Journal of Economic Geology

25-45

Authors: Reza Zarei Sahamieh

Introduction The study area includes Alam Baghi, Vashaghan, Sar Band and Ghermez Cheshmeh and is located in the northeast of Farmahin and the southwest of Tafresh. Based on the structural subdivisions of Iran, the mentioned area is a part of Central Iran and the Urumieh-Dokhtar magmatic belt (Hajian, 1970). The studied volcanic rocks consist of trachybasalt, trachyandesite, basaltic andesite, andesite, dacite, rhyodacite, rhyolite, ignimbrite, tuff and tuffit in composition and in terms of age they belong to the middle and upper Eocene. It seems that the volcanic activities are related to folding and faulting in the studied area. On the other hand, in addition to causing orogenic activity, at the middle and upper Eocene (Ghasemi and Talbot, 2006), locally extensional regime has played a main role in volcanic eruption. Similar to this scenario happened in other areas such as Taft and Khizrabad in Central Iran (Zarei Sahamieh et al., 2008). Porphyritic, microlite porphyritic and microlitic are the main textures in these rocks. Mineralogically, they contain plagioclase, clinopyroxene, amphibole, quartz and biotite as the main minerals and zircon, apatite, and opaque minerals as accessories. Materials and methods The major and trace elements of mineral composition are determined by electron probe micro-analysis (EPMA) using a Cameca SX100 instrument in the Iran Mineral Processing Research Center (IMPRC). Moreover, the whole-rock major and some trace elements analyses for a few samples were obtained by X-ray fluorescence (XRF), using an ARL Advant-XP automated X-ray spectrometer. Results Based on EPMA analyses, plagioclase mineral in basaltic andesite and trachybasalt samples range from labradorite to bytownite in andesite and trachyandesite has oligoclase- andesine and in dacite, rhyodacite, rhyolite has an albite-oligoclase composition. In the Wo-En-Fs diagram, all clinopyroxenes show augitic and a lessor amount of clinoenstatite composition and in the Q-J diagram located in the Mg-Fe-Ca (Quad) field and in the 2Ti+Cr+AlVI vs. Na+AlIV diagram (Morimoto et al., 1988) located above on the Fe3+=0 line that indicate high oxygen fugacity during crystallization. Microscopic study on these rocks such as oscillatory zoning, resorption rims in plagioclase and the presence of basic inclusions suggest the occurrence of magmatic contamination on the parent magma. The presence of oxidized amfibool rims (in hornbelende as oxy hornbelende) indicate the high temperature of the magma at the time of eruption. According to the classification diagrams such as total alkaline vs. SiO2 (Irvine and Baragar, 1971) TAS (Le Bas et al., 1986) and tectonic discrimination diagrams (Pearce et al., 1984) samples are plotted in sub-alkaline, basaltic-andesite, andesite, dacite and rhyodacite, subduction and volcanic arc fields, respectively. The geochemical diagrams such as AFM are used for the identification of magma series and show that the studied rocks are calc-alkaline and A/NK vs. The A/CNK diagram shows the metaluminous to peraluminous nature. Incompatible and LIL elements such as Ba, K and Rb enrichment show that the contamination of magma with continental crust has occurred. The similarity between the REE patterns in all of the collected samples in Alam Baghi, Vashaghan, Sarban and Ghermez Cheshmeh areas suggest the same source for all of the volcanic rocks. Discussion The tectonic setting diagrams show that these rocks belong to the continental margin which has been involved in a subduction zone. The position of the samples on the major elements vs. SiO2 diagrams indicate that magma differentiation has occurred. Spider diagrams show a positive anomalous in Rb and a negative anomalous in Nb and Ti This phenomenon shows a contamination between the magma and the crustal rocks (Rollinson, 1993). Also, MORB-normalized incompatible element patterns of the Farmahin area show that the parent magma has been contaminated. It appears that assimilation and fractional crystallization (AFC) were the dominant processes in the genesis of the studied volcanic rocks. As a conclusion and according to field evidence and geochemical characteristics presented in this article, the studied area is composed of lava flows and pyroclastic rocks such as andesite, dacite, rhyodacite, ignimbrite, tuff and tuffits that cross cut by younger dykes and belong to the middle to late Eocene age (middle to upper Lutetien). According to Sm/Yb vs. Sm diagram (Aldanmaz et al., 2000), all the studied samples in terms of composition are similar to enriched mantle-derived melts that are generated by varying degrees of partial melting (10% - 20%) from a spinel lherzolite to spinel-garnet lherzolite source. Considering the evidences, all rocks in the studied area belong to the subduction zone and the parent magma originated from mantle and was contaminated with continental crust during eruption and rising. Acknowledgments The authors wish to thank the Journal Manager and reviewers who critically reviewed the manuscript and made valuable suggestions for its improvement. References Aldanmaz, E., Pearce, J.A., Thirlwall, M.F. and Mitchell, J.G., 2000. Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey. Journal of Volcanology and Geothermal Research, 102(1–2): 67–95. Ghasemi, A. and Talbot, C.J., 2006. A new scenario for the Sanandaj-Sirjan zone (Iran). Journal of Asian Earth Sciences, 26 (6): 683–693. Hajian, J., 1970. Geological map of Farmahin, scale1:100000. Geological Survey of Iran. Irvine, T.N. and Baragar, W.R.A., 1971. A guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences, 8(5): 523–548. Le Bas, M.J., Le Maitre, R.W., Streckeisen, A. and Zanettin, B., 1986. A chemical classification of volcanic rocks based on the total alkali silica diagram. Journal of Petrology, 27 (3):745–750. Morimoto, N., Fabrise, J., Ferguson, A., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J., Akoi, K. and Gottardi G., 1988. Nomenclature of pyroxenes. American Mineralogist, 173(9–10):1123–1133. Pearce, J.A., Nigel, B., Harris, N.B.W. and Tindle, A.G., 1984. Trace Element Discrimination Diagrams for the Tectonic Interpretation of Granitic Rocks. Journal of Petrology, 25(4): 956–983. Rollinson, H.R., 1993. Using Geochemical Data: Evaluation, Presentation and Interpretation. Longman scientific and technical, London, 352 pp. Zarei Sahamieh, R., Tabasi, H. and Jalali, M., 2008. Petrology and tectonomagmatic investigation of volcanic rocks of Ashtian. Journal of Science, Kharazmi University, 8(3):227–240. (in Persian with English abstract)

61-76

Authors: Maryam Aminoroayaei Yamini, Faramarz Tutti, Mohammad Reza Aminoroayaei Yamini and Jamshid Ahmadian

Introduction Chemical and textural zoning patterns preserved in plagioclase phenocrysts can provide useful information on parameters that constrains the changing melt compositions in the magma systems. Many studies have utilized the compositional and textural information recorded in plagioclase from igneous rocks to infer the various aspects of magma chamber dynamics and the source of copper in the copper deposits (Viccaro et al., 2010). The Zafarqand porphyry copper deposit is located at the center of the Urumieh-Dokhtar magmatic arc and is mainly composed of Eocene volcanic and sub volcanic rocks, which were intruded by Miocene granodiorite. Alteration and mineralization in this area are superimposed onto the associated porphyritic body and the surrounding country rock (Aminoroayaei Yamini et al., 2016). In this paper, the growth of the plagioclase crystals in the magma is simulated on the basis of various microtextures and their profile composition. Magma mixing, magma recharge phenomenon, and the source of copper are also examined in this area. Materials and methods A total of 200 samples were collected by the variation of lithology from the volcano-plutonic unit of Zafarqand. About 60 thin sections were made and petrographic observations were carried out using a polarizing microscope. The major-element compositions of plagioclase were analyzed at EPMA Laboratories of Naruto University in Japan and the University of Oklahoma. For analyses, an accelerating voltage of 15 kV, a beam current of 20 nA, and 20s counting time was used. The EPMA data obtained from some representative samples are shown in Tables 2 and 3. Results Plagioclase is the most abundant phenocryst phase in Zafarqand plutonic rocks. Based on their textures, plagioclases found in the host granodiorites fall into three populations. The most common population consists of medium grains that have oscillatory zoning. However, synneusis texture is shown in this rock. Granodiorite plagioclase phenocrysts exhibit strong resorption zones and are composed of profuse network micron-sized glass inclusions. Plagioclases from andesitic dyke also fall into two populations: Plagioclase microlites and phenocryst grains. Phenocryst grains commonly have coarsely sieved interiors resulting from the presence of an extensive network of interconnecting inclusions that pervade the crystal periphery with oscillatory zoning. In many rhyodacites, plagioclase phenocrysts appear broken as evidenced by their cracked morphology. Resorption surfaces are the horizons, like an unconformity surface mark a boundary between the other phases. Discussion The magmatism of the “Zafarqand” district is often typified by the occurrence of mafic enclaves (cognate xenoliths) indicative of comagmatism and geochemical mixing trends (Aminoroayaei Yamini et al., 2016). This area corresponds to an intrusion that would be linked to a subduction-related geodynamic context. The overall similarity in the REE patterns of the volcano-plutonic rocks exhibits a common source and same geological features for them but different age (Aminoroayaei Yamini et al., 2016). However, from the plagioclase textural observations a simplified magma plumbing model is envisaged for the studied crystals. At the initial stage, water saturated high temperature magmas have undergone extensive crystallization at lower-crustal chamber depth (Deeper MASH Zone) where optically clear An-rich plagioclase is produced. When this crystal-rich magma ascends to shallow depths, the crystals have undergone varying rates of dissolution that causes the development of CS morphologies. Variation in dissolution intensity may be due to differences in the rate of decompression or H2O content dissolved in the magma (Viccaro et al., 2010). The crust chamber was dynamically active by the input of Shallow MASH Zone pulses. Consequently, the growth of both pre-existing and newly brought crystals was constrained by the heterogeneous superheating and convection processes. As a result, they developed OZ and RS textures. Dissolution happens during magma mixing. However, the presence of microgranolar mafic enclaves and OZ texture in granodiorite from Zafarqand precludes the possibility of end-member magma mixing in these rocks. Thus, RS is the result of superheating and intense dissolution by mafic magma recharge event. Such recharge events could be like a cryptic-mixing process in which the magma chamber experiences repeated addition of small pulses of primitive and hotter and more mafic magma with different ƒ(O2) or H2O contents (Ginibre et al., 2002). After the recharge event, the pre-existing crystals in the crust chamber interacted with new magma causing intense dissolution in the form of RS morphology. In addition to the heating and intense dissolution, crystals in the crust chamber also experienced repeated movements across the magmatic gradients by convection or turbulence as evidenced from the OZ domains in the plagioclase (Ginibre et al., 2002). Then, the magma chamber might have experienced under-cooling by degassing or water exsolution followed by violent aerial eruption producing microlites, broken crystals. The occurrence of sulfide melt in the grandmas of biotite and amphyole phenocrists, mafic enclaves and magma mixing feature, suggests that, similar to the Bajo de la Alumbrera deposit, the injection of more mafic magma may also contribute a large amount of ore metal to the magma chamber and generate Cu mineralization at the Zafarqand deposit. References Aminoroayaei Yamini, M., Futti, F., Haschke, M., Ahmadiam, J. and Murata, M., 2016b. Synorogenic copper mineralization during the Alpine-Himalayan orogeny in the Zafarghand copper exploration district, Central Iran: Petrogrography, geochemistry and alteration thermometry. Geological Journal, 25(2): 263–281. Ginibre, C., Kronz, A. and Wörner, G., 2002. High-resolution quantitative imaging of plagioclase composition using accumulated backscattered electron images: new constraints on oscillatory zoning. Contributions to Mineralogy and Petrology, 142(4): 436–448. Viccaro, M., Giacomoni, P.P., Ferlito, C. and Cristofolini, R., 2010. Dynamics of magma supply at Mt. Etna volcano (Southern Italy) as revealed by textural and compositional features of plagioclase phenocrysts. Lithos, 116(1–2): 77–91.

95-112

Authors: Jamshid Ahmadian, Hajar Gholamian, Ali Khan Nasr Esfahani and Maryam Honarmand

Introduction The Kolah-Ghazi granitoid assemblage is located in the south of Esfahan and in the Sanandaj-Sirjan magmatic-metamorphic zone. The Sanandaj-Sirjan zone is extended for 1500 km from Sirjan in the southeast to Sanandaj in the northwest of Iran and is situated in the west of Central Iranian terrane. The Sanandaj-Sirjan zone represents the metamorphic belt of the Zagros orogeny which is part of the Alpine- Himalayan orogenic belt. The Kolah-Ghazi granitoid assemblage consists of granodiorite, granites, quartz-rich granitoid and minor tonalite. The aim of this paper is to represent the mineralogy, geochemistry, petrogenesis and tectonic setting of this plutonic assemblage. Materials and methods More than 60 samples representing all of the rock units in the study area were chosen for microscopic studies. Then, 22 samples were selected for geochemical studies. The major elements were determined with XRF in the Naruto University, Japan. The trace and rare earth elements were analyzed by ICP-MS in the Acmelab, Canada. The geochemical results are presented in Table 1. Results and Discussion The Kolah-Ghazi granitoid assemblage intruded into the Jurassic sedimentary units and overlaid by lower Cretaceous sandstone and conglomerate which suggest Upper Jurassic as the possible age of the Kolah-Ghazi intrusion. Based on the modal studies, this granitoid assemblage is comprised of granite, granodiorite, quartz-rock granitoid and tonalite with different igneous textures including symplectic, myrmekitic, rapakivi, poikilitic and porphyroid. There are some xenoliths, microgranular enclaves and sur micaceous enclaves in the Kolah-Ghazi granitoid assemblage. Xenoliths are mostly derived from Jurassic shale and sandstones which have been trapped in the magma. The sur micaceousenclaves have tonalite composition. The sur micaceous enclaves are biotite-rich rock fragments which display metamorphic texture. The sur micaceous enclaves are classified as restite since they are poor in quartz. The essential minerals in this magmatic assemblage are quartz, plagioclase, alkali-feldspar and biotite as the only ferromagnesian mineral. There was no hornblende in the studied samples. The presence of andalusite, sillimanite and garnet in these rocks point to the sedimentary source of these granitoid melts. Zircon, apatite and opaque minerals occurred as accessory minerals. The secondary minerals included sphene, tourmaline, clay minerals, chlorite and opaque minerals. The Kolah-Ghazi rock samples plot on the granite and granodiorite fields on the geochemical classification diagrams. The geochemistry of these plutonic rocks show peralunimous, high K-calc alkaline features. On the Harker variation diagrams, it can be observed that the Al2O3, FeO, MgO, TiO2 and CaO contents decrease with the increase in SiO2, whereas K2O and Na2O show an ascending trend with increasing SiO2. Moreover, the fractionation of plagioclase and the crystallization of alkali-feldspar caused the observed trends of Rb and Sr in the Harker diagrams. Ba contents decrease with increasing SiO2 which is relevant to the biotite fractionation. All of the analyzed samples show similar patterns in the chondrite-normalized trace elements and the REE diagrams. All samples show LILE and LREE enrichment and HFSE and HREE depletion. The negative anomaly of Sr may be related to the lack of calcic-plagioclase in these samples or suggest the plagioclase rich restite during partial melting of the parental rock. The latter is in agreement with the Eu anomaly that appeared in the REE diagram. All of the Kolah-Ghazi samples show linear trends in the major and trace elements versus SiO2 diagrams and display similar REE patterns suggesting close relationship in the source and magmatic history. The field, petrography and geochemical evidences such as pegmatit veins in the pluton, biotite rich enclaves, lack of hornblende and titanite, occurrence of metamorphic minerals (e.g., garnet, andalusite and sillimanite), the predominance of ilmenite, A/CNK values (A/CNK >1), and crondom contents (more than 3% in norm) suggest that the Kolah-Ghazi plutonic assemblage can be classified as S-type granitoids. Moreover, all of the Kolah-Ghazi samples plot on the S-type field of the granite classification diagrams (Whalen et al., 1987; Chappell and White, 1992) which is in good agreement with mineralogical evidences. The sedimentary source, mostly shale and greywacke, can be suggested for Kolah-Ghazi melts according to the Rb/Sr vs. Rb/Ba diagram (Sylvester, 1998). Several discrimination diagrams such as Rb vs. Ta+Yb (Pearce et al., 1984) and R1-R2 (Batchelor and Bowden, 1985) were used to determine the tectonic setting of the Kolah-Ghazi granitoids. The Kolah-Ghazi samples lied between the fields of magmatic arc and syn-collisional granitoids in the discrimination diagrams. The geochemistry of the studied samples suggest a syntectonic environment for the Kolah-Ghazi granitoids which may be related to the late Cimmerian orogenic phase. References Batchelor, R.A. and Bowden, P., 1985. Petrogenetic interpretation of granitoid rock series using multicationic parameters. Chemical Geology, 48(1): 43–55. Chappell, B.W. and White, A.J.R., 1992. I- and S-type granites in the Lachlan Fold Belt. Transactions of the Royal Society of Edinburgh, Earth Sciences, 83: 1–2. Pearce, J.A., Harris, N.B.W. and Tindle, A.G., 1984. Trace Element Discrimination Diagrams for the Tectonic Interpretation of Granitic Rocks. Journal of Petrology, 25(4): 956–983. Sylvester, P.J., 1998. Post-collisional strongly peraluminous granites. Lithos, 45(1-4): 29–44. Whalen, J.B., Currie, K.L. and Chappell, B.W., 1987. A-type granites: geochemical characteristics, discrimination and petrogenesis. Contributions to Mineralogy and Petrology, 95(4): 407–419.

139-171

Authors: Fariba Asiay Soufiani, Mir Ali Asghar Mokhtari, Hossein Kouhestani and Amir Morteza Azimzadeh

Introduction The Qarachilar Cu-Mo-Au occurrence is located in the Arasbaran ore zone (AZ), NW Iran, some 70 km north of Tabriz. The AZ is characterized by occurrence of different types of mineralization and hosts many Cu-Mo porphyry (PCD), Cu skarn, and epithermal Au deposits (Jamali et al., 2010; Jamali and Mehrabi, 2015). The main rock unit exposed in the area is Qaradagh batholith (QDB). A variety of porphyry and vein-type Cu–Mo–Au mineralization are associated with QDB. The most pronounced occurrences are in Qarachilar, Qara-Dareh, Zarli-Dareh, Aniq and Pirbolagh. This type of mineralization can be followed in other parts of northwest Iran, such as Masjed-Daghi porphyry Cu–Au deposit and Mivehrood vein-type Au mineralization in the southwest of the QDB, the Sungun PCD and the related skarn in its southeast, and Astamal Fe skarn deposit in the south of the QDB. To date, no detailed study has been undertaken to understand the characteristics of the Qarachilar occurrence and its mineralization type is controversial. The recent work by Simmonds and Moazzen (2015) also did not present relevant information for an understanding of the Qarachilar occurrence. The Re–Os age data obtained in their work were compared with similar events along the Urumieh-Dokhtar magmatic arc (UDMA) and southern Lesser Caucasus in order to elucidate the temporal pattern of mineralization across the whole QDB and the UDMA. The present paper provides an overview of the geological framework, the mineralization characteristics, and the results of geochemistry and fluid inclusion studies of the Qarachilar Cu-Mo-Au occurrence with an application to the ore genesis. Materials and methods More than 37 polished thin sections from Qarachilar host rocks and mineralized and altered zones were studied by conventional petrographic and mineralogic methods at the University of Zanjan. In addition, 9 samples from non-altered and altered host rocks and mineralized veins were analyzed by ICP-MS for trace elements and REE at the Zarazma Co., Tehran, Iran. Microthermometric data were performed on primary fluid inclusions using the Linkam THMS600 heating–freezing stage at the Iranian Mineral Processing Research Center (IMPRC), Tehran, Iran. Results The rock units exposed in the Qarachilar area are different sets of magmatic phases of QDB including granodiorite-quartz monzodiorite, porphyritic granite, quartz monzonite and acidic-intermediate dikes. Granodiorite-quartz monzodiorite is the dominant phase which hosts the Qarachilar quartz-sulfide veins. Mineralization at Qarachilar occurs as three quartz-sulfide veins. The veins reach up to 700-m in length and average 1-m in width, reaching a maximum of 2-m. They are generally steeply-dipping to the NE at 80°. The reported grades of Mo, Cu and Au range from 20 ppm to 3.6 wt%, 0.7 wt% to 5 wt%, and 0.23 to 37.2 g/t, respectively. Four stages of mineralization can be distinguished at Qarachilar. Stage-1 is represented by quartz veins (ranging from centimeters up to ≤1-m width) that contain variable amounts of chalcopyrite and pyrite. Stage-2 is marked by <1-mm to 3-cm wide veins of quartz with molybdenite ±pyrite that usually cut Stage-1 mineralization, and, in turn, are cut by Stage-3 veins. The Stage-2 veins usually show a banded appearance. Disseminated texture is also observed in this stage. Molybdenite (0‒5%) occurs as large flakes or aggregates of anhedral, tiny shredded crystals, rosettes, or plates, with variable sizes of 200-μm to 3-mm within the quartz veins-veinlets. Stage-3 is represented by 1 to 10-cm wide Au-bearing Fe-hydroxide quartz veinlets. Stage-4 is represented by individual or sets of late quartz-carbonate veinlets that usually cut previous stages. No sulfide minerals are recognized with Stage-4. The hydrothermal alteration assemblages at Qarachilar range from proximal quartz, sericite and carbonate to distal sericite, epidote and calcite (propylitic alteration). Potassic alteration occurs locally in 5-cm-wide, quartz-albite-secondary biotite veins within granodiorite-quartz monzodiorite pluton. The ore minerals composed of chalcopyrite, pyrite, molybdenite, galena and quartz, calcite and ankerite are present as gangue minerals. Chalcocite, covellite, malachite, azurite, ferimolybdite and goethite are formed during the supergene stage. The ore minerals show vein-veinlet, brecciated, disseminated, vug infill, replacement and relict textures. The comparison of Chondrite normalized (Nakamura, 1974) REE patterns of non-altered and altered host granodiorite-quartz monzodiorite pluton and the mineralized samples at Qarachilar indicate that altered pluton and especially mineralized samples show lower concentrations of REE relative to non-altered plutonic host rocks. This signature indicates the mobility of REE by Cl and F-rich magmatic-hydrothermal fluids during alteration and mineralization processes. Homogenization temperatures (Th) of two-phase inclusions within quartz varies from 182-532°C, and salinity varies from 9.2 to 23.5 wt% NaCl equiv. Three-phase halite-bearing type-1 (Th>Tm-h) and type-2 (Tm-h>Th) inclusions are homogenized in the range of 197-530°C and 203-375°C, respectively. They have a calculated bulk salinity of 29.5 to 55.1 and 32.4 to 45.6 wt% NaCl equiv., respectively. The variations in salinity and Th could be explained by a combination of mixing and boiling hydrothermal fluids. These processes led to the deposition of Cu, Mo and Au in the veins. Geology, ore mineralogy, textures, geochemistry and microthermometric data of Qarachilar occurrence are comparable with vein-type Cu-Mo-Au mineralization related to Cu-Mo porphyry and intrusion related gold deposits. References Jamali, H., Dilek, Y., Daliran, F., Yaghubpour, A.M. and Mehrabi, B., 2010. Metallogeny and tectonic evolution of the Cenozoic Ahar-Arasbaran volcanic belt, northern Iran. International Geology Review, 52(4–6): 608–630. Jamali, H. and Mehrabi, B., 2015. Relationships between arc maturity and Cu-Mo-Au porphyry and related epithermal mineralization at the Cenozoic Arasbaran Magmatic Belt. Ore Geology Reviews, 65(2): 487–501. Nakamura, N., 1974. Determination of REE, Ba, Fe, Mg, Na and K in carbonaceous and ordinary Chondrites. Geochimica et Cosmochimica Acta, 38(5): 755–773. Simmonds, V. and Moazzen, M., 2015. Re–Os dating of molybdenites from Oligocene Cu–Mo–Au mineralized veins in the Qarachilar area, Qaradagh batholith (northwest Iran): implications for understanding Cenozoic mineralization in South Armenia, Nakhchivan, and Iran. International Geology Review, 57(3): 290–304.

195-216

Authors: Habib Biabangard, Farooq Alian and Marziyeh Bazamad

Introduction The Zendan salt dome is located at 80 Km north of Bandar-Lengeh and 110 Km west of Bandar-Khamir cities in the Hormozgan province. Based on the structural geology of Iran, the Zendan salt dome is placed in the southeastern part of the Zagros zone (Stocklin, 1968). Important units in this area are Hormuz, Mishan, Aghajari and Bakhtiari formations with the Precambrian age (Alian and Bazamad, 2014). The Hormuz formation with the four members of H1, H2, H3, and H4 is the oldest formation (Ahmadzadeh Heravi et al., 1991). Basalt and diabase rocks are mostly rocks that are exposed in the Zendan salt dome. Magnetite and hematite iron mineralization happened in all the building rocks of salt dome, and is not a uniform mineralization. Iron mineralization contains hematite, spicularite, magnetite, goethite, and iron hydroxides. Magnetite-hematite-oligist layers (red soil) are the most iron mineralization in the Zendan salt dome, which are usually broken and scattered with gypsum layers (mostly anhydrite), respectively. Another form of iron mineralization is a mixture of hematite and magnetite (about 10 to 15%) in diabase rocks. Copper mineralization consists of pyrite and chalcopyrite minerals that are mostly in tuff and shale units. The presence of low immobile trace elements in the Zendan salt dome and type of alteration shows that maybe the origin of this iron is deposited from brine fluid. Therefore, this deposit can be classified into VMS deposits. Materials and methods We have taken 60 samples rocks from the Zendan salt dome, and then prepared 20 thin and polished sections. Petrographic studies were done and 9 samples were selected for analysis. These samples were sent to the Zarzma laboratory and the amount of FeO was determined by the wet chemical method and other amounts of oxides were determined by XRF. Six samples were analyzed for determining the major elements with the XRF method in the Binalood laboratory. Nine samples from vines mineralization were sent to the Zarzma laboratory and were analyzed with Inductively Coupled Plasma (ICP-OES). Two samples of igneous rocks were analyzed for determining major, minor and trace elements with ICP in Zarzma laboratory. Discussion Magmatic and evaporate fluids are sources of hydrothermal iron mineralization (Barton and Johnson, 2004). Sodic-calcic, semi sub deep pottasic, low silicific and sericitic alterations are related to magmatic fluids (Barton and Johnson, 2004). In the Zendan salt dome it seems that plutonic rocks prepared the source of temperature and made brine liquids evaporate and then moved the metals. Sodic alteration is one of the frequency alterations in the hydrothermal iron deposits related to high brain liquids (Arencibia and Clark, 1996). Immobile elements such as Ni, P and V show a high amount of magmatic iron deposit (Nystrom and Henriquiz, 1994). There is a significant relationship between the amount of Fe and the frequency elements. With an increase in the Fe content, the amount of TiO2, K2O, SiO2 and Al2O3 oxides decrease and the amounts of Ni and Cr2O3 increase. Low immobile elements’ contents and alteration type in the Zendan salt dome show the iron mineralization effect of brines fluids. On the other hand, this deposit can be classified into VMS deposits. Results Iron mineralization in Zendan salt dome is often magnetite, hematite, pyrite and chalcopyrite. Iron mineralization in the Zendan salt dome consists mostly of hematite, limonite and oligist (red soil) layers. They are usually found as scattered discontinuous layers and are alternated with gypsum layers. Hematite is the most abundant and dominant. There is a significant relationship between the amount of Fe and frequency elements. With increasing the Fe content, the amounts of TiO2, K2O, SiO2 and Al2O3 oxides decrease and the amounts of Ni and Cr2O3 increase . Low immobile elements' contents and alteration type in the Zendan salt dome shows the iron mineralization effect on brines fluids. On the other hand, this deposit can be classified into the VMS deposits. Acknowledgements The authors would like to thank the Ashrafpour, Hagheghe and all miners. References Ahmadzadeh Heravi, M., Houshmandzadeh, A. and Nabavi, M.H., 1991. New concepts of Hormuz formations, stratigraphy and the problem of salt diapirism in south of Iran. International Journal of Geosciences, 3(7):1–22. Alian, F. and Bazamad, M., 2014. Petrography of Zendan salt dome (Hara), Bandar Lengeh. 6th Symposium of Iranian society of Economic Geology, Sistan and Baluchestan University, Zahedan, Iran. Arencibia, O.N. and Clark, A.H., 1996. Early magnetite-amphibole-plagioclase alteration-mineralization in the Island copper porphyry copper-gold-molybdenum deposit, British Columbia. Economic Geology, 93(2): 402–438. Barton, M.D. and Johnson, D.A., 2004. Footprints of Fe oxide (Cu-Au) systems. Geological Survey of Western Australia, University of Western Australia, Report 33, 116 pp. Nystrom, J.O. and Henriquiz, F., 1994. Magmatic features of iron ore of Kiruna type in Chile and Sweden. Economic Geology, 89(4): 820–839. Stocklin, J., 1968. Structural history and tectonic of Iran: a review. American Association of Petroleum Geologists Bulletin, 52(7): 1229-1258.

237-254

Authors: Mahdieh Hosseinjani Zadeh and Mehdi Honarmand

Introduction Remote sensing has shown tremendous potential in the identification of alteration zones. The importance of this science for mineral exploration and recognition of alteration zones with lower cost, time, and manpower is confirmed in many studies (Amer et al., 2012; Hosseinjani Zadeh et al., 2014; Tayebi and Tangestani, 2015; Shahriari et al., 2015). Gold is one of the byproducts in most of the porphyry copper deposits (PCDs). Although the gold assay is partly low and reaches between 0.012- 0.38 g/t in these deposits, the high tonnage of copper deposits provides a considerable source of gold which has an important economic value (Kerrich et al., 2000). Extension, intensity of alteration, assays and the type of mineralization vary in different deposits. For instance, many Au-poor porphyry copper deposits in southwest USA, Central Asia, and west of South America are associated with widespread phyllic alteration (Kesler et al., 2002). In addition, there is a positive correlation between gold and magnetite in PCDs (Kesler et al., 2002; Shafiei and Shahabpour, 2008; Sillitoe, 1979). Therefore, aeromagnetic investigation could be useful in identification of these deposits. The aim of this research is discrimination of alteration zones and investigation areas with high concentration of gold through processing of remote sensing and aeromagnetic data. Materials and methods A number of prone areas with different concentrations of gold in Dehaj-Sarduiyeh copper belt including Sar Kuh, Abdar, Meiduk, Sarcheshmeh, Darrehzar, Sara, Iju and Seridune were investigated using the processing of Advanced space borne thermal emission and reflection radiometer (ASTER), and aeromagnetic data. Pre-processing acts such as crosstalk correction and Internal Average Relative Reflection (IARR) calibration were implemented on the ASTER data in order to remove noise and acquire surface reflectance. The alteration minerals were discriminated by implementation of appropriate algorithms such as color composite and partial sub-pixel method, and Mixture tuned matched filtering (MTMF) on a pre-processed and calibrated ASTER data. The results were verified by field surveys and laboratory analyses such as spectroscopic studies, optical microscopy, and XRD. The boundary of each deposit was determined by the results obtained from ASTER data. The aeromagnetic data were also processed using different filters like the reduced to the pole first and second vertical derivatives. Then the aeromagnetic data were clipped according to the boundaries determined with ASTER data and were exported into the GIS environment along with the determined abundances of altered minerals for the investigation of the characteristics of areas with a high concentration of gold. Results The results of ASTER image processing revealed that the distribution of phyllic alteration is high in the area. It is shown that most of the poor-Gold porphyry copper deposits are associated with widespread phyllic (Kesler et al., 2002). Therefore, the high exposure of phyllic confirms the low amount of gold in the study area. According to aeromagnetic results, the maximum and minimum differences in magnetic intensity were observed at Abdar- Sarkuh and Iju- Seridun, respectively which have high and low concentrations of gold in these deposits. In addition, the results which were obtained from reduced to pole transform revealed most correspondence with gold differences in the deposits. Discussion ASTER datasets were conducted on the eight porphyry copper deposits (PCDs) of Urumieh–Dokhtar magmatic belt including Sar Kuh, Abdar, Meiduk, Sarcheshmeh, Darrehzar, Sara, Iju and Seridune to investigate and detect the high potential areas for gold mineralization. ASTER false color composite image of bands 4, 6, and 8 in red green, and blue determined argillic and sericite altered rocks, as light red to pink, and propylitic altered rocks, as dark to light green. The results obtained from MTMF revealed that sericite is the dominant alteration mineral in the area. The discriminated minerals at most occurrences, including Sarcheshmeh, Meiduk, Sereidun, Darrehzar, Abdar and Iju showed a circular to elliptical pattern with sericite as dominant zone, scattered kaolinite and sparse alunite–pyrophyllite, surrounded by a combination of epidote, chlorite, and calcite. Investigation of aeromagnetic data by applying different filters showed that the magnetic intensity is high in areas with a high concentration of gold. For example, the maximum differences in magnetic intensity were observed at the Sar Kuh and Abdar which contain a higher concentration of gold. Acknowledgements The authors would like to acknowledge the Institute of science and high technology and environmental sciences, Graduate University of Advanced Technology, Kerman, Iran for their financial support during this study under the contract number 7.395. References Amer, R., Kusky, T. and Mezayen, A.E., 2012. Remote sensing detection of gold related alteration zones in Um Rus area, Central Eastern Desert of Egypt. Advances in Space Research, 49(1): 121–134. Hosseinjani Zadeh, M., Tangestani, M.H., Roldan, F.V. and Yusta, I., 2014. Sub-pixel mineral mapping of a porphyry copper belt using EO-1 Hyperion data. Advances in Space Research, 53(3): 440–451. Kerrich, R., Goldfarb, R., Groves, D. and Garwin, S., 2000. The geodynamics of world-class gold deposits: characteristics, space-time distribution, and origins. In: S.G. Hagemann and P.E. Brown (Editors.), Gold in 2000. Society of Economic Geologists, Incorporation. Littleton, Colorado. pp. 501–552. Kesler, S.E., Chryssoulis, S.L. and Simon, G., 2002. Gold in porphyry copper deposits: its abundance and fate. Ore Geology Reviews, 21(1–2): 103–124. Shafiei, B. and Shahabpour, J., 2008. Gold distribution in porphyry copper deposits of Kerman region, Southeastern Iran. Journal of Science, Islamic Republic of Iran, 19(3): 247–260. Shahriari, H., Honarmand, M. and Ranjbar, H., 2015. Comparison of multi-temporal ASTER images for hydrothermal alteration mapping using a fractal-aided SAM method. International Journal of Remote Sensing, 36(5): 1271–1289. Sillitoe, R.H., 1979. Some thoughts on gold-rich porphyry copper deposits. Mineralium Deposita, 14(2): 161–174. Tayebi, M.H. and Tangestani, M.H., 2015. Sub pixel mapping of alteration minerals using SOM neural network model and Hyperion data. Earth Science informatics, 8(2): 279–291.

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Authors: Mohammad Maanijou and Leila Khodaei

Introduction There is an iron mining complex called Shahrak 60 km east of the Takab town, NW Iran. The exploration in the Shahrak deposit (general name for all iron deposits of the area) started in 1992 by the Foolad Saba Noor Co. and continued in several periods until 2008. The Shahrak deposit is comprised of 10 ore deposits including Sarab-1, Sarab-2, Sarab-3, Korkora-1, Korkora-2, Shahrak-1, Shahrak-2, Shahrak-3, Cheshmeh and Golezar deposits (Sheikhi, 1995) with a total 60 million tons of proven ore reserves. The Fe grade ranges from 45 to 65% (average 50%). The ore reserves of these deposits are different. Sarab-3 ore deposit with 9 million tons of 54% Fe and 8.95% S is located at the northeast of Kurdistan and in the Sanandaj-Sirjan structural zone at the latitude of 36°20´ and longitude of 47°32´. Materials and methods Sixty thin-polished, polished and thin sections are made for the study of mineralogy and petrology, and among them six thin-polished sections were selected for EPMA (Electron Probe Micro Analysis) on magnetite and hematite. EPMA was performed using the Cameca Sx100 electron microprobe at the Iran Mineral Processing Research Center (IMPRC) with wavelength-dispersive spectrometers. Results and discussion Based on field observations and petrographic studies, lithologic composition of intrusion (Miocene age) ranges within the diorite-leucodiorite, monzodiorite-quartz monzodiorite, granodiorite-granite. With the intrusion of those igneous bodies into carbonate rocks of the Qom Formation, contact metamorphism was formed. The formation of Sarab-3 iron deposit occurred at the three stages of metamorphism, skarnification and supergene. Based on field geology of the deposit, it is composed of endoskarn, exoskarn including Fe ore±sulfides. At the metamorphic stage, after intrusion of intrusive bodies in carbonate rocks, recrystallization took place and marble was formed. With more crystallization of magma, evolved hydrothermal fluids intruded into host rocks. Skarnification occurred at the two stages of progressive and regressive. At the progressive stage, the reaction of fluids and host rocks turned to the formation of anhydrous calc-silicate minerals such as garnet and clinopyroxene. At the regressive stage with the change of physicochemical conditions like decreasing temperature, these minerals converted to hydrous silicates (tremolite-actinolite, epidote) and phyllosilcates (chlorite, serpentine, talk, and phlogopite). Also, minerals such as oxides (magnetite and hematite), sulfides (pyrite and chalcopyrite) and calcite were formed. At a late stage, with activations of fluids, quartz-calcite mineralized veins formed. At the supergene stage, the oxidation process leads to the formation of alteration minerals from the main mineralization. Although there are magnesian minerals in the skarn, its main composition is calcic. The shape of the deposit is lentoid to horizontal and in some places bed formed along with some alteration halos. The ore minerals include low Ti-magnetite (with an average of 0.02 wt % Ti), hematite and sulfide minerals such as pyrite, pyrrhotite and chalcopyrite. Magnetite is the most important mineral with disseminated, vein, open-space filling, aggregate, accumulation, island and cataclastic textures. The magnetite at Sarab-3 is generated in 2 stages: At the first stage, magnetite has mass to mosaic textures that indicate the first phase of deposition in the area and at the second stage magnetite is gray magnetites that are placed as narrow bands around hematite or on the primary magnetite. Hematite in the area is formed either as hypogene hematite with plate or blade texture that is formed before the formation of early magnetite or supergene hematite that itself is formed due to alteration and weathering of magnetite in the superficial and shallow part of the deposit. In the surface area of the deposit, ore minerals are strongly altered to mixtures of oxide and hydroxide minerals like hematite, limonite and goethite which changed the color of the ore body to yellow, deep orange, red and brown. Pyrites are the most important sulfide minerals in the area that are formed in five stages respectively, mass texture (Py1), Melnikovity (py2), vein-veinlet (py3), inclusion (py4), and mineralized veins (py5). Sericitization, calcitization, serpentinization, chloritization, epidotization, uralitization, argilitization, propylitization and actinolitizion are the important alterations in the area from which chloritization-epidotization and calcitization in the ore and propylitic and argilitization alteration in the plutonic rocks are dominant. The EPMA analytical results on 23 points on magnetite and hematite mineral suggest that the amounts of TiO2 and V2O5 (0.03 wt % and 0.01 wt % in average, respectively) are low in contrast to MnO and Al2O3 (0.09 wt % and 1.59 wt % on the average, respectively). Therefore, it fits in the skarn ore deposit domain on Ni/(Cr+Mn) versus Ti+V and Ca+Al+Mn versus Ti+V discrimination diagrams of iron ore deposits (Dupuis and Beaudoin, 2011). High Mn in the rock samples of Sarab-3 may have resulted from the substitution of Fe by Mn in magnetite and hematite structure that can be a sign of hydrothermal skarn. Manganes, Al, Cu, Mg, and Ca show a negative correlation with Fe that may have resulted from the concentration and the substitution of these elements in tremolite-actinolite, epidote, chlorite, calcite, phlogopite and chalcopyrite. 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 the Sarab-3 deposit resemble to exoskarn magnetite of Goto and endoskarn Karakaen deposit of Senegal. Mineralographical and geochemical evidence from ore, the occurrence of iron in contact with the carbonates and calc silicates such as garnet, pyroxene, secondary calcite, epidote and chlorite suggest iron skarn genesis for the Sarab-3 deposit. References Dupuis, C. and Beaudoin, G., 2011. Discriminant diagrams for iron oxide trace element fingerprinting of mineral deposit types. Mineralium Deposita, 46(4): 319–335. 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)