined by X-Ray Fluorescence Spectrometry (XRF)، trace and rare earth elements were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in Geological Survey of Iran.

The abundances of trace elements were normalized to the continental crust values (Taylor and McLennan، 1981). The green calcite revealed enrichment in Rb and Sr، while green and white calcite were enriched in U. The U enrichment in the green calcite indicates the reduction condition of deposition. Incompatible elements such as Ba، Th، Nb and P depleted in all calcites. Varying the Sr/Ba value between 3. 18 and 5. 21% indicates the continental deposition environment and non-magmatic waters as well (Cheng et al.، 2013). The Sr2+ content of calcites varies from 123 to 427 ppm، indicates suitable condition for calcite precipitation. Eu anomalies for green، white and pink calcites were varied 0. 087، 0. 247 and 0. 997 respectively. The low amounts of Eu anomaly for green and white calcites attributed to low rock/fluid ratio (Nesbitt et al.، 1990) and relatively more pH value (Cheng et al.، 2013)، however، increasing the Eu anomaly may be due to high rock/fluid ratio and less pH value. Ce anomalies are 0. 0241، 0. 0113 and 0. 0131 in pink، white and green calcites respectively. The most negative Ce anomaly values show that calcite have precipitated under reduction conditions (Nesbitt et al.، 1990).

Recently، multiple attributes decision-making techniques help scientist to solve decision-making problems related to various controlling factors (Zhijun et al.، 2013). One of these techniques is a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) which is a quantitative weighted method (Momenei 2006). The identified criteria are CaO abundant in solution (C1)، Eu anomaly (C2)، Ce anomaly (C3)، Sr abundant (C4) and volume (C5). The Index-Rock matrix also includes A1، A2 and A3 alternatives; as pink، green and white calcite respectively. The weighted normalized decision matrix can be calculated by multiplying the normalized evaluation matrix with its associated weight to obtain the result. The result show that Eu anomaly، volume، Sr abundant and Ce anomaly in order have higher role to investigate the geochemical study of area. Calculation of the relative closeness to the ideal solution (Cl *) for pink، green and white calcites are 0. 837، 0. 445 and 0. 157 respectively. It can be deduced that the most preferable calcite to be sampled for investigating geochemically are pink and green calcites.

The study area is located in central part of the Khaf- Kashmar-Bardeskan belt which is volcano-plutonic belt at the north of the Dorouneh fault in the north of Lut block. The north of the Lut block is affected by tectonic rotation and subduction processes which occur in the east of Iran (Tirrul et al.، 1983). The magmatism of Lut block begins in Jurassic and continues in Tertiary (Aghanabati، 1995). Karimpour (Karimpour، 2006) pointed out the Khaf-Kashmar-Bardeskan belt has significant potential for IOCG type mineralization such as Kuh-e-Zar، Tannurjeh، and Sangan (Karimpour، 2006; Mazloumi، 2009). The data gathered on the I-type intrusive rocks include their field geology، petrography، U–Pb zircon dating and Sr–Nd isotope and also alteration and mineralization in the study area.

- Preparation of 150 thin sections of rock samples for study of petrography and alteration of the intrusive rocks. - Magnetic susceptibility measuring of intrusive rocks. - U-Pb dating in zircon of I-type intrusive rocks by Laser-Ablation Multi Collector ICP-MS method. - Sr-Nd analysis on 5 samples of I-type intrusive rocks by Multi-Collector Thermal Ionization Mass Spectrometer (TIMS) VG Sector 54 instrument. - Mineralography and paragenetic studies of ore-bearing quartz veins and geochemical analysis for 28 samples. - Production of the geology، alteration and mineralization maps by scale: 1:20000 in GIS.

Oblique subduction in southern America initiated an arc-parallel fault and shear zones in the back of continental magmatic arc (Sillitoe، 2003). Because of this event، pull-apart basins were formed and high-K to shoshonitic calc-alkalineI- and A-type magmatism occur (Sillitoe، 2003). Most important deposits accompany with this magmatism are Au-Cu deposits types and Fe-Skarns (Sillitoe، 2003). We have similar scenario to Neotethys subduction. Khaf-Kashmar-Bardeskan volcano-plutonic belt is located between Neotethys suture and Alborz- Sabzevar Back- arc (Asiabanha and Foden، 2012). We suggest Khaf-Kashmar-Bardeskan volcano-plutonic belt forms at the arc-parallel fault and shear zones in the back of continental magmatic arc. In the basis of all evidences (Shear zone system، high-K to shoshonitic calc-alkaline I- and A-type magmatism، typical alterations related to upper zones of IOCG deposits and IOCG mineralization)، we suggest IOCG (Au-Cu) mineralization in Kashmar.

On the basis of former regional (Muller and Walter، 1983) and local structural studies (this research)، regional compression causes sinistral strike-slip movements of Dorouneh and Taknar faults، shear zone، pull-apart and Riedel fractures (P، R and R'' types) in the study area. These events cause magma intrusion and circulation of hydrothermal fluids. On the basis of geology، geochemistry and magnetic susceptibility measuring of intrusive rocks، several high K to shoshonitic calc-alkaline to alkaline I-type and one A-type intrusive rocks are intruded in Kashmar area. Swarm dykes are the youngest and the agent for alteration and mineralization. U-Pb dating related to quartz monzonite body (preventative sample for I-type intrusive rocks which are older than A-type series) show 40 Ma (Middle Eocene) for this rock group in Kashmar. The mean of initial 87Sr/86Sr and 143Nd/144Nd are 0. 705-0. 707 and 0. 5135-0. 5126 for I-type series، respectively. εNd (i) amounts for I-type series are in negative to positive limit ranges (-1. 65 to 1. 33). These amounts show subduction source with contamination to continental crust. Two type alteration and mineralization occur in Kashmar: 1) primary alterations (advanced argillic+ sericite+ silicification) which are synchronous with sulfide base-metal veins (chalcopyrite+ pyrite± galena± quartz± chloride) and 2) Lateral alterations (carbonatization+ Fe-oxides+ silicification+ epidotization+ chloride+ sericite+ barite) which are synchronous with IOCG veins (specularite+ chalcopyrite+ pyrite± galena± sphalerite± barite± siderite ± etc.). Primary centralized and sulfide base-metal veins in crosscutting points between Dorouneh fault and minor faults. Bahariyeh، Uchpalang and Sarsefidal areas are located in these crosscutting points. Tourmaline (demorterite) ±chloride fill the fractures in the intrusive rocks of southern part of area next to the Dorouneh fault occasionally. Lateral alteration synchronous with IOCG veins occur in Kamarmard area. Geochemical data of all veins show Cu، Pb، Zn anomalies (>1%) in two type veins، Au anomalies (to about 15 ppm) only in IOCG veins، Mn anomalies in two type veins and Ba anomalies in IOCG veins. Alteration and mineralization in the world-class IOCG deposits identified by sodic-calcic and potassic (hydrothermal actinolite and biotite) and magnetite± gold in deep parts (Sillitoe، 2003) and advanced argillic+ pyrite+ sericite+ toulrmaline (demorterite) in shallow parts (Ray and Dick، 2002). Generally، alteration in the study area is similar to shallow parts of world-class IOCG deposits. Tanourjeh is a IOCG deposit next to the northwest of the study area. In Tanourjeh، the gold-bearing magnetite is synchronous to potassic alteration (hydrothermal biotite) and other alterations are advanced argillic، silicification and sericite. These characteristics are similar to deep parts of world-class IOCG deposits. Bahariyeh، Uchpalang and Sarsefidal have similarities to alterations in Tanourjeh. Considering Tanourjeh lie in the lower level rather to Bahariyeh، Uchpalang and Sarsefidal، we believe they erosion surface in Tanourjeh is lower. Kamarmard lies in the highest erosion surface in the study area. Alterations and Mineralization as similar to Kuh e Zar IOCG deposit (specularite+chalcopyrite+gold) which is next to the Kamarmard area in Northeast of study area. In Bahariyeh-Uchpalang areas we can see only one IOCG vein but in Sarsefidal area exist several IOCG vein. Because of current surface in Bahariyeh-Uchpalang areas is lower than Sarsefidal current surface in Sarsefidal is lower than Kamarmard، we believe that IOCG vein in Bahariyeh-Uchpalang area have been eroded. We Believe to two circulation of oxidized Fe-bearing hydrothermal fluid in Kashmar. During the first circulation، Potassic alteration and gold-bearing magnetite bodies in depth and primary alterations with sulfide base-metal veins was formed. At the second circulation، lateral alterations and IOCG veins was formed at the near of paleo-surface.

Hornblende-bearing gabbroic rocks are quite common in subduction-related magmatic suites and considered to represent magmatic differentiation process in arc magmas (Heliker، 1995; Hickey-Vargas et al.، 1995; Mandal and Ray، 2012). The presence of hornblende as an important mineral phase in gabbroic rocks of subduction zone has been considered either as an early crystallizing mineral from water-bearing mafic magmas (Beard and Borgia 1989; Mandal and Ray، 2012) or as a product of reaction of early crystallized minerals (olivine، pyroxene and plagioclase) and water-rich evolved melt/aqueous fluid (Costa et al.، 2002; Mandal and Ray، 2012). The careful study of petrology and geochemistry of hornblende-bearing gabbroic rocks from Chahak area، of Neoproterozoic age، can provide important information about their petrogenesis. Because of the special characteristics of Chahak hornblende gabbros according to their age and their situation in the main structural units of Iran، their study can present critical keys for the knowledge of geological history of Iran specially central Iran zone. This study carried out in two parts including field and laboratory works. Sampling and structural studies were carried out during field work. Geological map for the study area was also prepared. 65 thin and polished thin sections for petrographical purpose were studied. Major oxides، rare earth elements and trace elements were analyzed for 4 samples (92P-1، 92P-3، B1and B6) from hornblende gabbros on the basis of 4AB1 method using ICP-MS of ACME Laboratory from Canada. In addition، major oxides of three hornblende gabbro samples (89P-62، 89P-59 and 89P-46) were used from Partovifar (Partovifar، 2012). Fariman metamorphic terrains، of Proterozoic age، consist of metamorphosed sedimentary and igneous (plutonic and volcanic) rocks. Hornblende gabbros of the study area include plagioclase، hornblende، biotite pyroxene and olivine as major minerals and apatite، ilmenite and magnetite as minor minerals. In many examples، hornblende and biotite can be seen as corona textures around plagioclase، pyroxene and olivine، while plagioclase، pyroxene and olivine show obviously corrosion features. This can be considered to be formed by the reaction of early formed crystals with aqueous fluid/evolved melt. In some cases، amphiboles show rhythmic overgrowths. The rhythmic amphibole overgrowths represent deep-seated crystallization in a volatile-rich magma under conditions of high but varying gas pressure. In the study area، the most dominant texture of the hornblende gabbros is hypidiomorphic granular، but intergranular and porphyric textures are common too. Based on geochemical data from major and minor elements، studied rocks belong to tholeiite series with meta–aluminous nature. The geochemical behavior of main elements of the studied rocks reveals the normal trend of differentiation in their magma. Chondrite-normalized REE diagram of hornblende gabbros indicates an obvious enrichment of LREE in compare with HREE. MORB-normalized spider diagrams indicate variable enrichment in LILE and depletion in high field strength elements (HFSE). Primitive mantle-normalized spider diagram show negative anomaly for Nb and Zr. Gabbros from southeast of Fariman have an island arc tholeiite nature and based on trace element diagrams، they formed as a result of 3 to 10% partial melting of a garnet lherzolite source. The mineralogy، texture and geochemistry of the studied rocks show striking similarities with gabbroic rocks of subduction zone developed in supra subduction zone of arc-marginal basin setting.

Mesgar iron occurrence is located in northwestern part of the Central Iran، 115 km south of Zanjan. Although there is a sequence of volcanic-pyroclastic rocks accompanied by iron mineralization، no detailed works had been conducted in the area. The present paper provides an overview of the geological framework، the mineralization characteristics، and the results of geochemical study of the Mesgar iron occurrence with an application to the ore genesis. Identification of these characteristics can be used as a model for exploration of this type of iron mineralization in the Central Iran and elsewhere.

Detailed field work has been carried out at different scales in the Mesgar area. About 16 polished thin and thin sections from host rocks and mineralized and altered zones were studied by conventional petrographic and mineralogic methods at the Department of Geology، University of Zanjan. In addition، a total of 3 samples from least-altered volcanic host rocks and 2 samples from ore zones from the Mesgar occurrence were analyzed by ICP-MS and ICP-OES for whole-rock major and trace elements and REE compositions at the Zarazma Laboratories، Tehran، Iran.

Based on field observation، rock units exposed in the Mesgar area consist of Miocene sedimentary rocks and volcanic-pyroclastic units (Rādfar et al.، 2005). The pyroclastic units consist of volcanic breccia and agglomerate. They lie concordantly on the Miocene sedimentary units، and are in turn concordantly overlain by andesitic basalt lavas. The lavas show porphyritic texture consisting of plagioclase (up to 3 mm in size) and pyroxene phenocrysts set in a fine-grained to glassy groundmass. Seriate، cumulophyric، glomeroporphyritic and trachytic textures are also observed. Iron mineralization occurs as vein and lens-shaped bodies within and along the contacts of pyroclastic (footwall) and andesitic basalt lavas (hanging wall). The veins reach up to 150 m in length and average 1. 5 m in width، reaching a maximum of 3 m. Two stages of mineralization identified at Mesgar. Stage-1 mineralization formed before the hydrothermal brecciation events. This stage is characterized by disseminated fine-grained hematite in the andesitic basalt lavas. Clasts of stage-1 mineralization have been recognized in the hydrothermal breccias of stage-2. Stage-2 is represented by quartz، hematite and chlorite veins and breccias cement. This stage contains abundant hematite، together with minor magnetite and chalcopyrite. The hydrothermal alteration assemblages at Mesgar grade from proximal quartz and chlorite to distal sericite and chlorite-calcite. The quartz and chlorite alteration types are spatially and temporally closely associated with iron mineralization. The sericite and chlorite-calcite alterations mark the outer limit of the hydrothermal system. Supergene alteration (kaolinite) is commonly focused along joints and fractures. The ore minerals at Mesgar formed as vein and hydrothermal breccia cements، and show vein-veinlet، massive، brecciated، clastic and disseminated textures. Hematite is the main ore which is accompanied by minor magnetite and chalcopyrite. Goethite is a supergene mineral. Quartz and chlorite are present in the gangue minerals that represent vein-veinlet، vug infill، colloform، cockade and crustiform textures. The Mesgar volcanic host rocks are characterized by LILE and LREE enrichment coupled with HFSE depletion. They have positive U، Th and Pb and negative Ba، Nb، P and Ti anomalies. Our geochemical data indicate a calc-alkaline affinity for the volcanic rocks (Kuster and Harms، 1998; Ulmer، 2001)، and suggest that they originated from mantle melts contaminated by the crustal materials (Chappell and White، 1974; Miyashiro، 1977; Harris et al.، 1986). The ore zones show lower concentrations of REE، except Ce، relative to fresh volcanic host rocks. LREE are more depleted than HREE. These signatures indicate high rock-fluid interaction in Mesgar. Comparison of the geological، mineralogical، geochemical، textural and structural characteristics of the Mesgar occurrence with different types of iron deposits reveals that iron mineralization at Mesgar is originally formed as volcano-sedimentary، and then reconcentrated as vein mineralization by hydrothermal fluids (Barker، 1995; Marschik and Fontbote، 2001، Shahidi et al.، 2012).

Pyrite oxidation and acid mine drainage (AMD) are the serious environmental problems associated with the mining activities in sulphide ores. The rate of pyrite oxidation is governed by the availability of oxygen (Borden، 2003). Therefore، the identifying oxygen supplying mechanism is one of the most important issues related to the environmental assessment of waste rock dumps (Cathles and Apps، 1975; Jaynes et al.، 1984; Davis and Ritchie، 1986). Although comprehensive researches were performed on the mathematical description of oxygen transport processes using the numerical modeling (Morin et al.، 1988; Blowes et al.، 1991; Wunderly et al.، 1986; Elberling et al.، 1994; Jannesar Malakooti et al.، 2014)، so far، the interactions between these processes and geochemical and mineralogical characteristics has not been studied especially in waste rock dumps. Therefore the main objective of this study is to identify the evidences for knowing the oxygen transport mechanisms in the waste dumps and also، its role in intensity of pyrite oxidation. It is expected that such these structural studies could be useful for better understanding of dominant processes in numerical modeling and also providing environmental management strategies in the study area and other sites by similar characteristics.

In this study، thirty solid samples were collected from six excavated trenches in the waste rock dumps No. 19 and 31 of the Sarcheshmeh porphyry copper mine. Collected samples were studied using several methods such as XRD، ASTM-D2492، paste pH and grain size distribution. The results obtained from these methods were used with the field observations in order to characterize some detail information about oxygen supplying mechanisms for oxidation reactions in the waste rock dumps.

The main minerals found by the XRD analysis were quartz and muscovite which were present in all samples. Pyrite، orthose، albite، and chlorite were also present in some samples. The carbonate content as the major neutralizing agent was zero in all samples. Due to the presence of sulfide minerals، mainly as pyrite، and also lack of any carbonate minerals، the AMD generation from the Sarcheshmeh waste rocks during the weathering reactions is predictable. At the Sarcheshmeh mine waste، several secondary minerals such as butlerite، jarosite and gypsum were detected by XRD at some depths. Moreover، amorphous iron oxyhydroxide minerals visually observed in waste dumps were not detected by XRD due to being negligible and low level of crystallinity. Hence، they were measured in terms of (Feo-h) by ASTM standard test method. The ASTM-D2492 standard test showed that pyrite، sulphate and iron oxyhydroxide minerals (Feo-h) are present in all samples. Against the XRD method، the test even detected the negligible content of the minerals. The paste pH tests showed that 15 samples were acid-producing because they had pH lower than 4. On the basis of moisture content results، the samples by name A6، A7، B1 and B2 showed high level of moisture which can be sign of the particular status in them.

According to the field observations، channels with a strong flow of warm and humid air were detected in the depth of 3 to 5 meters of the investigated waste rock dumps. High content of humidity (8. 25 and 13. 43 percent) and sulfate (4. 5 and 7. 02 percent) were observed together with low content of pyrite (1. 5 and 6. 23 percent) and acidic paste pH values (3. 13 and 2. 88) around these channels. Therefore، from the relation of these occurrences، it can be inferred that the air convection is important for supply oxygen to pyrite oxidation in the waste dumps of Sarcheshmeh. The results also indicate that، two main factors including grain size distribution and formation of hardpan layer on top of old weathered rocks are responsible for the decreasing of oxygen transformation rate via the molecular diffusion mechanism through the waste rock dumps. Considering the presence of coarse grain and poorly graded material as a proper media for air convection and also hardpan layer as a confining factor in molecular diffusion of oxygen، it can be deduced that the air convection is the main important mechanism to supply oxygen for weathering and oxidation reactions in the waste rock dumps. The abundance of oxygen and high temperatures in such conditions are also favorable for bacterial activities، which can then accelerate the pyrite oxidation in lower depth of dump. It is expected that the results of this study could be useful as a basis for providing the remediation strategies to control acidic drainage. So that knowing the domination of air convection and presence of hardpan justify controlling the flux of oxygen from the coarse material in bottom of waste dump. Therefore، it would be wrong to construct the impermeable layer on the surface of waste dump for arresting the oxygen diffusion as a traditional method in the remediation.

One of the first principles in the formation of a reserve is mineralogical، construction and mineral textures studies and investigation of paragenetic relations in the ore minerals. In addition، to petrographic studies، isotopic investigates have wide applications in economic geology. In general، copper isotope variability in primary (high temperature) mineralization forms a tight cluster، in contrast to secondary mineralization، which has a much larger isotope range. A distinct pattern of heavier copper isotope signatures is evident in supergene samples، and a lighter signature characterizes the leached cap and oxidation-zone minerals. This relationship has been used to understand oxidation–reduction processes (Hoefs، 2009). Also for a better understanding of the origin of the Jian Cu deposit، this research focuses on the origin and composition of the fluid and elucidation of its evolution during the mineralization process. In order to achieve this end، field observations، vein petrography، microthermometry of fluid inclusions and stable isotope analyses of veins and minerals were investigated. The present study also compares high and low temperature sulfide samples in an attempt to document and explain diagnostic δ65Cu ranges in minerals from the Jian deposit.

The samples were taken from different depths to measure Cu isotope variations within each reservoir. Mineralogical composition was determined using X-ray diffractometry. In addition، chromatographic separation was carried out on all samples (except for native Cu samples) in a clean lab and was conducted as outlined in Mathur et al. (Mathur et al.، 2009). These samples were measured into a Multicollector Inductively-Coupled-Plasma Mass Spectrometer (MC-ICPMS، the Micro mass Isoprobe at the University of Arizona) in low resolution mode using a microconcentric nebulizer to increase sensitivity for the samples with lower concentrations of copper. Preparation and analysis of quartz for oxygen isotopes was performed using the standard techniques detailed by Clayton and Mayeda (Clayton and Mayeda، 1963). Fluid inclusions were extracted for δD measurement from quartz samples selected as far as possible to avoid late inclusions. The methods were standard and similar to those published in Fallick et al. (Fallick et al.، 1987). Stable isotope analysis for oxygen and hydrogen isotopes was undertaken at the isotope geochemistry laboratory، University of Queensland.

δ65Cu values for analyzed samples range from -0. 45 to +0. 49 ‰ in the secondary copper minerals (malachite). The δ18O values for analyzed quartz samples، collected from different quartz veins of the Jian deposit، fall in a narrow range varying from +15. 8 to +18. 4‰ (avg. +16. 7‰) for type A veins and +16. 6 to +17. 9‰ (avg. +17. 2‰) for type B veins. The δ18O values of the fluids calculated from the Jian quartz samples range from +7. 6 to +10. 7‰ (avg. +9. 1 ‰) for type A veins and +4. 7 to +5. 1‰ (avg. +4. 9 ‰) for type B veins. The δD values of the fluid inclusions hosted by quartz samples range from -33. 1 to -41. 2‰ (avg. -37. 6‰) for type A and -52. 3 to -54. 9‰ (avg. -53. 1‰) for type B veins.

Based on mineralization style and structures، Th، salinity and composition of fluid inclusions، stable isotope systematics، timing of the mineralization with respect to deformation and metamorphism، host rocks، ore and gangue minerals، the Jian deposit can be classified either as a metamorphogenic or mesothermal Cu-bearing quartz deposit. Precipitation of secondary Cu+-sulfide minerals from the Cu+ complexes present in this fluid would result in sulfide minerals with low copper isotopic variations (-0. 45 to +0. 49‰) in the Jian copper deposit. This could explain why a low variation in the isotopic composition of Cu is observed in a horizontal plane. Isotopically، mineralization is most probably the result of varied isotopic fractionation processes including low copper leaching، Cu+ to Cu2+ oxidation-reduction reactions، and fluid-mineral fractionations. Oxygen and hydrogen isotope compositions suggest that the main metallization occurred from a metamorphic dehydration in type A veins. These sulfide-bearing quartz veins are interpreted as a small-scale example of redistribution of mineral deposits by metamorphic fluids. This study suggests that mineralization at Jian is interpreted as metamorphogenic in style، probably related to a deep-seated mesothermal system.

Mineral composition of source rock is one of the most important factors for concentration and distribution of heavy metals in sediments. Therefore، study on distribution of these elements and the related minerals in sediments provides information about natural origin of elements. Moreover، the interpretation of origin and distribution of sandy sediments is considerably enhanced by mineralogical and geochemical studies of these sediments. The main objective of this research is to evaluate distribution of Zn، Cu، Sr، Cd، Fe and Mn in sand sediments of the Oman Sea، their relationship with mineral composition of the sediments and also determining their provenance.

Sampling of surface sediments of the Oman Sea was performed in 16 sampling stations. Heavy minerals and rock fragments of the sediments in fine and coarse sand sizes respectively were qualitatively and quantitatively studied by polarizing microscope (Folk، 1974; Pettijohn et al.، 1981; Tucker، 1988). Concentration of the heavy metals were also analyzed by AAS method (Mico et al.، 2008).

Mineralogical composition of the studied sediments contain quartz، feldspars and heavy minerals in their order of abundances. The rock fragments consist of sedimentary، igneous and metamorphic in their order of frequencies as well. The concentrations of the studied heavy metals (in ppm) in the sediments are Cd (1. 42)، Cu (9. 99)، Zn (36. 72)، Sr (181. 18)، Mn (377. 33) and Fe (20247. 55) in their order of abundances. Distribution of the Zn concentration generally shows decreasing trend from west of the study area to the Guatr Bay. The concentrations of Zn and Cu show close relationship with the frequencies of biotite and muscovite. The Cu concentration also shows positive correlation with the Zn and Fe concentrations. Distribution of the Sr and Cd concentrations is similar to variation of the calcium carbonate content. The Cd and Sr concentrations also show positive correlation with each other and the calcium carbonate content of the sediments. A close relationship is also observed between the concentrations of Fe and Mn elements and the total amount of heavy minerals. Among the heavy minerals existing in the samples، biotite has the closest relationship with Fe and Mn. Among the rock fragments existing in the sediments، the amount of granitic rock fragments also has a very similar trend to variation of these two elements especially Fe.

According to presence of Fe and Mn in structure of many heavy minerals such as biotite (Mange and Wright، 2007; Bradl، 2005)، their main provenance can be biotite-bearing granites of Ghalaman complex، granodiorites existing in the ophiolite-melanges and the gabbros located in north of the Fanuch area mostly transported to the Oman Sea via the Rabech and Bahookalat water drainage basins. The clastic carbonate grains were mostly transported to the Oman Sea by Rabech and Sergan-Mochgar watersheds to the Oman Sea. Biotite and muscovite could mainly originate from the granodiorite، granite، ophiolite-melange gabbro and the Eocene flysches of northeast of the region. The main provenance of Zn could be granodiorites and gabbros existing in the Iranshahr ophiolites and flysches. According to close relationship between Cu and muscovite، provenance of this element can be granites، pegmatites and schists existing in the ophiolites and flysches of the region. Therefore، Zn and Cu are mostly transported to the Oman Sea and Guatr Bay via Bahookalat River. Provenance of Sr and Cd are mainly the Fanuch and Chabahar carbonate formations. According to the enrichment factor (Sutherland، 2000) of the studied elements، the sediments are extra-highly to very highly enriched in Cd. The enrichment of Sr changes from medium to very high. Zn shows low to medium enrichment and the sediments are depleted in Fe، Cu and Mn.