The eastern part of Ravar town in the southeastern Tabas Block of Iran hosts several sediment-hosted strata-bound copper-type deposits. These deposits occur within the Upper Jurassic Garedu Red Bed Formation, which includes red sandstone, conglomerate, siltstone and reduced siliciclastic layers with evaporite interbeds. We studied five major ore bodies/occurrences (Khormo, Mianrood, Dehoj, Godar-Rigi and Gazak), collectively known as the Khormo-Gazak Mining District. The copper mineralization in this district is primarily contained in woody fragments and the palaeo-permeability resulting from intragranular spaces and evaporite beds. The palaeo-permeability has been improved by the dissolution of diagenetic carbonate cements in bleaching zones. The spatial distribution of the woody fragments played a fundamental part in the copper mineralizing system. Two different stages of mineralization were distinguished based on the mineralogical and textural relationships and the morphology of the minerals studied: (1) reddening, bleaching and the formation of framboidal pyrites in the early diagenesis stage; and (2) the replacement of woody fragments, framboidal pyrites and cements with copper sulfides in the late diagenesis stage. The red, bleaching and ore zones are indicative of the main ore-forming event and are volumetrically the most important zones. The major ore minerals found in the studied deposits are, in order of abundance, chalcocite, bornite, chalcopyrite, digenite, yarrowite, djurleite, roxbyite, native copper, native silver, pyrite, atacamite, covellite, malachite and azurite, accompanied by minor amounts of chrysocolla, neotocite and hematite. The geochemistry of the ore-bearing ore horizons in the Khormo-Gazak Mining District deposits indicates a distinct variation in copper and nickel concentrations during the formation of different ore zones. On the basis of the mineral chemistry, the chalcocite in the Khormo deposit is enriched in silver, in contrast with the chalcocite at Gazak. Isotopically very light sulfur indicates that the chalcocite was supplied from diagenetic framboidal pyrite derived from the destruction of woody fragments. The destruction of organic matter leads to the creation of reducing environmental conditions and reducing geochemical traps for the deposition of sulfides. The Khormo-Gazak Mining District deposits are considered as a typical example of sediment-hosted strata-bound copper-type mineralization in which the minerals were deposited when oxidized brines flushed through the basin successions. The liberated copper was transported to units containing carbon-rich horizons, where the metals were deposited.

The Malayer-Esfahan Metallogenic Belt (MEMB) is one of the largest undeveloped Zn-Pb belts in the world. The Jurassic-Lower Cretaceous sedimentary-(volcanic) rocks in the MEMB contain stratiform and strata-bound Zn-Pb (+/- Ba +/- Ag), Fe-Mn-Pb (+/- Ba +/- Cu) and Ba mineralizations. This article provides a summary of the highlights of the MEMB deposits and discusses the type of mineralization, structural evaluation and important mineralization controls, based on geological observations and previous literature. The ore deposits of the MEMB occur in local basins that evolved in a back-arc tectonic setting. The sedimentary and volcanic layers of these basins were deposited in three phases: synrift, transition from synrift to sag phase and sag-phase deposition. The synrift sequence includes all Jurassic rocks deposited in a fault-bounded extensional basin. Synrift sequences are overlain by shallow-marine mudstones, carbonates, volcanic rocks and sandstones that extend over the rifted areas alike, forming a transitional stage from the synrift phase to the sag-phase sequence. The largest volume of volcanic and volcanoclastic rocks in the MEMB basin was formed during this stage. Kc(1), Kc(2) and Kcv units of the Lower Cretaceous sequences are related to the transitional phase. In the MEMB, sag-phase sediments (Km, Kl, Klsd and Ku units) have been repeated in several stages, and this phenomenon has led to the formation of numerous mineralizations in several ore-bearing horizons during this stage of the MEMB evolution. Nine major mining districts have been identified in the MEMB, with the main deposits located in Jurassic rocks and the Kc, Kl and Ks units of the Lower Cretaceous sequence. Ore mineralizations occur by two processes: (1) as sedimentary exhalative ores (SEDEX and hybrid SEDEX-VMS) in seafloor brines; (2) as subseafloor replacement mineralizations in the SEDEX (or Irish) style. The exhalative ores in shale, sandstone and volcanic rocks are located SE of Malayer, south of Arak, NW of Golpayegan, at Aligoudarz and south of Shahreza mining districts. Most of these deposits were formed during the Jurassic period and in the Kc(2), Kcv, Kc(2), Kc(3) and Klsd units, during the synrift and transitional stages of basin evolution. The SEDEX (or Irish) subseafloor replacement deposits are limited to early permeable reaction layers in the Lower Cretaceous rocks, including carbonate and carbonate-siliciclastic rocks. The most important of this type of deposits or occurrences are Irankuh, Shamsabad, Emarat, Robat, Khanabad, Anjireh and Khaneh-Sormeh. These deposits are formed in the sedimentary sequence of the sag phase. The delta S-34 values of sulfide minerals in the MEMB deposits indicate that sulfur originates from seawater through thermochemical sulfate reduction (TSR) and bacteriogenic sulfate reduction (BSR). The delta S-34 values of barite in the MEMB deposits range from +10.3 to +32 parts per thousand. This shows that the sulfur in these deposits originates from Jurassic-Early Cretaceous marine sulfate. Fluid inclusion studies in the MEMB deposits indicate that the ore-bearing fluids originated from basinal and marine waters with moderate to high temperature and moderate salinity. This paper presents a new regional geological model for the MEMB that provides a more detailed understanding of Zn-Pb (+/- Ba +/- Ag), Fe-Mn-Pb (+/- Ba +/- Cu) and Ba mineralizations, and is a new tool to expand the knowledge of SEDEX, hybrid SEDEX-VMS and subseafloor replacement mineralizations with carbonate host rocks, which can be an exploratory guide for future research in the MEMB.

ABSTRACT The Chah‐Nar Pb–Zn deposit in the southern Sanandaj–Sirjan Zone, Iran, represents Early Palaeozoic stratiform sulfide mineralization hosted by organic‐rich volcano‐sedimentary rocks deposited in a Proto‐Tethyan back‐arc basin. Despite the occurrence of stratiform Pb–Zn mineralization in the Southern Sirjan Basin, the origin, fluid evolution, and regional metallogenic significance of the Chah‐Nar deposit remain insufficiently constrained. This study integrates field observations, ore petrography, lithogeochemistry, fluid inclusion microthermometry, and SCO isotope data to evaluate the ore‐forming processes and genetic setting of the deposit. Mineralization occurs as stringer, massive, and bedded ore facies, which are best interpreted to record a transition from early seafloor to shallow subseafloor sulfide deposition to later hydrothermal replacement. Fine‐grained bedded sulfides are interpreted to represent an early synsedimentary to early diagenetic stage, whereas coarser massive and replacement sulfides are most consistent with later focused hydrothermal flow, possibly guided by synsedimentary extensional faults. Fluid inclusions in quartz associated with the stringer and massive ore facies yield homogenization temperatures of 165°C–268°C and salinities of 3.0–9.9 wt.% NaCl equivalent, consistent with low‐ to moderate‐salinity basinal fluids. Sulfur isotope compositions of sulfides (δ 34 S CDT = −5.8‰ to +16.9‰) indicate seawater‐derived sulfur modified by multiple reduction pathways, with bacterial sulfate reduction dominant in the bedded ores and thermochemical sulfate reduction more important in the stringer and massive ores. Carbon and oxygen isotope data further indicate fluid–rock interaction involving seawater‐derived basinal fluids, organic‐rich sediments, and isotopically lighter hydrothermal components. Collectively, the geological, textural, geochemical, fluid inclusion and isotopic evidence indicates that the Chah‐Nar deposit formed by discharge of metal‐bearing basinal fluids into a reduced, organic‐rich sedimentary environment, with fluid flow focused by synsedimentary faulting. The integrated dataset is most consistent with interpretation of Chah‐Nar as a SEDEX‐type Pb–Zn system developed in an Early Palaeozoic back‐arc rift setting. These results refine the metallogenic model for the southern Sanandaj–Sirjan Zone and highlight the roles of basin architecture, focused fluid flow and redox‐controlled sulfur reduction in Palaeozoic Pb–Zn mineralization in Iran.

In Iran, celestite deposits/occurrences are found in two structural zones of the (1) Central Iran zone, and (2) Zagros Folded Thrust Belt. The host rock age of the celestite deposits in the world varies from Silurian to Pliocene but in Iran this mineralization’s are specific to the Neogene carbonate-evaporite sequences, which is the (1) Oligo-Miocene Qom Formation in Central Iran zone; (2) the Oligo-Miocene Asmari Formation; and (3) the Early-Middle Miocene Gachsaran-Mishan Formations in the Zagros Folded Thrust Belt, which is known as the youngest host of celestite mineralization in Iran. The marl-carbonate members of the Oligo-Miocene Qom Formation in Central Iran zone hosts the most significant and largest celestite deposits, such as Arvaneh-Aftar, Davazdah-Emam, Siah-Kuh, Madabad, Mazraeh, Nakhjir-Kuh, Kuh-Talhe, Abardej, Kazemabad, Qaleh-Boland, Deh-Namak, Baztab, Paiiez, Pis-Kuh in Jandag area, Tapeh-Gobar, Khoushab-Rood, Zand-e-Fashafoieh, Maranjab, Gand-Aab, Huk, and Makresh deposits. Molkabad deposit in the Central Iran zone, with a reserve of 2Mt, which are typically associated with shallow marine environments is the largest and most important celestite deposit in Iran and also one of the largest celestite deposits in the world. In the Zagros Folded Thrust Belt, the most important celestite deposits located in the Asmari carbonatic Formation in the Bangestan anticline which including Tang-Ban, Tang-e-Nayab, Gonbad-Bardi, Kal-Ahmadi, Posht-Par, Dopar-Nazari, Tortab, Tarak, Gudben, Abolfares, Mokhdan, Konj-e-Konj, Takhtan, Hormuz, Doghonbadan, Abdanan, Pirmored, and Dasht-e-Ahoo deposits. The well-known deposits of Gachsaran-Mishan Formations are the Likak, and Baba-Mohammad deposits. It seems that the evaporite lithology of the Gachsaran Formation can be a suitable environment for celestite mineralization in the Zagros Folded Thrust Belt. According to the Cenozoic celestite mineralization in Iran, it can be concluded the Neo-Tethys oceanic cycle and the geodynamic evolution of the related sedimentary basins played a role in the formation of these deposits. The largest celestite deposits formed during diagenetic replacements and open-space filling processes in coastal carbonate- evaporite sequences. Shallow epicontinental basins are the main geological environment for celestite deposits. Qom back-arc environment and Zagros foreland basin are the main depositional environments for celestite mineralization’s. Saline Sr-rich fluids, shallow depositional environment, regression of sea water, karst-dolomitization process, and semi-arid climate are among the most important factors controlling Iranian celestite deposits. Understanding of the temporal-spatial distribution of celestite deposits in Iran provides valuable insights for exploration and exploitation efforts.

There are several deposits and mineral occurrences of sedimentary phosphorite (SP) mineralization in Iran. The main tectonic-structural zones of Iran that host SP deposits are: (1) Alborz Magmatic Belt (AMB), (2) the Central Iran and (3) Zagros Folded Thrust Belt (ZFTB). These deposits were formed during separate time: (1) Neoproterozoic-Early Cambrian (Soltanieh Formation), (2) Ordovician-(Silurian) (Shirgesht, Mila and Seyahou Formations), (3) Upper Devonian (Jeirud Formation), (4) Permian to Jurassic (Abkhory, Taleqan and Hosseinabad area) and (5) Cretaceous to Paleogene (Gurpi and Pabdeh Formations). The stratigraphic sequences of these deposits are commonly formed from sedimentary rocks, which are similar to other SP districts in the Middle East and North Africa. The main period of SP mineralization in Iran was from the Neoproterozoic-Early Cambrian, Upper Devonian and Late Cretaceous to Paleogene. The Jeirud Formation of the Upper Devonian and the Pabdeh Formation of the Paleocene-Eocene contained the largest sedimentary phosphorites in Iran. The formation and distribution of sedimentary phosphorite deposits in the different structural zones can be explained by divergent and convergent events related to the Proto, Paleo, and Neo-Tethyan oceans. The SP deposits hosted by the Neoproterozoic-Early Cambrian Soltanieh Formation are related to the Proto-Tethys Ocean. Mineralization in the Ordovician Mila and Shirgesht formations and Upper Devonian Jeirud Formation are age related to the Paleo-Tethys Ocean, and finally, the SP deposits formed in the Cretaceous- Paleogene (Gurpi and Pabdeh formations) sequence were formed the evolution of the Neo-Tethys Ocean cycle. Passive margins are the principal plate tectonic settings for Iranian SP deposits. Iranian SP deposits are stratigraphically controlled in which phosphorite mineralization occurs as laminae, disseminated grains, and replacement. SP mineralization is commonly closely related to framboidal pyrite and biologic events. The AMB and ZFTB are the main tectonic zones for Iranian sedimentary phosphorite deposits. These zones are the most favorable metallogenic provinces for the exploration of sedimentary phosphorite deposits, representing in excess of 80% of the as of now known SP deposits and occurrences in Iran. High sea level, low oceanic anoxic events (OAE's), warm climates, latitude and longitude close to the equator and shallow slope environments are among the most important factors controlling Iranian SP deposits.

Meymeh sideritic-ankeritic iron deposit in the eastern part of Malayer-Esfahan Metallogenic Belt (MEMB) is formed in the sedimentary-volcanic rocks of the Early Cretaceous sequence. Ore mineralization in the study area based on stratigraphic location and type of host rocks divided in two ore horizons. Lower ore horizon located in the dolomitic-sandy limestone (Kc3) unit, which upper ore horizon is formed in thin-bedded limestone (Km) rocks. Petrographic studies indicates that mineralization comprises three ore facies: stockwork, bedded and massive ore facies. The most important primary minerals are siderite, ankerite, ferroan-dolomite, pyrite, pyrolusite, barite and minor chalcopyrite. The most frequent textures in the ore zones include laminae, replacement, vein-veinlet, massive and banded. Dolomitization and silicification are the main wall rock alteration styles; alteration intensity increases towards the ore zones. Based on relationships between ore minerals and rock forming minerals, ore mineralization (hypogene and supergene) in the Meymeh deposit formed during three main stages: fine-grained Fe-carbonate bands are intricately interlayered with dolomite beds. Sideritic-ankeritic bands exhibit classic sedimentary textures, such as laminations and bedding, indicative of a syn-sedimentary to early diagenesis origin. Coarser-grained stage two siderites and ankerites show breccia and vein-veinlet textures, and are considered to have formed by replacement during burial diagenetic sub-seafloor fluid flow. In stage three, siderite and ankerite were converted to secondary iron oxides such as oxide/hydroxide Fe minerals during meteoric water flow through the inverted normal and thrust faults and uplift. The primary two-phase fluid inclusions in the quartz-2 and ankerite-2 minerals that have been investigated from the ore mineralization section of the Meymeh deposit are homogenized at temperatures between 110.3 to 226.9 degrees C. Salinities of the primary fluid inclusions range from 3.39 wt.% to 14.77 % NaCl eq. This finding suggests that hydrothermal brine fluid mixing with seawater could be the primary mechanism that prompted ore formation. The similarity of REE patterns between siderite and ankerite in different ore facies and host rock carbonates indicates their derivation from the same ore fluids. The Meymeh deposit is considered a typical case of sedimentary hydrothermal diagenetic sideritic-ankeritic mineralization, in which minerals deposited when hydrothermal fluid was released from anoxic to suboxic water columns.

The Cretaceous was an important period of manganese deposition in Iran, as evidenced by a series of medium-sized manganese deposits along the edge of the Neotethys ocean. This study characterizes representative example that occurs in Late Cretaceous volcanic rocks in the Goft deposit. This manganese deposit is typically volcanic hosted, with manganese-containing minerals, such as pyrolusite, psilomelane, cryptomelane, braunite, and manganite. The ore bodies hosted by red tuff are predominantly layered and usually have nodular structures. Replacement of Cretaceous foraminifers and radiolarians fossils by manganese minerals is also frequently observed in the Goft deposit. This deposit is a high-quality ore characterized by low P and Fe grades and an average Mn grade of approximately 14%. The average Mn/Fe, Co/Ni, Co/Zn, and V/(V + Ni) ratios in the Goft manganese deposit are 9.73, 0.24, 0.18, and 50, respectively. The overall REE contents are among 17.7 to 181 ppm, with an average of 87 ppm. The Ce/Ce* values of manganese ores vary from 0.26 to 0.99, with the mean of 0.53. The Eu/Eu* anomalies of the manganese oxide-hydroxide ores are close to 1 with a range of 0.70 to 1.22. Most manganese samples show negative Ce anomalies, indicating that the ore formation environment was predominantly oxide and cold conditions. The geochemical behavior of trace elements, including the REEs of the manganese oxide, provides clear evidence a low-temperature hydrothermal origin. The mineralogical and geochemical characteristics presented in this study strongly suggest a volcanogenic-exhalative genesis for Goft manganese deposit.

The southwest Sabzevar basin in northeast Iran is one of the most important areas for volcanogenic stratiform manganese deposits. The Mohammadabad Mn deposit, found in this basin, is hosted by the upper late Cretaceous marly tuffs in a region that has an active history of tectonism. Their geology, mineralogy and geochemistry, including major, trace and rare earth elements (REE), are described in this work. The main ore minerals include pyrolusite, psilomelane, cryptomelane, with minor braunite and manganite. Four styles of manganese mineralization are recognized: (1) layered; (2) nodular; (3) disseminated; and (4) replacement to massive. Regardless of style, pyrolusite, psilomelane, and cryptomelane usually tend to parallel the stratification of sediments, while braunite veins occur in high angle fractures. The replacement of radiolarian and foraminiferal fossils by manganese minerals during diagenesis near the seawater-sediment interface suggests that mineralization occurred in oxygen-rich conditions under the influence of low-temperature hydrothermal fluids. The geochemistry of trace elements of manganese oxides and rare earth elements gives clear evidence of hydrothermal-exhalative origin for Mohammadabad deposit. In general, ore minerals have Co/Ni ratios above 0.12, and U/Th ratios vary from 0.13 to 11.29. The presence of negative Eu anomalies in manganese minerals shows that the ore-forming fluids were generally low-temperature and oxic during mineral formation. In-situ mineralogy studies based on SEM-EDS have distinguished syngeneic and diagenetic Mn systems during the formation of manganese mineralization. The Mohammadabad deposit is considered a typical case of volcanic hydrothermal exhalative-diagenetic Mn mineralization, in which minerals deposited when hydrothermal fluid was released from oxic to dysoxic water columns.

The Eastern Haft-Savaran Zn-Pb-(Ba) deposit, located in the southeastern part of the Arak Mining District of the Malayer-Esfahan Metallogenic Belt, Iran, is hosted in the uppermost part of an early Cretaceous massive limestone unit that is capped by shale. The mineralization has a sheet-like geometry and is associated with intense dolomitization and silicification. The mineralization is mineralogically zoned: chalcopyrite-galena-pyrite-sphalerite-tetrahedrite occurs in the southern part of the deposit; sphalerite-galena-pyrite occurs in the central part of the deposit; and barite-galena-sphalerite-pyrite occurs in the northern part of the deposit. The thickest mineralization and most intense alteration are in the southern part of the deposit, associated with an aphyric rhyodacite flow containing minute euhedral barite crystals and Cu-bearing sulphides in vein/veinlets and disseminations, indicating this was the mineralizing fluid upflow site. Three hydrothermal mineralization stages are recognized. The first is mud lime sedimentation, framboidal pyrite, minute euhedral barite, sphalerite, galena and early dolomite. Minute euhedral barites are cut by microsparite formed by micrite recrystallization during diagenesis. First stage sphalerite and galena occur as inclusions in framboidal pyrite, and these were remobilized into inclusions in euhedral pyrite during recrystallization. The second (main) stage mineralization includes sphalerite, galena, chalcopyrite, tetrahedrite, pyrite and barite that with dolomite and quartz as gangue minerals replaced first stage mineralization and is associated with silicification and dolomitization. The third stage of mineralization comprises sphalerite and galena that is associated with dolomitization and calcitization. The occurrence of mineralization in an extensional back arc setting, massive limestone host rock, intense and pervasive host rock alteration, Fe-dolomite associated with main stage mineralization, the presence of mineralization load casts and minute euhedral barite, the remobilization of first stage of mineralization during diagenetic evolution of framboidal pyrite to euhedral pyrite, and timing of mineralization during early diagenesis of mud lime collectively indicate the Eastern Haft-Savaran deposit can be classified as an Irish-type deposit.

Early Cretaceous carbonates are the most common host rocks for Irish-type deposits in Iran. They are largely concentrated in the Malayer-Esfahan metallogenic belt (MEMB) in southwestern Iran, and Yazd-Anarak metallogenic belt in Central Iran. They include some world‐class ore deposits such as Mehdiabad, Irankuh, and Ahangaran. These stratabound deposits are hosted mostly in carbonates with minor siltstones and volcanic components, that formed in extensional and passive margin environments that are related to the Nain-Baft back-arc basin. The deposits are stratabound and comprise wedge-shaped to tabular sulphide-barite orebodies and occur in several different stratigraphic horizons. Dolomitization and silicification are the main wall-rock alteration styles. Replacement textures are common, and orebodies represent complex textures of sulphides and barite, such as brecciated, colloform, zebra, minor laminated, and banded replacement. Barite is an important gangue mineral in the MEMB and YAMB deposits, partly replaced by coarse-grained galena, sphalerite, and chalcopyrite. Sulphides from these Irish-type deposits have a wide spread of light δ34S values (with the majority falling between -25 to +5‰) with mostly bacterial sulphate reduction (BSR) origin. Fluid inclusion studies show that homogenization temperatures of ore minerals are typically 120 to about 280°C (majority 225-275°C), and salinities range from 2 to 24 wt.% NaCl eq, with the majority falling between 8 and 22 wt% NaCl eq. Using the criteria outlined in this study, early Cretaceous extensional sedimentary basins (e.g., Nain-Baft) are highlighted as target areas for exploration of world-class Irish-type ore deposits and correspond well with the periods of expulsions of Cretaceous CaCl2-rich brines.

The Zaylik-Sarilar epithermal deposit is located 35 km southeast of Ahar in the Ahar-Arasbaran Zone in the Alborz-Azerbaijan Magmatic Belt, NW Iran. Exposed rocks in the Zaylik-Sarilar deposit are mainly composed of Eocene volcanic rocks and Miocene dacite-rhyodacite that are intruded by younger intrusions. The deposit occurs within a sequence of Eocene porphyritic andesite and andesitic lithic tuff. Mineralization occurs as open space filling, taking place as irregular veins, veinlets, and hydrothermal breccias. The mineralization zones can be categorized into two main groups according to sulfides and sulfosalts mineralogy, alteration assemblages, ore textures, and fluid inclusion data. The first group consists of gold-bearing quartz-sulfide +/- breccia veins, silic-ified-phyllic +/- argillic zones, and a few quartz-calcite veins. The second group is composed of barren milky (or white) quartz veins, silicified lithocaps, and argillic-kaolinite +/- silicic zones. Pyrite, chalcopyrite, bornite, galena, sphalerite, and Au-Ag sulfosalts were identified in ore paragenesis of the gold-bearing veins. Pyrite is the main sulfide mineral in the barren quartz veins and silicified lithocaps. Gold and silver were enriched during oxidation and supergene alteration of the gold-bearing veins. Textural evidences from the gold-bearing veins, such as mosaic breccia monomicts, floating clast breccias, hydrothermal breccias, colloform-crustiform textures, ginguro bands, dendrite textures, and rarely lattice-and parallel-bladed calcite replacement textures, suggest that boiling occurred in the veins. Comb, cockade, reed molds, zonal, and feathery textures are common in the barren veins and silicified lithocaps. Fluid inclusion data show a decreasing trend in salinity and homogenization temperature (Th) from the gold-bearing quartz veins to the barren ones. The average salinity and homogenization temperature (Th) of fluid inclusions from the gold-bearing veins are 1.05 wt% NaCl equiv. and 297 degrees C, respectively; higher than the average salinity (0.68 wt% NaCl equiv.) and homogenization temperature (192 degrees C) of fluid inclusions from the barren quartz veins. Th versus salinity diagram suggests that boiling was the main mechanism of ore deposition in the gold-bearing quartz veins and silicified zones. These data propose that the barren quartz veins and silicified lithocaps were formed by cooling. A combination of the geologic, mineralogic, alteration, and fluid inclusion data from the Zaylik-Sarilar deposit represents an epithermal system of low-sulfidation type. Structurally, mineralization has been controlled through the NW-trending strike-slip principal displacement zone and it's subsidiary Riedel fractures in response to a N-trending compression in the Arabia -Eurasia collision zone.

The Early Cretaceous Shams-Abad deposit, with proven reserves of 48 Mt grading 35 wt% Fe, is the largest Fe-(Mn) deposit in the Malayer-Esfahan metallogenic belt (MEMB), Iran. The mineralization is stratabound and restricted to Early Cretaceous dolomitic limestone (Kld) and felsic tuffs. The primary ore consists mainly of siderite-ankerite, and minor pyrite, galena, and chalcopyrite. Secondary Fe-oxide-hydroxides (hematite, goethite) are also present. Iron mineralization in the Shams-Abad deposit was emplaced in two paragenetic stages: stage 1, a large volume of host rocks (Kld) was replaced by fine-grained siderite (Sid1) and ankerite (Ank1); stage 2, coarse-grained siderite (Sid2) and ankerite (Ank2) show vein-veinlets and massive textures and were formed by replacement of stage 1 mineralization. Fluid inclusions in hydrothermal dolomite (stage 2) have homogenization temperatures of 170 to 283 °C, with salinities ranging from 2.50 to 11.70 eq. wt. % NaCl. These temperatures and salinities are similar to the ranges reported for some sideritic Fe exhalative deposits elsewhere. The δ13CPDB and δ18OSMOW values of stages 1 and 2 hydrothermal ankerite and siderite suggest that CO2 (or H2CO3) in the hydrothermal fluid mainly originated from marine carbonate rocks. The textural, mineral, chemical, and isotopic evidence suggests that main-stage (stage 2) ore (primarily siderite) was precipitated by mixing between hydrothermal fluid and seawater below the seafloor in the dolomitic limestone host rocks. Subsequently, siderite and ankerite were converted to secondary iron oxides such as goethite and hematite during meteoric water flow through the inverted normal fault and thrust faults and uplift.

The Kahak, Raveh, and Khoreh stratabound sideritic-ankeritic iron deposits are located in the Malayer-Esfahan metallogenic belt (MEMB), Iran. Geological, geochemical, fluid inclusion and S isotope studies have been carried out on the Kahak, Raveh, and Khoreh deposits which are hosted by different types of Lower Cretaceous dolomite, sandstone, and tuff in the Delijan mining district (DMD). Ankerite and siderite ores display a strong lithological control and form stratabound stacked ore lenses hosted in different horizons by Kc2, Kcv, Kc3, and Km units. Economic orebodies are restricted to the hanging wall of the syn-sedimentary normal faults. Three ore types can be distinguished based on the petrographic studies: stringer zone ore facies, bedded ore facies, and massivereplacement ore facies. Ore minerals are predominantly ankerite, siderite, barite, chalcopyrite, sphalerite, galena, and pyrite. Ore mineralization in the Kahak, Raveh, and Khoreh deposits has emplaced in two stages. The fine-grained ore bands (stage 1) which are intricately interlayered with host rock beds, exhibit sedimentary textures such as lamina and bedding and indicate a syn-sedimentary origin. The coarser-grained stage 2 ores show massive and vein-veinlet textures that are considered to form by replacement during sub-seafloor fluid flow. Hydrothermal alteration minerals developed in the wall rock include dolomite, quartz, and calcite. A microthermometric study of fluid inclusions from the barite samples indicates homogenization temperatures between 162 and 210 degrees C. Salinities of ore-forming fluids range from 7.8 to 16.8 wt% NaCl eq. Fluid inclusion studies suggest that the ore-forming fluids were derived from basinal or formational brines. Fluid mixing (basinal brine and seawater) may have played an important role during Fe mineralization. Calculated delta 34S values for the ore fluid vary between + 10.69 and + 31.98 parts per thousand. Sulfur isotopic compositions suggest that the source of sulfur for barite was derived from seawater. These data show that the Kahak, Raveh, and Khoreh ankeritic-sideritic iron deposits are comparable with those of sub-seafloor carbonate-replacement SEDEX-type deposits.

Stratabound or "Manto-type/volcanic red-bed" Cu-(Ag) deposits occur along the Urumieh-Dokhtar magmatic arc (UDMA), Sanandaj-Sirjan Zone (SSZ), Alborz Magmatic Assemblage (AMA), Sabzevar Zone, and Lut Block structural zones of Iran, and are hosted by Cretaceous and Eocene volcanic and volcano-sedimentary rocks. The most important deposits of this type are East Narbaghi, Khankishi, Kahak, Veshnaveh, and Koshkouieh in the UDMA; Keshtmahaki in the SSZ; Mari, Qeblebolagh, and Yamaghan in the AMA; Abbasabad, Dochileh, Gol-Cheshmeh, Zangaloo, Abri, Rahbari, and Cheshmeh-Marzieh in the Sabzevar Zone; and Vorezg in the Lut Block. Back-arc extensional basins are the principal tectonic setting for the Manto-type deposits of Iran, that developed during the subduction of the NeoTethyan crust beneath the Iranian micro-continental plates. The stratigraphic sequences of these deposits are commonly formed from volcanics, volcaniclastics, and sedimentary rocks, which are similar to other volcanic-hosted stratabound copper districts around the world. Iranian Manto-type deposits are stratigraphically controlled in which Cu-(Ag) mineralization occurs as vein-veinlets, dissemi-nated grains, and filling vesicles. Copper mineralization is commonly closely related to framboidal pyrite and pyrobitumen. The mineralogy of the Cu-(Ag) mineralization in all Manto-type deposits of Iran is simple and consists of chalcocite, bornite, native copper, chalcopyrite, acanthite, and minor secondary digenite, covellite, cuprite, tenorite, chrysocolla, anilite, malachite, azurite, and Ag-bearing clausthalite as the main economic minerals, accompanied by pyrite, chlorite, calcite, quartz, and zeolite. Copper sulfides occur mainly as a replacement of diagenetic pyrite, which in turn, replaced pyrobitumen. Iranian Manto-type deposits are inter-preted to be the result of mineralizing hydrothermal fluids derived from footwall volcanic rocks that migrated upwards, driven by the late diagenetic processes. The UDMA and Sabzevar Zone are the most favorable met-allogenic provinces in Iran for Manto-type Cu-(Ag) exploration since these two zones host the largest copper deposits of this type, including Abbasabad, Koshkouieh, East Narbaghi, and Abri deposits. Consequently, reconstruction of orebearing basins, such as presented, is not only critical to understanding the genesis of ancient deposits and their tectonic setting, but also for guiding exploration in deposit-proximal areas.

Mineralization of the southern Chah-Palang W (Cu–Au) deposit in the Yazd Block, central Iran are ore-bearing veins and veinlets commonly hosted by Jurassic sandstone and shale rocks of the Shemshak Formation that is intruded by younger dacitic domes. Tungsten and gold are temporally and spatially related to NW-trending, subvertical hydrothermal breccias veins with silicic–chloritic alterations. The deposit formed during granitic magmatism. Three stages of veins–veinlets are recognized: early-stage quartz 1, wolframite, scheelite 1, pyrite 1, chalcopyrite 1, and arsenopyrite1 vein–veinlets; intermediate stage: quartz 2, scheelite 2, gold, pyrite 2, chalcopyrite 2, arsenopyrite 2, pyrrhotite, bornite, native bismuth, niccolite, cobaltite, and sphalerite vein–veinlets; late-stage hematite: quartz and carbonate vein–veinlets. The first two stages are economic significance. The homogenization temperatures (Th) and salinities of fluid inclusion groups from the early stage (milky quartz) range from 260 to 288 °C and 5.1 to 12.7 wt.% NaCl equiv., respectively. In the intermediate stage (white quartz), the fluid temperature and salinity range from 223 to 247 °C and 3.5 to 9.5 wt.% NaCl equiv. The δ34Sfluid values of pyrrhotite and chalcopyrite range between 5.7 and 9.2‰. The southern Chah-Palang mineralization is related to a magmatic geothermal system. δ18Ofluid (8.61 to 3.44‰ values) suggest that the early-stage ore-forming fluids were primarily extracted from magmatic fluid, with the addition of meteoric water in the intermediate stage. Early-stage apatite precipitated mainly from a volatile-rich magmatic fluid. The oxygen isotopic data, fluid inclusions, and mineral chemistry of the apatite samples indicate that the ore-forming fluids of the vein-type southern Chah-Palang deposit were dominated by magmatic-hydrothermal fluids during the early stage and that meteoric water was added during fluid evolution.

Mineral chemistry of sulfide and sulfosalt minerals in the Cheshmeh-Noghreh barite (gold- silver) deposit, Sabzevar subzone, NE Kashmar

The Bukan Ductile Shear Zone contains the Ghaluzendan, North Ghaderabad, and South Ghaderabad iron deposits. It is situated northwest of the metamorphic Sanandaj-Sirjan Zone and completely defonned subzone. The primary magnetite with volcano-sedimentary origin has formed within the volcano-sedimentary host rocks. These rocks have formed under the influence of dynamo-thermal regional metamorphism at greenschist and deformation simultaneously with the collision of the Zagros orogeny in the Late Proterozoic (phase 1). These host rocks have formed under the influence of dynamo-thermal regional metamorphism at amphibolite facies conditions and ductile sheared deformation with intense strain related to the closure of the Neotethys and post-collision of the Zagros orogeny in the Late Cretaceous (phase 2). The sheared magnetite derived from primary magnetite during progressive shearing of the metavolcanic and metaplutonic host rocks and has increased the iron ore grade in this stage. Then, the host rocks under the influence of retrograde metamorphism from amphibolite to greenschist facies conditions and low-temperature brittle deformation in the Eocene (phase 3); were cut by andesite and andesitic-basaltic dykes and brittle faults, which has caused a decrease in iron ore grade. According to microstructural and microprobe studies of samples from the Bukan iron deposits, three generations of sheared magnetite were recognized derived from primary magnetite due to the ductile sheared deformation (phase 2) and progressive shearing in the Late Cretaceous in the metavolcanic and metaplutonic host rocks. The first generation of coarse-grained magnetite (magnetite-1/mushketovite) with long-rotational and complex strain fringes, defined by fibrous-elongate quartz, feldspar, sericite, and muscovite formed during mushketovitization is assigned to the stage of pre-/early shearing. The second generation of medium-grained magnetite (magnetite-2) is characterized by single-non-rotational strain fringes equivalent to the youngest fringe of magnetite-1, and grew at mid-/late-stage of shearing. The third generation of fine-grained magnetite (magnetite-3) is devoid of any pressure shadow and formed in the closing stage of shearing. There are pyrite inclusions in the first and second generations of sheared magnetite, indicating that the pre to late stage of shearing was associated with sulfide mineralization, while the closing stage of shearing lacks any sulfide mineralization.

The southwest Sabzevar basin situated in the Sabzevar zone is considered to be an attractive metallogenic province in Iran that hosts both volcanogenic massive sulfide (VMS) and stratiform manganese deposits. The Nudeh Besshi-type VMS deposit is located in the Lower Late Cretaceous volcano-sedimentary sequence. The ore mineralization in this deposit is hosted in the alkali olivine basalt flow and tuffaceous silty sandstone rocks. The Nudeh VMS deposit consists of 2 million metric tons of Cu-Zn massive sulfide overlying a Cu-Fe-rich stringer. The massive sulfide orebody consists dominantly of pyrite, chalcopyrite, friedrichite, magnetite, and sphalerite, together with minor quartz, chlorite, and sericite. Chloritization, silicification, and sericitization are the main wall-rock alteration types; alteration intensity increases towards the stringer zone. Chloritized footwall rocks extend up to 20 m below the stringer zone. The quartz-bearing stringer veins also contain pyrite, chalcopyrite, magnetite, and bornite. Magnetite crystals from the stringer ores show variable contents of many elements, such as MgO (0.05 wt%), Al 2 O 3 (0.63 wt%), TiO 2 (0.07 wt%), V 2 O 3 (0.045 wt%), SiO 2 (0.65 wt%), CoO (0.10 wt%), NiO (0.009 wt%), ZnO (0.023 wt%), and CaO (0.03 wt%). The moderate to high V contents are interpreted to result from relatively reduced, seafloor hydrothermal activiy. Compositional variations of magnetite are possibly related to variations in oxygen fugacity, temperature, and water/rock interaction. Within the stringer zone, chlorite 2 (Chl-2) in the vein-veinlets and chlorite 1 (Chl-1) in the chloritized alkali olivine basalt rock are chemically indistinguishable, with 26.92–34.67 wt% FeO and 5.99–14.01 wt% MgO. Chlorite geothermometer studies indicate crystallization formation temperatures of 414 °C (Chl-1) and 303 °C (Chl-2), respectively.

The genetic model, including conditions under which mineralization formed, and relative timing of mineralization are critical questions for SEDEX (or shale-hosted massive sulfide, SHMS) deposits. There is increasing awareness that sub-seafloor replacement is an important process in the formation of some SEDEX deposits. We have studied the Hossein-Abad and Western Haft-Savaran Zn-Pb SEDEX deposits located in the Arak basin of the Malayer-Esfahan Metallogenic Belt, Iran, to address these questions of genesis. This metallotect formed in a backarc paleotectonic setting as a result of the subduction of the Neo-Tethys oceanic plate beneath the SanandajSirjan Zone. The rocks that host the mineralization are Jurassic organic matter-bearing, fine-grained sandstones, siltstones, and shales. Asymmetric lenticular bedding, unidirectional flow (based on oblique silt lamination direction relative to horizontal bedding), graded bedding, and clay-rich interbeds indicate sediments were deposited from turbidity currents in a low-energy basin environment. There are three ore facies in the Hossein-Abad and Western Haft-Savaran Zn-Pb deposits: 1) bedded ore; 2) massive ore; 3) feeder zone. Bedded ore contains pyrite framboids and polyframboidal clusters. The size range of the pyrite framboids (3 to 6 mu m in diameter) indicates they formed in the water column and not in the subsurface. Characteristic structures in bedded ore are: 1) sulfide-bearing silt injections into clay-filled burrows, 2) injection of sulfide-bearing silt into flame structures of claystone laminae, and 3) organic matter in claystone oriented obliquely relative to bedding. These structures are the result of seismic deformation induced by synsedimentary earthquakes, whereby sulfides that formed in permeable unconsolidated sediment were injected into the organic matter-bearing claystone unit. The delta O-18 and delta C-13 values of siderite, calcite and dolomite in veins from the feeder zone and massive ore range from 12.2 to 23.8% and 16.7 to 1.7%, respectively. These values indicate that formational water, seawater and organic matter oxidation-decomposition all played a role in hydrothermal carbonate formation. Melting and homogenization temperatures for CO2 for CO2-bearing fluid inclusions range from 57.5 to 60 degrees C and 6.6 to 29.5 degrees C, respectively, and indicate the presence of < 15 mol percent CH4. The CO2 homogenization temperature range suggests the CO2-rich phase is a CO2-CH4 mixture. The CH4 and CO2 in the H2S-bearing fluid were likely generated by biodegradation and oxidation of organic matter via BSR and methanogenesis. The sulfur isotope compositions of pyrite, galena, sphalerite and chalcopyrite from the feeder zone and the massive ores range from delta S-34 4.3 to + 7.2% and display equilibrium fractionations, indicating that the sulfur originated from two processes: (a) bacterial reduction of seawater sulfate (BSR) (distal from mineralization site), and (b) thermochemical reduction of seawater sulfate (TSR) (in both massive ore and feeder zone). Sulfur isotope geothermometric calculations (.galena-sphalerite) for two samples give temperatures in the range 209-224 degrees C for the massive ore facies. Such high temperatures negate a contribution of sulfur from BSR. However, BSR likely occurred in sediments distal to the feeder zone, where seawater sulfate was bacterially reduced to H2S, and this H2S migrated to the mineralization site during diagenesis. Collectively, the stable isotope data indicate mineralization formed in response to mixing occurred between ascending hot metalliferous hydrothermal fluid that rose up the fault and fracture network, with H2S-bearing fluid and sulfate-bearing percolating seawater, triggering sulfide deposition.

Iran is hosting to numerous sediment-hosted stratabound copper (SSC-type) deposits/occurrences. The major structural zones of Iran that host SSC-type deposits are: (1) the Zagros zone, (2) the Tabas Block, (3) the Central Iranian geological and structural gradual zone (CIGS), (4) the Sabzevar zone, and (5) the Kopeh Dagh zone. The SSC-type deposits formed during discrete time periods and in Iran mostly comprise: (1) the Early Cambrian-Ordovician (with the Dehmadan and Khongah deposits in the Zagros zone), (2) the Permian (with the Ghareh Tapeh deposit in the CIGS), (3) the Upper Jurassic (that include Cu mineralizations in the Garedu Red Bed Formation of the Ravar-Tabas-Eshghabad area (RTEA)), (4) the Upper Jurassic to Lower Cretaceous (with SSC mineralization in the Shurijeh Formation of the Kopeh Dagh zone), (5) the Oligocene to Miocene (including the Bande-Gheychi deposit, the SSC deposits of the Boustanabad-Tabriz-Tasuj area, Avaj-Dozkand-Moshampa area and the Torbat-e-Heidarieh SSC-type deposits), and finally (6) the Pliocene (with the Ghareh Aghaj deposit in the CIGS). Extensional basins that have passed through phases of continental rifting and post-collisional extension are the principal plate tectonic setting for the Iranian SSC-type deposits. All of the SSC-type deposits in the Jurassic and Oligocene-Miocene clastic sedimentary rock sequences formed within continental rifts and post-collisional extension settings, respectively, that developed during subduction of the Neo-Tethyan crust beneath the Iranian plate. Intra continental back-arc spreading settings are recognized in the Paleo-Tethys domain in Iran, and these host Cu-bearing dolomitic host rocks (Dehmadan and Khongah area) in the Zagros zone. The stratigraphic sequences of Iranian SSC-type deposits commonly formed from clastic continental red beds, evaporites and limestone, which are similar to other sediment-hosted stratabound copper districts around the world. The copper mineralization is generally closely related to plant fossils (e.g. wood fragments) and the main ore minerals include chalcocite, chalcopyrite, bornite, pyrite, galena, sphalerite, covellite and chrysocolla, the latter two generally have supergene origin. Copper sulfides occur mainly as replacement of diagenetic pyrite, which in turn, replaced organic matter (e.g. wood fragments). Copper mineralization is mainly controlled by the organic matter content and paleo-permeability from intragranular pore space, evaporate layers and brittle fractures. The paleo-permeability has locally been enhanced by calcite dissolution of diagenetic cements. The main period formation of SSC-type mineralization in Iran is from the Jurassic to Miocene. The Tabas Block and CIGS zone are the most promising metallogenic provinces in Iran for SSC-type exploration, because these domains have the greatest abundance and the largest of these copper deposits. These include the Markasheh deposit in the Tabas Block and substantial copper mineralization in the Miocene Red Bed sequence of the Boustanabad-Tabriz-Tasuj and Avaj-Dozkand-Moshampa regions in the CIGS.