Journal of Economic Geology

267-294

Authors: Mohammad Hassan Karimpour, Azadeh Malekzadeh Shafaroudi, Abbas Esmaeili Sevieri, Saeed Shabani, Julien M. Allaz and Charles R. Stern

Introduction The Irankuh mining district area located at the southern part of the Malayer-Isfahan metallogenic belt, south of Isfahan, consists of several Zn-Pb deposits and occurrences such as Tappehsorkh, Rowmarmar 5, Kolahdarvazeh, Blind ore, and Gushfil deposits as well as Rowmarmar 1-4 and Gushfil 1 prospects. Based on geology, alteration, form and texture of mineralization, and paragenesis assemblages, Pb-Zn mineralization is Mississippi-type deposit (Rastad, 1981; Ghazban et al., 1994; Ghasemi, 1995; Reichert, 2007; Timoori-Asl (2010); Ayati et al., 2013; Hosseini-Dinani et al., 2015). Geology of the area consists of Jurassic siltstone and shale and different types of Cretaceous dolostone and limestone. The aim of this research is new geological studies such as revision of old geologic map, study of different types of textures and mineral assemblages within carbonate and clastic host rocks, and chemistry of galena, sphalerite, and dolomite. Finally, we combined these results with isotopic and fluid inclusion data and discussed on ore-fluid conditions. Materials and Methods In order to achieve the aims of this work, at first field surveying and sampling were done. Then, 200 thin and 70 polished thin sections were prepared. Some of the samples were selected for microprobe analysis and galena and sphalerite minerals were analyzed by using JEOL- JAX-8230 analyzer at Colorado University, USA. The chemistry of dolomite and fluid inclusion data are used after Boveiri Konari and Rastad (2016) and stable isotope is used after Ghazban et al. (1994). Discussion The Irankuh mineralization is hosted by carbonate rocks (dolostone and limestone) and minor clastic rocks as epigenetic. Mineralization has occurred as breccia, veinlet, open space filling, spoted, dessiminated, and replacement (carbonate hosted rock). The mineral assemblages are Fe-rich sphalerite, galena, minor pyrite, Fe- and Mn-rich dolomite, bituminous, ankrite, calcite ± quartz ± barite within carbonate host rocks, whereas Fe-rich sphalerite, galena, pyrite, minor chalcopyrite, low Fe-dolomite, quartz, bituminous, ± barite ± calcite are important primary minerals at clastic host rocks. There is positive correlation between Ag and Sb values within galena mineral. Sb/Bi ratio in galena is up to 20, which is an indicator of low temperature deposits (Malakhov, 1968). The Irankuh homogenization temperature (170 to 260 ºC) is higher than that of US Mississippi-type deposits (80 to 120 ºC). Based on comparison of Th and Fe and Cd contents in sphalerite from Irankuh and US deposits (Viets et al., 1992), homogenization temperature of deposit has a positive relation with Fe values and a negative relation with Cd contents in sphalerite. Fe content in Irankuh sphalerite has reached up to 5% and Cd value is lower than 2000 ppm. In addition, carbonate hosted rock hydrothermal dolomites that are Fe-rich and ankrite have formed at some places. The evidence shows that Irankuh ore-fluid is Fe-rich. However, clastic hosted rock hydrothermal dolomites are low-Fe due to reaction of Fe and S resulting in pyrite formation. Based on O isotope (16–19 ‰) value from hydrothermal dolomites (Ghazban et al., 1994), ore-fluid has been derived from continental crust. Results Fe-rich sphalerite and dolomite and ankrite are the most important characteristics of Irankuh mining district. Temperature and Fe-rich nature of ore-fluid and mineralogy signatures of Irankuh area can be used for exploration of this type of mineralization in Iran and the world. The Irankuh mining district is MVT type mineralization. Acknowledgements The Research Division of the Ferdowsi University of Mashhad, Iran, supported this study (Project No. 40221.3). Thanks to Bama Co. (especially Mr. Eslami) for the collaborations. References Ayati, F., Dehghani, H., Mokhtari, A.R. and Mojtahedzadeh, H., 2013. Geochemistry and mineralogy studies of Gushfil Pb-Zn deposit, Irankuh, Isfahan. Analytical and Numerical Methods in Mining Engineering, 6: 83-91 (in Persian). Boveiri Konari, M. and Rastad, E., 2016. Nature and origin of dolomitization associated with sulphide mineralization: new insights from the Tappehsorkh Zn-Pb (-Ag-Ba) deposit, Irankuh Mining District, Iran. Geological Journal, DOI: 10.1002/gj.2875 Ghasemi, A., 1995. Facies analysis and geochemistry of Kolah-Darvazaeh, Goud-Zendan, and Khaneh-Gorgi Pb-Zn deposits from south of Irankuh. M.Sc. thesis, Tarbiat Modares University, Tehran, Iran, 158 pp. (in Persian) Ghazban, F., McNutt, R.H. and Schwarcz, H. P., 1994. Genesis of sediment-hosted Zn-Pb-Ba deposits in the Irankuh district, Esfahan area, west-central Iran. Economic Geology, 89: 1262-1278. Hosseini-Dinani, H., Aftabi, A., Esmaeili, A. and Rabbani, M., 2015. Composite soil-geochemical halos delineating carbonate-hosted zinc–lead–barium mineralization in the Irankuh district, Isfahan, west-central Iran. Journal of Geochemical Exploration, 156: 114-130. Malakhov, A.A., 1968. Bismuth and antimony in galena, indicators of conditions of ore deposition. Geokhimiya, 11: 1283-1296. Rastad, E., 1981. Geological, mineralogical and ore facies investigations on the Lower Cretaceous stratabound Zn – Pb – Ba – Cu deposits of the Irankuh mountain range, Isfahan, west central Iran. Ph.D. thesis, Heidelberg University, Heidelberg, Germany, 334 pp. Reichert, J., 2007. A metallogenetic model for carbonate-hosted non-sulphide zinc deposits based on observations of Mehdi Abad and Irankuh, Central and Southwestern Iran. Ph.D. thesis, Martin Luther University Halle Wittenberg, Halle, Germany, 152 pp. Timoori-Asl, F., 2010. Sedimentology and petrology of Jurassic deposits and Basinal brines studies in formation of Irankuh deposit. M.Sc. thesis, Isfahan University, Isfahan, Iran, 120 pp. (in Persian) Viets, J.G., Hopkins, R.T. and Miller, B.M., 1992. Variation in minor and trace metals in sphalerite from Mississippi Valley-type deposits of the Ozark Region: genetic implications. Economic Geology, 87:1897–1905.

313-334

Authors: Ali Kananian, Fatemeh Ghahramani, Fatemeh Sarjoughian, Jamshid Ahmadian and Kazem Kazemi

Introduction Granitic rocks are the most abundant rock types in various tectonic settings and they have originated from mantle-derived magmas and/or partial melting of crustal rocks. The Oligo-Miocene Feshark intrusion is situated in the northeast of the city of Isfahan, and a small part of Urumieh–Dokhtar Magmatic Arc is between 52º21' E to 52º26'E and 32º50' N to - 32º53' N. The pluton has intruded into lower Eocene volcanic rocks such as rhyolite, andesite, and dacite and limestone. Analytical methods Fifteen representative samples from the Feshark intrusion were selected on the basis of their freshness. The major elements and some trace elements were analyzed by X-ray fluorescence (XRF) at Naruto University in Japan and the trace-element compositions were determined at the ALS Chemex lab. Results The Feshark intrusion can be divided into two phases, namely granodiorite with slightly granite and tonalite composition and quartz diorite with various quartz diorite and quartz monzodiorite abundant enclaves according to Middlemost (1994) classification. The quartz diorite show dark grey and are abundant at the western part of the intrusive rocks. Granodiorite are typically of white-light grey in color and change gradually into granite and tonalite. The granodiorite and granite rocks consist of quartz, K-feldspar, plagioclase, biotite, and amphibole, whereas in the quartz diorites the mineral assemblages between different minerals are very similar to those observed in the granodiorite. However, amphibole and plagioclase are more abundant and quartz and K-feldspar modal contents are lower than in the granodiorite whereas pyroxene occurs as rare grains. They are characterized as metaluminous to mildly peraluminous based on alumina saturation index (e.g. Shand, 1943) and are mostly medium-K calc-alkaline in nature (Rickwood, 1989). Discussion In the Yb vs. La/Yb and Tb/Yb variation diagrams (He et al., 2009), the studied samples show small variations in La/Yb and Tb/Yb ratios, suggesting fractional crystallization. Chondrite-normalized REE patterns (Sun and McDonough, 1989) of all the samples essentially have the same shape with light REE (LREE) enrichment, flat high REE (HREE) and significant negative Eu anomalies. All of the samples exhibit similar trace element abundance patterns, with enrichment in large ion lithophile elements (LILE) and negative anomalies in high field strength elements (HFSE; e.g. Ba, Nb, Ta, P, and Ti) compared to primitive mantle (Sun and McDonough, 1989). The enrichment of LILE and LREE relative to the HFSE and HREE along with Nb, Ta, and Ti anomalies display close similarities to those of magmatic arc granites (Pearce et al., 1984) and also negative Nb–Ti anomalies are thought to be related to the fractionation of Ti-bearing phases (titanite, etc.). Moreover, these are the typical features of arc and / or crustal contamination (Kuster and Harms, 1998), while the negative P anomalies should result from apatite fractionation. The increasing of Ba and slightly decreasing Sr with increasing Rb, indicate that plagioclase fractionation plays an important role in the evolution of the studied intrusion. Tectonic environment discrimination diagrams such as Nb vs. Y, Nb vs. Yb+Ta (Pearce et al., 1984) and Th/Yb vs. Ta/Yb (Pearce, 1983) with enrichment in the LILE and LREE relative to HFSE and HREE and negative anomaly in the Nb, Ti and Eu indicate that their initial magma is generated in the subduction zone related to an active continental margin setting. ‏The rocks genesis determining diagrams such as Nb vs. Nb/U (Taylor and McLennan, 1985), Ti vs. Ti/Zr (Rudnick et al. 2000), (La/Sm)cn vs. Nb/U (Hofmann et al., 1986), and Sr/Y vs. Y (Sun and McDonough, 1989) show that the magma was probably generated by partial melting of amphibolitic continental crust. References He, Y., Zhao, G., Sun, M. and Han, Y., 2009. Petrogenesis and tectonic setting of volcanic rocks in the Xiaoshan and Waifangshan areas along the southern margin of the North China Craton: Constraints from bulk-rock geochemistry and Sr-Nd isotopic composition. Lithos, 114(1-2): 186-199. Hofmann, A.W., Jochum, K.P., Seufert, M. and White, W.M., 1986. Nb and Pb in oceanic basalts: new constraints on mantle evolution. Earth and Planetary Science Letters ,79(1-2): 33-45. Kuster, D. and Harms, U., 1998. post – collisional potassic granitoids from the southern and northwestern parts of the late neoporterozoic East African Orogen: a review. Lithos. 45(1-4):177-195. Pearce, J.A., 1983. The role of sub-continental lithosphere in magma genesis at destructive plate margins. In: C.J. Hawkesworth and M.j. Norry (Editors), continental basalts and mantle xenoliths. Shiva Publications, Nantwhich, pp. 230-249. Middlemost, E.A.A. 1994. Naming materials in the magma/igneous rock system. Earth- Science Review. 37(3-4): 215–224. 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. Rickwood, P.C., 1989. Boundary lines within petrologic diagrams which use of major and minor element. Lithos, 22(4): 247-263. Rudnick, R.L., Barth, M., Horn, I. and McDonough, W. F., 2000. Rutile-Bearing Refractory Eclogites: Missing Link Between Continents and Depleted Mantle. Science, 287(5451): 278-281. Shand, S.J., 1943. The Eruptive Rocks. 2nd edition. John Wiley, New York, 444 pp. Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. Geological Society, London, Special Publications, 42, pp. 313-345. Taylor, S.R. and McLennan, S.M., 1985. The continental crust: its compositions and evolution. Blackwell, Oxford, 312 pp.

357-374

Authors: Shokouh Riahi, Nader Fathianpour and Seyed Hassan Tabatabaei

Introduction The growing demand for base metals such as iron, copper, lead and zinc on the one hand and the diminishing of surficial and shallow resources of these elements on the other hand have forced explorationists to focus on detecting deep deposits of these metals. As a result, the discovery of such deep deposits requires more advanced and sophisticated methods in the course of preliminary prospecting stages. Since the discovery of new deposits is getting to be increasingly difficult, deploying new prospecting technologies that employ more deposit attributes in the course of combining exploratory evidence may reduce the exploration costs with lower uncertainties. In the past two decades, a number of new data mining and integrating approaches capable of incorporating direct and indirect mineralization indicators, based on expert knowledge, data, or a combination of both, have been proposed )Bonham-Carter, 1994(. In the first step, the input exploratory data layers are corrected and validated through applying some statistical pre-processing algorithms such as background and outlier removal methods. In order to detect a mineralization occurrence, it is necessary to find the proper exploratory geological, geochemical and geophysical data layers which have direct or indirect associations with the governing mineralization followed by constructing these models in an appropriate GIS platform (Malkzewski, 1999). Due to the imperfect available data and a number of unknown parameters affecting the mineralization process, the application of conventional GIS integration methods such as Boolean or weighted overlay or even fuzzy logic methods alone may not produce appropriate results, pointing to a need for deploying multi-criteria decision-making methods such as TOPSIS. In the present study, the pre-processed exploratory data including geological, remotely sensed geophysical and geochemical imagery were used to detect favorable mineralization zones through applying the multi-criteria decision-making method. Finally, the selected favorable areas in the metallogenic strip located at the south to the south-east of the Sarcheshmeh porphyry copper deposit are prioritized and introduced for further follow up ground exploration operations. Methodology In order to solve complex decision-making problems like the problem of mapping favorable porphyry copper mineralization zones under great uncertainties, the TOPSIS method is considered as an appropriate approach offering significant simplicity, flexibility and capability (Ataei., 2010). The TOPSIS method is considered to be an efficient method due to having very high accuracy, speed, sensitivity as well as being easy to implement and interpret the outputted results (Hwang and Yoon, 1981). It has found many applications in important areas of mining industry where there is a need to make decisions under risky conditions and data uncertainties. One basic issue in applying decision-making methods in the field of mineral exploration is to rank and propose the best possible candidates among all potentially favorable areas for the next stage of mineral exploration. In this regard, the best favorable areas are selected based on exploratory data layers including favorable lithologies, alterations, structures plus geochemical and geophysical anomalies (Pazand et al., 2012). Results and discussion In the first step, the area located south to the southeast of one the largest porphyry copper deposits in Iran known as Sarcheshmeh was investigated for favorable areas using all available exploratory data as mentioned in the previous section using fuzzy logic integration approach in the GIS environment. Evaluating the highly favorable areas presented by the fuzzy logic approach showed great consistency with the already known copper mineralization prospects. Next, the first 20 priorities obtained from the fuzzy logic approach were chosen as the best candidates to be ranked using the TOPSIS multi criteria decision-making method. Among these favorable prospects, the one with the highest coefficient close to the ideal solution of 0.796 was found to be coincident with the Darehzar area that is a well known porphyry copper deposit 12 kilometers south of the Sarcheshmeh deposit. The favorable areas numbered 5 and 8 that correspond to well known porphyry copper mineralization prospects called Sereydoon and North Sereydoon were ranked as the second and third priorities with scores of 0.721 and 0.604, respectively. Other favorable areas ranked by the TOPSIS method were also prioritized and presented for further follow up explorations. To assess the sensitivity of the results obtained by the TOPSIS method, an amount of 10% of the values of each of the criteria were added and the outputted ranking results were compared to that of the original TOPSIS results. It was concluded that a slight change in the values of the criteria would not have significant impact on the results. However, 10 percent change of each criteria weight would greatly affect the prospects priorities obtained by re-applying the TOPSIS method. References Ataei, M., 2010. Multi Criteria Decision Making. Shahrood University Publications, Shahrood, 333 pp Bonham–Carter, G.F., 1994. Geographic information system for geoscientists-molding with GIS. Geological Survey of Canada, Ontario, Canada, 398 pp. Hwang, C.L. and Yoon, K., 1981; Multiple Attribute Decision Making: Methods and Applications, Springer-Verlag, Berlin, 228 pp. Malkzewski, J., 1999, GIS and Multi Criteria Decision Analysis. John Whily and Sons, Canada, 387 pp. Pazand, K., Hezarkhani, A. and Ataei, M., 2012. Using TOPSIS approaches for predictive porphyry Cu potential mapping: A case study in Ahar-Arasbaran area (NW, Iran). Computers & Geosciences, 49(1): 62-71.

397-418

Authors: Amir Ali Tabbakh Shabani, Morteza Delavari Kooshan and Mahsa Hajiabdolrahim Khabbaz

Introduction The Upper Eocene basic volcanic rocks that have cropped out in Karaj formation in the Boumehen and Roudehen area in the east of Tehran are characterized by fibrous zeolites filling their vesicles, cavities and fractures creating amygdale texture. The study area is located structurally in the Central Alborz orogenic belt. The presence of large volumes of shoshonitic magma during the Middle to Late Eocene in southern–central Alborz implies that partial melting to produce shoshsonitic melts was not a local petrological event. Thus, their ages, formation processes, and interpretations are of regional tectonic significance. In this study, we present a detailed petrography, mineral chemistry, and whole-rock geochemistry of high-K (shoshonitic) basic rocks to understand the petrogenesis and source region and to deduce the nature of the tectonomagmatic regime of the Alborz. Materials and methods In this study, we present new major and trace element data for a selection of 4 of the least altered samples by a combination of X-ray fluorescence (XRF) and ICP-OES techniques at the Zarazma Mineral Studies Company. Mineral analyses were obtained by wavelength dispersive X-ray spectrometry on polished thin sections prepared from each rock sample described above for 12 elements using a Cameca SX-50 electron microprobe at the Istituto di Geologia e Geoingegneria Ambientale, C.N.R., University La Sapienza of Rome, Italy. Typical beam operating conditions were 15 kV and probe current of 15 nA. The accuracy of the analyses is 1% for major and 10% for minor elements. A total of 24 point analyses were collected. Results and Discussion The extent of alteration in the study rocks varies from slight to severe and shows porphyritic to glomeroporphyritic textures. Pyroxenes are generally subhedral to euhedral and occur as discrete crystals as well as aggregates. Olivine may occur only as relics filled with iddingsite, chlorite and calcite. Plagioclase is subhedral to euhedral and occurs both as pheocrysts and microliths in the glassy groundmass. The plagioclase crystals are variably sassuratised and sometimes replaced by zeolites. Microprobe data indicate a restricted range of chemical composition for pyroxene falling in diopside and augite fields of ternary pyroxene classification diagram (Morimoto, 1988). The plagioclase composistions have been plotted in the fields of labradorite and bytownite in the orthoclase–albite–anorthite ternary diagram (Deer et al., 1992). On the F1-F2 tectonic discrimination diagram of Nisbet and Pearce (1977), pyroxene compositions plot mainly in volcanic arc basalt field consistent with their whole rock geochemistry. Thermobarometry based on pyroxene composition (Soesoo, 1997) displays a range of temperatures from 1150 to 1250 0C and pressure from 3 to 8 kbar for its crystallization. Whole rock compositions show that the variations of SiO2 contents are narrow (47.08 – 47.47 wt%) and TiO2 (1.1 – 1.24 wt%). Relatively higher contents of K2O show a shoshonitic affinity in the K2O–SiO2 diagram (Peccerillo and Taylor 1976). Trace element and rare earth element (REE) distribution patterns for the basaltic samples normalized to the primitive mantle (McDonough et al., 1992) and chondrite values (Sun and McDonough, 1989) show similar patterns. The samples are all enriched in large-ion lithophile elements (LILEs), such as Rb, Ba, and K, and light rare earth elements (LREEs) ((La/Sm)N= 2.3–3.2) relative to the more immobile elements (e.g., Hf, Ti and Y). The plot of analyzed samples in a series of different tectonic discrimination diagrams shows that the Boumehen-Roudehen alkaline basalts are consistent with characteristics of subduction related (active continental margins) tectonic environments. In addition, enrichment in LILE and depletion in HFSE on spidergram create patterns which are very similar with the pattern of Andean counterparts indicating an arc setting. Acknowledgments Marcello Serracino is thanked for microprobe analyses. The authors are grateful to Journal Manager and reviewers who critically reviewed the manuscript and made valuable suggestions for its improvement. References Deer, W.A., Howie, R.A. and Zussman, J., 1992. An Introduction to the Rock Forming Minerals. Longman, London, 696 pp. McDonough, W.F., Sun, S.-S., Ringwood, A.E., Jagoutz, E. and Hofmann, A.W. 1992. Potassium, Rubidium and Cesium in the Earth and Moon and the evolution of the mantle of the Earth. Geochimica et Cosmochimica Acta, 56(3): 1001-1012. Morimoto, N., Fabries, J., Ferguson, A.K., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J., Aoki, K. and Gottardi, G., 1988. Nomenclature of pyroxenes. American Mineralogist, 73)9-10:( 1123–1133. Nisbet, E.G. and Pearce, J.A., 1977. Clinopyroxene composition in mafic lavas from different tectonic settings. Contributions to Mineralogy and Petrology, 63)2:(149-160. Peccerillo, A. and Taylor, S.R.,1976 . Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey. Contributions to Mineralogy and Petrology, 58(1): 63-81. Soesoo, A. 1997. A multivariate statistical analysis of clinopyroxene composition: Empirical coordinates for the crystallisation PT- estimations. Journal of the Geological Society of Sweden, 119(1): 55-60. Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts; implications for mantle composition and processes. In: A.D., Saunders and M.J., Norry (Editors), Magmatism in the ocean basins. Geological Society, London, Special Publications, 42. 313-345.

439-461

Authors: Zahra Vahedi Tabas, Seyyed Saeid Mohammadi and Mohammad Hossein Zarrinkoub

Introduction Basaltic volcanoes are one of the volcanisms that have occurred in different parts of the world. The study of these lavas is important for petrologists, because they are seen in different tectonic settings and therefore diverse mechanisms affect their formation (Chen et al., 2007). Young volcanic rocks such as Quaternary basalts are one of latest products of magmatism in Iran that are related to deep fractures and active faults in Quaternary (Emami, 2000). The study area is located at 140km east of Birjand at Gazik 1:100000 geological map (Guillou et al., 1981) and have 60̊ 11' to 60̊ 15 '27" eastward longitude and 32̊ 33' 24" to 32̊ 39' 10" northward latitude. On the basis of structural subdivisions of Iran, this area is located in the northern part of the Sistan suture zone (Tirrul et al., 1983). Because of the importance of basaltic rocks in Sistan suture, this research is done with the aim of investigating the petrography and mineralogy of basaltic lavas, the nature of basaltic and intermediate magmatism and finally determination of tectonomagmatic regime. Materials and methods After field studies and sampling, 85 thin sections were prepared and carefully studied. Then ten samples with the lowest alteration 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 Acme laboratories, Vancouver, Canada. Electron probe micro analyses of clinopyroxene and olivine were done at the Iranian mineral processing research center (IMPRC) by Cameca SX100 machine. X-ray diffraction analysis of minerals was done at the X-ray laboratory of the University of Birjand. Results In 60km south of GaziK at the east of the southern Khorasan province and the northern part of the Sistan suture zone, volcanic rocks with intermediate (Oligomiocene) and basic (Quaternary) compositions outcropped above ophiolitic units. Electron probe micro analyzer (EMPA) data indicated that clinopyroxene in basalt is diopside and olivine from chrysolite type with Mg# around 81-82 percent. The whole rocks geochemical data prove calc-alkaline and alkaline nature for andesites and basalts, respectively. Trace element patterns, especially for andesites show enrichment in Ba, K, Cs, Sr and Th, depletion in P, Nb, Ti and enrichment in LREE relative to HREE. Electron probe micro analyses of clinopyroxene in olivine basalt support alkaline nature and within plate tectonic setting for this rock. Thermobarometry of clinopyroxene in olivine basalt record crystallization conditions about 1200 oC and 6-10kbars. Discussion The origin of intraplate volcanism is diverse and not always well understood. Most intraplate volcanos have been attributed to (i) mantle plumes and hot spots, (ii) continental rift, (iii) back-arc extension and (iv) lithosphere delamination and thinning (Chen et al., 2007). Although volcanism at intraplate settings is less common than along mid-ocean ridges and subduction zones, it is of significant importance for both preventing geological hazards and understanding mantle geochemistry. It is believed that alkaline oceanic island basalts (OIB) are only derived from the asthenospheric mantle (Alici et al., 2002). However, the intracontinental alkaline magmas can be produced by partial melting of metasomatized mantle enriched in LREE and LILE (Upadhyay et al., 2006). On the basis of trace element diagrams, Ratouk basaltic rocks placed within plate volcanic zone (WPVZ) and andesitic samples have been located within the active continental margin (ACM). The studies that took place about young basaltic volcanism (Alishahi, 2012; Mollashahi et al., 2011; Ghasempour et al., 2011; Pang et al., 2012; Walker et al., 2009) have shown that the mechanisms of their occurrence are similar such that all of them have been formed in intraplate extensional environments and active fault zone and originated from enriched mantle or asthenosphere. Lithospheric thickness maps derived from the speed of shear waves show that the lithosphere is thin in east of Iran and volcanic activity has occurred along strike-slip faults (Walker et al., 2009). Therefore, according to other similar basaltic eruptions that have occurred in the Sistan suture zone, we can say that all of them are from the same origin and as a result of deep fractures within continental plates that provide conditions for the eruption of basaltic magma. Andesitic units in the Ratouk area are located within the active continental margin and show similar characteristics to rocks of the Subduction Zone in terms of composition. Acknowledgements The authors would like to thank reviewers for the constructive comments which greatly contributed to the improvement of the manuscript. References Alici, P., Temel, A. and Gourgaud, A., 2002. Pb-Nd Sr isotope and trace element geochemistry of Quaternary extension-related alkaline volcanism: a case study of Kula region western Anatolia, Turkey. Journal of Volcanology and Geothermal Research, 115(3): 487-510. Alishahi, E., 2012. Petrology and Geochemistry of volcanic rocks in Nasfandeh area (east of Nehbandan) –Iran. M.Sc. Thesis, University of Birjand, Birjand, Iran, 211 pp. (in Persian with English abstract) Chen, Y., Zhang, Y., Graham, D., Su, S. and Deng, J., 2007. Geochemistry of Cenozoic basalts and mantle xenoliths in Northeast China. Lithos, 96(1): 108–126. Emami, M.H., 2000. Magmatism in Iran. Geological Survey of Iran, Tehran, 608 pp. Ghasempour, M.R., Byabangard, H., Boomeri, M. and Moridi, A., 2011. Geochemistry and tectonic setting of Plio-Quaternary basaltic rocks in SE Nehbandan, eastern Iran. Iranian Journal of Crystallography and Mineralogy, 18(4): 695-708. (in Persian with English abstract) Guillou, Y., Maurizot, P., Vaslet, D. and Dellavillen, H., 1981. Geological map of Gazik, Scale1:100000. Geological Survey of Iran. Mollashahi, N., Zarrinkoub, M.H., Mohammadi, S.S. and Khatib, M.M., 2011. Petrology of young volcanic in Hamun Lake area (East of Iran). Iranian Journal of Crystallography and Mineralogy, 19(3): 519-528. (in Persian with English abstract) Pang, K.W., Chung, S.L., Zarrinkoub, M.H., Mohammadi, S.S., Yang, H.M., Chu, C.H., Lee, H.Y. and Lo, C.H., 2012. Age, geochemical characteristics and petrogenesis of Late Cenozoic intraplate alkali basalts in the Lut–Sistan region, eastern Iran. Chemical Geology, 306-307: 40-53. Tirrul, R ., Bell, L.R., Griffis, R.J. and Camp, V.E., 1983. The Sistan suture zone of eastern Iran. Geological Society of America Bulletin, 94(1): 134-150. Upadhyay, D., Raith, M.M., Mezger, K. and Hammerschmidt, K., 2006. Mesoproterozoic rift-related alkaline magmatism at Elchuru, Prakasam Alkaline Province, SE India. Lithos, 89(3): 447-477. Walker , R.T., Gans, P., Allen, M., Jackson, J., Khatib, M.M. and Zarrinkoub, M.H., 2009. Late Cenozoic Volcanism and rates of active faulting in eastern Iran. Geophysical Journal International, 177: 783-805.

483-507

Authors: Faezeh Nabiloo, Behnam Shafiei Bafti and Arash Amini

Introduction Upper part of Elika Formation (middle Triassic) in the central Alborz as one of the most important fluorite districts in Iran is the host of some carbonate rock-hosted fluorite deposits such as Kamarposht, Pachi-Miana, Shashroodbar, Era (Alirezaee, 1989; Gorjizad, 1996; Rastad and Shariatmadar, 2001; Rajabi et al., 2013; Vahabzadeh et al., 2013; Zabihitabar and Shafiei, 2015). One of the main active fluorite mines in the central Alborz is Kamarposht which is located at the southeast of DoAb in the Mazandaran province. The Kamarposht mine has 75000 tons of ores and mining there has begun in 2005. The effects and evidences of underground mining in the northern and southern parts of this mine indicate high-grade and coarse-grained ore zones which have fluorite, galena and barite. Until now, basic economic geology studies in the Kamarposht mine including mineralogy, fabric and texture of mineralization for introducing a new fluorite mine in Iran have not been carried out. The present study is based on field observations and macroscopic as well as microscopic studies aimed at identification of morphology and mode of occurrence of the ore body, mineralogy and fabric of mineralization and discussion of as well as presentation of a new genetic model for the Kamarposht mine. Materials and methods For the present research study, field geology and sampling were carried out to collect 100 samples from various fluorite ore-types and carbonate host rocks. The samples prepared for thin section (n=55) and polished-thin sections (n=22). Results Field observations indicate that economic mineable ore zones of the Kamarposht mine are mainly hosted by dolomitic limestone and silicified carbonate horizons of the Elika Formation. The ore zones have fluorite, barite and galena which are mainly located in fractured and faulted zones as well as karstic cavities in the host horizons. Coarse grain and euhedral fluorites with various colors, significant presence of barite as massive and vein, abundant galena and near contact between mineralization zones in carbonate host rocks (Elika Fm.) and pyrite-bearing coalified shales (base of Shemshak Fm.?) as faulted and/or interbedded are all distinctive geological features for the Kamarposht mine. Fluorite mainly occurs as interrupted, dense and voluminous massive bodies with/without galena which have occupied cavities and open spaces between brecciated fragments of dolomitic limestone relative to the form of disseminate grains, veinlets and geode. Massive and voluminous accumulations of barite in dissolution and karstic cavities and also as discordant veins relative to the bedding of the host rock which have been generated radial, breccias and zebra structures in barite ores. Galena occurs as veinlets and breccias with medium to coarse grain size with/without fluorite in dolomitic and silicified host rocks and also as vein-veinlets into and/or rime of massive barites. Discussion Based on field evidences and mode occurrence of ore minerals and ore textures, mineralization in the Kamaposht mine has occurred as syn-diagenetic (primary) and post-diagenetic/epigenetic (main) fabrics. Ores with disseminate particles of ore minerals, stylolite, geode and tiny veinlets fabrics have been interpreted as primary textures that co-exist with diagenesis of host rocks. These fabrics have been formed under diagenetic processes such as nucleation, re-crystalization and disolution of host rocks by diagenetic phreatic reactions that have caused increasing temperature-pressure due to increasing depth of burial diagenesis (Force et al., 1991; Fontbote and Gorzawski 1990; Rastad and Shariatmadar, 2001; Haeri-Ardakani et al., 2013). The main textures of mineralization in the Kamarposht mine namely open-space filling fabrics including veins and breccias fabrics with replacement, network and zebra textures which are associated with dolomitized and silicified host rock have been caused by late and/or post-diagenetic processes (Fontbote and Gorzawski 1990; Sangster, 1996; Leach et al., 2005). Change and conversion of diagenetic mineralization fabrics to epigenetic ones which is associated with developing and increasing the intensity of fluorite-barite-galena mineralization, is attributed to the function of hydrothermal solutions/basianl brines generated due to the main Cimerian orogeny (Rajabi et al., 2013). The increasing dissolution of host rock along with its dolomitization and silicification were probably the main processes responsible for epigenetic mineralization in the Kamarposht mine. Finally, the present study shows that the Kamarposht mine is a fluorite-rich MVT deposit with poly-genetic origin. References Alirezaee, S., 1989. Contribution to stratigraphy and mode of generation of F-Pb-Ba deposits in Triassic of eastern Alborz. M.Sc. Thesis, Tehran University, Tehran, Iran, 87 pp. (in Persian with English abstract). Fontbote, L. and Gorzawski, H., 1990. Genesis of the Mississippi Valley-Type Zn-Pb Deposit of San Vicente, Central Peru: Geologic and Isotopic (Sr, O, C, S, Pb) Evidence. Economic Geology, 85(7): 1402-1437 Force, E.R., Eidel, J.J. and Maynard, J.B., 1991. Sedimentary and diagenetic mineral deposits: A basin analysis approach to exploration. Society of Economic Geologist Publication, Reviews in Economic Geology 5 , USA, 217 pp. Gorjizad, H., 1996. Study on geology, mineralogy, facies analysis and genesis of Pachi Miana fluorite deposit. M.Sc. Thesis, Tarbiat Modaress University, Tehran, Iran, 156 pp. (in Persian with English abstract) Haeri-Ardakani, O., Al-Asem, I., Coniglio,M. and Samson, I., 2013. Diagenetic evolution and associated mineralization in Middle Devonian carbonates, southwestern Ontario, Canada. Bulletin of Canadian Petroleum Geology, 61(1): 41–58. Leach, D., Sangster, D., Kelley, K., Large, R., Garven, G., Allen, C., Gutzmer, J. and Walters, S., 2005. Sediment- hosted lead-zinc deposits: a global perspective. In: J. Hedenquist, J. Thompson, R. Goldfarb, and J. Richards, (Editors), 100th Anniversary Volume of Economic Geology, Society of Economic Geologist Publication, USA, pp. 561-607. Rajabi, A., Rastad, E. and Canet, C., 2013. Metallogeny of Permian-Triassic carbonate-hosted Zn-Pb and F deposits of Iran: A review for future mineral exploration. Australian Journal of Earth Sciences, 60(2): 197-216. Rastad, E. and Shariatmadar, A., 2001. Sheshroodbar fluorite deposits, sedimentary and diagenetic fabrics and its depositional environment (Savad Kuh, Mazandaran province). Journal of Geosciences, 10(41-42): Sangster, D.F., 1996. Carbonate-hosted lead-zinc deposits. Society of Economic Geology, Special Publication No.4, 664 pp. Vahabzadeh, G., Khakzad, A., Rasa, I.¬ and Mosavi, M.R., 2014. Fluorite REEs geochemistry in fluorite deposits of central Alborz. New Finds of Applied Geology, 16(1): 58-70. (in Persian with English abstract) Zabihitabar, Sh. and Shafiei, B., 2015. Mineralogy and mode occurrence of sulfides, sulfates and carbonates at fluorite mines in East of Mazandaran province. Iranian Journal of Geology, 33(1): 62-78. (in Persian with English abstract)

545-559

Authors: Atefeh Ghaedi, Abbas Moradian and Hamid Ahmadipour

Introduction Borate deposits are often important constituents of economic non - marine evaporates. They produce under arid climatic conditions in playa lakes (Floyd et al., 1998). In the south – western parts of the Kerman province, such as the Khatoonabad area (east of the city of Shahr –e –Babak) and Robat – Marvast basin (west of Shahr – e – Babak), there are several borate deposits. They can be seen mainly in Sanandaj – Sirjan depressions and they occur as borate bearing nodules beneath a thin layer of soil. In general, boron considerably reduces the thermal expansion of glass, provides good resistance to vibration, high temperatures and thermal shock, and improves its toughness, strength, chemical resistance and durability. It also greatly reduces the viscosity of the glass melt. These features, and others, allow it to form superior glass for many industrial and specialty applications (Garrett, 1998). In the past, the ancient residents used them as co-melting matters. Ulexite which is frequently found in the Khatoonabad playa (at 30 km South East of Shahr Babak) have Jewel properties (Ghaedi et al., 2014). Materials and methods After reviewing and Library Studies, geological field studies on the borate deposits were carried out from Shahr – e – Babak Playa. In order to take better samples, several pits were excavated with a depth of 30 cm to 1 meter so that borate minerals became apparent. X-ray diffraction analysis (IMIDRO, Karaj), and ICP AES (ALS CHEMEX, Canada) methods were carried out on representative samples taken from the studied area. Discussion Field observations show that in the studied areas, borate bearing basins are fed by rivers which have originated from Sanandaj – Sirjan metamorphic rocks, Nain – Baft colored mélanges and igneous rocks of Urumieh – Dokhtar magmatic belt. Borate minerals also occur in fibrous aggregates and massive forms. Mineralogy XRD results show that the studied borate minerals mainly belong to the hydrated borates and contain ulexite, borax, gowerite, sassolite and inyoite. Geochemichal data indicate that the boron is the dominant constituent in the studied playa. Borate minerals are divided into two groups of hydrated and non-hydrated borate category (Palache et al., 1952.; Garrett, 1998). Both hydrated and non-hydrated borate minerals have been formed in the Shahr-e-Babak playa. Hydrated borate in the study areas: Hydrated borates are those borates in which water molecules are involved (Garrett, 1998). In the studied area, the hydrated borate minerals include: Borax, Ulexite, Inyoite, Gowerite. Non-hydrated borate in the study areas: In the Shahr-e-Babak playa, Sassolite non-hydrated borate minerals are abundant. According to the XRD analyses performed on samples from the study areas, the hydrated borate minerals are more important minerals. The main economic valuable minerals include: 1- Ulexite (NaCaB5O9.8H2O): Crystal Data: Triclinic. Point Group: 1 (Ghose et al., 1978). In the Shar – e - Babak playa, ulexite occurs as deposits with massive, cauliflower-like nodules and fibrous textures. 2- Borax (Na2B4O5(OH)4 •8H2O): Crystal Data: Monoclinic. Point Group: 2/m. Crystals are commonly short to long prismatic [001] (Levy and Lisensky, 1978). In the studied borate samples, it can be found in association with the other borate minerals, and often occurs in the form of salt marsh. 3- Gowerite (CaB6O8(OH)4 •3H2O): Crystal Data: Monoclinic. Point Group: 2/m (Erd et al., 1959). In the Khatoonabad samples, it was found as prismatic and spherical crystals along with ulexite. 4- Inyoite (CaB3O3 (OH)5 •4H2O): Crystal Data: Monoclinic. Point Group: 2/m (Christ, 1953). This mineral has been detected in the studied area by XRD. Sassolite (H3BO3): Crystal Data: Triclinic. Point Group: 1 and as scaly pseudohexagonal crystals (Allen and Kramer, 1957). This mineral is found frequently in the Marvast Playa. Geochemistry Geochemical data indicate that in the studied playa, boron is very abundant. Good correlation between the elements, such as B and Ca confirms the formation of Calcium bearing borate mineral in the studied areas. Origin Field observations show that in the studied areas, borate bearing basins are fed by rivers which have originated from the Sanandaj – Sirjan metamorphic rocks, Nain – Baft colored mélanges and igneous rocks of the Urumieh – Dokhtar magmatic belt. Result The XRD results show that the studied borate minerals mainly are hydrated ones and contain ulexite, borax, gowerite, sassolite and inyoite. Geochemichal data confirm the frequency of boron in the playa. Good correlation between the elements such as B and Ca verifies the formation of Calcium bearing borate mineral in the studied areas. Acknowledgements The authors wish to thank IMIDRO for performing XRD analyses. References ‏‏ Allen, R.D. and Kramer, H., 1957. Ginorite and sassolite from Death Valley, California. American Mineralogist, 42(1-2): 56-61.‏ Christ, C.L., 1953. Studies of borate minerals, 2. X-ray crystallography of inyoite and meyerhofferite -x-ray and morphological crystallography of 2CaO. 3B2O3. 9H2O. American Mineralogist, 38(1 - 11): 912-918. Erd, R.C., McAllister, J.F. and Almond, H., 1959. Gowerite, a new hydrous calcium borate, from the Death Valley Region, California. American Mineralogist, 44(9-10): 911-919.‏ Floyd, P.A., Helvaci, C. and Mittwede, S.K., 1998. Geochemical discrimination of volcanic rocks associated with borate deposits: an exploration tool? Journal of Geochemical Exploration, 60(3): 185-205.‏ Garrett, D.E., 1998. Borates: handbook of deposits, processing, properties, and use. Academic Press, USA, 483 pp. Ghaedi, A., Moradian, A. and Ahmadipour, H., 2014. Reviewing and introduction of mineralogical properties of Ulexite an unknown gem in Khatoonabad (Shahr Babak, Kerman Province). The 1st National Symposium of Gemology- Crystallography of Iran, Shahid Bahonar University of Kerman, Kerman, Iran. Ghose, S., Wan, C. and Clark, J.R., 1978. Ulexite, NaCaB5O6 (OH)6 . 5H2O: structure refinement, polyanion configuration, hydrogen bonding, and fiber optics. American Mineralogist, 63(12): 160–171. Levy, H.A. and Lisensky, G.C., 1978 .Crystal structures of sodium sulfate decahydrate (Glauber's salt) and sodium tetraborate decahydrate (borax). Redetermination by neutron diffraction. Acta Crystallographica, 34(12): 3502-3510. Palache, C., Berman, H. and Frondel, C., 1952. Dana's System of Mineralogy. Geologiska Föreningen i Stockholm Förhandlingar, 74(2): 218-219.‏

587-616

Authors: Fayeq Hashemi, Fardin Mousivand and Mehdi Rezaei-Kahkhaei

Introduction The Varandan Ba-Pb-Cu deposits are located15 km southwest of the town of Qamsar and approximately 7 km south west of the Qazaan village, in the Urumieh- Dokhtar magmatic arc. The Kashan region that is situated in west-central Iran hosts several barite-base metal deposits and occurrences, the biggest ones are the Varandan Ba-Pb-Cu (case considered in this study) and the Tapeh-Sorkh (Khalajmaasomi et al., 2010) and Dorreh Ba (Nazari, 1994) deposits. Previous researchers (Izadi, 1996; Farokhpey et al., 2010) have proposed an epithermal model for formation of the Varandan deposit. However, based on some feature of the deposit, it seems that this genetic model may not be correct. Therefore, it is necessary to do more precise research studies on the deposit. The main purpose of this paper is to discuss the genesis of the Varandan deposit based on geological, ore facies, mineralogy, wall rock alterations, and geochemical studies. Materials and methods A field study and sampling was performed during the summer of 2013. To assess the geochemical characteristics of the deposit, about 17 systematic samples from different ore facies of the first, second and third sub-horizon were collected for petrography and mineralogy, and for inductively coupled plasma-atomic emission spectroscopy(ICP-AES), X-ray diffraction (XRD) and X-ray fluorescence (XRF) geochemical analysis methods. The microscopic studies were done in the optics laboratory of the Shahrood University, and the geochemical analyzes were conducted in laboratories of the Center of Research and Mineral Processing Ore Minerals of Iran, Karaj, Iran. Results The host sequence in the Varandan deposit involves three units, from bottom to top: Unit1: grey, green siliceous tuff, brecciated tuff, crystal tuff and andesite; Unit2: white grey nummulitic limestone, limy tuff and marl: and Unit3: tuff breccia and crystal lithic tuff. Mineralization in the Varandan deposit has occurred as four ore sub-horizons in Unit1, as lenticular to tabular ore bodies concordant to layering of the host rocks. Based on textural, structural and mineralogical studies, the Varandan deposit consists of five ore facieses including: 1) veins-veinlets (stringer zone) that involves cross-cuting barite, quartz and sulfide veins-veinlets, 2) brecciated barite and massive pyrite (vent complex zone) involving replacement texture, 3) massive barite and sulfide (massive zone), 4) alternations of barite- and galena- rich bands (Bedded-banded zone) and; 5) iron-manganese-bearing hydrothermal-exhalative sediments. Primary ore minerals are barite, galena, chalcopyrite, pyrite, sphalerite, tetrahedrite, magnetite, oligiste, braunite, pyrolusite and bornite, accompanied with secondary minerals such as native copper, cuprite, digenite, covellite, chalcosite, goethite, hematite and malachite. Gangue minerals consist of chlorite, sericite, quartz and calcite. Major wall rock alterations in the deposit are chloritic and quartz- sericitic. For determining the type of ore of the Varandan deposit, the Cu/Zn ratio for the barite and sulfide ore of the first, second and third sub-horizon are 1.08, 0.12 and 11.08, respectively. This lies in the yellow ore for the first and third sub-horizon, and it falls in the black ore for the second sub-. Discussion According to the basic characteristics of mineralization such as geometry of ore bodies, textures and structures, ore facies, wall rock alterations, mineralogy, fluid inclusions data, metal zonation and geochemical features, the Varandan deposit could be classified as a bimodal-felsic or Kuroko-type voclanogenic massive sulfide (VMS) deposit, similar to those of the Hokuroko basin in Japan (Ohmoto and Skinner, 1983; Hoy, 1995, Huston et al., 2011). The Varandan deposit has been formed in an intra-arc setting due to subduction of the Neo-Tethyan oceanic crust beneath the Iranian plate during the Middle Eocene. Acknowledgements The authors are grateful to the Grant Commission for research funding of Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and the University of Shahrood. References Farokhpey, H., Shamsi-Poor, R. and Nasre-Esfahani, A. 2010. Economic petrology of granitoid Ghazaan: study of metal deposit. The Conference on Applied Petrology, Khorasgan Azad university, Tehran, Iran. Hoy, T., 1995. Noranda/kuroko Massive Sulphide Cu-Zn deposits. In: D.V. Lefebure and G.E. Ray (Editors), Selected British Colombia Mineral deposit Profiles, volum 1- Metallics and Coal. British Columbia Ministry of Energy of Employment and Investment open file, Canada, pp. 53-54. Huston, D., Relvas, J., Gemmell, J.B. and Drieberg, S., 2011. The role of granites in volcanic-hosted massive sulphide ore-forming systems: an assessment of magmatic-hydrothermal contributions.Journal of Mineralium Deposita, 46(5-6): 473-507. Izadi, H., 1996. Geology, petrografy and genises of Ba-Pb Kashan Ghamsar Ghazaan. M.Sc. thesis, Khorasgan Azad university, Tehran, Iran. 160 pp. Khalajmaasomi, M., Lotfi, M. and Nazari, M., 2010. Tapeh-Sorkh Mine mineralization model designation Bijegan-Delijan Central Province. Journal of Land and Resources, 1(2): 33-43. (in Persian) Nazari, M., 1994. Study of mineralogy and ore genesis Dorreh deposit in the Kashan. M.Sc. Thesis, Tarbiat-moallem University, Tehran, Iran, 147 pp. (in Persian with English abstract) Ohmoto, H. and Skinner, B.L., 1983. The Kuroko and related volcanogenic massive sulphide deposits: Introduction and summary of new findings. In: H. Ohmoto and B.J. Skinner (Editors), Kuroko and Related Volcanogenic Massive Sulphide Deposits. Economic Geology, Canada, pp. 1-8.