Journal of Economic Geology

155-174

Authors: Abbas Golmohammadi; Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi; Seyed Ahamad Mazaheri

Sangan magnetite skarn mine is located 300 km southeast of Mashhad, along the eastern part of Khaf-Drouneh volcanic-plutonic belt. Granitoids from three areas within the Sangan mine A, C-North and Dardvay were studied. Within the study area, three intrusive rocks including biotite-hornblende monzonite porphyry, biotite syenite and syenogranite were recognized. Based on field cross cutting, absence of garnet-magnetite skarn around the contact, and alteration by younger hydrothermal fluids, these granitoids are older than the magnetite skarn. U-Pb zircon age of the granitoid is 42 Ma (Middle Eocene). Magnetic susceptibility of the granitoids are 310-900 × 10-5 (SI units) and therefore, they are classified as belonging to the magnetite-series (oxidant type) I-type. Chemically, these granitoids are metaluminous, alkali-calcic to alkali and shoshonite to ultrapotassic. Enrichment of LREE, relative to HREE and enrichment of LILE (Sr, Cs, Rb, K and Ba) relative to HFSE (Nb, Ta, Ti, Hf and Zr) indicate that the magma formed in island arc setting. This magma originated from low partial melting (<1%) of garnet-spinel lherzolite (low garnet) and was contaminated in the continental crust. Based on the ratio of (La/Yb)N 6.23-34.73, indicate that small amount of garnet was left in the source rock. High ration of Rb/Sr, LILE/HFSE and high content of K2O, Th and Nb indicative of continental crust contamination. Petrognesis and geochronology of Sangan granitoid will help to know more about tectonomagmatic of Khaf-Kashmar-Drouneh volcanic-plutonic belt and their mineralization.

201-214

Authors: Mohamad Ali Rajabzadeh; Nazanin Zamansani

Manganese ore deposits occurred in various types of syngenetic, diagenetic and epigenetic mineralization in association with radiolarian cherts in colored melange of Neyriz ophiolite in Abadeh Tashk area, eastern Fars Province. Microscopic study and XRD analyses show a simple mineralogy for manganese compounds in all types. Psylomelane and braunite are the primary manganese compounds in syngenetic type that are found as alternative bands with amorphous silica and quartz in a sedimentary environment. Braunite and bixbite occur in lens shape deposits, showing diagenetic type of mineralization that formed in fold hinges during diagenesis process. Pyrolusite, auororite and rancieite are major minerals of epigenetic type that formed during remobilization and reprecipitation of manganese compounds in radiolarian cherts from upper horizons as open space fillings by supergene processes. Manganese ores show low values of TiO2 (0.012-0.13 %), Fe/Mn (0.02-5.45) and Al2O3 (0.019-2.13) and high values of Si/Al (21.84-427.46). The ores contain low contents of Co (31-131 ppm), Cu (17-277 ppm) and Ni (12-193 ppm) and have negative anomalies of Ce and positive Eu, low total REE and enriched LREE compared to HREE, indicating that primary manganese compounds and host cherts formed close to mid oceanic ridges above seafloor hydrothermal fluid channels.

235-254

Authors: Mehrdad Barati; Meysam Gholipoor

Zafarabad iron deposit is located northwest of Divandareh, in the northern margin of Sanandaj-Sirjan plutonic-metamorphic zone. The deposit is in lentoid to tubular shape, within a shear zone and occrrued in host rocks of calc-schist and limestone. Magnetite with massive, cataclastic and replacement textures are the main phases, while pyrite and other sulfide minerals are found. Major and trace elements are measured by ICP-MS and ICP-AES methods. Based on some ratios of trace elements in the ore samples and (Ti+V vs. Cal+Al+Mn and Ti+V vs. Ni/(Cr+Mn)) diagrams which are used for classification of iron deposit types, Zafarabad iron deposit fall in the range of skarn deposits. Spider diagrams show a steady decline from LREE to HREE elements with Eu (mean value of 0.06 ppm) and Ce (mean value of 0.94 ppm) negative anomalies. Comparing the distribution patterns of REE for the Zafarabad magnetites with those of various types of iron deposits shows that the REE pattern for Zafarabad is similar to these deposits. Analysis of calculated parameters for REE shows that the hydrothermal fluids responsible for mineralization are mainly of magmatic origin through fractionation and crystallization processes of a deep iron rich fluid phase and its emplacement within the carbonate rocks, forming iron skarn.

267-290

Authors: Mohammad Hasan Karimpour; Azadeh Malekzadeh Shafaroudi; Mehrab Moradi Neghondar; J. Lang Farmer; Charles Stern

Kalateh Ahani is located 27 km southeast of Gonabad within the Khorasan Razavi province. The area is part of Lut Block. Sub-volcanic monzonitic rocks intruded regional metamorphosed Shemshak Formation (Jurassic age). Magnetic susceptibility of less altered monzonitic rocks is < 25 ×10-5 SI, therefore they belong to reduced type ilmenite granitoid series. Both intrusive and metamorphic rocks are altered to argillic, propylitic, silicification and some iron oxides. Argillic alteration is dominant within the intrusive rocks. Two major quartz sulfide (sulfides are oxidized) veins trending NW-SE are recognized within the study area. Based on core logging, both disseminated and veinlet mineralization types are recognized within the intrusive and metamorphic rocks. Eight types of veinlet and vein are identified within the intrusive rocks. Maximum density of the veinlets is about 35 per meter within the biotite monzonite porphyry. Hypogene minerals include pyrite, chalcopyrite, sphalerite, galena and quartz. Secondary minerals comprise malachite, hematite, chrysocolla, goethite and gangue minerals are quartz and siderite. Rock geochemistry shows high anomalies of Cu, Pb, Zn, Sn, As, and Au both in the surface and within the mineralized core. Cu > 0.6%., As, Pb and Zn > 1%, Au up to 150 ppb and Sn = 133 ppm. The Sn content of vein in the northern part of Kalateh Ahani (Rud Gaz) is > 1%. Based on mineralization, alteration and geochemistry, it seems that Sn mineralization is associated with the Cretaceous monzonitic rocks. Zircon U–Pb dating indicates that the age of the monzonitic rocks associated with mineralization is 109 Ma (Lower Cretaceous). Based on (87Sr/86Sr)i = 0.71089-0.710647 and (143Nd/144Nd)i = 0.512113-0.51227 of the monzonitic rocks, the magma for these rocks were originated from the continental crust. This research has opened new window with respect to Sn-Cu mineralization and exploration within the Lut Block which is associated with Cretaceous granitoid rocks (reduced type, ilmenite series) originated from the continental crust.

307-324

Authors: Ali Imamalipour; Mastoureh Yousefi; Mahdiyeh Karimlou

Alteration of ophiolitic ultramafic rocks, formation of listwaenite and associated mineralization are interesting phenomena of metallogeny of Khoy ophiolite. It seems that the hydrothermal circulations responsible for mercury mineralization were derived from geothermal systems caused by intermediate to acidic magmatism in Neogene-Pleistocene time. Reactivation of brecciated serpentinite with hydrothermal solutions led to the silica-carbonate hydrothermal alteration and formation of listwaenite. The importance of these alteration types is due to associated Hg-Au mineralization. Based on the microscopic mineralogical studies, XRD analysis, geochemical characteristics and field relationships, three types of listwaenite including silica, silica-carbonate and carbonate have been recognized. Tavreh mercury occurrence has formed in relation with silica type listwaenite which also named as birbirite. Alteration zones have structural controls and are restricted to shale (marl)/serpentinite fault type contacts. Mineralogically, silica type listwaenite mainly consists of quartz, chalcedony, opal and secondary iron hydroxides. Magnesite, dolomite, calcite and clay minerals are the minor phases. Toward silica-carbonate and carbonate listwaenites, silica minerals decrease while carbonate minerals increase. Geological field relations and existence of residual chrome spinel in the listwaenite of Tavreh area confirmed the ultrabasic host rock. Based on geochemical studies, average values of SiO2, Fe2O3, MgO and L.O.I as the main components of silica listwaenite are 82.6, 6.99, 1.02 and 3.74 wt %, respectively. Among rare elements, average values of Hg, Pb, As and S have been obtained as 646.2 ppm, 517.7 ppm, 329.1 ppm and 281 ppm, respectively. Mass changes (gains and losses) of major and minor elements during the alteration process in the Tavreh area have considered, using Gresens’ equation in this study. Cinabar-bearing silica listwaenite is enriched in SiO2, Al2O3, K2O and Hg components and is depleted in MgO and MnO. Silica-carbonate type shows enrichment in CaO, Na2O, Al2O3, K2O and TiO2 and deplection in MgO, MnO P2O5, SiO2, Cr2O3 and Fe2O3. Carbonate type shows increase in CaO and Sr and reduction in SiO2, Na2O, MgO, Al2O3, Fe2O3, TiO2 and MnO.

1-22

Authors: Zahra Alaminia; Mohammad Hassan Karimpour; Seyed Masoud Homam; Fritz Finger

Arghash – Ghasem-Abad area in NE Iran is located in the rim of the Sabzevar structural zone. Tertiary outcrops include granite and quartz monzodiorite porphyry associated with dacite and andesite volcanic rocks. In the study area, quartz gabbro and quartz monzodiorite dykes intruded the older rocks. Granite and volcanic rocks host Au-Sb-bearing quartz-calcite veins. Mineralized veins are mainly located around the dykes in the southern part of the area. According to geochemical studies, granites have high-K calc-alkaline affinity with transitional I/A-type features. The volcanic rocks with adakitic composition contain high abundances of Sr and Ba. The dykes in the area show characteristics of lamprophyric rocks. U-Pb zircon dating of granite yielded an age of 55.4±2.2 Ma (Lower Eocene). Initial 87Sr/86Sr and εNd values for the granites are 0.704142 and +5.84, respectively. Initial 87Sr/86Sr ratios strongly suggest a depleted mantle source for the magma. This dating demonstrates that the Au-Sb mineralization occurred later than Lower Eocene. Based on field observation, the mineralization is more related to the lamprophyric dykes than to the adakitic rocks.

37-47

Authors: Ali Reza Zarasvandi; Mohsen Rezaei; Houshang Pourkaseb; Adel Saki

The Nasirabad manganese deposit is located 5 km south of Nasirabad, 8 km SW of Neyriz in the Fars province. Structurally, the area is placed in the southeastern part of Zagros thrust belt. In this area, the manganese mineralization occurred as ore layers and nodules, interlayered with Pichakun radiolarite chert deposits. In this study, mineralogy and geochemistry of uranium, thorium and lead isotopes were used to investigate the primary and secondary processes. In this way, in addition to petrographic and XRD studies, ICP-MS analysis was carried out in order to measure the U, Th and Pb isotopes. The strong fractionation of Fe and Mn phases and also the absence of Fe-bearing minerals in the XRD results, presence of syngenetic todorokite and quartz crystals, high U/Th ratios in some samples and Th versus U diagrams, all indicate entrance of Mn-bearing hydrothermal fluids into the sedimentary basin of the Nasirabad manganese deposit. The pyrolusites in radiolarites tests as replacement textures, host rock space filling and fracture filling pyrolusites, indicates the influence of secondary exogenic processes on primary hydrothermal mineralization. Non-homogenous 206Pb/Pb204, 207Pb/Pb204 and 208Pb/Pb204 values show non-steady hydrothermal processes in the sedimentary basin and indicate mixing of hydrothermal lead isotopes with another secondary source. Strong positive correlation between absolute values of radiogenic lead isotopes and insoluble High Field Strength Elements (HFSE) such as 207Pb vs Nb (r=0.81), 207Pb vs TiO2 (r=0.93), 207Pb vs Th (r=0.79) and strong correlation between these elements and some mafic components like 208Pb vs Fe2O3 (r=0.94) and Th vs MgO (r=0.86) represent entrance of radiogenic lead with mafic detrital materials into the sedimentary basin. Similar linear trend among 206Pb/Pb204 vs 208Pb/Pb204 and 207Pb/Pb204 ratios in nodules and manganese layers show the same geochemical condition in Mn-nodules and layers formation and indicate that isotopic ratios were unaffected by secondary processes including leaching and redeposition of manganese.

65-82

Authors: Samineh Rajabi; Ghodrat Torabi

The Eocene volcanic rocks from the southwest of the Jandaq (Kuh-e-Godar-e-Siah, Central-East Iran micro-continent) are andesitic basalt and andesite in composition. These rocks contain xenoliths with granulitic mineralogy. Mineral assemblage of these xenoliths is plagioclase + phlogopite + corundum + sillimanite + chlorite + phengite with granublastic, poiklioblastic and foliated textures in the pick metamorphic condition. Thermometry of phlogopite in these xenoliths suggests the average temperature 782oC. The characteristics of the xenoliths are consistent with the granolitic facies metamorphism of the Al-saturated Si-undersaturated crustal sediments at the lower crust condition. Melting of these granulites forms the magma which crystallized the S-type granitoids. Differentiation and crystallization of this magma causes the S-type granite formation. Therefore, the S-type granites in the study area are probably generated from melting of the granulites parts of which brought to the surface as xenoliths by Eocene magmatism in south of the Jandaq (Kuh-e-Godar-e-Siah). S-type granites in the study area are located along the Doruneh, Chupanan and Aeirakan faults in the Aeirakan area and Jandaq ophiolite. These granites are the source of uranium, thorium and uranium ore in southwest of the Aeirakan mountain.

93-104

Authors: Mohamad Ali Rajabzadeh; Soheila Esmaeili

Jian Cu deposit is hosted by Surian volcano-sedimentary complex of Permo-Triassic age on the eastern edge of the Sanandaj-Sirjan metamorphic zone at a distance of 195 km from Shiraz, southwestern Iran. The complex consists mainly of metabasalt, chlorite-quartz schist, chlorite-muscovite schist, mica schist and graphite schist. Pyrite is the most important sulfide and chalcopyrite is the major Cu-bearing mineral occurring as disseminated grains and veinlets in host chlorite-quartz schist and chlorite-muscovite schist. Chondrite-normalized REE pattern of metabasalt with La/LuN=2/9 indicates mantle tholeiitic basalt as the source of metamorphosed igneous rocks. Geochemical data on the metabasalts, especially the content of immobile elements (e.g., Ti) and High Field Strength Elements (HFSE) (e.g., Zr، Nb and Y), show low degree of partial melting for parental magma with E-MORB affinity. Chloritic, silicification and minor sericitic assemblages are the main alteration types associated with the Jian Cu deposit. The Y/Ho ratio of Cu ores varies from 29.9 to 32.5, indicating the important role of sea water in the mineralizing system. Petrographical and geochemical data indicate that the Jian Cu deposit was formed as volcano-sedimentary hosted massive sulfide. The Ishikawa alteration index (AI) in association with chlorite-carbonate-pyrite index (CCP) is useful for the geochemical exploration of Cu deposits in the study area.

117-136

Authors: Hossein Hajimirzajan; Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi; Mohammad Reza Haidarian Shahri; Seyed Javad Hamooni

Roudgaz prospect area is a Cu, Sn, Pb, Zn, and Au polymetal vein system located to the southeast of Gonabad and in the northeast of Lut block. Oxidan subvolcanic Tertiary rocks with monzonite to monzodiorite porphyry composition intruded the metamorphic rocks of middle Jurassic. The majority of intrusive bodies are affected by carbonation, argillic, sericitic, and silicification-tourmaline alteration. Mineralization in the area is controlled by fault and is present as vein with domination of NW-SE direction and 85-90º dip. Primary minerals are quartz, tourmaline, chalcopyrite, pyrite, and secondary minerals are malachite, azurite, and goethite. Geochemical sampling using chip composite method indicated high anomalies of Cu, Sn, Pb, and As (up to 10000 ppm), Zn (up to 5527 ppm), and Au (up to 325 ppb). Broad gossan zone is present in the area and is related to the oxidation of sulfide minerals. IP/RS survey was performed over the geochemical anomalies for identification of the location and extension of sulfide mineralization at depth. Generally, chargeability increases in gossan zones, veins, old workings and geochemical anomalies. Resistivity over the quartzite unit and also in locations where mineralized vein is associated with quartz has a high anomaly of up to 425 ohm-m. Due to high geochemical anomaly of Sn and its relation with reduced subvolcanic intrusives, ground magnetic survey was performed to identify the location of magnetite (oxidant) and ilmenite (reduced) series at depth. Variation of Total Magnetic Intensity (TMI) is 335.1 Gamma in the TMI map. The highest magnetic anomalies in the RTP map are located to the north of the survey area which is related to magnetite series (hornblende biotite monzodiorite porphyry) and extend to the south at depth. The lowest magnetic anomaly is located to the center of the survey area and particularly to the east of the Roudgaz village correlating the highest chargeability and geochemical anomaly. Based on coincidence of geochemical and chargeability anomalies, two holes were drilled in the area and 24 samples were collected from the core drills for geochemical analyses. The highest anomalies are accompanied by silicification and chlorite alteration and locations of extension of secondary Fe oxides.

171-198

Authors: Mohammad Ali Jazi; Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi

One of the most intensive occurrences of magmatism in Iran was in the middle Jurassic period. Among the granitoid intrusions in this period as discrete bodies or complexes can be pointed to Aligoodarz, Alvand, Astaneh, Boroujerd, Malayer, and Chah-Dozdan in the Sanandaj-Sirjan zone; Shir-kuh and Ayrakan in the Central Iran zone; Shah-kuh, Sorkh-kuh and Kalateh-Ahani in the Lut Block. These granitoids are mostly peraluminous and belong to high-K calc-alkaline series. CaO/Na2O ratios (0.12 to 8.37) mostly suggest a clay-free source for formation of the intrusive rocks magma. Chondrite-normalized Rare Earth Elements (REEs) diagram do not display high enrichment of Light Rare Earth Elements (LREEs) than Heavy Rare Earth Elements (HREEs) and general pattern is relatively flat. In addition, diagram shows Eu negative anomaly, which can be attributed to indicate reducing conditions in formation of magma and/or magma derived from plagioclase depth as source. The lower continental crust-normalized spider diagram indicates enrichment in LILE (Rb, Cs, and K) and LREE (La and Ce) and depletion in Ba, Nb, Ta, Sr, and Ti. Initial 87Sr/86Sr ratios are 0.70609 to 0.71938 and initial εNd values are negative (from -6.51 to -1.1) indicating that magma derived from continental crust. Geochemical and isotopic evidence of the intrusive rocks shows continental crust origin (S-type granitoid) and due to continental collision. Geological findings such as stop in sedimentation, regional metamorphism, ophiolite displacement, and continental collision-related mineralization confirm continental collision between Iranian and Arabian plates in the Middle Jurassic period.

217-239

Authors: Mohammad Maanijou; Mohammad Mostaghimi; Mehdi Abdollahy Riseh; Ali Asghar Sepahi Gerow

Mineralization occurred by intrusion of granodioritic stock of middle Miocene in volcano–sedimenrary rocks in Sarcheshmeh of early Tertiary age. This research is based on samples of new drilled boreholes and benches of 2500m elevation. Based on mineralogy and crosscutting relationships, at least four groups of veinlets pertaining to four stages of mineralization were recognized. Sulfur isotope studies in the Sarcheshmeh porphyry copper deposit were conducted on pyrite, chalcopyrite, molybdenite and anhydrites of four groups of veinlets. The δ34S values in the sulfides and sulfates range from -2.2 to 1.27‰ and from 10.2 to 14.5 ‰, respectively. The average δ34S value in the sulfides is 1‰ and that for the sulfates is about 13‰. Considering these results, it can be concluded that the sulfides made up of a fluid that its sulfur has a magmatic origin. Also, fluid inclusions of different veinlet groups were studied, showing high temperature, high salinity and the occurrence of boiling in the mineralizing fluids. Moreover, these studies indicate presence of three types of fluids including magmatic, meteoritic and mixture of these two fluids in alteration and mineralizion processes.

257-269

Authors: Mehdi Hashemi Gahrouei; Behnam Shafiei; Gholamhossein Shamanian; Hossein Taghizadeh

In order to assess the potential of copper mineralization and its associated elements in Soltan Meydan basaltic formation situated in the north of Shahrud, the method of stream sediment and heavy mineral has been used. To achieve this aim, totally 68 samples of sediments (-80 mesh in particle size) and 6 samples of heavy minerals (-20 mesh in particle size) have been collected in an optimized network of sampling. Stream sediment samples have been analyzed in for Cu, Pb, Zn, Co, Mn, Fe and Ni. Statistical processing of geochemical data resulted in identifying of elements with anomaly values, discrimination between anomalous and background values, and also assigning the inter-element relationships. Among the elements, Cu and Ni show first and second order anomalies in the samples. Results show that Fe, Pb, and Zn are associated together and also indicate positive correlation with Co and Mn, strongly (r≥0.5). The study of heavy mineral samples indicates the presence of magnetite, hematite, goethite, limonite, pyrite, oxidized pyrite, ocher, barite, apatite, rutile, zircon, nigrine, anatase, sphene, leucoxene, gold and ferromagnesian silicates. Statistical processing of heavy mineral data shows the association of Au, Ti, and Fe-oxides. The results of geochemical data processing and their integration with results of distribution pattern of fractures indicates good correlation between geochemical anomalies and highly fractured regions, as a result promising area for Cu and Ti mineralization has been identified and suggested for performing of further exploration.

285-301

Authors: Ehsan Salati; Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi; Mohammad Reza Hydarian Shahri; Lang Farmer; Chuck Stern

Keybarkuh area is located 70 km southwest of Khaf, Khorasan Razavi province. The study area is situated in northeastern Lut block. The rock units in the area are Paleozoic metamorphic rocks and Cretaceous to Tertiary subvolcanic intrusions intruded as dike, stock and batholith; their composition varies from granite to diorite. Based on magnetic susceptibility, the intrusive rocks are divided into oxidant and reduced series. In this study, the oxidant intrusions are discussed. These intrusions are mostly high-K to shoshonitic and also meta-aluminous type. Their magma formed in subduction magmatic arc and they belong to I-type granitoid series. Enrichment of Large Ion Lithophile Elements (LILE) such as Rb, Cs, K, Ba, and Th relative to High Field Stength Elements (HFSE) such as Nb, Zr, and Ti supported the idea. Enrichment of Light Rare Earth Elements (LREE) and depletion of Heavy Rare Earth Elements (HREE) are also typical of subduction magmatism. Negative anomalies of Eu/Eu* can be attributed to the presence of residual plagioclase in a mantle source and contamination of magma by reduced continental crust. The amount of Nb > 11 ppm, lower ratio of Zr/Nb < 2, the initial 87Sr/86Sr isotope ratio (> 0.706), initial 143Nd/144Nd (> 0.512) and εNd (< -3.5) indicate that magma contaminated by reduced continental crust. Hornblende biotite granodiorite porphyry dated using U-Pb zircon geochronology at 43.44 Ma (Middle Eocene). Based on calculated TDM, magma derived from ancient slab with 820 Ma age in the Keybarkuh area, was affected by the highest continental crust contamination during its ascent.

319-333

Authors: Morteza Cheshmehsari; Ali Abedini; Akram Alizadeh; Seyed Mohammad Moussavi

The Dalir phosphate horizon is located ~57 km southwest of Chalous, Mazandaran province. The horizon developed as stratiform within upper shale of Soltanieh Formation (late Neoproterozoic - early Cambrian). According to mineralogical data, the major minerals of the phosphate horizon are calcite, fluorapatite, dolomite, quartz, pyrite, muscovite, and illite. Microscopic evidence such as existence of the fabric similar to grumeuse fabric indicates a vital role for diagenetic processes and dynamic pressures in the evolution of the horizon. The distribution pattern of Rare Earth Elements (REEs) normalized to PAAS reveals weak fractionation of Light REEs from Heavy REEs and negative Ce anomaly during phosphatization. Incorporation of the obtained results from mineralogical and geochemical studies suggests that the behavior and distribution of REEs were affected by the function of factors such as diagenesis, preferential sorption, presence and decomposition of organic matter, oxidation-reduction potential, and function of pore-waters. Further geochemical considerations show that fluorapatite, xenotime, muscovite, Mn-oxides and illite are the potential hosts for REEs.

1-27

Authors: Mohammad Hassan Karimpour; Azadeh Malekzadeh Shafaroudi; Lang Farmer; Chak Stern

Tertiary intrusive granitoids within the Lut block in the Khorasan Razavi and South Khorasan provinces are mainly sub-volcanic with porphyry texture and their composition varies from granite to diorite but monzonite is dominant. With the exception of Hired, these are classified as belonging to the magnetite-series of I-type granitoids. Chemically, these rocks are meta-aluminous. Those with mineralization are K-rich and those without mineralization such as Najmabad are Na-rich. All intrusive rocks plot in the field of calc-alkaline to adakite except Najmabad that plot in the adakite field. Based on low content of Nb (30), low initial 87Sr/86Sr (17 ppm), low ratio of Zr/Nb (0.707) and low initial εNd value (-3), magmas in the Kaybar-Kuh were more contaminated in the continental crust. Based on depletion in HREE and high ratio of (La/Yb)N (17-23), magma in Najmabad originated in the deep region in which garnet was present. Based on REE pattern and ration of Eu/Eu* (0.8-1), intrusive rocks within Maherabad, Khoopik, Chah-Shaljami, Kuh Shah and Dehsalm are calc-alkaline and their magma formed in an oxidant condition whereas Kaybar Kuh magma with low ratio of Eu/Eu* (

47-58

Authors: Rasool Ferdowsi; Ali Asghar Calagari; Ghader Hosseinzadeh; Ghahraman Sohrabi

Kamtal skarn is located 15 km northeast of Kharvana, East-Azarbaijan. A quartz-monzonitic stock of Oligocene age intruded the upper Cretaceous sedimentary sequence (claystone, limestone, marl, and siltstone) developing noticeable metamorphic (marble, hornfels) and metasomatic (skarn) alteration zones along the contact. Kamtal skarn is of calcic type and consists of both endoskarn and exoskarn zones. Exoskarn includes two zones of garnet skarn and epidote skarn. Skarnification processes are divided mainly in two major stages (1) prograde and (2) retrograde. During prograde stage, the emplacement of intrusive body caused isochemical metamorphism of the wall rocks and developed marble and hornfels units in enclosing rocks. Crystallization of intrusive body led to evolvement of hydrothermal fluid phase which infiltrated into enclosing rocks. Reaction of these fluids with the early-formed metamorphosed wall rocks brought about extensive progressive metasomatic alteration characterized by the formation of anhydrous calc-silicate minerals such as garnets and pyroxenes at a temperature range of 420-550°C and ¦O2=10-22-10-25. Retrograde stage was accompanied by some physicochemical changes (decrease in temperature to <420°C and increase in ¦S2) which caused the alteration of pre-existing anhydrous calc-silicates to hydrous calc-silicates (epidote, and tremolite-actinolite), silicates (quartz, chlorites, and other clay minerals), oxides (magnetite and hematite), sulfides (pyrite, chalcopyrite, and tetrahedrite), and carbonate (calcite). Comparison of Kamtal skarn with some other ones of corresponding type from Iran and other countries shows that Kamtal skarn well resembles to Anjerd and Pahnavar skarns in East-Azarbaijan.

77-107

Authors: Maryam Abdi; Mohammad Hassan Karimpour

The Kuh Shah prospecting area is located in Tertiary volcano-plutonic belt of the Lut Block. More than seventeen subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, were identified in the study area. The intrusions are related to hydrothermal alteration zones and contain argillic, propylitic, advanced argillic, silicified, quartz-sericite-pyrite, gossan and hydrothermal breccia which overprinted to each other and are accompanied by weathering which made it complicated to distinguish zoning. Mineralization is observed as sulfide (pyrite and rare chalcopyrite), disseminated Fe-oxides and quartz-Fe-oxide stockwork veinlets. Intrusive rocks are metaluminous, calc-alkaline with shoshonitic affinity with high values of magnetic susceptibility. The Kuh Shah intrusive rocks are classified as magnetite-series of oxidant I-type granitoids. Based on zircon U–Pb age dating, the age of these granitoid rocks is 39.7± 0.7 Ma (Middle Eocene). The radioisotope data (initial 87Sr/86Sr and 143Nd/144Nd ratios as well as εNd) and geochemical data suggest that the Kuh Shah granitoid rocks formed from depleted mantle in a subduction-related magmatic arc setting. Geochemical anomalies of elements such as Cu, Au, Fe, Pb, Zn, As, Sb, Mo, Bi, Hg and also Mn, Ba, Te and Se, correlated with quartz-sericite-pyrite, gossan-stockwork-hydrothermal breccias, irregular silicified bodies and advanced argillic hydrothermal alteration zones. Geophysical anomalies correlated with hydrothermal alteration and mineralization zones. The interpretation of the results represents complex patterns of sub-circular to ellipsoid shape with north-east to south-west direction. These evidences are similar to the other for known Cu-Au porphyry and Au-epithermal systems in Iran and worldwide.

123-134

Authors: Adel Saki; Hoshang Purkaseb

The Cheshin meta-calcareous rocks (Permo Triassic) in southeast Hamedan outcrop in association with a variety of pelitic schists and hornfels rocks. The intrusion of the Alvand Batholith (Jurassic age) into pelitic and calcareous host rocks has produced metamorphic rocks in the Hamedan area (Cheshin village). On the basis of the dominance of calcite/dolomite, silicate and ore minerals, the calcareous rocks can be divided into two groups: a) marbles and calc-silicates; b) skarn rocks. The ore bodies occur in a contact zone between sillimanite-hornfels and calc-silicate rocks and formed the skarn rocks. Based on mineralogy, skarn rocks in the studied area consist mainly of diopside, garnet, tremolite, vesuvianite, epidote and ore minerals (magnetite and hematite). The skarnification processes occurred at two stages: (1) prograde metamorphism; and (2) retrograde metamorphism. The first stage involved prograde metasomatism and anhydrous minerals such as garnet and pyroxene formed. Second stage of retrograde skarn development is also recognized. In addition to Fe, Si and Mg, substantial amounts of Fe, along with volatile components were added to the skarn system. Consequently, considerable amounts of hydrous minerals, oxides and carbonates replaced the anhydrous minerals in the host rocks and hydrous minerals such as epidote+chlorite+amphibole formed. Using multiple equilibria by THERMOCALC® program, temperature (~630 ºC), pressure (~4 kbar), and fluid composition (XCO2 as low as 0.17) have been calculated for the formation of the calc-silicate rocks. Skarn mineralogy shows good agreement with these calculations.

155-168

Authors: Babak Talaei; Ali Abedini

Qahr-abad fluorite deposit is located 58 km southeast of Saqqez, in northwestern Kordestan province and in northern end of Sanandaj-Sirjan Zone. The factors such as change in physicochemical conditions of mineralization environment (pH and Eh), variation in pressure and temperature, alteration, metamorphism, oxidation of organic matters, adsorption, activity and solubility of associated anions, residual enrichment, and leaching of clay minerals have played important roles in distribution of major, trace and rare earth elements as well as development of the deposit. Further geochemical consideration using distribution of rare earth elements indicates that the bulk contents of REE in the samples are few and violet fluorites formed in early-stage mineralization along with enrichment of LREE (as a result of assimilation and replacement of wall rock) and blue and colorless fluorites in the late-stage mineralization along with enrichment of MREE and HREE (as a result of recrystallization and remobilization). The mineralization of violet fluorites in the deposit occurred in a relatively oxidizing-basic condition, while colorless to light yellow and blue to greenish blue fluorites occurred in a relatively reducing-acidic condition. Using Tb/Ca vs. Tb/La diagram, it can be deduced that fluorites are from hydrothermal types and the genetic model for the deposit is as replacement in carbonate rocks.

97-110

Authors: Farid Moore; Saleh Deymar; Batoul Taghipour

Most skarn deposits are directly related to magmatic activity, and there is a systematic correlation between composition of causative plutons and the metal contents of the related skarns. Darreh Zerreshk deposit is located in southwest of Yazd. Petrological and geochemical studies show that Darreh Zerreshk granitoid ranges in composition from granite through quartz monzodiorite and has subalkaline, calc-alkaline and metaluminous to prealuminous characteristics like most worldwide skarn granitoids. This study shows that geochemical characteristics of the Darreh Zerreshk granotoid rocks are similar to granitoids of Millstream Cu-Fe skarn deposit in Canada, Fe skarns in British Columbia and Au-Cu skarns in the RioNarcea gold belt in Spain. The similarity between REE patterns in Darreh Zerreshk intrusion and skarns also confirms the strong petrogenetic relationship between magmatic and skarnization processes.

127-145

Authors: Mehrab Moradi; Mohammad Hasan Karimpour; J Eleng Farmer; Charlz Stern

The study area is located south of Ghonabad in Eastern Iran. This area is situated between two major faults, Darouneh to the north and Dashtbyaz to the south. The movements of these faults cased major dislocation of this block. Najmabad granodiorite to granite batholith is elongated trending east-west 2×8 Km2. Mineralization is associated with granite and monzonite. Alteration zones are: propylitic, sericitic, argillic and silicification. Chemically, granite-granodiorite is met-aluminous,, spider diagram normalized to lower continental crust show enrichment of LILE such as Rb, Cs, K and LREE (La, Ce) , depletion of Ti, Sr, Ta, Nb, Ba, Cs. Based on low values of magnetic susceptibility [(5 to 11) × 10-5 SI], therefore it is classified as belonging to the ilmenite-series (reduced type).The result of U-Pb zircon age dating of granodiorite is 161.85 Ma (Middle Jurassic, Callovian time). Based on Initial εNd isotope values for granodiorite is -6.51, initial 87Sr/86Sr and 143Nd/144Nd ratios for granodiorite is (0.70913 and 0.512095), the magma for granite and granodiorite originated from the continental crust. During Middle Jurassic (Callovian) due to continental collision, Upper Triassic to Lower Jurassic rocks is regionally metamorphosed. During the continental collision, Middle Jurassic (164-162Ma) reduced type granitoid magma (Ilmenite series, continental crust melting) formed and intruded these regional metamorphosed rock in Najmabad, Shah Kuh and Sorkh Kuh area.

165-181

Authors: Ali Abedini; Rahim Masumi; Ali Asghar Calagari

Kajal kaolin deposit is located ~20 km northwest of Hashtjin, Ardebil province. Field evidence and laboratory investigations show that the deposit is an alteration product of ignimbrites, tuffs, and trachy-andesites of Eocene age. According to mineralogical data, the major rock-forming minerals include kaolinite, montmorillonite, polygorskite, orthoclase, zeolite (stilbite), quartz, and chalcedony. Mass change calculations of elements, with assumption of Ti as immobile monitor element, indicate that leaching and fixation are two prominent regulators for concentration of major, minor, trace, and rare earth elements in the deposit. The distribution pattern of REEs, normalized to ignimbrite, in kaolin samples illustrates a weak fractionation of LREEs from HREEs coupled with strong negative Eu anomaly during the evolution of the deposit. Calculations of correlation coefficients among elements show that there is a high intrinsic correlation between HREEs in the studied samples. According to geochemical indices, it can be inferred that the hypogene alterations are superimposed by supergene ones in the course of evolution of the deposit. In accordance with the mode of distribution of elements in the deposit, it appears that the behavior of elements during kaolinization of ignimbrites was affected by the function of factors such as pH, redox potential, temperature variations, high fluid to rock ratio, preferential adsorption by clays and iron oxides, discrepancies in the stability rate of minerals, abundance of complex-forming ions (CO32-, F־, Cl־, PO43-, and SO42-), and isomorphic substitution. The obtained results indicate that epithermal acid-sulfate solutions along with acidic supergene solutions originated from oxidation of hypogene pyrites played an important role in development of the deposit. Further geochemical considerations show that clay minerals along with secondary phosphates like monazite, rabdophane, and xenotime are the potential hosts for REEs in the deposit.

193-216

Authors: Mohammad Hasan Karimpour; Azade Malekzadeh Shafaroudi; Akbar Esfandiarpour; Hasan Mohammad Nejad

Neyshabour turquoise mine is located in northwest of Neyshabour, southern Quchan volcanic belt. Eocene andesite and dacite forming as lava and pyroclastic rocks cover most of the area. Subvolcanic diorite to syenite porphyry (granitoids of magnetite series) intruded the volcanic rocks. Both volcanic and subvolcanic rocks are highly altered. Four types of alteration are recognized including: silicification, argillic, calcification and propylitic. Silicification is dominant followed by argillic alteration. Mineralization is present as stockwork, disseminated and hydrothermal breccia. Hypogene minerals are pyrite, magnetite, specularite, chalcopyrite, and bornite. Secondary minerals are turquoise, chalcocite, covellite, and iron oxides. A broad zone of gossan has developed in the area. Oxidized zone has a thickness of about 80 m. Mineralized samples show high anomalies of Cu, Au, Zn, As, Mo, Co, U, LREE, Nb, and Th. Both aeromagnetic and radiometric (U and Th) maps show very strong anomalies (10 × 5km) within the mineralized area. Based on geology, alteration, mineralization, geochemistry, and geophysics, Neyshabour turquoise mine is a large Iron oxide Cu-Au-U-LREE (IOCG) mineralized system. In comparison with other IOCG deposits, it has some similarities with Olympic Dam (Australia) and Candelaria (Chile). In comparison with Qaleh Zari and Kuh Zar mines, Neyshabour turquoise mine is the first Iron oxide Cu-Au-U-LREE (IOCG) mineralized system discovered in Iran.

231-249

Authors: Vahideh Alipour; Ali Abedini

The Zonouz kaolin deposit is located ~15 km northeast of Marand, East-Azarbaidjan province. Based on physical features in field investigations, such as color, five distinct kaolin types including (1) white, (2) lemon, (3) gray, (4) brown, and (5) yellow are distinguished in the deposit. Field evidence and petrographic studies indicate that the deposit is genetically close to trachy-andesite rocks. According to mineralogical data, the deposit contains quartz, kaolinite, montmorillonite, calcite, pyrophyllite, chlorite, muscovite-illite, dolomite, hematite, and anatase minerals. Geochemical data indicate that function of alteration processes on trachy-andesite rocks during development of Zonouz ore deposit was accompanied by leaching of elements such as Al, Na, K, Rb, Ba, V, Hf, Cu, Zr, Tm, Yb, and Lu, enrichment of elements such as U, Nb, and Ta, and leaching-fixation of elements such as Si, Fe, Ca, Mg, Ti, Mn, P, Cs, Sr, Th, Co, Cr, Ni, Y, Ga, LREE, Tb, Dy, Ho, and Er. Incorporation of obtained results from mineralogical and geochemical studies show that physico-chemical conditions of alteration environment, the relative stability of primary minerals, surface adsorption, preferential sorption by metallic oxides, existing of organic matters, scavenging and concentration processes, and fixation in neomorphic mineralogical phases played important role in distribution of elements in the deposit. Geochemical studies show that development of the deposit is relative to two types of processes, (1) hypogene and (2) supergene. The distribution pattern of REEs indicates that differentiation degree of LREEs from HREEs in supergene kaolins is more than hypogene kaolins. Geochemical studies indicate that minerals such as Mn-oxides, zircon, anatase, hematite, cerianite, and secondary phosphates (monazite, rhabdophane, churchite, and zenotime) are the potential hosts for rare earth elements in this deposit.