Economic Geology
Elnaz Zahmatkesh; Seyed Mehran Heidari
Abstract
Zavarian gold occurrence formed within andesitic volcanic units in northwestern Iran. The volcanic complex is in fact a part of magmatism related to Urumieh-Dokhtar magmatic belt crosscutting northwestern rim of Central-Iran zone. This system is a part of the volcanic-sedimentary sequence of the Qom ...
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Zavarian gold occurrence formed within andesitic volcanic units in northwestern Iran. The volcanic complex is in fact a part of magmatism related to Urumieh-Dokhtar magmatic belt crosscutting northwestern rim of Central-Iran zone. This system is a part of the volcanic-sedimentary sequence of the Qom Basin that is formed as an intercontinental stratovolcane in a tension environment. Gold has the highest correlation with Mo, Bi, As, Sb, Ag, Cd and Cu which indicates relationship mineralization with magmatic fluids and role of bi-sulfide complexes in gold transport. Hydrothermal alteration in this area is most in the vicinity and within intrusions, and along fractures with NE-SE trending and have more intense around siliceous zones. The activity of hydrothermal system starts by alterations related to the subvolcanic intrusive, and creates the first mineralization phase by oxid-silicic alteration along the fractures. This mineralization phase continued by hydrothermal breccia with tourmaline and copper sulfide, and finally finished with high sulfide mineralization and deposition of gold mineralization in the cavities and fractures. Therefore, Characteristics of this mineralization indicate that it is most similar to epithermal related to subvolcanic deposits.
Sedimentology
keyvan ahzan; Nader Kohansal Ghadimvand; Seyed Mohsen Aleali; Davood Jahani
Abstract
The Jahrum Formation (Paleocene-Mid Eocene) is one of the most important reservoir units in the Zagros basin and the Persian Gulf. The thickness of this formation in Binaloud oil field in Persian Gulf, which mainly consists of limestones and Dolomites, is about 660 meters. In this research, depositional ...
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The Jahrum Formation (Paleocene-Mid Eocene) is one of the most important reservoir units in the Zagros basin and the Persian Gulf. The thickness of this formation in Binaloud oil field in Persian Gulf, which mainly consists of limestones and Dolomites, is about 660 meters. In this research, depositional environment, sequence stratigraphy and effective diagenesis processes on Reservoir quality of the Jahrum Formation were investigated in Binaloud oil field. The Jahrum succession, which consists of crystalline limestones and dolomites, is overlain by the Asmari Formation and is underlian by the Tarbur Formation unconformably. According to study of cutting samples, eleven microfacies that were deposited in four facies belts, have determined . The most important diagenetic process that was observed in this formation as follows: bioturbation, cementation, dolomitization, dissolution, porosity generation and fracture systems wich is worthy to mation bioturbation and anhydrite cement causes the reduce of reservoir quality and dolomitization , dissolution and secondary porosity causes the reservoir quality. improvement most of facies jahrum formation are mud supported and have very low primary porosity. According to sequence stratigraphy studies, a third order sedimentary sequence with type SB1 boundary was identified in Jahrum subsurface succession.
M. H. Kazemzadeh; A. Sadeghi; M. H. Adabi; H. Ghalavand
Abstract
In order to determine biostratigraphy, depositional environment and sequence stratigraphy of the Kalat Formation in the Sheikh Syncline (north east of Bojnurd), Four stratigraphic sections including South Sheikh, North Sheikh, Qaleh Zu and Ziarat were selected and sampled. The thickness of the Kalat ...
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In order to determine biostratigraphy, depositional environment and sequence stratigraphy of the Kalat Formation in the Sheikh Syncline (north east of Bojnurd), Four stratigraphic sections including South Sheikh, North Sheikh, Qaleh Zu and Ziarat were selected and sampled. The thickness of the Kalat Formation in the South Sheikh, North Sheikh, Qaleh Zu and Ziarat sections were 25, 16, 25 and 5m respectively, and its lithology consists mainly of brown to yellow limestones. The reason of changes in thickness in studied sections is tectonic factors, subsidence and different rates of sedimentation. The layer of conglomerate in the base part of the Kalat Formation at South Sheikh and Qaleh Zu sections and the layer of sandstone in the base part of the Kalat Formation at Ziarat section were recognized. In the biostratigraphic studies, 15 species belonging 23 genera of foraminifera were recognized and one biozone including Siderolites calcitrapoides-Sirtina orbitoidiformis assemblagezone was identified. The age of the Kalat Formation in all of studied sections based on the above biozone and fossil contents Maastrichtian were determined. Petrographic analysis led to recognition two silliciclastic and eight carbonate facies belonging to four depositional environments including tidal flat, restricted and semi-restricted lagoon, shoal and open marine. Based on the recognized facies and its gradual trend, abundance of shoal facies, absence of reefs and sediment of turbidite flows such as Falling and sliding sediments, the sedimentation of the Kalat Formation was occurred on the homoclinal ramp setting. Based on the vertical changes of facies and recognized depositional environments, one third-order depositional sequences was represented. This depositional sequence consists mainly of shoal facies rich in bioclast, intraclast, benthic foraminifera, echinoid, rudist (Hyporite) and bivalve. MFS of this sequence is represented by open marine facies rich in echinoid.
Sedimentology
Najmeh Etemad-Saeed; Mahdi Najafi; Navid Zeinolabedin Qavim; Ghods Abdolreza
Abstract
The present study provides a detailed facies and depositional environment analyses of the Neogene sediments in the northern Dezful embayment, footwall of the Zagros Mountain Front fault. The Neogene sediments in this area, including the Mishan, Aghajari, and Bakhtyari formations, constitute the thickest ...
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The present study provides a detailed facies and depositional environment analyses of the Neogene sediments in the northern Dezful embayment, footwall of the Zagros Mountain Front fault. The Neogene sediments in this area, including the Mishan, Aghajari, and Bakhtyari formations, constitute the thickest Zagros foreland succession, with more than 5 km of thickness. As these sediments were deposited synchronous with the main phase of the Zagros orogeny, they have recorded the history of deformation events. During the current study, 9 lithofacies have been identified on the basis of lithology, grain size, sedimentary structures, and bed geometry, which can be classified into three facies assemblages including: gravel dominated (Gm, Gp), sand dominated (Sh, St, Sp, Sr), and mud dominated (Fm, Fl). Furthermore, two major marine ichnofacies, the skolithos and the Cruziana ichonafacies, have been identified at the base of the Aghajari Formation. As the results indicated, the vertical stacking of facies represents an overall shallowing-upward succession that was deposited in marginal marine (Mishan), siliciclastic shoreline (base of Aghajari), meandering river (top of Aghajari) and braided river (Bakhtyari) depositional environments, from base to top respectively. Considering eustatic sea-level fluctuations in the deposition period (13 to 3 Ma), these results propose that evolution of the Neogene sedimentary basin in the North Dezful likely controlled by tectonic folding and faulting.
Stratigraphy and Palaeontology
Somayeh Baharlouei Yancheshmeh; Ebrahim Ghasemi Nejad; Hossain Rahimpour-Bonab; Seyyed Ali Aghanabati
Abstract
Permo- Triassic subsurface section at Lavan 3 Well in Lavan Gas Field exhibits a 85 m-thick succession of limy dolostone and dolomitic limestone bearing anhydrite in the upper Dalan Formation, as well as a 154 m-thick succession of limy dolostone and dolostone with anhydrite ...
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Permo- Triassic subsurface section at Lavan 3 Well in Lavan Gas Field exhibits a 85 m-thick succession of limy dolostone and dolomitic limestone bearing anhydrite in the upper Dalan Formation, as well as a 154 m-thick succession of limy dolostone and dolostone with anhydrite intercalations in Kangan Formation. In the present study, 116 species belonging to 55 foraminifera genera were identified which were divided into two biozones, namely Charliella altineri- Paraglobivalvulina mira- Dagmarita chanackchiensis Assemblage zone (Dzhulfian in age) and Claraia aurita- Spirorbis phlyctaena Assemblage zone (Anisian in age). Nine primary microfacies were identified in the upper Dalan Formation, while, 13 microfacies were detected in Kangan Formation, together with different sub-environments (sabkha, tidal flat, lagoon, submarine ridge, and open marine) which were found to be deposited in a shallow marine carbonate platform in the form of a homoclinal ramp. Based on microfacies changes, aggradational, progradational and retrogradational stacking patterns of deposits and by conformation with the Gama-ray log, these strata could be divided into a couple of third-order sedimentary sequences for the upper Dalan Formation, as well as a couple of third-orders for the Kangan Formation, including two system tracts (TST and HST). On a global scale, the findings are comparable to the upper part of the Absaroka supersequence.
Abbas Dehkar; Vali Ahmad Sajjadian; Mohammad Reza Noora; Kazem Shabani Goorji
Abstract
The Fahliyan Formation of Khami Group is hosting important hydrocarbon reserves in Iran and also is a main reservoir rock in the Abadan Plain oil fields which is Neocomian in age. In the studied wells its thickness is about 406 meters. In the Abadan Plain, the Fahliyan Formation transitionally overlies ...
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The Fahliyan Formation of Khami Group is hosting important hydrocarbon reserves in Iran and also is a main reservoir rock in the Abadan Plain oil fields which is Neocomian in age. In the studied wells its thickness is about 406 meters. In the Abadan Plain, the Fahliyan Formation transitionally overlies of the Garau Formation and its upper boundary changes into the Gadvan Formation. According to thin sections examinations prepared from cores analysis 11 microfacies is recognized by various facies including dolostone and dolomudstone of tidal flat, skeletal wackestone to packstone of the open and restricted lagoon, bioclastic intraclastic grainstones, peloid grainstone and coralinrudist-algae grainstone (boundstone) of the barrier setting and fine grained echinoderm rudist bearing deposits of the slope. high frequency of core facies belong to restricted and open marine lagoon deposits composed of benthic foraminifera, shell fragments and peliods. They are often observed in wackestone to packstone fabrics. The remained rock facies is composed of the bioclastic skeletal lime grainstones characterizing by large rudists and echinoderm debries which are interpreted to constitute the platform margin in this well. Tidal flat dolomudstone with a few bioclast contribute, which they often show moderate reservoir quality.
L. Azad Shahraki; H. Rahimpour Bonab; M. Ranjbaran; A. Kangazian
Abstract
The Lower Cretaceous (Neocomian) carbonates of the Fahliyan Formation are considered as important reservoir rocks in the Zagros Basin. In this study, the sedimentary successions of this formation in Lar (620m thick) and Khami (517m thick) anticlines, located in the Izeh zone, were investigated to analyze ...
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The Lower Cretaceous (Neocomian) carbonates of the Fahliyan Formation are considered as important reservoir rocks in the Zagros Basin. In this study, the sedimentary successions of this formation in Lar (620m thick) and Khami (517m thick) anticlines, located in the Izeh zone, were investigated to analyze microfacies, depositional environment, and diagenetic phenomena. Based on petrographic studies, 16 microfacies related to five facies belts of tidal flat, lagoon, carbonate shoal, mid ramp and outer ramp were recognized. Grainstone microfacies were found more abundant in the Lar stratigraphic section than the Khami section. Lack of turbidite deposits and reefal facies, and transitional changing of the facies show that the Fahliyan Formation was deposited in a homoclinal carbonate ramp. Abundance of mud dominated facies and rarity of high energy facies (like shoal facies) show that the ramp was a leeward one. According to petrographic studies, the main diagenetic features of the carbonates were micritization, cementation, dissolution, neomorphism, compaction, fracturing, and dolomitization. Due to deposition in the photic zone and high sedimentation rate, the thickness of the Fahliyan Formation in both stratigraphic sections is considerable, but based on the drawn isopach map, the thickest succession of the formation is found in the Lar section. Therefore, the Lar area is considered as the depocenter of the Fahliyan Formation. Difference in the thickness of the Fahliyan successions of Lar and Khami, most probably, is caused by the syndepositional activity of the north-south trending basement faults (like Kazeroon fault) in the region. Also, difference in the quantity of the burial compaction of the carbonate successions (caused by facies and diagenetic differences) played a role in secondary (burial) thickness changes.
Stratigraphy and Palaeontology
M. Allameh; A. Mahboubi; R. Moussavi-Harami; M. Khanehbad
Abstract
The Aitamir Formation (Albian-Cenomanian) composed of siliciclastic rocks and several carbonate horizons. In order to study depositional environment and sequence stratigraghy, two stratigraghic sections studied in east Koppeht Dagh basin near the Baghak and Shurijeh villages. Field and petrograghic studies ...
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The Aitamir Formation (Albian-Cenomanian) composed of siliciclastic rocks and several carbonate horizons. In order to study depositional environment and sequence stratigraghy, two stratigraghic sections studied in east Koppeht Dagh basin near the Baghak and Shurijeh villages. Field and petrograghic studies led to siliciclastic and carbonate facies that deposited in lagoon, barrier, shoreface and open marine environments. Sequence stratigraghy analysis led to identification of three depositional sequences in both sections. Comparision of interpreted sea level curves at studied area with Albian-Cenomanian global curve shows similarities and differences that can be relatedto tectonic setting and sedimentation rate.
M Khazaee; M Hosseini-Barzi; A Sadeghi; H Mosaddegh
Abstract
The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain ...
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The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain by dark carbonate deposits of the Mobarak Formation. The clastic deposits of the Jeirud Formation include conglomeratic, sandy and muddy facies. The conglomeratic deposits comprises three facies A1, A2 and A3 that are equivalent to Gcm, Gt and Gmm/Gmg of Miall facies respectively. Also, five sandy facies of B1, B2, B3 and B4 equivalent to St, Sh, Sm and Sr of Miall respectively and B5 (Shc) with hummocky cross stratification (HCS) sedimentary structure have been identified. Muddy facies including C1 and C2 are equivalents to Miall’s Fsm and Fl facies. Carbonate facies (D) comprising small amounts of the stratigraphic column is almost entirely dolomitized. Field and petrographic studies provide five facies association: fluvial, foreshore-backshore, shoreface, offshore transitional zone and offshore and carbonate facies interpreted as Proximal carbonate tempestites and distal carbonate tempestites based on evidences such as basal erosional surface, normal grading, HCS and coexisting clastic facies . In the study area, the Jeirud Formation deposits initiate with fluvial sequences that have been followed by storm dominated marine deposits as foreshore-backshore deposits and alternations of shoreface to offshore deposits. Study of sequence stratigraphic surfaces especially important subaerial unconformities and also stratal stacking patterns of the formation resulted in determination of three subaerial unconformity bounded depositional sequences plus transgressive part of the 4th sequence.
A Ramezani Akbari; H Rahimpor-Bonab; M.R Kamali; R Moussavi-Harami; A Kadkhodaie
Abstract
The Fahliyan Formation of Khami Group is hosting important hydrocarbon reserves in Iran and also is a main reservoir rock in the Abadan Plain oil fields which is Neocomian in age. In the studied wells its thickness is about 440 meters. In the Abadan Plain, the Fahliyan Formation transitionally overlies ...
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The Fahliyan Formation of Khami Group is hosting important hydrocarbon reserves in Iran and also is a main reservoir rock in the Abadan Plain oil fields which is Neocomian in age. In the studied wells its thickness is about 440 meters. In the Abadan Plain, the Fahliyan Formation transitionally overlies the argillaceous limestone of the Garau Formation and its upper boundary changes into marl and argillaceous limestone of the Gadvan Formation. According to thin sections examinations prepared from cuttings and cores plus electrofacies analysis 11 microfacies and 2 lithofacies are recognized. This formation consists of two carbonate and mixed carbonate-siliciclastic (mixed zone) members. The Lower Fahliyan was deposited in carbonate ramp environment while, the Upper Fahliyan was deposited in a mixed carbonate–siliciclastic environment. To determine electrofacies, the rock types were modeled with using MRGC method. Best correlation between petrographical and electrofacies is 12 cluster model (in MRGC method). These results suggest that the electrofacies model is in agreement with heterogenetic rock type such as mixed carbonate–siliciclastic environment observed in petrography. Also, in homogenous rock type such as carbonate ramp environment electherofacies can’t completely determine geological facies. Based on petrographical and electrofacies this formation is composed of three third order sequences with type sb2 sequence boundaries. But, the third sequence in mixed carbonate–siliciclastic zone is terminated with sb1 sequence boundary just below the Gadvan Formation.
M. Mehdinia; R. Moussavi Harami; D. Jahani
Abstract
The goal of this study is to use petrographic and other sedimentary features to interpret depositional environment of Faraghan Formation (Lower Permian) in one of the wells in Golshan Field. Golshan Gas Field is located at about 180 km South East of Bushehr between South Pars and North Pars and Ferdowsi ...
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The goal of this study is to use petrographic and other sedimentary features to interpret depositional environment of Faraghan Formation (Lower Permian) in one of the wells in Golshan Field. Golshan Gas Field is located at about 180 km South East of Bushehr between South Pars and North Pars and Ferdowsi Fields. In this study, 130 thin sections of cuttings have been studied, and 8 petrofacies and 3 microfacies and 2 hybrid arenite fasies were identified in the well. Textural maturity of sediments, such as well- sorted and rounded quartz grains, show that the Faraghan Formation was deposited in coastal and shallow marine environments. The identified Facies has been deposited in sabkha, estuarine, foreshore, shoreface and offshore subenvironments.
B. Alizadeh; S. H. Hosseini
Abstract
Sargelu Formation is deeply buried and has limited distribution in Dezful Embayment (limited to the northern part), hence, investigation of petroleum potential of this formation has attracted many petroleum geologists. In this study, hydrocarbon potential of Sargelu Formation in Northern Dezful Embayment ...
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Sargelu Formation is deeply buried and has limited distribution in Dezful Embayment (limited to the northern part), hence, investigation of petroleum potential of this formation has attracted many petroleum geologists. In this study, hydrocarbon potential of Sargelu Formation in Northern Dezful Embayment is evaluated geochemically. For this purpose 34 drill cuttings from well numbers, 309, 310, 312 and 316 in Masjid-i-Soleiman (MIS) oilfield were selected, and geochemical analyses such as Rock-Eval VI pyrolysis and PY-GC were performed. The results reveal that the formation has “Very Good” hydrocarbon potential because of its high amounts of Total Organic Carbon (TOC). Results were plotted on Van-Krevelen as well as on HI vs. Tmax diagrams, and demonstrated mixed Kerogen Type III and IV due to low HI caused by higher thermal maturity, in well numbers 309, 310 and 312. However, the prominent Kerogen type was determined to be of mixed Kerogen type II and III. In all, the organic matter in well No. 316 has a better Kerogen type (mixed type II and III). All the Samples plotted on Smith Diagram have more than 0.1 S1/TOC ratios and capable of generating hydrocarbon. The Pr/nC17 vs. Ph/nC18 ratio demonstrates marine environment for Sargelu Formation. Pyro and thermograms reveal that normal alkanes are dominated in C15 – C20 range, while heavy normal alkanes are missing due to its high thermal maturity. In all it can be concluded that Sargelu Formation in MIS oilfield, due to its paleoenvironment as well as burial depth exclusively has a good quality of organic matter with adequate maturity at the end of oil window and hence is gas-prone.
