Journal of Economic Geology

217-234

Authors: Masoumeh Goodarzi; Seyyed Saeid Mohammadi; Mohammad Hossein Zarrinkoub

Introduction
The area reviewed and studied in this paper is located 5 km southeast of Sarbisheh city at eastern border of the Lut block (Jung et al., 1983; Karimpour et al., 2011; Richards et al., 2012) in eastern Iran between 59° 47′ and 59° 53′ E longitude and 32°30′ and 32°34′ N latitude. The magmatic activity in the Lut block began in middle Jurassic (165-162 Ma) and reached its peak in Tertiary (Jung et al., 1983). Volcanic and subvolcanic rocks of Tertiary age cover over half of Lut block with up to 2000 m thickness and formed due to subduction prior to the collision of the Arabian and Asian plates (Camp and Griffis, 1982; Tirrul et al., 1983; Berberianet et al., 1982). Most of magmatic activity in the Lut block formed in middle Eocene (Karimpour et al., 2011) The andesitic volcanics were erupted together with the dacites and rhyodacites during a time interval of some 50 Ma from early Cretaceous to early Neogene. It can be assumed that the intensity of the volcanic activity was varying significantly during this time span (Jung et al., 1983).Tertiary volcanic rocks (Eocene-Oligocene to Pliocene) with intermediate composition associated with pyroclastic rocks cropped out in eastern parts of Salmabad village, southeast of Sarbisheh. The main purpose of this paper is better understand the tectono-magmatic setting of the Tertiary volcanic rocks in southeast of Sarbisheh, eastern Iran based on geochemical characteristics.

Materials and methods
Eleven samples were analyzed for major elements by inductively coupled plasma (ICP) technologies and trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), following a lithium metaborate/tetraborate fusion and nitric acid total digestion, at the SGS Laboratories, Toronto, Canada.

Results
In the Salmabad area, Tertiary volcanic rocks with mainly intermediate (andesitic) composition are exposed associated with pyroclastic deposits such as tuff, breccia and agglomerate. Extrusive rocks include andesite (pyroxene andesite) and basaltic andesite. Zoning, sieve texture and embayment of plagioclase phenocrysts and existence of reaction rims around pyroxenes are evidences for disequilibrium conditions during magma crystallization. These rocks have medium to high-K calc-alkaline nature and show enrichment in LILE (except for Ba) and depletion of HFSE. The Salmabad area lavas have 102-155 ppm total REE and display coherent REE patterns characterized by enrichment in LREEs relative to HREEs ((La/Yb)N=7.35-9.71; (Ce/Yb)N=5.43-6.81)), nearly flat HREEs ((Tb/Yb)N=1.05-1.40) and weak negative Eu anomalies (average Eu/Eu*=0.78). Geochemical characteristics of the Salmabad volcanic rocks such as enrichment in LREEs relative to HREEs in association with enrichment in LILE and negative anomalies of Nb, Ti and P show their relation to subduction zone. The range of Mg# is 45.1-57.1 for the Salmabad andesites and 69.8 in basaltic andesite indicating the involvement of mantle components. The isotopic compositions (87Sr/86Sr)i=0.7045 and εNd(t)=3.1 for the Salmabad andesites point to a mantle origin.

Discussion
Orogenic magmas are defined geochemically as showing diagnostic Nb-Ta trough and enrichment in large ion lithophile elements (LILE) such as Th, Pb, Sr and K in primitive mantle normalized trace element variation diagrams (Kuscu and Geneli, 2010). The origin of this kind of geochemical signature is commonly interpreted as subduction-related setting (Gill, 2010), in sources that had undergone mantle wedge metasomatism (Seghedi et al., 2001) or crustal contamination of mantle-derived magmas (Harangi et al., 2007). The andesitic magma in Salmabad area displays an orogenic signature, i.e., enrichment in LILE and Th, and relative depletion in Nb, Ti and P. The dominance of positive εNd(t) values (3.1) for the studied rocks indicate a mantle origin. High values of Sr, Th and U in these rocks can be related to crustal contamination. Thus, the orogenic signature of these rocks is attributed to the mantle source, presumably metasomatized by the Sistan ocean subduction. The trace element features are consistent with the roles played by subducted sediments and fluid released from the subducted slab in magma genesis.

Acknowledgements
The authors would like to thank reviewers for the constructive comments which greatly contributed to the improvement of the manuscript.

References
Berberian, F., Muir, I.D., Pankhurst, R.J. and Berberian, M., 1982. Late Cretaceous and early Miocene Andean type plutonic activity in northern Makran and Central Iran. Journal of the Geological Society, 139(5): 605-614.
Camp, V.E. and Griffis, R., 1982. Character, genesis and tectonic setting of igneous rocks in the Sistan suture zone, eastern Iran. Lithos, 15(3): 221-239.
Gill, R., 2010. Igneous rocks and processes. Wiley-Blackwell, Malaysia, 428 pp.
Harangi, S., Downes, H., Thirlwall, M., Gmeling, K., 2007. Geochemistry, Petrogenesis and Geodynamic Relationships of Miocene Calc-alkalineVolcanic Rocks in the Western Carpathian arc, Eastern Central Europe. Journal of petrology, 48(12): 2261-2287.
Jung, D., Keller, J., Khorasani, R., Marcks, Chr., Baumann, A. and Horn, P., 1983. Petrology of the Tertiary magmatic activity the northern Lut area, East of Iran. Ministry of mines and metals, Geological survey of Iran, geodynamic project (geotraverse) in Iran, Tehran, Report 51, pp. 285-336.
Karimpour, M.H., Stern, C.R., Farmer, L., Saadat, S. and Malekezadeh, A., 2011. Review of age, Rb-Sr geochemistry and petrogenesis of Jurassic to Quaternary igneous rocks in Lut Block, Eastern Iran. Geopersia, 1(1):19-36.
Kuscu, G.G. and Geneli, F., 2010. Review of post-collisional volcanism in the central Anatolian volcanic province(Turkey), with special reference to the Tepekoy volcanic complex. International Journal of Earth Sciences, 99(3): 593-621.
Richards, J.P., Spell, T., Rameh, E., Razique, A. and Fletcher T., 2012. High Sr/Y Magmas Reflect Arc Maturity,High Magmatic Water Content, and Porphyry Cu ± Mo ± Au Potential:Examples from the Tethyan Arcs of Central and Eastern Iran and Western Pakistan. Economic Geology, 107(2): 295–332.
Seghedi, I., Downes, H., Pecskay, Z., Thirlwall, M.F., Szakacs, A., Prychodko, M. and Mattey, D., 2001. Magmagenesis in a subduction-related post-collisional volcanic arc segment: the Ukrainian Carpathians. Lithos, 57(4): 237–262.
Tirrul, R., Bell, I.R., Griffis, R.J. and Camp, V.E., 1983. The Sistan suture zone of eastern iran. Geological Society of America Bulletin, 94(1): 134-156.

259-276

Authors: Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi; Saeid Saadat

Introduction
Arefi quartz-bearing conglomerate (Middle Jurassic) is situated within Binalud structural zone. The unit is trending NW-SE located 25 km south of Mashhad. More than 97% of the pebbles are quartz as mono-crystalline, poly-crystalline, and minor fragments of chert, quartzite, and mica schist. Less that 3% of the remaining minerals are feldspar, mica, chlorite, hornblende, tourmaline, zircon, sphene, and opaque minerals. The cement is mainly silica. Hashemi (Hashemi, 2004) suggested this unit is orthoquartzitic polymictic conglomerate.
In this study, we carried out detailed mineralogical studies, geochemical analyses for SiO2 and troublesome elements, determination of quartz pebbles source using geological observations and fluid inclusion microthermometry, and industrial application studies with new insight for porcelain and ceramic factories as the nearest silica-rich reserve to Mashhad.

Material and methods
1. Preparing geologic map in 1:10000 scale in the Arefi area. 2. Petrographic study of 65 samples from the quartz-bearing conglomerate unit. 3. Major elements such as SiO2, TFeO, TiO2, and CaO were analyzed at the Maghsoud Porcelain Factories Group, using a Philips PW1480 X-ray spectrometer.
4. Ore dressing analyses in Danesh Faravaran Engineering Company.
5. Fluid-inclusion studies in 4 samples doubly-polished wafers of quartz crystals were studied using standard techniques (Roedder, 1984) and Linkam THM 600 heating-freezing stage (from –190 to 600ºC) mounted on a Olympus TH4–200 microscope stage at Ferdowsi University of Mashhad, Iran. Salinities and density of fluid inclusions were calculated using the Microsoft Excel spreadsheet HOKIEFLINCS-H2O-NACL (Steele-MacInnis et al., 2012; Lecumberri-Sanchez et al., 2012)

Results and Discussion

Fluid Inclusion studies of both mono- and poly- crystalline quartz revealed that the inclusions consist of three phases (LVS) with NaCl crystals. Homogenization temperature is between 484 and more than 600ºC with average 559ºC and the salinity is between 49.6 and 72.1 wt% NaCl with average 61.2 wt% NaCl. These data indicate a magmatic origin according to Kesler (Kesler, 2005) diagram. Homogenization temperature of two phases (LV) inclusions in the metamorphosed quartz is between 287 and 365ºC with average 318ºC. The main source of quartz pebbles is quartz veins formed within the top of pegmatite-granite (upper Triassic) of Khajeh-Morad area and quartz veins formed due to regional metamorphism.
Based on chemical analysis of 93 samples which were taken from the surface (channel method) and power drilling, the SiO2 content is more than 98%, TFeO is less than 0.42% and TiO2 is less than 0.16%. The proved ore reserve is more than 50 million tonnes. Using dry magnetic method, the TFeO became less that 0.03% and TiO2 less than 0.02%. Arefi silica deposit is a first-class reserve and can be used in different types of ceramic.

Acknowledgments
The Research Foundation of Ferdowsi University of Mashhad, Iran, supported this study (Project No. 29057.2). We also thank Danesh Faravaran Engineering Company for the ore dressing analyses.

Reference
Hasemi, S.F., 2004. Petrology and depositional environment of Jurrasic conglomerate in south of Mashhad. Unpublished M.Sc. thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 200 pp. (in Persian)
Kesler, E.S., 2005. Fluids in Planetary Systems: ore-Forming Fluids. Elements, 1(1): 13–18.
Lecumberri-Sanchez, P., Steel-MacInnis, M. and Bodnar, R.J., 2012. A numerical model to estimate trapping conditions of fluid inclusions that homogenize by halite disappearance. Geochim Cosmochim Acta, 92: 14-22.
Roedder, E., 1984. Fluid inclusions. Reviews in Mineralogy 12, 644 pp.
Steele-MacInnis, M., Lecumberri-Sanchez, P. and Bodnar, R.J., 2012. HOKIEFLINCS-H2O-NACL: A Microsoft Excel spreadsheet for interpreting microthermometric data from fluid inclusions based on the PVTX properties of H2O–NaCl. Computers Geosciences, 49: 334–337.

291-304

Authors: Farhad Ghaseminejad; Ghodrat Torabi

Introduction
Geological background
Ophiolites have played a major role in our understanding of Earth’s processes ranging from seafloor spreading, melt evolution and magma transport in oceanic spreading centers, and hydrothermal alteration and mineralization of oceanic crust to collision tectonics, mountain building processes, and orogeny. They provide the essential structural, petrological, geochemical, and geochronological evidence to document the evolutionary history of ancient continental margins and ocean basin. Ophiolites include a peridotitic mantle sequence, generally characterized by high-temperature plastic deformation and residual chemistry, and a comagmatic crustal sequence (gabbros, diabase dikes, and submarine basalts), weakly or not deformed. According to this interpretation, ophiolites were allochthonous with respect to their country rocks. They were assembled during a primary accretion stage at an oceanic spreading center, and later tectonically emplaced on a continental margin or island arc (Dilek, 2003).
The indigenous dikes of pyroxenites and gabbros that were injected into a melting peridotite, or intrusive dikes of pyroxenite and gabbro that injected when the peridotite was fresh and well below its solidus, are discussed in different ophiolite papers. Pyroxenite formation and contact of gabbro and mantle peridotite are discussed in different articles (Dilek, 2003). When a gabbro intrude a fresh mantle peridotite could not significantly react with it, but if intrusion occurs during the serpentinization, the gabbro will change to rodingite.

Geological setting
The Naein ophiolitic melanges comprise the following rock units: mantle peridotites (harzburgite, lherzolite, dunite, with associated chromitite), gabbro, pyroxenite, sheeted and swarm dikes, massive basalts, pillow lava, plagiogranite, radiolarian chert, glaubotruncana limestone, rodingite, listvenite, and metamorphic rocks (foliated amphibolitic dike, amphibolite, skarn, banded meta-chert, and succession of schist and marble) (Davoudzadeh, 1972; Jabbari, 1997; Pirnia Naeini, 2006; Torabi, 2012; Shirdashtzadeh, 2006). In this ophiolite, the leucogabbro intrusions crosscut all other rock units.

Materials and Methods
Mineralogical analyses were conducted by wavelength-dispersive EPMA (JEOL JXA-8800R) at the Cooperative Centre of Kanazawa University (Japan). The analyses were performed under an accelerating voltage of 15 kV and a beam current of 15 nA. JEOL software using ZAF corrections was employed for data reduction. Natural and synthetic minerals of known composition are used as standards. The Fe3+ content in minerals was estimated by assuming mineral stoichiometry.

Results
In the contact zone of leucogabbros and mantle peridotites of the Naein ophiolite, wehrlite and olivine clinopyroxenite are formed. Rock-forming minerals of these wehrlites are olivine (chrysolite), clinopyroxene (diopside), Cr-spinel, serpentine, amphibole (tremolite and tremolitic hornblende), epidote and magnetite.
Comparison of mineral chemistry of olivine, clinopyroxene and chromian spinel in wehrlites and mantle peridotites indicate that chemical composition of clinopyroxene and olivine in these rocks are different, but chemistry of Cr-spinels in harzburgite and wehrlite are nearly same.

Discussion
According to the resistance of Cr-spinel against the metamorphism and alteration, it can be concluded that the wehrlites in contact zone of gabbros and mantle peridotites are formed at the expense of harzburgite. Olivine and clinopyroxene of wehrlites are formed by serpentine metamorphism and interaction of serpentine and calcium of gabbro, respectively. Field study of the research area shows that the leucogabbro intrudes the harzburgite. This research shows that after the serpentinization of mantle harzburgite, the gabbro intrusions crosscut the serpentinized peridotites, and wehrlite and olivine clinopyroxenite formed in the contact zone.

Acknowledgements
The authors thank the University of Isfahan for financial support.

References
Dilek, Y., 2003. Ophiolite concept and the evolution of geological thought. Geological Society of America Special Paper 373, 504.
Davoudzadeh, M., 1972. Geology and Petrography of the area north of Nain, Central Iran. Geological Survey of Iran, Tehran, Report 14, 92 pp.
Jabbari, A., 1997. Geology and petrology of the northen Naein ophiolites. M.Sc. Thesis, University of Isfahan, Isfahan, Iran, 162 pp. (in Persian)
Pirnia Naeini, T., 2006. Petrology of mantle peridotites of the Naein ophiolite. M.Sc. Thesis, University of Isfahan, Isfahan, Iran, 191 pp. (in Persian with English abstract)
Torabi, G., 2012. Central Iran ophiolites. Jahad daneshgahi, Isfahan, 443 pp. (in Persian)
Shirdashtzadeh, N., 2006. Petrology of metamorphic rocks in the Naein ophiolite (Isfahan province). M.Sc. Thesis, University of Isfahan, Isfahan, Iran. 194 pp. (in Persian with English abstract)

315-329

Authors: Alireza Bajelan; Morteza Sharifi

Introduction
In the east and northeast of Sanandaj in the Qorveh-Bijar-Takab axis, there are series of basaltic composition volcanoes with Quaternary age. The study area is part of the Sanandaj-Sirjan zone and is located between 47°52' and 47°57' E longitudes and 35°26 and '35°30' N latitudes. Due to the location of the volcanic cone on Pliocene clastic sediments and Quaternary travertine, the age of these volcanoes is considered to be Quaternary. The cones mostly consist of low scoria, ash, volcanic bombs, lapilli deposits and basaltic lava (Moein Vaziri and Aminsobhani, 1985). Petrological and geochemical studies have been carried out to evaluate Quaternary magmatism in the area and to determine the nature of the lithological characteristics, such as the evaluation of source rocks and magma type, degree of partial melting and the tectonic setting of Ghezel Ghaleh rocks (Moein Vaziri, 1997). Simplified geological map of the study area is characterized by ER-Mapper software.

Materials and methods
In the course of field studies in the region, 40 samples were taken, 30 thin sections were prepared and polished. XRD analyses were performed on some whole rock samples. All major, minor and trace elements were assessed by ICP-MS at Lab Weft Laboratory in Australia.

Results
Based on the classification of structural zones, the area is located in the Sanandaj-Sirjan zone, hundred kilometers away from the main Zagros thrust along the NW-SE direction. After early Cimmerian orogeny, andesitic volcanic activity took place (Moein Vaziri and Aminsobhani, 1985). A major secondary mineral in these rocks is iddingsite, formed by hydration and oxidation of the olivine (Shelley, 1993). According to SiO2 against Na2O + K2O (TAS) diagram (Irvine and Baragar , 1971) and cationic R1 and R2 diagram (De La Roche et el., 1980), volcanic rocks of the area indicate alkaline series.

Discussion
To obtain more information on the tectonic setting of these rocks, the Zr/Y-Zr diagram by Pierce (Pearce and Norry, 1979) as well as Nb/Y versus Ti/Y diagram of Pierce (Pearce and Cann, 1973), show that alkali basalt rocks in the study area are fitted in the field of within plate basalts. To determine the genesis of rocks from melting curve of Aldanmaz and Colleagues (Aldanmaz et al., 2006) based on changes in REE (La on Sm/Yb), the samples show approximately 1 to 5% partial melting of garnet lherzolites. The spider diagrams indicate that the studied rocks are enriched in LREE and LILE, depleted in HFSE with no Eu anomaly, Cs, Sr, and Pb positive anomalies which are the characteristics of alkaline magmas and high concentrations of incompatible elements and alkaline elements in the lava, implying the melting of the lower part of the mantle source. Light rare earth elements, are incompatible with the primary crystallized phases such as olivine, clinopyroxene and plagioclase, consequently focused increasingly during phase crystallization and fractionation in the remaining fluid (Hirschman, 1998).

Conclusions
Based on microscopic and geochemical data, these rocks are alkali basalt, basanite and tephrite. The rocks contain olivine, pyroxene, feldspar, and minerals such as iddingsite, opaque and secondary minerals, calcite with porphyritic texture and microlitic and glassy matrix, vesicular and some glomeroporphyritic, vitrophyric and amygdaloidal textures. Most minerals have undulose extinction which indicates mantle deformation. Geochemical data for the rocks indicate high-K alkaline characteristic of the primary magma. The spider diagrams indicate that the studied rocks are enriched in LREE and LILE, depleted in HFSE with no negative Eu anomaly, positive anomalies of Cs, Sr, Pb which are characteristics of alkaline magmas. These rocks are produced by partial melting of garnet-lherzolite rich under lithospheric mantle. Based on tectonomagmatic diagrams, they are within plate basalts and by magmatic series graphs are alkali basalts. Microscopic evidence such as disequilibrium textures in the minerals (zoned state, solution and twinning) shows a magmatic contamination in mixing volcanic mass.

References
Aldanmaz, E., Koprubasi, N.O., Gurer, F., Kaymakci, N. and Gournaud, A., 2006. geochemical constraints on the Cenozoic, OIB-type alkaline volcanic rocks of NW Turkey: implications for mantle sources and melting processes. Lithos, 86 (1–2) pp. 50–76.
De La Roche, H., Leterrier, J., Grand claude, P. and Marchel, M., 1980. A classification of volcanic and plutonic rocks using R1-R2 diagrams and major elements, it’s relationships with current nomenclature. Chemical Geology, 29(1-4): 183–210.
Hirschman, M., 1998. Origin of the transgressive granophyres in the layered series of the Skaergaard intrusion, East Greenland. In: D.J. Geist and C.M. White (Editors.). Journal of Volcanology and Geothermal Research, 52(1-3): 185–207.
Irvine, T.N. and Baragar, W.R.A., 1971. A guide to chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences, 5(8): 448– 523.
Moein Vaziri, H., 1997. The history of magmatism in Iran. Tehran University Press, Tehran, 440 pp. (in Persian)
Moein Vaziri, H. and Aminsobhani, A., 1985. Study of young volcanic region being involved in –Qorveh- Takab. Tehran University Press, Tehran, 350 pp. (in Persian)
Pearce, J.A. and Cann, J.R., 1973. Tectonic setting of basaltic volcanic rocks determind using traceelements analysis. Earth and Planetary Science Letters, 19(2): 290– 300.
Pearce, J.A. and Norry, M.J., 1979. Petrogenetic implications of Ti, Zr, Y and Nb variation in volcanic rocks. Contributions to Mineralogy and Petrology, 69(1): 33– 47.
Shelley, D. (Translated by Mohamadzadeh, F.), 1993. Igneous and metamorphic rocks under the microscope, classification, textures, microstructures and mineral preferred-orientations. Chapman and Hall, Unwin, London, 445 pp.

355-374

Authors: Mohammad Maanijou; Rahimeh Salemi

Introduction
There is an iron mining complex called Shahrak 60 km east of Takab town, NW Iran. The exploration in the Shahrak deposit (general name for all iron deposits of the area) started in 1992 by Foolad Saba Noor Co. and continued in several periods until 2008. The Shahrak deposit comprising 10 ore deposits including Korkora-1, Korkora-2, Shahrak-1, Shahrak-2, Shahrak-3, Cheshmeh, Golezar, Sarab-1, Sarab-2, and Sarab-3 deposits )Sheikhi, 1995) with total 60 million tons of proved ore reserves. The Fe grade ranges from 45 to 65% (average 50%). The ore reserves of these deposits vary and the largest one is Korkora-1 with 15 million tons of 55% Fe and 0.64% S. The Korkora-1 ore deposit is located in western Azarbaijan and Urumieh-Dokhtar volcanic zone, at the latitude of 36°21.8´, and longitude of 47°32´.

Materials and methods
Six thin-polished sections were made on magnetite, garnet, and amphibole for EPMA (Electron Probe Micro Analysis). EPMA was performed using a JEOL JXA-733 electron microprobe at the University of New Brunswick, Canada, with wavelength-dispersive spectrometers.

Results and discussion
Outcropped units of the area are calc-alkaline volcanics of rhyolite, andesite and dacite and carbonate rocks of Qom Formation in which intrusion of diorite to granodiorite and quartzdoirite caused contact metamorphism, alteration plus skarnization and formation of actinolite, talc, chlorite, phlogopite, quartz, calcite, epidote and marblization in the vicinity of the ore deposit.
Iron mineralization formed at the contacts of andesite and dacite with carbonates in Oligo-Miocene. The study area consists of skarn, metamorphic rocks, and iron ore zones. The shape of the deposit is lentoid to horizontal with some alteration halos. The ore occurred as replacement, massive, disseminated, open-space filling and breccia. The ore minerals of the deposit include low Ti-magnetite (0.04 to 0.2 wt % Ti), minor apatite, and sulfide minerals such as pyrite and chalcopyrite. Magnetite is the most important mineral and has 0.2 to 4 mm grain size and partly transformed into hematite, limonite and goethite. In some places, magnetite can be seen as euhedral grains in hand specimen. Supergene minerals such as chalcocite, malachite, azurite, and covellite are also present. Hematite formed as primary and secondary types in which primary type occurred in deeper parts of the ore body along with magnetite and has lamellar texture with up to 0.2 mm grain size. Meanwhile, secondary type of hematite formed from martitization along magnetite grain boundaries and fractures. In the surface area of the deposit, ore minerals strongly altered to mixtures of oxide and hydroxide minerals (ochre) like goethite, hematite, limonite and lepidochrocite which changed the color of the ore body to yellow, deep orange, red and brown. Pyrite is the most important sulfide mineral and formed in three stages. In the first stage, pyrite occurred with magnetite and has 0.1 to 0.3 mm subhedral to anhedral grains which altered to oxide and hydroxide minerals. At the second stage, pyrite has 0.2 to 1 mm euhedral grains, occurred between the magnetite and gangue minerals and converting to chalcopyrite. At the third stage, pyrite with magnetite, calcite and quartz filled fractures as open-space fillings and are pretty unaltered.
The skarn zone includes garnet, pyroxene, secondary calcite, epidote, and chlorite and the metamorphic zone includes marble. Sericitization, silicification, calcitization, chloritization-epidotization, argilitization, propylitization and actinolitizion are the important alterations in the area from which chloritization-epidotization and calcitization in the ore and propylitic alteration in the volcanics are dominant.
The EPMA analytical results on 30 points on magnetite and hematite suggest that the amount of Ti and V (0.004 wt % and 0.002 wt % in average, respectively) are low in contrary to Mn and Al (0.33 wt % and 5.32 wt % in average, respectively). Therefore, it fits in the skarn ore deposit domain in Ni/(Cr + Mn) versus Ti + V and Ca + Al + Mn versus Ti + V discrimination diagrams of iron ore deposits (Beaudoin et al., 2007). High Mn in the rock samples of Korkora-1 can be resulted from substitution of Fe+2 by Mn+2 in magnetite structure that can be a sign of hydrothermal skarn. Titanium, Mn, V and Zn show a positive correlation and Al, Cu, Mg, P, Si, Ca, Ni and Cr show a negative correlation with Fe. According to the chemistry of magnetite and plotting them on V2O5 versus TiO2 and V2O5 versus Cr2O3 diagrams, it can be recognized that the samples of Korkora-1 deposit resemble exoskarn magnetite of Goto deposit. The analysis of goethite of Korkora-1 show the amount of 2.5 to 4 wt % SiO2, 76 wt % Fe, and Ni (110 ppm) without Ti and Cr in its structure.
Mineralographical and geochemical evidence from ore, occurrence of iron in contact with carbonates and skarn mineralogy such as garnet, pyroxene, secondary calcite, epidote and chlorite suggest iron skarn genesis for Korkora-1 deposit. Fluids generated from intrusive bodies like diorite and quartz-diorite with variations in physicochemical conditions, produced skarn in contact with carbonates and volcanic rocks. The heat from intrusive bodies caused recrystallization of carbonates and formed marbles in the footwall of the deposit. Meteoric water has also less important contribution in the ore-forming fluids. Fluid inclusion studies show existing of two types of fluids, a low salinity (10 wt % NaCl equiv.) and a medium salinity (25 to 30 wt % NaCl equiv.) fluid. Mixing magmatic and meteoric waters makes decreasing in the temperatures and deposition of ore fluids. The Korkora-1 deposit formed in four stages: 1) intruding the intrusive bodies, 2) entering Fe and SiO2 into Qom carbonates and forming calc-silicates, 3) mixing magmatic and meteoric fluids, hydrolysis of calc-silicates, consuming H+, instability of Fe complexes and deposition of iron oxides, 4) retrograde alterations of hydrous and non-hydrous calc-silicates with low temperature and high fO2 fluids and forming chlorite, calcite, clay minerals and hematite.

Acknowledgements
We gratefully thank Mr. Reza Sheikhi from Saba Noor Co. who kindly helped us during the research. We also thank Professor David Lentz from University of New Brunswick for advising and supporting the research.

References
Sheikhi, R., 1995. Economic geology study of Shahrak Fe deposit, east of Takab. M.Sc. Thesis, Shahid Beheshti University, Tehran, Iran, 161 pp. (in Persian with English abstract)
Beaudoin, G., Dupuis, C., Gosselin, P. and Jebrak, M., 2007. Mineral chemistry of iron oxides: application to mineral exploration. In: C.J. Andrew (Editor), Ninth Biennial SGA meeting, SGA, Dublin, pp. 497−500.

393-409

Authors: Malihe Nakhaei; Mohammad Hasan Karimpour; G. Lang Farmer; Charles Stern; Seyyed Ahmad Mazaheri; Mohammad Hossein Zarinkoub; Mohammad Reza Heydarian Shahri

Introduction
The study area is located 196 km south of Birjand in eastern border of the Lut block )Berberian and King, 1981) in eastern Iran between 59°05′35" and 59°09′12" E longitude and 31°42′29" and 31°44′13" N latitude. The magmatic activity in the Lut block began in the middle Jurassic such as Kalateh Ahani, Shah Kuh and Surkh Kuh granitoids that are among the oldest rocks exposed within the Lut block (Esmaeily et al., 2005; Tarkian et al., 1983; Moradi Noghondar et al., 2011-2012). Eastern Iran, and particularly the Lut block, has great potential for different types of mineralization as skarnification in Bisheh area which has been studied in this paper. The goal of this study is to highlight the geochronology, geochemistry of major and trace elements, Rb-Sr, Sm-Nd isotopes for skarnified pyroxene-bearing diorites.

Materials and methods
Major element compositions of thirteen samples were determined by wavelength-dispersive X-ray fluorescence (XRF) spectrometry, using fused discs and the Phillips PW 1410 XRF spectrometer at Ferdowsi University, Mashhad, Iran. These samples were analysed for trace elements using inductively coupled plasma-mass spectrometry (ICP-MS) in the Acme Analytical Laboratories, Vancouver, British Columbia, Canada.
Zircon grains were separated from pyroxene diorite porphyrys using heavy liquid and magnetic techniques at the Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan. Zircon U-Pb dating was performed by laser ablation-inductively-coupled plasma-mass spectrometry (LA-ICP-MS), using an Agilent 7500 s machine and a New Wave UP213 laser ablation system, equipped at the Dr Shen-Su Sun memorial laboratory in the Department of Geosciences, National Taiwan University, Taiwan.
Strontium and Nd isotopic analyses were performed on a six-collector Finnigan MAT 261 thermal-ionization mass spectrometer at the University of Colorado, Boulder, Colorado, United States. 87Sr/86Sr ratios were determined using four-collector static mode measurements. Several measurements of SRM-987 during the study period yielded a mean of 87Sr/86Sr = 0.71032 ± 2 (error is the 2σ mean). Measured 87Sr/86Sr ratios were corrected to SRM-987 = 0.71028. Measured 143Nd/144Nd was normalized to 146Nd/144Nd = 0.7219. Analyses were conducted as dynamic mode, three-collector measurements. Several measurements of the La Jolla Nd standard during the study period yielded a mean of 143Nd/144Nd = 0.511838 ± 8 (error is the 2σ mean).

Results
In the Bisheh area that is located east of Lut block, pyroxene-bearing dioritic rocks are high-K calk-alkaline and meta-aluminous. Primitive mantle-normalized trace element spider diagrams display strong enrichment in LILE, such as Rb, Ba, and Cs, and depletion in some HFSE, e.g., Nb, P, Ti, Y and Yb. Chondrite-normalized REE diagrams show (La/Yb)N ratios ranging from 7.75 to 8.63 and small negative Eu anomalies. These features along with high Th/Yb and Ta/Yb ratios show that magmatism is related to continental margin subduction. Obvious depletion of Nb and Ti, relatively high values of Mg#, initial 87Sr/86Sr (0.70606) and 143Nd/144Nd (0.512424) ratios as well as εNd (-3.05) suggest that the magma originated from an enriched mantle with crustal contamination. High values of Rb, Th and K and low amount of P and Ti support the magma contamination in upper crust during magma evolution. Zircon U-Pb age dating for a porphyritic pyroxene diorite sample yield an age of 44.07±0.69 Ma indicating middle Eocene (Lutetian).

Discussion
The isotopic value for the Bisheh dioritic porphyry can be considered as indicative of lithospheric mantle melting. The trace element characteristics of these rocks can be used to characterize their mantle source. The MORB normalized trace element pattern (Pearce, 1983) of all samples shows a negative anomaly for Nb, Ti and Ta. The negative anomaly of these elements can be explained by the presence of a residual TNT phase (Ti-Nb-Ta, e.g., rutile, ilmenite and perovskite) during the melting of the source (Reagan and Gill, 1989). This pattern followed that of calc-alkaline magmas derived from a sub-arc mantle, with scarce or no garnet in the source. Furthermore, Bisheh subvolcanic bodies were enriched in Rb, Ba and Th, indicating that they had experienced interaction with the continental crust (Kuşcu et al., 2002). The chondrite-normalized rare earth element pattern of the studied rocks shows a high ratio of light rare earth elements (LREE) to heavy rare earth elements (HREE). All the samples have been plotted in the VAG field.
The dioritic rocks from the Bisheh have relatively high Mg# (0.4-0.56), which is consistent with derivation from mantle melts contaminated by continental crust (Rapp and Watson, 1995). The initial 87Sr/86Sr of Bisheh pyroxene diorite porphyry was 0.70606 and the (143Nd/144Nd)i isotope compositions and εNd value of these rocks was 0.512424 and -3.05, respectively. These values show that the magma originated from an enriched mantle with crustal contamination.

Acknowledgements
The authors are grateful to Professor Sun-Lin Chung from the Department of Geosciences, National Taiwan University, for supporting the researchers in the use of U-Th-Pb zircon age dating.

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