ژئوشیمی

Open Access Article

1 - Petrography, geochemistry and petrogenesis of Abbas Abad volcanic rocks (East Shahroud) with emphasis on associated alteration and copper mineralization
Rasa Alirezaei Ahmad Kazemi Mehrnia لیلا صالحی

Abbas Abad ore district lies in a volcanic and volcanosedimentary belt in East Shahroud and hosts eight copper deposits. This belt is part of volcanic arc in north of central Iran. Copper mineralization is dominated by chalcocite with minor bornite, digenite and covelli More

Abbas Abad ore district lies in a volcanic and volcanosedimentary belt in East Shahroud and hosts eight copper deposits. This belt is part of volcanic arc in north of central Iran. Copper mineralization is dominated by chalcocite with minor bornite, digenite and covellite. Mineralization occurs as disseminated, veinlet, and stock works. Four alterations (silicification, carbonatization, epidotization and chloritization) are detectable in the host rocks. Lithologies of the volcanic rocks are trachyandesite, trachyandesit basalt and trachybasalte and they have high potassium calc-alkaline to shoshonitic nature. Fractional crystallization and crustal contamination processes are involved in magma evolution. Plagioclase and pyroxene are main minerals and the most important texture (porphyric and glomeroporphyritic) has been observed in this rocks. Zoning, sieve textures and re-absorption in plagioclases, and sieve textures, the effects of corrosion on the margins of pyroxene, and roundness of mineral implies the existence of non-equilibrium conditions during solidification of magma. LREE and LILE enrichment and depletion of HFSE with negative anomalies of Nb, Ti and Ta elements in studied samples show the alkaline nature associated with arc (active continental margin). Ratio of Ba/La and Th/Ta in rocks confirm subducting continental arc for tectonic environment of this rocks. Manuscript profile

Open Access Article

2 - Geochemical Studies of Stable Isotopes (Carbon and Oxygen) in Mahallat Travertine Deposits (South East Arak)
لیلا صالحی

Fresh water carbonates are different in geochemical characteristics, especially in isotopic geochemical characteristics. Stable carbon and oxygen isotopes of carbonates such as travertine is one of the most important methods of study. Mahallat area with large traverti More

Fresh water carbonates are different in geochemical characteristics, especially in isotopic geochemical characteristics. Stable carbon and oxygen isotopes of carbonates such as travertine is one of the most important methods of study. Mahallat area with large travertine deposits, is talented to geochemical studies. this area is located in the southeast of Arak and this is a part of central Iran structural zone. Based on stable isotope studies, there are two types of travertine: thermogene and meteogene types. Thermogene C-isotope composition range between -4 ‰ and 8 ‰. However, δ13C value for meteogene type range between -11 ‰ and 0 ‰. Mahallat area travertine C-isotope composition range between 1.69 ‰ and 9.70 ‰ which indicate thermogene type. In addition, Another way to distinguish the type of travertine, is determination of carbon dioxide source. Low values of 〖〖δ^13 C〗_( CO)〗_2 imply to thermogene type and 〖〖δ^13 C〗_( CO)〗_2 Mahallat area travertine show -8.47‰ and this confirm thermogene type for these deposits. Also, water temperature during the travertine precipitation can calculate by oxygen isotope study. The temperature in Abegarm travertine is 43°C which it is evidence for thermogene type. Manuscript profile

Open Access Article

3 - Petrology and geochemistry of igneous rocks in Lower Red Formation, Garmsar Area
Habibollah Ghasemi

Numerous shallow depth basic intrusions crops out in the Lower Red Formation in Garmsar area. These intrusions have gabbro-dioritic compositions and granular, intergranular, ophitic and subophitic textures. Plagioclase, augitic clinopyroxene, amphibole and biotite are t More

Numerous shallow depth basic intrusions crops out in the Lower Red Formation in Garmsar area. These intrusions have gabbro-dioritic compositions and granular, intergranular, ophitic and subophitic textures. Plagioclase, augitic clinopyroxene, amphibole and biotite are their main minerals and olivine, phlogopite, alkali feldspar, apatite, magnetite and sphene are their minor and accessory minerals. Their secondary minerals composed of serpentine, zeolite, chlorite, sericite, prehnite, sphene, uralite, quartz and calcite. These rocks plotted in gabbro-diorite realm in chemical classification diagrams. Geochemical trends of samples in major and trace elements variation diagrams versus differentiation index and in incompatible-incompatible and incompatible-compatible diagrams indicate the liquid line of descent and differentiation relations between samples. In the chondrite and primitive mantle normalized diagrams, enrichment in LREEs and LILEs, depletion in HREEs, absence of Eu anomaly, positive anomalies in K, Ba, Rb and Sr in all samples and strongly depletions in Nb and Ta in some samples and absence of depletion in Ti and P, are the characteristics features of these rocks. This indicates the crustal contamination of the mafic mantle magma formed these rocks. These rocks rather have the features of proto-back-arc basin (BAB) alkaline basaltic magmas, not the characteristics of the subduction related rocks. The dependence of these rocks to the back-arc basin basalts can be confirmed by different tectonic setting discrimination diagrams. It seems that the primary basic magma of these rocks has been generated from partial melting of an enriched mantle source under the continental lithosphere of Central Iran in an extensional proto-back-arc basin, during Late Oligocene time and intruded in lower part of Lower Red Formation. Manuscript profile

Open Access Article

4 - Geochemistry of Salafchegan quartz diorite pluton
Mahbobeh Nazari Shahryar Keshtgar Ali Kananian Mohammad Boomeri

The Salafchegan quartz diorite pluton which is located at 45 km southwest of Qom, has intruded sandstone and sandy limestone of the Upper Red Formation as small subvolcanic intrusion. A zigzag pattern of major and trace elements variations in these intrusive rocks, from More

The Salafchegan quartz diorite pluton which is located at 45 km southwest of Qom, has intruded sandstone and sandy limestone of the Upper Red Formation as small subvolcanic intrusion. A zigzag pattern of major and trace elements variations in these intrusive rocks, from margin to the center of the pluton, may indicate periodical magma chamber refreshments. These subvolcanic rocks show geochemical calc-alkaline affinity and in the case of aluminum saturation index, they could be classified as meta-aluminous rocks, similar to I type granitoids. These rocks are enriched in LILE, and LREE but depleted in HREE. In addition, they show negative anomalies of Nb and Ti, low Ce/Pb, high Ba/La and Ba/Th ratios associated with high Al content. They illustrate porphyritic texture accompanied by inequilibrium phenocrysts such as zoned plagioclase or reaction rims surrounding hornblende crystals. Based on petrographical studies and geochemical analysis, it could be suggested that the parent magma of these subvolcanic rocks was related to a subduction zone and has emplaced in a magmatic arc. Manuscript profile

Open Access Article

5 - Mineralogy, Geochemistry and Alteration of Ore Minerals in Glojeh Epithermal Veins, North of Zanjan
Majid Ghasemi Siani Behzad Mehrabi Mohammad khanazizi

The polymetallic epithermal Glojeh ore deposit is located in the middle of the Tarom-Hashtjin metallogenic province in Alborz-Azarbayejan (western Alborz). It consists of four major epithermal veins, in the South Glojeh and the North Glojeh areas. Andesitic basalt and More

The polymetallic epithermal Glojeh ore deposit is located in the middle of the Tarom-Hashtjin metallogenic province in Alborz-Azarbayejan (western Alborz). It consists of four major epithermal veins, in the South Glojeh and the North Glojeh areas. Andesitic basalt and dacite are hosting the mineralization in the South Glojeh and the North Glojeh veins, respectively. The in Glojeh area rocks include intrusive rocks (granodiorite, granite and quartzmonzonite), diabasitic dikes, and volcanic rocks (dacite, rhyolite, andesitic basalt and tuff). Based on genetic and crossed relations of vein and vienlets, mineralization in the Glojeh occurs in three stages: (1) early stage of Cu-Au-As-Sb-Fe-bearing minerals; (2) mid stage of Pb-Zn-Cu-Cd-Ag-bearing minerals and (3) late stage of hematite-goethite-Ag-Bi-Au-Pb minerals. Mineralogy and minerals chemistry studies show that galena in stage 2 (substage 2B) have inclusions of silver bearing minerals. Important silver bearing minerals in Glojeh veins are argentite, native silver, Ag-tetrahedrite, polybasite, matildite and marrite. Gold mineralization occured in substage 1B (stage 1), and is associated with specular hematite (specularite) as native gold and in substage 3A (stage 3) as inclusions of native gold and eletrum in hematite and quartz. Alteration in Glojeh district consists of propylilitization, argillization, sericitization and silicification, that have well-developed and zoned in the around Glojeh veins and extends ≈ 30 meters into the host rocks. Chlorite geothermometry in argillic zone (stage 2) and propylitic zone (stage 3) are 275°C and 200°C, respectively. Mass balance calculations indicate that Al, Zr, Ti, Y, Nb, and HREE were immobile elements during alteration. Manuscript profile

Open Access Article

6 - Petrology, geochemistry and ore potential of the Samen granitoid (SW Malayer, Hamedan)
Hassan Zamanian Farhad Ahmadnejad Akram Krami Taghipour

The Samen granitoid is located along the northwestern part of the Sanandaj- Sirjan Zone in the Southwestern of Malayer. Based on mineralogical and geochemical characteristics, five main facies have been recognized in the Samen granitoid which included granodiorite, monz More

The Samen granitoid is located along the northwestern part of the Sanandaj- Sirjan Zone in the Southwestern of Malayer. Based on mineralogical and geochemical characteristics, five main facies have been recognized in the Samen granitoid which included granodiorite, monzogranite, syenogranite, alkali-feldspar granite and quartz-monzonite. Granodiorite is the main facies of the pluton and is more wide spread than other facies. Geochemistry of major elements indicates that the Samen granitoid is metalomious (ACNK=0.75) to peralomious (ACNK=1.21) and is classified as volcanic arc granites (VAG) related to active continental margins and petrochemically belongs to calc alkaline with high K rock series. Depletion in Nb, Zr, Hf, Y, Ti and HREE and enrichment in K, Rb, Cs, Th and LREE is consistent with an arc setting related to the subduction of Neo-Tethyan oceanic crust beneath the Sanandaj-Sirjan zone. The pluton has been contaminated by interaction with upper crust. In the Samen district both calcic exoskarn (grossular-andradite/augite-diopside) and endoskarn (tremolite-actinolite/epidote) occur along the contacts between granitoid and marble. The present study indicates that geochemical characteristics of the granodiorite and quartz-monzonite Samen rocks are similar to the averages for Au-Cu- and Fe- skarns granitoids, whereas the geochemical characteristics of the monzogranite, syenogranite and alkali-feldspar granite are similar to averages for Sn- and Mo-skarn granitoids. Based on oxidizing conditions and magma evolution, the Samen granitoid is characterized by relatively unevolved to moderately evolved and oxidized suites, as in most Au-Cu core metal associations globally. Manuscript profile

Open Access Article

7 - Geochemistry and tectonic setting of Zargoli granodiorite in Sistan suture zone (South East Iran)
Shahryar Keshtgar Mohammad Boomeri Ali Kananian Mahbobeh Nazari

The Zargoli granodiorite is located in the northwest of Zahedan in Sistan suture zone. This granodiorite intruded a flysch-like unit at Oligocene and its SiO2 contents range from 62.4 to 66 wt. %. This gronodiorite is calc-alkaline, metaluminous and I-type. The Zargoli More

The Zargoli granodiorite is located in the northwest of Zahedan in Sistan suture zone. This granodiorite intruded a flysch-like unit at Oligocene and its SiO2 contents range from 62.4 to 66 wt. %. This gronodiorite is calc-alkaline, metaluminous and I-type. The Zargoli granodiorite shows negative anomaly of Ta, Ti, Nb, Eu and positive anomaly of Rb, Ce, La, Ba, Sr in spider diagrams suggesting that these rocks have been derived from the partial melting of lower crust. This magma was contaminated with flysh- type sediments during emplacement in Sistan suture zone. Discriminative diagrams indicate a volcanic arc (VAG) and active continental margin (ACM) tectono-magmatic setting for this pluton. Manuscript profile

Open Access Article

8 - Geochemistry of ore facies and alteration zoning pattern of the Varandan Ba-Pb-Cu volconogenic massive sulfide deposit, southwest of Qamsar
Fayegh Hashemi Fardin Mousivand Mahdi Rezaei-Kahkhaei

The Varandan Ba-Pb-Cu deposit is located in southwest of Qamsar which is part of Urumieh-Dokhtar magmatic-arc zone. Mineralozation occurred as four sub-horizons in the unit1 of volcaniclastics and volcanics (acidic tuff and andesite) of Middle-Late Eocene. Each sub-hori More

The Varandan Ba-Pb-Cu deposit is located in southwest of Qamsar which is part of Urumieh-Dokhtar magmatic-arc zone. Mineralozation occurred as four sub-horizons in the unit1 of volcaniclastics and volcanics (acidic tuff and andesite) of Middle-Late Eocene. Each sub-horizon consists of five ore facies including: 1) stringer zone, 2) vent complex zone, 3) massive zone, 4) bedded-banded zone and 5) hydrothermal-exhalative sediments of Fe and Mn bearing. Main wall rock alterations in the deposits include chloritic-quartz and quartz-sericitic. Alteration zoning is observed in the deposit as chloritic-quartz at the core and quartz-serisitic in the margins of the footwall of the ore sub-horizon. Electron microprob analysis (EPMA) on the chlorite in stringer zones of the second and third sub-horizons show that these chlorites are Fe-rich chlorite and close to the clinochlor field. Geochemical studies indicate that grades of Ag, As, Cu, Sb and Sr in the stratiform ore (bedded-banded and massive) of the third sub-horizon are much higher than the other sub-horizons, and are 41, 273, 1945, 390 and 1013 ppm, respectively. All geochemical studies show that metal zoning in this deposit is clear, this is characteristic of VMS deposits. Development of zone-refining and over refining processes caused leaching of Cu from the stringer zone and vent complex facies and its later precipitation in the bedded ore facies. Among across to different sub-horizons in the Varandan deposit, third sub-horizon is recognized as economic for Ag extraction . Manuscript profile

Open Access Article

9 - Hybrid fuzzy c-means clustering algorithm and multilayer perceptron for increasing the estimate accuracy of the geochemical element concentration case study: eastern zone of porphyry copper deposit of Sonajil
Moharam Jahangiri SeydReza Ghavami Behzad tokhmechi

Pattern recognition methods are able to identify the hidden relationships between exploration data, especially in the case of limited number of data. The geochemical distribution patterns of the elements are identified and generalized using these methods. Multilayer per More

Pattern recognition methods are able to identify the hidden relationships between exploration data, especially in the case of limited number of data. The geochemical distribution patterns of the elements are identified and generalized using these methods. Multilayer perceptron, MLP, is one of the pattern recognition methods which is used for the estimation of geochemical element concentrations in mineral deposit studies. In the current study, multilayer neural network was used to estimate the concentration of geochemical elements based on 1755 surface and borehole samples, analyzed by ICP. Fuzzy c-means, FCM, clustering algorithm was used to increase the neural network estimation accuracy. The optimal number of clusters in the dataset was identified by validation indices and was used to design estimator. The clustering data on average showed an increase of 13% accuracy compared to normal mode. The average accuracy was increased from 75 percent to 88 percent. Elements with the lowest estimation accuracy showed an acceptable increase on the estimation accuracy by using clustering data. Mean squared error was 0.079 using all data and decreased to 0.025 while using hybrid developed method. Manuscript profile

Open Access Article

10 - Geochemistry and petrology of Qareh-Dash rhyolites from Shahindej- NW Iran: Geochemical features of post- collision volcanism
Masoumeh Ahangari معصومه نظری Mohsen Moazzen

20.1001.1.17357128.1399.14.56.4.7

Qareh-Dash rhyolites from the Shahindej area are peraluminous rocks with high SiO2 and K2O contents. These rocks are mainly composed of quartz, K- feldspar and rare plagioclase phenocrysts in a fine-grained K-feldspar rich matrix. Geochemically, Qareh-Dash rhyolites sho More

Qareh-Dash rhyolites from the Shahindej area are peraluminous rocks with high SiO2 and K2O contents. These rocks are mainly composed of quartz, K- feldspar and rare plagioclase phenocrysts in a fine-grained K-feldspar rich matrix. Geochemically, Qareh-Dash rhyolites show enrichment in LREEs and LILEs and depletion in HREEs. Field studies, textural and petrographical relations, along with whole rock geochemistry, demonstrate that the parental magma of the Qareh-Dash rhyolites was originated from the crust. The composition of the parental magma was modified due to fractional crystallization of plagioclase and titanomagnetite evidenced by negative Eu, Sr and Ti anomalies in multielement diagrams. The chemical characteristics of Qareh- Dash rhyolites such as Rb/Nb, K/Rb, Rb/Sr, Rb/Ba and Ga/Al ratios are similar to A-Type granites/ rhyolites associated with post- collision tectonic settings. According to Precambrian age for the Qareh-Dash rhyolites, formation of these rocks might be related to extensional phases which were probably taken place after closure of proto- Thetys Ocean. Manuscript profile

Open Access Article

11 - Assessment of mineralization potential using Stage factor analysis method (SFA) in Khoshnameh area, Hashjin, Ardabil province
Samira Hoseinpore Nejati Kamal Siahcheshm seyyed ghafour alavi pouya Zargari

20.1001.1.17357128.1400.15.57.8.0

The Khoshnameh altered area is located about 20 km south of Khalkhal (Ardebil province) and lies in the Hashjin metallogenic district. The formation of extensive serictic, argillic, silicic, chloritic and iron oxides alterations in the Chenar, Mahmudabad and east of Kho More

The Khoshnameh altered area is located about 20 km south of Khalkhal (Ardebil province) and lies in the Hashjin metallogenic district. The formation of extensive serictic, argillic, silicic, chloritic and iron oxides alterations in the Chenar, Mahmudabad and east of Khoshnameh, as well as the copper-lead-zinc mineralization events (e.g. Senjedeh, Shalvali and Ommabad) appears to be intimately affiliated to the fluids derived from upper Oligocene granodiorite intrusions which were emplaced within the Eocene trachy-basalt, andesite and pyroclastic rocks. The key point of this research is to investigate the preference of the Stage Factor Analysis (SFA) to evaluate the geochemical dispersion of mineralization and the visualization of real anomalies throughout the Khoshnameh area. Since the concentration of rock forming elements that are not related to mineralization has a negative effect on the factor privilege of elements, then the number of factors to increase the severity of anomalies must be reduce. For this purpose, initially nine factors were calculated based on the chemical composition of the samples. At this stage, non-representative elements and elements that did not participate in any of the factors were identified and removed from the data set and factor analysis was re-applied. After applying three stages of analysis on the data, the most effective predictive and important factors in terms of mineralization were deduced. Consequently, the number of factors decreased to 5. Therefore, using this method increases the prediction rate and success of the exploration, compared to the typical factor analysis method. Thus, the probable anomalies of Ba, Sn, Pb and Mo mineralization from the first factor and As, Cd and Sb mineralization from the fourth factor are predicted and introduced. Manuscript profile

Open Access Article

12 - Garmichay metapelites, NW Iran: whole rock chemistry, provenance and metamorphic conditions
Amir Mahamed Mohsen Moayyed Monir Modjarrad

20.1001.1.17357128.1400.15.57.4.6

The whole rock chemistry of the Garmichay metapelites located in the north of Miyaneh, NW Iran, is investigated to reveal the provenance and metamorphic conditions of the rocks. Petrofabric observations have revealed the syn-tectonic nature of regional metamorphic cordi More

The whole rock chemistry of the Garmichay metapelites located in the north of Miyaneh, NW Iran, is investigated to reveal the provenance and metamorphic conditions of the rocks. Petrofabric observations have revealed the syn-tectonic nature of regional metamorphic cordierite porphyroblasts in the metapelites. C' shear band structure is another feature that is observed in the rocks. Two regional metamorphic phases (RMP1, RMP2), one contact metamorphic phase (CMP) and two deformation (D1, D2) phases are identified. The major oxide geochemistry implies two sedimentary shale and greywacke parent rocks. Based on major, rare earth and trace elements (Ti, Ni, TiO2, Zr and K2O) the igneous source rock has been an andesite to dacite/rhyodacite. The CIA (chemical index of alteration) and CIW (chemical index of weathering) parameters imply a medium degree of alteration in the igneous source area. The Garmichay metapelites, in comparison with the PAAS and UCC, are enriched in Cs, La and Ce and depleted in Sr, Nb and Ta. The representative samples lie inside the paragenetic triangles of the compatibility diagrams that imply their thermodynamically stable conditions. Finally, based on the standard pseudosections, the maximum temperature and pressure range has been determined as 535-635 °C and 1-3 kb, respectively. Manuscript profile

Open Access Article

13 - Analysis of geochemical features of sabzevar dust, using Marble Dust Collector (MDCO)
آرش امینی بهنام شفیعی

20.1001.1.17357128.1401.16.63.1.2

Dust is one of the atmospheric phenomena that has adverse environmental effects and consequences. In order to study dusts in Sabzevar, samples were collected at the end of each season in 1390. In this research, sampling containers were installed in 16 locations on t More

Dust is one of the atmospheric phenomena that has adverse environmental effects and consequences. In order to study dusts in Sabzevar, samples were collected at the end of each season in 1390. In this research, sampling containers were installed in 16 locations on the roofs of houses and governmental offices based on the main and sub geographical directions and trapped samples in MDCO were measured by 0.0001 accuracy scale. For geochemical studies due to the volume of dust collected and the importance of the samples, basic oxides and trace elements of fine dust were measured using atomic absorption and ICP methods. Results has shown that the maximum dust volume were collected in the spring while the concentration of most polluting elements is higher in autumn. In terms of pollution, Cadmium and Zinc are of primary importance in sabzevar due to their very high pollution coefficient. Chromium and Nickle are of secondary importance with being in the range of moderate pollution and significant pollution coefficient. In the current situation, the pollution of elements such as copper, lead and arsenic in the dust of Sabzevar is not critical and worrying. Manuscript profile

Open Access Article

14 - Separation of geochemical anomalies of gold-copper by concentration -Number Fractal (C-N) method in southeast of Nain
B. Gholipour A. Kananian Sh. Niroomand A. Tarhani M. Fersowsi Rashed

20.1001.1.17357128.1401.16.61.1.8

In this paper, concentration-number fractal method was used to study regional exploration and geochemical anomaly separation; also anomalies of index elements including gold, arsenic, silver, copper, antimony, lead, zinc and molybdenum in the Qalehdar exploration area ( More

In this paper, concentration-number fractal method was used to study regional exploration and geochemical anomaly separation; also anomalies of index elements including gold, arsenic, silver, copper, antimony, lead, zinc and molybdenum in the Qalehdar exploration area (Isfahan province) was investigated. For this purpose, 336 samples of rock units were collected and analyzed by ICP-MS. Then the chemical analysis data were categorized and prepared after replacing the sensor data for processing..Using concentration-number fractal method, elemental anomalies in that area was identified and the anomalies were mapped. The results of geochemical studies in the area showed that different geochemical anomalies of Au, Mo, Cu, As, Sb, Pb, Zn are closely related to alteration zones and shallow plutons. These studies also led to the identification of a geochemical system.. After drawing the geochemical maps and identifying the anomalous regions, the anomalies of the various elements were correlated and a zoning was recognized. In this zoning from the center to the outside of the system,the anomalies respectively, include molybdenum (Mo), copper-molybdenum (Cu Mo), lead-zinc (Pb Zn) anomalies and finally the gold-arsenic anomaly (As Au) which is located at the periphery of the system. Manuscript profile

Open Access Article

15 - Mineralogy, geochemistry, and fluid inclusion characteristics of the Madanjoo skarn iron deposit, Sangan mining district, NE Iran
M. Fotovat Jami Masoud Alipour-Asll

20.1001.1.17357128.1401.16.62.3.2

The Madanjoo prospect is one of the eastern anomalies in the Sangan mining district. This area is located in the eastern part of the Cenozoic Alborz volcanic-plutonic arc. The geology of the area includes Jurassic shaly sandstone, lime mudstone, and sandstone, Upper Cre More

The Madanjoo prospect is one of the eastern anomalies in the Sangan mining district. This area is located in the eastern part of the Cenozoic Alborz volcanic-plutonic arc. The geology of the area includes Jurassic shaly sandstone, lime mudstone, and sandstone, Upper Cretaceous limestone and dolomitic limestone, and Upper Eocene tuff and lava flow sequences, Middle Eocene skarn rocks, and Quaternary sediments. The most important occurrence in the Madanjoo area is the penetration of ferrous fluids into terrigenous and carbonate formations, skarnization, and iron mineralization, which is characterized by the presence of magnetite and calcsilicates minerals. based on type and frequency of calcsilicates, The skarn zones include olivine-pyroxene-garnet skarn, garnet-pyroxene skarn, garnet skarn, pyroxene-wollastonite-magnetite skarn, magnetite skarn, phlogopite skarn, tremolite-actinolite skarn, and epidote skarn. Iron mineralization occurred as massive, banded, vein-veinlets, breccia, and disseminated forms mostly in the Upper Cretaceous limestone and dolomite rocks and along NE-SW fault zone trend. Magnetite is the main ore mineral accompanied with pyrite, chalcopyrite, pyrrhotite, and secondary iron minerals. The composition of the Madanjoo garnet, pyroxene, and olivine are andradite-grossular (mostly andradite), diopside-hedenbergite (mostly diopside), and forsterite, respectively. Thermobarometry study based on pyroxene chemistry show that pyroxenes crystallized in temperature range of 458-689 °C, pressure of 2.21 kb, and depth range of 1-2.5 km. Three main paragenetic stages of skarn formation and ore deposition were recognized in the Madanjoo deposit: (1) a prograde stage developed with prograde garnet and pyroxene forming at 330° to 410 °C with a fluid salinity between 33 to 58 wt.% NaCl equivalent, (2) a retrograde garnet, tremolite- actinolite, and calcite which formed at 120° to 300 °C with fluid salinity of 16 to 49 wt.% NaCl equivalent, and (3) a post-ore stage with calcite and minor quartz veins that developed at 95° to 190 °C with salinity range of 2 to 15 wt.% NaCl equivalent. Possible iron ore formation mechanisms include: fluid mixing, boiling, and dilution with meteoric waters along with decreasing temperature. Finally, the Madanjoo iron mineralization is introduced as a magnesian exoskarn iron deposit. Manuscript profile

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