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    Tytuł:
    Mineralogical, geochemical and stable isotope studies of kaolin deposits in north-west Gonabad district (eastern Iran)
    Autorzy:
    Zirjanizadeh, S.
    Rocha, F.
    Samiee, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059765.pdf
    Data publikacji:
    2018
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    kaolinite
    Iran
    REE
    O isotope composition
    Opis:
    Kaolin deposits, situated ~10 km north-west of Gonabad (eastern Iran), formed by the intrusion of hydrothermal fluids from a granite dyke in the western part of the study area, and the alteration of rhyolite, dacite and rhyodacite related to Eocene volcanism. There are four major kaolin quarries. The rocks in the investigated area are mainly slate, dacite, rhyolite, andesite-trachyandesite, and lithic and felsic tuffs. The mineralogical compositions of the kaolin deposits are dominated by quartz, kaolinite, dickite and illite with minor chlorite, montmorillonite, albite, hematite, pyrite and gypsum. Sanidine and plagioclase crystals in rhyolite-rhyodacite are sericitized and kaolinized. Whole rock chemistry of the kaolin deposits shows high contents of SiO2 and Al2O3. Enrichments of Sr in some samples demonstrate retention of Sr and depletion of Rb, Ba, Ca and K during hydrothermal alteration of sanidine and plagioclase within the volcanic units. The chondrite-normalized rare earth element patterns of the clay deposits show LREE enrichments (La/Lu)cn = 6.75 to 57.74, pointing to kaolinization in low-pH waters. The isotope composition of the kaolin (δ18O ~+5‰) is consistent with formation at isotopic equilibrium with water of hydrothermal/magmatic origin. The mineralogical composition, REE contents and elemental ratios in these deposits suggest provenance of the kaolin deposits mainly from felsic rocks and hydrothermal fluids. The O isotopic character also supports these results.
    Źródło:
    Geological Quarterly; 2018, 62, 2; 385--399
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cretaceous magmatic evolution in the Deylaman igneous complex, Alborz zone, Iran : change from extensional to compressional regime
    Autorzy:
    Akmali, Sheida
    Asiabanha, Abbas
    Haghnazar, Shahrooz
    Powiązania:
    https://bibliotekanauki.pl/articles/2058637.pdf
    Data publikacji:
    2019
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    back-arc magmatism
    Cretaceous
    Neotethys
    Alborz
    Iran
    Opis:
    The Deylaman igneous complex, as a part of the Late Cretaceous rock unit that lies behind the Paleogene Alborz magmatic arc, in the northern Alborz zone, is composed of basaltic sheet lavas alternating with the pelagic calcareous sediments, basaltic pillow lavas, felsic lavas and gabbroic-monzodioritic intrusions. The pelagic calcareous deposits contain microfossils representing the Santonian-Maastrichtian ages. Furthermore, petrographic textures such as the hyalomicrolitic texture and swallow-tail plagioclase crystals in the pillow lavas, and also segregation vesicles in the basaltic sheet lavas, imply high external (hydrostatic) pressures as the magma was extruded in a deep-water environment. The rock samples show both compositional bimodality and characteristic trends in the variation diagrams. Also, some geochemical characteristics imply that the basaltic lavas originated from the partial melting of an undepleted deep mantle source containing spinel lherzolite: the enrichment patterns of LREE/HREE ratios of the samples [(La/Yb)n = 3.93-4.16 for basaltic lavas and 10.92 for felsic lavas] lying between those characteristic of OIBs [(La/Yb)n = 12.92] and EMORBs [(La/Yb)n = 1.91]; similarities between the patterns of multi-element spider-diagrams; LILE bulges in the basaltic samples compared with those of OIBs. Moreover, the samples show influence from two geotectonic environments: supra-subduction zone (SSZ) settings and plume-type within-plate magmas. Therefore, because of the deep submarine environment inferred for the effusive volcanic eruptions in Santonian-Maastrichtian time, it seems that the Deylaman igneous complex evolved through two stages: first, a tensional regime in a supra-subduction zone (farther from the Mesozoic magmatic arc) and formation of an embryonic rift-related oceanic basin in the Late Jurassic-Early Cretaceous; secondly, a compressive regime in the Late Cretaceous-Early Paleocene and inland migration of the magmatic arc. Consequently, the Cretaceous magmatism can be interpreted as a prelude to the Eocene magmatic flare-up in the magmatic arcs of Iran.
    Źródło:
    Geological Quarterly; 2019, 63, 4; 757--770
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geochemistry and tectonic setting of the volcanic host rocks of VMS mineralisation in the Qezil Dash area, NW Iran : implications for prospecting of Cyprus-type VMS deposits in the Khoy ophiolite
    Autorzy:
    Imamalipour, Ali
    Barak, Samaneh
    Powiązania:
    https://bibliotekanauki.pl/articles/2058590.pdf
    Data publikacji:
    2019
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    geochemistry
    massive sulphide mineralisation
    IAT
    ophiolite
    Khoy
    Iran
    Opis:
    The uppermost part of the Khoy ophiolite includes submarine volcanic lavas. These rocks are found as two different types including basaltic pillow lavas and andesitic to andesitic basalt massive-sheet lavas known as the Qezil Dash unit. These last rocks host volcanogenic massive sulphide mineralisation (VMS). Concordant small lenticular massive sulphides associated with widespread stockworks, extensive wall rock alteration and simple mineralogical parageneses are characteristic of this mineralisation. The Qezil Dash lavas are characterized by HFSE depletion (such as in Nb, Zr, and Hf) and LILE enrichment, low Yb, Y and Ni contents and low Zr/Hf and Nb/Ta ratios. These rocks have low Ti contents and are of LKT type. These geochemical characteristics can be interpreted as indicating SSZ magmatism and suggesting that the Qezil Dash rocks belong to an early stage of island arc formation. Geochemically, this host rock is comparable with the Lasail unit, part of a volcanic sequence within the Oman ophiolite. In the Troodos and Oman ophiolites VMS mineralisation has occurred at the contacts of MOR-basalt and island arc tholeiite (IAT) lavas, so prospecting for VMS deposits in the Khoy area should be estabilished based on geochemical investigations of the volcanic rocks and recognition of their field boundaries.
    Źródło:
    Geological Quarterly; 2019, 63, 3; 435--448
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Conodont biostratigraphy of the Frasnian-Famennian boundary in the Esfahan and Tabas areas, Central Iran
    Autorzy:
    Gholamalian, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059517.pdf
    Data publikacji:
    2007
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Iran
    Late Devonian
    Frasnian-Famennian boundary
    biostratigraphy
    conodonts
    Opis:
    The Frasnian-Famennian (F-F) boundary in Central Iran has been investigated on the basis of conodont faunas (34 species and subspecies) from four sections: Chahriseh near Esfahan, and Kal-e-Sardar, Howz-e-Dorah and Ghale-Kalaghu near Tabas. The F-F boundary in the Chahriseh section is located in a one-metre interval between beds EX1 and F-F9 whereas in the Kal-e-Sardar section it is at the base of bed Cly1. The F-F boundary can not be recognized in the Howz-e-Dorah and Ghale-Kalaghu sections be cause of uncon form able relation ships and erosion of the upper most late Frasnian beds indicated incidentally by reworked boulders (indicating con temporaneous tectonic activity) and by the abrupt appearance of contrasting environments, including tempestites at the base of the lower Famennian. The best conodont and palaeoenvironmental data were obtained from the Kal-e-Sardar section where a deeper marine environment prevailed during the late Frasnian, be coming shallower in the early Famennian; the Chahriseh section displays small fluctuations in sea level during the early Famennian. The conodont faunas display the inception of the Polygnathus communis group in the late Frasnian (rhenana-linguiformis zones) and the appearance of Icriodus alternatus mawsonae in the Late rhenana Zone. A new age-range is suggested for Polygnathus aequalis Klapper and Lane, from the transitans to the linguiformis zones. Three conodont biozones are represented in the late Frasnian to early Famennian of the Chahriseh section, two late Frasnian and one early Famennian in the Kal-e-Sardar section and two biozones in the late Frasnian and early Famennian of both the Howz-e-Dorah and Ghale-Kalaghu sections. Two new species are described: Polygnathus tabasianus (Early to Late crepida zones) and Polygnathus vachiki (Late rhenana-linguiformis zones).
    Źródło:
    Geological Quarterly; 2007, 51, 4; 453-476
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Late Devonian facies variety in Iran: volcanism as a possible trigger of the environmental perturbation near the Frasnian-Famennian boundary
    Autorzy:
    Mahmudy Gharaie, M. H.
    Matsumoto, R.
    Kakuwa, Y.
    Milroy, P. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058813.pdf
    Data publikacji:
    2004
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Frasnian-Famennian boundary
    Iran
    black shales
    ironstone
    greenhouse
    volcanism
    Opis:
    Upper Devonian successions surrounding the Frasnian-Famennian (F-F) boundary in Iran consist of mixed carbonate/silisiclastic deposits. The successions are characterized by conspicuous ferruginous limestones, clay-rich units, black shales, and mafic volcanic rocks that provide important insights into palaeoenvironmental conditions during this interval of Earth’s history. An increase of kaolinite/illite ratio in clays associated with the F-F boundary suggests that increased chemical weathering was facilitated by warm and humid climatic conditions. Distinctive ferruginous-oolite deposits overlying the crucial Frasnian-Famennian boundary interval indicate a high supply rate of Fe-bearing clay originated during enhanced weathering under such climatic conditions. Black shales associated with the F-F boundary are interpreted to be the result of a high primary productivity caused by an increased influx of land-derived nutrients and regional volcanic activity. Widespread rift-related, basaltic activity along eastern Laurussia and northern Gondwana during the mid-Late Devonian is believed to have contribution to this global warming surrounding the F-F boundary.
    Źródło:
    Geological Quarterly; 2004, 48, 4; 323-332
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Provenance and tectonic setting of the Middle Eocene lower Akhoreh Formation, Nain area, Central Iran, assessed using petrography and geochemistry
    Autorzy:
    Salehi, Mohammad Ali
    Mallah, Mohammed
    Jafarzadeh, Mahdi
    Powiązania:
    https://bibliotekanauki.pl/articles/27324243.pdf
    Data publikacji:
    2023
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    petrography
    geochemistry
    palaeogeography
    Nain Ophiolite
    Akhoreh Formation
    Central Iran
    Opis:
    The Middle Eocene Akhoreh Formation is superbly exposed in the western corner of the Central-East Iranian Microcontinent (CEIM). This formation covered the northeastern flank of the Cretaceous Nain Ophiolite Mélange (NOM) and is adjacent to the Paleogene Urmieh–Dokhtar Magmatic Arc (UDMA) formed in the southwest of the CEIM. This terrigenous succession is composed of a thin basal conglomerate followed by mostly pink to purple sandstones alternating with shales. The clast composition and clast imbrication of the conglomerates show local source areas towards the north-north-east. Modal components of lower Akhoreh Formation sandstones reveals immature lithic arkose (Q8F48L44) and feldspathic litharenite (Q8F44L48) sandstones that are rich in mafic and ultramafic igneous and volcanic rock fragments. Mafic to ultramafic source rocks are also indicated by geochemical data (enrichment of Mg, Cr and Ni and Cr/V) in the sandstone and shale samples analyzed. However, geochemical data suggests an intermediate igneous rock origin for the shale samples studied, most likely from the nearby continental arc. Based on petrographic data, these sandstones have characteristics of a transitional to undissected arc tectonic setting. Geochemical discrimination diagrams using major and trace elements indicate an oceanic island arc tectonic setting for the lower Akhoreh Formation sandstones and shales, probably due to a predominance of ophiolitic source rocks. Furthermore, the chemical index of alteration and modal analysis indicate a weak to moderate degree of chemical weathering with arid climatic conditions in the source area. The exhumed NOM, together with the UDMA in the southwest, were dominant sources of sediment to the lower Akhoreh Formation, that lay to the northeast in a local retroarc basin of the Central Iranian Microplate, during the Middle Eocene.
    Źródło:
    Geological Quarterly; 2023, 67, 2; art. no. 14
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mineral chemistry and thermobarometry of plutonic, metamorphic and anatectic rocks from the Tueyserkan area (Hamedan, Iran)
    Autorzy:
    Sepahi, A. A.
    Borzoei, K.
    Salami, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2060560.pdf
    Data publikacji:
    2013
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Alvand Pluton
    Hamedan
    Iran
    mineral chemistry
    Sanandaj-Sirjan zone
    thermobarometry
    Opis:
    The study area is a part of the NW to SE striking Sanandaj–Sirjan metamorphic belt in western Iran. The Alvand Pluton, consisting of rocks that range in composition from gabbro to granite, is the major magmatic rock complex of this area. Gabbroic rocks include olivine gabbro, gabbro norite, norite and gabbro. Rocks around the Alvand Pluton were subjected to different P–T conditions due to polymetamorphism. Common metamorphic rocks are meta-pelites, but some meta-psammites, meta-basites and meta-carbonates also occur. Slates, phyllites, schists, migmatites and hornfelses are major rock units of meta-pelites in the metamorphic sequence. Based on mineral chemistry, the highest temperature of crystallisation (1300°C) was determined for the olivine gabbros, and the lowest temperature (950°C) was calculated for the hornblende-bearing gabbros. Clinopyroxene–plagioclase barometry suggests that pressures near 5 to 6 kbars prevailed during the crystallisation of the various mafic rocks. P–T estimates yield maximum temperatures of 700–750°C at 5–6 kbars for the high-grade metamorphic rocks from the metamorphic aureole around the pluton. These results indicate that the heat released from the Alvand Pluton (T = 950–1300°C), which intruded the metamorphic rocks at middle and upper crustal levels, was sufficient to cause partial melting leading to formation of the metatexites, diatexites and restite-rich S-type granites. During this process, part of the deep-seated gabbro-dioritic rocks were transported to higher crustal levels by viscous, enclave- and crystal-rich granitic magmas of the partial melting zone.
    Źródło:
    Geological Quarterly; 2013, 57, 3; 515--526
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geochemistry of skarn and porphyry deposits in relation to epithermal mineralization in the Arasbaran metallogenic zone, NE Tabriz, Iran
    Autorzy:
    Alavi, Ghafour
    Radmard, Kaikhosrov
    Zamanian, Hassan
    Hosseinzadeh, Mohammad Reza
    Khalaji, Ahmad Ahmadi
    Powiązania:
    https://bibliotekanauki.pl/articles/2058563.pdf
    Data publikacji:
    2020
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Arasbaran metallogenic zone
    porphyry deposits
    skarn deposits
    epithermal deposits
    fluid inclusions
    Iran
    Opis:
    The Arasbaran metallogenic zone in northern Iran is part of the Alborz-Azerbaijan magmatic zone, which developed along the southern margin of Eurasia during the Early Mesozoic-Late Cenozoic. This region hosts precious and base metal mineralization, including porphyry, skarn, and epithermal copper, molybdenum, and gold deposits. Rare earth element variations across all the deposits are similar, indicating a similar source for these elements. The north-west trending belt comprising the Nabijan to the Sonajil deposits consistently shows chiefly alkaline conditions of formation. Fluid inclusion studies indicate that both high and low temperature hydrothermal fluids participated in the formation of all of the deposits. The mineralization age decreases from north to south and east to west and, although metal zonation is complex, the Cu-Au association post-dated the Cu-Mo mineralization reflecting that the ore fluid evolved in terms of both cooling and chemical changes due to fluid-fluid and fluid-rock interactions. In this region most deposits record a concentric zonation, with the centres preserving porphyry and skarn deposits and deposits becoming progressively epithermal toward the outer parts of the mineralizing system. According to this, the mineralization age decreases from the porphyry and skarn deposits to the epithermal deposits. The homogenization temperature and salinity both decrease from the centre to the outer zone. The pattern of homogenization temperature zonation, which is concordant with salinity zonation, suggests that fluids migrated up-dip and towards the margins of the zonation system.
    Źródło:
    Geological Quarterly; 2020, 64, 1; 141--164
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Palaeobiogeography, palaeoecology, and sequence stratigraphy of the Upper Jurassic carbonate succession of the Lar Formation, central Alborz Zone, Iran
    Autorzy:
    Saleh, Zahra
    Reháková, Daniela
    Powiązania:
    https://bibliotekanauki.pl/articles/27324245.pdf
    Data publikacji:
    2023
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Upper Jurassic
    microfacies
    foraminifera
    ammonites
    calcareous dinoflagellates
    biostratigraphy
    sequence stratigraphy
    Alborz Zone
    Iran
    Opis:
    Foraminifera, ammonites, and calcareous dinoflagellates were used for stratigraphy and, together with microfacies, for the assessment of the palaeoenvironmental conditions of the Upper Jurassic deposits in the central Alborz Zone of northern Iran. The Lar Formation (Lar Fm.) in the Polur section is of latest Oxfordian to early Kimmeridgian age. The ammonite Subnebrodites planula and the calcareous dinoflagellate Colomisphaera nagyi have been introduced as new biomarkers of the lower Kimmeridgian in the central Neo-Tethys. The distribution of calcareous dinoflagellates reflects possible dispersal routes along a narrow seaway between the western Neo-Tethys and the Alborz Zone in the central Neo-Tethys. The Terebella-Crescentiella associations of the Lar Fm. represent a low-energy setting under dysoxic conditions in the Central Neo-Tethys Ocean. The benthic foraminiferal assemblages in this formation show a high dominance of infaunal taxa and r-selected strategists. This assemblage is reminiscent of eutrophic conditions and low oxygen levels in the lower part of the Lar Fm. Good preservation of the hexactinellid sponges in the upper part of the Lar Fm. also indicates an oxygen-minimum zone. Three third-order depositional sequences can be distinguished in the study area based on six microfacies. Depositional sequence 1 (DS1) is composed mainly of argillaceous limestone and medium- to thick-bedded limestone, corresponding to an outer ramp-to-middle ramp environment. Depositional sequence 2 (DS2) comprises breccia limestone and thick-bedded limestone facies in its lower part and thin-bedded limestone to massive limestone in its upper part. The breccia limestone facies may be associated with subaerial exposure and reworking of previously deposited sediment during a relative sea level fall. The thin-bedded limestone to massive limestone of DS2 consists mainly of bioclastic mudstone to wackestone (outer ramp). These represent an deep-water outer homoclinal ramp facies. Depositional sequence 3 (DS3) consists mainly of massive limestone to thick-bedded limestone with a bioclastic peloidal microbial Crescentiella packstone (middle ramp). The relative stratigraphic positions of DSs1–3 and sequence boundaries in the uppermost Oxfordian to lower Kimmeridgian of the Polur area show a fair match to the upper Oxfordian to lower Kimmeridgian sequences (JOx7, JOx8, JKi1 and JKi2) on the global sea level curve.
    Źródło:
    Geological Quarterly; 2023, 67, 2; art. no. 15
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Identification of the Oligocene-Miocene boundary in the Central Iran Basin (Qom Formation) : Calcareous nannofossil evidences
    Autorzy:
    Parandavar, Mohammad
    Hadavi, Fatemeh
    Powiązania:
    https://bibliotekanauki.pl/articles/2058670.pdf
    Data publikacji:
    2019
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Oligocene-Miocene boundary
    calcareous nannofossils
    biohorizons
    Central Iran Basin
    Qom Formation
    “c1” Sub-member
    Opis:
    A diverse Late Oligocene to Early Miocene calcareous nannofossil assemblage was examined from the Qom Formation in the Central Iran Basin, and the Oligocene-Miocene boundary was identified based on the quantitative analysis of the assemblages in 303 smear slides. Eleven well-established calcareous nannofossil bio-events are delineated in the Upper Oligocene through Lower Miocene. The results clearly show that the Highest Occurrence (HO) of Sphenolithus delphix is the closest bio-event to the boundary as traditionally delineated on the lithostratigraphic criteria, and provides a distinct biohorizon below it. The Lowest Occurrence (LO) of the species Discoaster druggii is the oldest Miocene bio-event that is observed shortly after the HO of S. delphix, showing that calcareous nannofossils are well suited for approximating the Oligocene-Miocene boundary in the Qom Formation. The Oligocene-Miocene boundary is placed in the upper part of Sub-member “c1” in all three sections studied here and it is traceable throughout the Central Iran Basin, which makes a potentially reliable marker horizon for sequence stratigraphic and hydrocarbon studies in the area.
    Źródło:
    Geological Quarterly; 2019, 63, 2; 215--229
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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