Petrology
Leili Bastami; Reza Moussavi; Mahboobeh Hosseini-Barzi; Bahaedin Hamdi Hamdi
Abstract
The sandstones of the Dorud Formation (Early Permian) have been subjected to petrographic and geochemical studies in order to investigate provenance, tectonic setting, source rock and paleoclimate conditions in Khur section, Central Alborz. The Dorud Formation with a thickness of 360 m is mainly composed ...
Read More
The sandstones of the Dorud Formation (Early Permian) have been subjected to petrographic and geochemical studies in order to investigate provenance, tectonic setting, source rock and paleoclimate conditions in Khur section, Central Alborz. The Dorud Formation with a thickness of 360 m is mainly composed of fine to medium grained sandstones with lesser amounts of carbonate and mudstone. In order to achieve the above-mentioned goals, 125 thin sections were subjected to petrographic studies. Modal analysis was performed on 20 thin sections and 13 samples of sandstones were analysed for major and trace elements. Based on petrographic studies the sandstones of the Dorud Formation are classified as quartzarenite with high textural and mineralogical maturity. Plotting point counting data on (Qt99.6, F0.2, L0.2( and (Qm95.9, F0.2, Lt3.9) triangles implies craton interior provenance. Also, major and trace elements based geochemical diagrams indicate that these sandstones deposited in a passive continental margin tectonic setting. According to petrographic and geochemical evidence the sandstones of the Dorud Formation derived from erosion of middle- to high-grade metamorphic, felsic igneous and quartoze sedimentary rocks. High mineralogical maturity, high values of chemical index of weathering (CIW) and chemical index of alteration (CIA) as well as SiO2 (%) versus Al2O3 + K2O + Na2O (%) diagram imply moderate to intense weathering under warm and humid climatic conditions. Passive continental margin tectonic setting and warm and humid paleoclimatic conditions is consistent with paleogeographic position of Iran during the Early Permian.
Sedimentology
Majid Khazaee; Mahbobeh Hosseini-Barzi; Abbas Sadeghi; Hossein Mosaddegh
Abstract
The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of ...
Read More
The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of basic to acidic igneous rocks and recycling of older sedimentary rocks as the provenance that weathered under cold and arid to semi-arid climatic conditions. An integration of modal analysis and heavy minerals results into the geochemical studies including Roser and korsch diagram (Log K2O/Na2O versus SiO2) and Verma and Armstrong-Altrin Functional diagrams, indicate that, siliciclastic rocks of Jeirud, resulted from weathering of acidic-intermediate to basic rocks of collisional tectonic provenances (recycled orogens) and transporting on craton interior and have been deposited on a passive margin basin. Investigations and comparison with McLennan et al., studies, represent that geochemical results and proportions of study area are consistent with those of old upper continental crust (OUC) typical of collisional tectonic settings.
N Etemad-Saeed; M Hosseini-Barzi; M.H Adabi; A Sadeghi
Abstract
The Kahar Formation at its type locality in the KaharMountain, 75 km NW of Tehran, consists of about 1000 m of siliciclastic rocks (mainly mudrocks). This study focuses on the mineralogical and geochemical composition of these mudrocks to identify possible source areas and their tectonic setting. The ...
Read More
The Kahar Formation at its type locality in the KaharMountain, 75 km NW of Tehran, consists of about 1000 m of siliciclastic rocks (mainly mudrocks). This study focuses on the mineralogical and geochemical composition of these mudrocks to identify possible source areas and their tectonic setting. The optical microscopy and XRD studies suggest that the mudrocks are rich in quartz and feldspar (especially plagioclase) and have low phyllosilicates (mostly illite and chlorite). SEM-EDX petrographic investigation of mudrocks reveals that platy illite and chlorite may have formed during the diagenesis (illitization and chloritization). Classification of studied mudrocks based on the maturity index, indicate that they are tectic and phyllo-tectic types, deposited in basins related to an (continental) island arc tectonic setting. The Chemical Index of Alteration (average 70) and A–CN–K parameters indicate that a moderate chemical weathering has taken place in the source region of the Kahar mudrocks. In addition, the chemical composition of mudrocks suggests that the amount of sediment recycling is very low in the Kahar deposits. The geochemical discrimination diagrams, immobile trace element ratios and Rare Earth Elements of mudrocks suggest that the Kahar mudrocks were derived mainly from the felsic sources and deposited in the basins related to an island arc tectonic setting. The resulting model for the tectonic setting of the Kahar basin during the Late Neoproterozoic can be best explained by recently models that considered Iran as part of Peri-Gondwanan terranes, similar to the Avalonia and Cadomia arc terranes, occupying the northern margins of Gondwana.
N Etemad-Saeed; M. H Adabi; A. Sadeghi; M. Hosseini- Barzi
Abstract
This work is focused on tectonic provenance of the Late Neoproterozoic Kahar Formation in the northern Iran. KaharMountain (type locality) provides valuable information on tectonic events during this time. The Kahar Formation in this area is a well preserved sedimentary sequence and consists of about ...
Read More
This work is focused on tectonic provenance of the Late Neoproterozoic Kahar Formation in the northern Iran. KaharMountain (type locality) provides valuable information on tectonic events during this time. The Kahar Formation in this area is a well preserved sedimentary sequence and consists of about 1000 meters of predominantly fine grained siliciclastic rocks and minor sandstones, conglomerates and dolomitized stromatolites. Kahar lithic arkose sandstones with low compositional and textural maturity, contain abundant feldspar (plagioclase and K feldspar), quartz, and volcanic lithic fragments and have an average composition of Q38F40L22, Qt39F40L21, Qm32F40Lt28,Qp27Lvm60Lsm13 and Qm44P33K23 suggesting a proximal source and a dissected arc setting. The type of lithic fragments in the sandstones show andesitic and felsic volcanic rock sources. Heavy mineral analysis (abundant metastable and unstable minerals such as biotite, and pyroxenes) indicate that Kahar sandstones were derived from unroofing of arc-type magmatic rocks. The low diversity of heavy mineral assemblages in the Kahar sandstones indicates that the source rocks were uniform and localized. Considering the two common tectonic views regarding the Late Neoproterozoic condition of Iran (rift-passive margin and magmatic arc-subduction zone), the results of this study which confirm the magmatic arc tectonic setting of Alborz-Iran at that time seems critical.
A. Mahdavi; E. Rastad; M. Hoseini Barzi
Abstract
Markasheh occurrence, includes redbed sediments (Garadu Redbeds) of Jurassic-Cretaceous age that extend in a large area for over 400 km in an area. Garadu Redbeds include alternate of red oxidized sandstone, conglomerate and siltstone that is partly reduced. Mineralization occurred in reduced horizons ...
Read More
Markasheh occurrence, includes redbed sediments (Garadu Redbeds) of Jurassic-Cretaceous age that extend in a large area for over 400 km in an area. Garadu Redbeds include alternate of red oxidized sandstone, conglomerate and siltstone that is partly reduced. Mineralization occurred in reduced horizons and is related with paleochannels. In the Markasheh area two obvious main reduced horizons and four sub-horizons occur. Each of these horizons includes three zones: Red oxidized zone, Bleached zone and Reduced mineralized zone. Based on characteristics of Markasheh Cu occurrence such as lithology, lens like and layered shape (in geometry), regional extent, replacement and disseminated textures, simple mineralogy, presence of plant fossils and concentration of copper mineralization in relation to fossils, Markasheh Cu occurrence is considered as a Red bed sediment-hosted copper deposit type. The mineralization has been occured after early diagenesis before burial of the host roks.
M. Hosseini-Barzi; M. Saeedi
Abstract
The sandstones of Padeha Formation with 390m thickness in section of Samirkooh in Kerman, Zarand have been studied to illuminate their provenance, tectonic provenance, diagenesis by omitting the effect of diagenetic process on sandstone composition. In this direction, petrography of 91 thin sections, ...
Read More
The sandstones of Padeha Formation with 390m thickness in section of Samirkooh in Kerman, Zarand have been studied to illuminate their provenance, tectonic provenance, diagenesis by omitting the effect of diagenetic process on sandstone composition. In this direction, petrography of 91 thin sections, modal analysis of 30 appropriate samples, and use of SEM and EDX analyses of 6 sandstone samples were accomplished .We can point to diagenetic processes including mechanical compaction, coating hematite around the detrial grains (eogenetic stage) and growing up authigenic cholorite and illite, chemical compaction, quartz cementation, dolomite cementation, dedolomitization, albitization of feldspar and corrosion of grains by dolomite cement (mesogenetic stage) and fracturing as well as filling them by calcite, quartz and anhydrite cement (telogenetic stage). We studied tectonic provenance of these sandstones using Qt92 F7 L1, Qm77 F 7 Lt 16, Qp92Lvm4Lsm4, after recognition of diagenetic process and omitting their effect on the results of modal analysis. These results show quartzolithic facies with cratonic, recycled orogen and rifted continental margin tectonic provenance. Using diamond diagram drawn based on particulars quartz grains and also petrographic evidences in these sandstone, we can say that these sandstone derived from multi provenance. The log Qt/F+RF vs. Qt/F+RF climate diagram and QRRF triangle indicate humid climate during deposition of the Padeha Formation.
A. M. Ali Khasi; M. Hosseini Barzi; M. Shadan
Abstract
Determination of sedimentary environment, provenance and tectonic setting of Ab-Haji Formation sandstones (Lower Jurassic) have been carried out in Cheshmeh Bakhshi and Sartakht-e-Shotoran sections which are located in Kalmard Block. Facies analysis of sedimentary facies in mentioned sections implies ...
Read More
Determination of sedimentary environment, provenance and tectonic setting of Ab-Haji Formation sandstones (Lower Jurassic) have been carried out in Cheshmeh Bakhshi and Sartakht-e-Shotoran sections which are located in Kalmard Block. Facies analysis of sedimentary facies in mentioned sections implies three clastic faceis associations including delta plain, delta front and prodelta and two carbonate facies, relevant to bar. The obtained results from modal analysis and geochemical data point to cratonic tectonic setting and presence of qurtzose rocks in the source area in the course of recycling processes. Moereover, using the tectonic discrimination diagrams suggest that Ab-Haji sandstones have been deposited in a passive continental margin. The calculated chemical index of alteration (CIA) and the plagioclase index of alteration (PIA), based on major element oxides, denote moderate to intense weathering in the hinterland. This consequence is conformed with the modal analysis and petrographic evidence referring to humid and semi-humid climate.
A. Bayet goll; M. Hosseini-Barzi
Abstract
Geochemical analysis of major elements from 12 sampels from Shirgesht Formation sandstones and shales with Ordovicien age in sections of kuh-Asheghan and Kuh-Rahdar at Kalmard block in Central Iran zone, and plotting these data on silisiclastic rocks classification diagrams, show that they are quartzarenite ...
Read More
Geochemical analysis of major elements from 12 sampels from Shirgesht Formation sandstones and shales with Ordovicien age in sections of kuh-Asheghan and Kuh-Rahdar at Kalmard block in Central Iran zone, and plotting these data on silisiclastic rocks classification diagrams, show that they are quartzarenite and shale. Moreover, the use of discrimination, biplot triangular diagrams determined the quartzose recycled provenance (craton and recycled orogen) and passive margin tectonic setting for these deposites. These data suggest the quartzose sedimentary provenace for sandstones and intermediate to felsic ignious provenance for shale. Furthermore, determination of weathering influence in source area, by using CIA index, indicated that the source area of these deposites has been exposed to intense weathering. This can be explained by humid weather in source area of passive continental margin.
M. Hosseini-Barzi; N. Etemad Saeed
Abstract
The Early Cambrian Lalun Formation in Poshte- Badam block has been studied in Bahmoo section with 550 m thickness, to illuminate its sedimentary environment and sea level changes. The field investigations, collection of 110 paleocurrent data, petrography, study of SEM images and XRD analysis of shale ...
Read More
The Early Cambrian Lalun Formation in Poshte- Badam block has been studied in Bahmoo section with 550 m thickness, to illuminate its sedimentary environment and sea level changes. The field investigations, collection of 110 paleocurrent data, petrography, study of SEM images and XRD analysis of shale samples have been used for facies analysis, paleocurrent recognition and sedimentary environment reconstruction. The facies analyses imply 5 silisiclastic coarse grained (Gm), medium grained (Sp, St, Sh) and fine grained (Fl) lithofacies and 1 carbonate (dolomite) microfacies. The lithofacies, bipolar bimodal paleocurrent pattern and petrographic evidences such as the existence of glauconitic sandstones with high textural and compositional maturity imply deposition of these sediments in a Tidal Flat environment. Studying the relative sea level changes of Lalun deposits in this area imply two sequences which have been bounded between SB1 unconformities.
M. Hosseini-Barzi; M. Houshyar; H. Ghalavand
Abstract
Field study, calcimetery and petrography of thin sections from Gurpi type section and petrography of cuttings from Ziloee oil field (well No. 5 and well No. 8) represent two carbonate members and two hybrid (mostly marl and in a few samples clay marl) members in these deposits. Microfacies analysis of ...
Read More
Field study, calcimetery and petrography of thin sections from Gurpi type section and petrography of cuttings from Ziloee oil field (well No. 5 and well No. 8) represent two carbonate members and two hybrid (mostly marl and in a few samples clay marl) members in these deposits. Microfacies analysis of the carbonate members implies 2 microfacies belong to open sea of a carbonate ramp model. Moreover, authigenic glauconite and phosphate and framboidal pyrite propose deposition of these sediments in an anoxic condition. XRD and SEM analysis of marl members provide existence of illite and chlorite as clay minerals by certain detrital source and smectite by digenetic and probability detrial source in the upper marl member and existence of quartz in lower member. Coexistence of these minerals proposes a temperate climate during deposition of the upper marl member. Semi-quantitative analysis of XRD data represents descending trend for relative amounts of illite and ascending trend for smectite during deposition of upper marl member of Gurpi Formation which implies deepening of the sedimentary basin and relative climate warming. The digenetic processes in these deep marine deposits are limited to cementation, illitization, hematization and fracturing. Moreover, studying SEM images evident autogenetic origin of smectite in two samples from upper cretaceous (under K/T boundary) which can form during fluid exchange with mafic minerals and/or detrial clay minerals such as detrial smectite, illite. The absence of digenetic smectite in two samples from Paleocene (over K/T boundary) can be related to change in basin condition in Zagros basin, this period of time. Also, studying relative abundance of K and Th in NGS logs of well number 8 in Ziloee oil field shows that clay minerals in this formation are illite and montmorillonite.
M. Hosseini-Barzi; R. Alinejad-Kurdi; H. Ghalavand
Abstract
The calcimeteric analysis of samples from Pabdeh Formation, in type section (north of Dezful embayment subzone), represent a marl and shaly marl lithology. SEM images from these samples represent chlorite flakes with diagenetic origin (transformation of illite to chlorite) and imply the possible existence ...
Read More
The calcimeteric analysis of samples from Pabdeh Formation, in type section (north of Dezful embayment subzone), represent a marl and shaly marl lithology. SEM images from these samples represent chlorite flakes with diagenetic origin (transformation of illite to chlorite) and imply the possible existence of other detrital clay minerals (include chlorite). However, XRD analysis of selected samples indicates the existence of montmorillonite, illite and chlorite showing a descending trend for clay percent and montmorillonite and ascending one for illite and chlorite from bottom to top of these deposits. Based on these evidences, we introduced the possibility for cooling in climate condition and shoaling in depth of deposition, from bottom to top of the Pabdeh Formation.
Study of Th, K & Th/K peaks of NGS log represents the existence of montmorillonite and illite, as common clay mineral. Calculating clay mineral percent, shale percent and uranium trend imply an anomaly at the uppermost part of the Pabdeh Formation which could be related to fault activity in Central Dezful embayment subzone and sediment supply probably due to Pyrrenean orogeny.
Therefore, investigation of clay mineral represent difference in sedimentary framework between northern Dezful embayment subzone and central Dezful embayment subzone and their different response to change in geological condition.