2024-03-28T22:17:25Z
https://jtethys.journals.pnu.ac.ir/?_action=export&rf=summon&issue=497
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
Geochemistry of diabasic dikes and andesitic-basaltic lavas in Noorabad-Kermanshah ophiolite
The Noorabad-Kermanshah ophiolite is part of Eastern Mediterranean-Zagros-Oman Tethyan ophiolites, that this area is located in south-southwest of the Main Zagros Thrust fault. This ophiolite consists of peridotites, serpentinites and pegmatite gabbros as mantle sequence whereas crustal sequences are composed of locally layered gabbros, isotropic gabbros, sheeted dike complex, basaltic to andesitic lavas and sedimentary rocks (radiolarites and late Cretaceous pelagic limestones). The diabase dikes enriched in LREE relative to HREE elements)La(n)/Yb(n)=1.7-3.3). Also, the andesites are enriched in LREE relative to HREE elements)La (n)/Yb(n)=3.1-5.37) and the pillow lavas are enriched in LILE (Th(n)/La(n)=2.1) while show a depletion in HFSE (Nb(n)/La(n)=0.07-0.2). The Basaltic-andesitic lavas exhibiting mainly calc-alkaline, with minor island-arc tholeiitic affinities, are characterized by enrichment in LILE and LREE and depletion in HFSE. These geochemical characteristics compared with other Tethyan ophiolites along the Bitlis-Zagros suture zone reveal a supra-subduction zone environment for the genesis of the Noorabad-Kermanshah ophiolites.
Diabasic dikes
Basaltic-andesitic lavas
Geochemistry
Supra-subduction zone
Noorabad ophiolites
2015
03
01
1
15
https://jtethys.journals.pnu.ac.ir/article_2838_b2e4b70700d280e8b0448033d9f7e20f.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
Investigation of kinematic analysis in the Tanumah area, Arabian shield, Saudi Arabia
New structural, metamorphic, finite strain and kinematic vorticity data for granitic gneiss and metavolcano-sedimentary rocks of theTanumaharea in the Arabian shield in Saudi Arabia reveal a history of deformation reflecting different tectonic regimes. Kinematic analysis shows their relationship to the nappe contacts between the granitic gneiss and metavolcano-sedimentary rocks and explains the nature of the subhorizontal foliation typical for theTanumaharea. The vorticity analysis of porphyroclasts was determined in high temperature mylonites. The kinematic vorticity number for the mylonitic granitic and metavolcano-sedimentary samples in the Tanumaharea range from 0.60 to 0.90, and together with the strain data suggest deviations from simple shear. The data indicate oblate strain symmetry (flattening) in the Tanumah area and the strain magnitudes do not increase towards the tectonic contacts. It is suggested that the accumulation of finite strain was not associated with any significant volume change. The penetrative subhorizontal foliation is subparallel to the tectonic contacts with the overlying nappes and foliation was formed during nappe thrusting and intrusion of granite rocks under semi-brittle to ductile deformation in the Tanumah area. It can be concluded that the accumulation of ductile strain during thrusting was not by simple shear and involved a component of vertical shortening, which caused the subhorizontal foliation in Tanumaharea and adjacent units.
Kinematic Analysis
Deformation
Tanumah Area
Arabian Shield
Saudi Arabia
2015
03
01
16
30
https://jtethys.journals.pnu.ac.ir/article_2839_6a3b697810fe9f88030196208f13a148.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
The Role of Carbonate-Host Rocks on the Genesis of Pb-Zn Deposits, Northern Thrust Zone, Kurdistan Region, Iraq
Pb-Zn deposits in the Kurdistan Region, northern Iraq, have occurred mainly as a stratabound and open-space filling ore bodies. They are hosted by dolostone and dolomitic-limestone of platform carbonates. The ore deposits at the studied Dure and Lefan areas are respectively hosted by Kurra Chine (upper Triassic) and Bekhme (upper Cretaceous) formations. Pyrite, sphalerite and galena are the major sulfides minerals, but the mineral paragenesis and relative proportions of these sulfides vary from deposit to other. They have commonly been deposited through dissolution/replacement process and/or through void infilling. Homogenization temperatures of primary and secondary fluid inclusions in Dure and Lefan deposits range from 45 oC to 183 oC and from 68oC to 284 oC, respectively. The salinity is ranging from 13.93 wt% NaCl equiv. to >23 wt% NaCl equiv. in Dure deposit, and from 3.06 wt% NaCl equiv. to 14.57 wt% NaCl equiv. in Lefan deposit. The average δ34S‰ values for sulfide minerals (pyrite, sphalerite and galena) of the Dure and Lefan deposits are -0.8 ‰ and 1.8 ‰, respectively. Sulfur isotope analysis implies that the sulfur in sulfide deposits is originated from a mixture of different sources. The δ13C and δ18O values of carbonate host rocks fall in the range of marine carbonates. Petrographic evidence and stable isotope data with fluid inclusions suggest that Pb-Zn mineralization was caused by deeply circulating high temperature mineralizing fluids (brines) within the source basin or by tectonic processes, which possibly leached metals from either the diagenesis of host rocks and/or the dewatering of deeper buried siliciclastic beds. The studied carbonate-hosted Pb-Zn deposits share many similarities with the Mississippi Valley Type (MVT) deposit.
Carbonate rocks
Pb-Zn deposit
Fluid inclusions
Stable isotopes
Iraq
2015
03
01
31
47
https://jtethys.journals.pnu.ac.ir/article_2840_1a2b7c8857446b421711ec69f49b26a6.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
Discriminative mapping of geological formations and silica-rich zones using ASTER images: A case study of Ardakan area, Iran
The Kalut-e-Ashrafa area is located in the north-east of Ardakan area in central Iran, Yazd province. This area promises copper mineralization. The most of the minerals in this study area are silica-rich veins and veinlets. Therefore, in order to identify geological formations with silica zones and to determine potential mineralization areas, ASTER images and remote sensing methods were used. Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) images helped to make discriminative maps of those geological formations and to spot silica rich zones in that area. For this purpose, Color-Ratio-Composite (CRC), False Color Composite (FCC) images of band4/band1 (Red), band3/band1 (Green), and band12/band14 (Blue) ratios were employed to enhance the FCC images and make them more distinctive, a decorrelation stretch procedure was applied to CRC images. Discrimination of silica-rich zones was performed using Matched Filtering methods applied to ASTER spectral bands. Geological formations were distinguishable in the FCC images of the study area, and the sand dunes were distinctive in the images with bluish pixels. Also, setting a threshold of x+2s on the digital numbers of the MF rule images provided implication that red areas had a high probability of being silica-rich zones.
ASTER
Color-ratio-composite
Remote sensing
Matched filtering
Ardakan
2015
03
01
48
55
https://jtethys.journals.pnu.ac.ir/article_2841_acf1c88d4f7e981c6251705d2bdfd824.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
Lineaments Analysis of Tabnak Field Using LANDSAT Images
Geological studies are basic formof operations for the exploration and development of oil and gas fields.Preparation of topographical and geological maps and drawingcross section from thesemaps formspart of these operations. Existing lineaments in the study area are important, and should be considered in drawing the geological sections. The evaluation of wells stability is one of the important issues in engineering geology, because the instability of walls means the acceptance of unknown risks. The existing lineaments in the area can have an important role in the stability or instability of the walls of wells. The purpose of this study is to investigate surface lineaments arrangements. To achieve this goal, Landsat satellite images were used. Images were processed using different techniques and lineaments map was provided. In the next stage, artificial lineaments were removed from lineaments map and remaining lineaments largely reflected existing fractures in the region. In order to study more precise lineaments, field studies were conducted at 3 stations and dip and strike of fractures were measured at each station and rosette plot, contour plot, scatter plot and pole plot were plotted for each station. The results of this study show that the density of lineaments in different parts of the field is not the same, but in the northwestern part of the field, lineaments density is higher than the other parts. Lineaments extend in different directions, but the extension of lineaments in NE-SW direction is dominant.
Lineaments
Image processing
Fracture
Satellite Images
Arrangement
2015
03
01
56
67
https://jtethys.journals.pnu.ac.ir/article_2842_188aa56e34003cdfcdc5f0f23c8cecab.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
Metamorphic evolution of high-pressure Quartz Schists in the Zhan metamorphic complex, Sanandaj-Sirjan zone, Iran
The study area is located at the Sanandaj-Sirjan zone in the west and north-west of Azna and north-east of Doroud, Iran. The Quartz-Schists are divided into two main groups: amphibole-quartz schist and garnet-quartz schist. Field and microstructural studies show several deformational phases. The D1 episode which is represented by S1, matches with M1 metamprphism and D2 deformation matches with M2 metamorphism. Sodic-amphibole, phengite, garnet and plagioclase are the minerals of M1 metamorphism stage; and calsic-amphibole, garnet, plagioclase, muscovite, biotite and chlorite are the minerals of M2 metamorphism stage. The estimated P-T using Thermocalc indicates that minerals paragenesis in M1 stages have average temperature of 633±76 ◦C and also pressure of 15.2±1 Kbar; and in M2 stages have average temperature of 588±41 ◦C and also pressure of 6.8±1 Kbar. Based on calibration methods, minerals paragenesis in M1 stages have average temperature of 621±5 ◦C and also pressure of 14-16 Kbar and in M2 stages have average temperature of 546±91 ◦C and also pressure of 8.7-8.01 Kbar. Based on calibrated curves and thermocalc measurement the stability range of mineral paragenesis in M1 are in echlogitefacies and the stablility of mineral paragenesis in M2 are in amphibolite facies. This complex generated in subduction zone (Tethys under central Iran) in late Triassic and exhumed in Cretaceous and thrusted on Zagros during collision between Afro-Arabi and central Iran micro continent in Miocene.
Petrology
Zhan complex
Sanandaj-Sirjan
Metamorphism
Quartz schist
Thermobarometry
2015
03
01
68
81
https://jtethys.journals.pnu.ac.ir/article_2843_aaec325c2c310092fbebf34cf3d977e9.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2015
3
1
Application of Seismic and Resistivity methods to investigate Amiriyeh (Iran) site geology characterization from seismic Micro-zonation point of view
This paper is devoted to compiling a site geology map for town of Amiriyeh, from seismic Macro-zonation point of view using geophysical methods of shallow seismic, down-hole seismic and resistivity surveys. In this map site geology has been classified based on shear wave velocity, according to the criteria for site geology classification offered in the Iranian code of practice for seismic resistant design of buildings. Amiriyeh is a small town with approximately 9000 inhabitants, located in Semnan province, central Iran. In the first step, the town was initially investigated from geological, topographical and facilities aspects for geophysical surveying and some locations were selected for the investigations. In each one of the selected locations, a refraction seismic profile involving 2 or 3 shot points and 24 geophones as well as a vertical electrical resistivity sounding was surveyed. A down-hole seismic survey was also carried out in a few existing wells. The acquiesced data was processed and interpreted and geological layers were identified according to the seismic and resistivity properties. Shear and compressional wave velocities for each layer were estimated. Then velocity maps were compiled for different thicknesses of the soil, (from the surface to various depths). Finally, a site geology Micro-zonation map was compiled for Amiriyeh town. In this map the zones were classified based on the soil (site) classification criteria offered in the Iranian seismic code. According to the obtained results, Amiriyeh is located over soft soils which are involved in groups of IV and III (very close to IV) of the seismic code.
Site geology
Micro-zonation
Shear wave
Resistivity
Amiriyeh
Iran
2015
03
01
82
95
https://jtethys.journals.pnu.ac.ir/article_2844_823df29529535e6bff11b01412f0519a.pdf