فهرست مطالب

Earth Sciences - Volume:9 Issue:1, 2017
  • Volume:9 Issue:1, 2017
  • تاریخ انتشار: 1396/04/30
  • تعداد عناوین: 7
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  • Mohammad Elyas Moslempour*, Morteza Khalatbari-Jafari, Tomoaki Morishita Page 1
    Mantle peridotites exposed in south Jazmourian comprise of lherzolite and porphyroclastic Cpx-bearing harzburgite in the lower part with chromitite lenses in the upper parts. Petrography and microprobe studies shows evidence of melt-peridotite interactions; post melting processes and subsolidus interactions, which has been associated with appearance of two generations of deformed primary pyroxene-olivine and fine-grained pyroxene-olivine-amphibole neoblasts. Second generation of minerals formed as inclusion, interstitial and fine-grain. These two groups of minerals have different geochemical characteristics, So that, the first group are comparable with abyssal peridotites and second group are comparable to suprasubduction (SSZ) peridotites. Thus, the chemical compositions of different generations minerals show different petrogenesis for ultramafic rocks in south Jazmourian. Whole rock chemical data indicate south Jazmourian peridotites have a depleted MORB mantle source which undergoing 10-20% partial melting. Thus this peridotites have experienced multistage evolution and show characteristics of the abyssal environment to suprasubduction zone. We are belived that peridotites transition from the abyssal environment to suprasubduction and affected by fluids derived from the subducted slab.
    Keywords: Iran, Makran, Jazmourian, Peridotite, Supra-subduction zone (SSZ)
  • Delineation of enriched zones of Mo, Cu and Re by concentration-volume fractal model in Nowchun Mo-Cu porphyry deposit, SE Iran
    Lili Daneshvar Saein* Page 6
    The purpose of this study is to identify the enriched zones of Cu, Mo and Re in Nowchun Mo-Cu porphyry deposit (SE Iran) based on subsurface data and using of concentration–volume (C–V) fractal model. The C-V model illustrates four and five geochemical zones based on Mo and Cu distributions respectively and there are three geochemical populations for Re. The main mineralization for Mo, Cu and Re commence from251 ppm, 0.2% and 2238 ppb respectively, based on the C-V fractal modelling. However, elemental enriched zones contain Mo ≥ 501 ppm, Cu ≥ 0.4% and Re ≥ 4466 ppb. Based on a correlation between results derived via the C-V and geological models, the supergene enrichment zone with Cu≥ 0.4% occurs in very small area of NE part of the Nowchun deposit within chalcocite accumulation. The enriched zones for Mo and Re derived via the C-V model are located in the NE, central and SW parts of the deposit. Mo and Re enriched zones correlate with molybdenite in the deposit.
    Keywords: Concentration–volume (C–V) fractal model, Mo-Cu porphyry deposit, Enriched Zones, re, Nowchun, Iran
  • Microbiostratigraphy and depositional history of Turonian- Santoin Surgah Formation at the northern flank of Kuh-e Sepid Anticline, Lorestan Basin
    Iraj Maghfouri Moghaddam * Page 7
    In this research, microbiostratigraphy and depositional environmental implications related to the Surgah Formation at the northern flank of Sepid kuh anticline, Lorestan Basin, is discussed. A study of small planktonic foraminifera from the 101m-thick Surgah Formation led to the identification of three Turonain- Santonian biozones: 1-Helvetoglobotruncana helvitica, 2-Marginotruncana sigali,3-Dicarinella concavata. The age of Surgah Formation in the study area is determined as Turonian- Santonian. The Surgah Formation overlies the Sarvak Formation and underlies Ilam Formation in the studied stratigraphic section. Based on analysis of pelagic foraminiferal assemblages and microfacies features 7 different microfacies have been recognized, which can be grouped into three depositional environments: inner, middle and outer ramp.
    Keywords: Turonian, Santonian, Planktonic foraminifera, Biostratigraphy, Lorestan Basin
  • Mehdi Reza Poursoltani * Page 17
    The Upper Bajocian- Lower Bathonian succession in the Kopet-Dagh Basin of NE Iran represents fluvio-deltaic to turbidite deposits. The Kashafrud Formation provides an excellent opportunity to study the interplay between deep-water sedimentation and syndepositional tectonic subsidence (or uplift) in the region. The effects of these processes caused sea-level changes, variation in depositional sequences, and formation of different types of sequence boundaries. The Kashafrud Formation is recognized as a super-sequence and is overlain and underlain by type 1 sequence boundaries. Based on sedimentological analysis, twelve lithofacies and three facies associations have been identified in the Kashafrud Formation. The succession is represented by parasequences formed as part of a second order super-sequence, and a fourth order regression. The thickness variations indicate a strong influence of basin-floor topography on the location of depositional successions. High rates of sea-level fall led to the development of a limited number of major incised channels; in contrast the major thick-bedded mudstone indicates high rates of sea-level rise for prolonged periods. The interpreted sea-level curve during deposition of the Kashafrud Formation can be correlated with the world sea-level curve for the Middle Jurassic, with differences mainly related to local structural events in the basin. Tectonism, compaction and rate of deposition were the main factors that controlled the vertical facies transitions in these parasequences.
    Keywords: Kashafrud Formation, Kopet Dagh Basin, Iran, sequence stratigraphy
  • Safwan Dawod *, Ali Al-Mishwat, Abdulkarim Al Abdalla Page 31
    The Cenozoic volcanic activity of the Harrat Ash Sham volcanic field in south of Syria is a part of the extensive magmatism that took place in the auxiliary extension faults along the Dead Sea Fault Zone from upper Eocene to Holocene. Pliocene volcanic rocks form an important part of igneous succession in Syrian Part of Harrat as Sham. These rocks vary from basalts flows to scoria. Pliocene basalts are divided into three primary petrographic groups: olivine basalt, olivine-pyroxene basalt and basanite. The three petro-types are alkaline and have similar compositional ranges of major and trace elements. Variations in the contents of major and minor elements in the Pliocene basaltic rocks are very slight. Such homogeneity in the chemical composition indicates to the operation of petrological processes that reinforced each other during the genesis of these rocks. The geochemical characteristics of the Pliocene basalt rocks reflect crystallization from primitive basic magmas that have experienced limited crystal fractionation process subsequent to their derivation by partial melting of the upper mantle.
    Keywords: Harrat Ash-Sham, Pliocene, basalt, volcanism
  • Reza Arjmandzadeh *, Vahid Shafiei Rashvanlou, Rahim Dabiri, Alireza Almasi Page 39
    The Quchan fault is located in Quchan - Shirvan area which is a part of Chenaran- Bojnourd plain in Kopeh-Dagh zone, NE Iran. The Quchan active fault with northwest – southeast trending is one of the most important strike-slip faults in the area which its activity led to the numerous historical and instrumental earthquakes. The Neo-tectonic activities of this fault are investigated by the drainage patterns, displacement of the waterways, the impact on the alluvial fan deposits and the Quaternary sediments cutting. Here, we aim to employ instrumental seismicity along with satellite imagery data, thermal images, shuttle radar topography mission (SRTM) data plus field observations to explain the mechanism and active tectonics of the southeast Quchan fault termination. Processing Landsat-8 image synchronous with the maximum micro-seismic occurrences reveals that thermal anomaly is positive and corresponds to the major lineaments. Thermal anomaly images have also revealed three hidden faults which have not yet been distinguished in the field surveys. The continuous strike slip activity of the Quchan fault over the time resulted in the formation of compression zone and new thrusts along the southeastern end. By continuance of thrust activity, the anticline starts to accrete and the older thrusts are covered with folding sedimentary rocks, thus thrust loader continues until now. This research is the first successful attempt in Iran to detect hidden active faults and investigate fault termination by employing satellite thermal surveys.
    Keywords: Quchan fault, drainage pattern, Landsat-8, thermal anomaly
  • Nasser Ashrafi *, Behzad Hajalilou Page 48
    The mineralogy and geochemistry of Paleocene shales and interbedded siltstones in the southwestern of Ahar town (NW Iran) were studied by optical microscopy, XRD, SEM, XRF, and ICP-MS techniques. The mineralogical composition, mainly characterized by calcite, quartz, feldspar, dolomite, muscovite, magnesiohornblende, chlorite, illite, montmorionite, palygorskite, and koninckite, suggests relatively fast erosion of the parent rocks and incipient metamorphism for the studied sediments. The values of weathering indices and the Index of Compositional Variability, as well the mineralogy of the sediments imply moderate weathering in the parent rocks and deposition as first cycle sediments. The shales exhibit higher Al2O3/TiO2 (≈21), La/Sc, and Th/Cr values corresponding to felsic and/or intermediate source rocks. The geochemical character of sediments including ∑REE=116 ppm, (La/Yb)N=8.3, (Eu/Eu)=0.78, and the immobile elemental ratios values suggest an immature continental arc setting. The typical shale and chondrite normalized REE patterns of the shales are comparable with continental arc terrigenous sediments and Andean-type andesites. The inferred tectonic setting for the studied shale is in agreement with the tectonic evolutionary history of NW Iran during the Upper Cretaceous-Upper Paleocene. According to the present data, we conclude that the ultimate provenance of the studied shale and its interbedded siltstone and thin detritic limestone was probably the Upper Cretaceous sediments with the geoenvironment of acidic to intermediate volcanic rocks and marl.
    Keywords: SEM-EDX analysis, shale, interbedded siltstone, Neo-Tethyan subduction, Goouradaraq