جستجوی مقالات مرتبط با کلیدواژه « zahedan » در نشریات گروه « زمین شناسی »

The study area is located 12 km south of Zahedan city, Sistan and Baluchistan province. Rock units in this area include a series of slightly altered flysch facies units with Eocene age, subvolcanic rocks and basic to intermediate dikes with probably Oligocene-Miocene age. Subvolcanic rocks in the form of stocks and domes intruded into the flysch unit and were cut by intermediate dykes in the later stages. The subvolcanic units of the region have two main compositions diorite-monzodiorite and quartzdiorite-quartzmonzodiorite with porphyry texture. The subvolcanic units of this area are in the range of metalalumin to slightly peralumin and I-type. This is consistent with the evidence such as the widespread presence of hornblende, apatite and sphene in the studied subvolcanic units, which indicates the oxidic conditions and high oxygen fugacity for these rocks at the time of formation. Spider diagrams drawn for trace and rare earth elements show the single origin and the role of fractional crystallization in the formation of these rocks. Based on the spider diagram of rare earth elements, the studied subvolcanic units of LREE elements show a enrichment toward to HREE elements, which is one of the prominent characteristics of calc-alkaline rocks in the subduction zones of the continental margin. These rocks are placed in the tectonomagmic environment diagrams in the adakitic range and in the category of shoshonite and high potassium calc-alkaline rocks, related to subduction environments.

Hesaruiyeh granitoid is located about 85 Km east of Zahedan city, in the Sistan suture zone. This granitoid occurs as small stocks in Cretaceous ophiolite melange and Eocene Flysch. This granitoid is composed of granite, granodiorite and diorite. Granite and granodiorite consist mainly of quartz, plagioclase, orthoclase, biotite and hornblende and diorite is composed of plagioclase and hornblende.  These rocks have mainly granoular texture. This granitoid has mafic enclaves and cut by dioritic dikes. This enclaves and dikes have similar mineralogy as main pluton but they have microlitic and microlitic porphyry textures. Geochemical studies show that Hesaruiyeh granitoid is calcalkaline, metaluminous and I type, and enrichmed from LREE compared to HREE and LILE to HFSE. Tectono magmatic diagrams show Hesaruiyeh granitoid rocks are related to an active continental margin environment. It seems that this pluton was formed from rising residual melts from partial melting of an oceanic crust (Neo-Tethys) during collision of the Lut and Sistan blocks (especially Sistan oceanic crust and mantle wedge on it) and magma effacted by continental crust (Flysch and greywake metamorphosed deposite).

Garagheh granitoid is located in the northwest Zahedan batholite and is exposed in Zahedan-Saravan granitoid belt and Sistan suture zone. This granitoid is composed of granite (synogranite, monzogranite) and granodiorite. These rocks have mainly consist of plagioclase, orthoclase, microcline, quartz, biotite and hornbelend with granoular texture. This pluton cut by microdioritic dykes. Garagheh granitoid have metapellitic enclaves with enrich from quartz and mica minerals with granoular texture. This granitoid is calc-alkaline, metalluminous, with (I) and slightly to S typs, enrichment from in LREE and LILE and depleted from in HREE and HFSE. Tectono magmatic diagrams show Garagheh granitoid is related to active continental environments. Positive anomalies in K and Cs elements and negative anomalies in Zr, Sr, and Ti elements show patterns similar to the subduction environment. Based on the Sr/Y versus Y and FeOt+MgO+TiO2+ Al2O3 versus Al2O3/FeOt+MgO+TiO2 digrams, it is thought that the constituent magma of this pluton is similar to the Zahedan granite due to the melting of amphibolite source, that resulted during closure of the Neothytean ocean east of Iran, located between the Lut and Helmand plates, during the Eocene-Oligocene to Miocene times.

The Rigmalak granitoid is located East of Taftan volcano, southeast of Zahedan, in Sistan Suture Zone.This pluton (Oligo-Miocene) has intruded into Eocene Flysch deposidt and cause low metamorphism in the borders. This pluton is composed of granite, synogranite, monzogranite, granodiorite, tonalite, pegmatitie and diorite in composition. The main minerals in this pluton are quartz, plagioclase, orthoclase, biotite and hornbelande and they are mainly granoular to pegmatitic in texlures. Presence of biotite and hornbelends minerals in this granitoides show that it is simillar to Zahedan granitoid and it is belonging to I type granite.  Geochemical studies show that these rocks have calcalkaline to low alkaline magmatic series and metaluminous, I type, enrichment from LREE and LILE and depleted from HREE and HFSE. Major, rare and trace elements digramas of shows crystal defferintation is important role the formation pluton. Digrams normalized to chondorite and primitive mantle show that rocks formed this pluton are enriched in LREE to HREE and dominantly simillar and parall trends. Also, Zr and Th elements show positive anomalyes and Sr, Nb and Ti negative anomalyes, similar to subduction zones.Tectono magmatic diagrams show Rigmalak granitoid rocks related to syncollision to low post collision environments. Geochemical evidence of Rigmalak samples showed that crystal differentiation was not the only effective process in the formation of magma but may be several phases or melting of a phase with different degrees also may happened in the region. It seems that the formation of this granitoid in the Sistan suture zone is related to the collisions between Lut and Afghan blocks.

The 43Ma Gapdan granitoid pluton is a part of Zahedan-Saravan granitoid belt and is located about 50 km NW of Zahedan. The pluton is mainly composed of biotite granite and granodiorite in composition and consists of quartz, plagioclase, K-feldspar, biotite, Fe-Ti oxides, zircon, apatite, and allanite. The granitoid rocks are mainly granular in texture, although they display poikilitic, perthite and myrmekite textures. The present paper aims to determine nature, the physico-chemical of crystallization and tectonic setting of the pluton based on mineral chemistries of biotite and feldspar. The biotite chemistry represents that the pluton is I-type and calc-alkaline which formed in an active continental margin. Biotite thermo-barometry presents that the mineral has been crystalized at 850 oC and 2-5 kbar, while two-feldspar thermometry shows temperatures of 555-734 oC which is a subsolidus re-equilibrium temperature of elements for Gapdan granitoid rocks. The pluton hosted lots of sedimentary and igneous enclaves, suggesting the parent magma was contaminated with country rocks during ascending and emplacement.

Natural hazards have created widespread problems and nodes in many centuries in relation to the development of human societies. According to the study, factors such as the presence of faults around the city, demographic density, high marginalization and, consequently, non-standard housing and lack of open and green spaces, have made Zahedan to be vulnerable to natural hazards. Among the examples of people's participation is capacity building, capacity building led by local institutions and organizations, provides a way to enhance public participation opportunities and achieve successful outcomes for sustainable development and, on the other hand, make progress in sustainable development dependent on social capacity building. Descriptive-analytic method has been used to investigate the reduction of natural hazards (earthquakes) on urban environment with emphasis on capacity building. In order to collect information from research, a questionnaire was used to survey the reliability of questionnaires using the Kronbach Alpha method and the coefficient 845 / ; Their validity was determined on the basis of Delphi technique and the expert judgment of the bachelor's degree. For more certainty, the CVI and CVR indices were used to determine the accuracy of the content validity because the coefficient above 70 /. , A desirable validity was obtained. To evaluate the normal distribution of data, the Kolmogorov-Smirnov test and the differences in the values of the variables were used for ranking and T test. Based on the results of the T test, in the institutional dimension, the "access to safe places in the event of a possible earthquake in the level of 0.05 and other sub-criteria is less than 0.001 in the level. In the physical-spatial dimension, the components of "access to the main and arterial passages and the level of exhaustion of the residential houses in your neighborhood, at the level of 0/05 and the components of trust in the residential unit in terms of architecture and engineering at 01/0 and other sub-criteria", has a significant difference And in the socioeconomic dimension, the sub-criteria "The amount of general information to the residents in the event of an earthquake and consultation with the informed people in order to reduce the vulnerability at the level of 0.05 and below the level of coverage of your housing insurance at the level of 0.01 is significant. According to the geographic conditions of the region and the existence of various faults, there is a probability of earthquake occurrence in the city. In terms of access to open and green spaces, vulnerability and resilience are different in different regions, so that the central, southeastern and marginal areas of access In the open spaces and the least vulnerable, the eastern parts of the city, due to the use of such as airports and military sites and the northern areas of the city, are exposed to the mountains with the lowest level of access to green space and open space, less resilience and more vulnerability. Based on the results of the research, capacity building in the institutional dimension is in a rather desirable situation. However, in socio-economic and spatial -physical dimensions, in the unfavorable situation, the need for more authorities to strengthen these dimensions is necessary.

Zargoli granitoid is located in the northwest of Zahedan and south-east of Iran. This granitoid is composed mainly of granodiorite. Mineral chemistry of biotite was studied in granodioite rocks with the aid of EPMA and the results of this study were compared with the mineral chemistry data of biotite in Zahedan granitoids. Total amount of aluminum in comparison to Fe / (Fe Mg) ratio in biotites of Zargoli granodiorite indicates the presence of aluminous upper crust materials (metamorphosed sediments) in magma by digestion process. Total Al amounts of biotites of Zahedan granodiorite were lower than those of Zargoli granodiorite and it is indicative that the magma of Zahedan granodiorite is less contaminated by crustal rocks. The study of mineral chemistry of biotite determines that the studied granodiorites were I-type and composed of a calc-alkaline granitic magma. This magma climbed in a subduction environment and contaminated with sedimentary rocks of the upper crust. The chemistry study of biotite determines a relatively high oxygen fugacity (10-12 to 10-13 bar) and an oxidant conditions for granodioritic magmas studied. The amount of oxygen fugacity in the Zahedan granite magma is obtained from 10-14 to 10-15 bar which in fact represents a weak oxidizing condition in the Zahedan granite magma.

The Eocene dykes in the north and the west of Zahedan exposed into the flysch and Zahedan granitoid rocks in the Sistan suture zone. These rocks, including mafic dykes, ultramafic and felsic are mostly alkaline in nature and sometimes are contaminated. The dykes in discussion, display mostly porphyritic and glomeroporhyric textures. Plagioclase, hornblende and biotite are the main phases as well as the matrix of the rocks. The presence of rounded plagioclase and corrosion Gulf of quartz, normative changes and variation in minor and trace elements are indicative of contamination with continental crust. Enrichment of LREE relative to HREE and the lack of Eu anomaly are important characteristics of all of the studied rocks. High ratios (La/Sm)N, and (La/Yb)N and(Sm/Yb)N and the alkaline nature of most of the samples, indicate a melting process about 1 percent of a mantle with garnet lherzolite composition. Such conditions may be completion of subduction of Sistan oceanic lithosphere beneath the Afghan block ended. Slab sinking to a considerable down, fluid released from the edge caused some chemical and mineralogical changes of mantle wedge, and to facilitate partial melting of the rocks. The fluid migration to higher levels due to the lower parts of the upper crust and mantle wedge are batch melting. As the molten materials increased, they were transferred to higher levels in the Oligo-Miocene period and have been emplaced in the upper parts of the crust. It seems that after the Oligo-Miocene time and as subduction continued, fractures developed and the ascending magma emplaced into these fractures, which finally gave rise to the formation of the study dykes.

The Lakhshak pluton, a part of Zahedan-Saravan granitoid belt, is located about 15 km NW of the Zahedan city. The plutonic rocks are granodiorite in composition and are cut by a numerous of microdiorite and dacite dykes. The rocks of Lakhshak pluton consist of plagioclase (oligoclase-andesine), K-feldspar, quartz, biotite, amphibole (pargasite - edenite), sphene, apatite and opaque minerals. In this research, the composition of these minerals have been considered as the geo-thermometer and geo-barometer, hence they have good potential for calculating crystallization and emplacement conditions of a magma and tectonic setting. The presence of calcic amphiboles and primary biotite are evidence of Lakhshak pluton igneous origin (I). The amount of Altot in the pluton amphiboles are 1.02 to 1.32 representing the pluton emplacement at the depth of 3.8 to 8.4Km; while the core of those amphiboles analyzed from dikes contain Altot = 1.9-2.3 showing the depth of magma chamber in middle-lower crust (16.9-23 Km) as these dykes are thin and cooled fast after emplacment. The thermometry done on Lakhshak pluton and its dykes indicated cessation of exchange and equilibrium of minerals temperatures 645-732ºC for pluton, 730-824ºC for dacite dikes and for andesitic dikes are 808-945ºC. Moreover, biotites were plot in calc-alkaline field of Abdul Rahmans diagram, which represents the Lakhshak pluton might be formed in an active continental margin during the subduction of Sistan oceanic lithosphere beneath Afghan Block.

Zargoli intrusive pluton is located in the North West of Zahedan city and along Zahedan-Saravan granitoidic band. Main litology of the pluton is I-type granodiorite rocks and nature of their magma is a calc-alkaline granitic magma which formed in orogenic subduction invironment and partially contaminated with sedimentary rocks of the upper crust. Notable feature of this granodiorites, is abundance presence of metasedimentry enclaves in them. There is not amphibole mineral in granodiorite rocks of Zargoli intrusive pluton but it is observed as major mafic mineral in metasedimentry enclaves and diorite dikes which presence in the pluton. Respectively, amphiboles analyzed from diorite dikes and metasedimentry enclaves of Zargoli pluton are tschermakite and magnesio-hornblende which sometimes have been alterated into actinolite. Amphiboles of diorite dikes formed at higher pressure and temperature then amphiboles of metasedimentry enclaves. Amphiboles analyzed from metasedimentry enclaves have been crystallized at 770oC temperature and about 2Kbar pressure while amphiboles analyzed from diorite dikes formed in the temperature range 750 to 775oC and relatively wide pressure of 4 to 7Kbar. Calculated pressure for amphiboles analyzed from metasedimentry enclave is indicator emplacement pressure of the intrusive pluton, after possibly Zargoli intrusive pluton has been emplacement at about 2Kbar pressure and 7 kilometer depth.

Nakhilab igneous complex is located in 145 km northwest of Zahedan and is geologically situated between Lut block and the Sistan-suture zone. Rock units in the area range from Cretaceous to Quaternary and consist of sedimentary and igneous types. The igneous rocks occur as intrusive and extrusive in the Nakhilab. The extrusive rocks occur as lava and pyroclastic and consist of basalt, basaltic andesite, andesite and rhyolite. The intrusive rocks occur as stock and dyke and consist of gabbro, diorite and granodiorite. These rocks are porphyry and granular in texture. In these rocks, plagioclase, pyroxene, hornblende, biotite and quartz are the main minerals and apatite, sphene and magnetite are the accessory minerals. The intrusive rocks that were altered by hypogene and supergene processes are associated with Cu mineralization in the central part. The igneous rocks in the Nakhilab are metaluminus and calcalkaline. Patterns of minor and rare earth elements normalized to MORB and Chonderit show that LREE and LILE contents are sharply higher than HREE and HFSE contents, respectively. Higher contents of LREE and LILE compared to HREE and HFSE, respectively, negative anomalies of Zr, Ti, P and positive anomalies of K, Rb, Sr, suggest that the study samples may belong to an active continental margin. The studied igneous rocks were probably solidified from a basaltic magma by AFC processes that derived from partial melting a subducting oceanic crust and it`s above mantle wedge.

Shurchah antimony deposit is located in flysch zone of eastern Iran. The antimony mineralization was formed in silicic veins that hosted by highly silicified and brecciated granitoids and low-grade metamorphic rocks which are rich in phyllosilicate minerals. Stibnite is the most aboundant Sb-bearing ore mineral in the veins and is associated with pyrite, chalcopyrite, arsenopyrite and gold. Senarmontite and cervantite are antimony oxides present in the deposit. The host rocks were potentially able to cause the acidification needed to induce stibnite-gold mineral precipitation. Based on paragenetic relations and thermodynamic data, stibnite is the stable antimony phase in the study deposit and its deposition is controlled by temperature decrease and reduction, except under alkaline conditions where acidification is the principal cause of mineralization. Both stibnite and gold can be transported in appreciable concentrations in the form of bisulfide complexes and their deposition occurred by pH decreases. Homogenization temperature and salinity of fluid inclusions in quartz crystals associated with mineralized veins, are 146.5 to 327.9˚C and 0.21 to 5.71 wt.% NaCl eq. respectively suggesting a meteoric origin for ore-bearing fluid and these values confirm the epithermal to mesothermal type of mineralization.

The Cheshme-Bid Granitoids is located in SE Zahedan, Sistan and Balouchestan P Province. These granitoids are in Middle Eocene Neh metamorphosed flysch zone. The main minerals in these granites are quartz, plagioclase, biotite and amphiboles. Based on microprobe analysis, amphiboles are calcic in composition and set on magnesio-hornblende and actinolite classes. Based on chemical classification of micas, these minerals are located between siderophyllite and biotite. The Fe/(Fe + Mg) > 0.33 ratio shows that mica minerals are biotites and they are separated from phlogopites. The composition of plagioclase is between 19.56 to 32.51 An and the average of anorthite is 23.78 %. Estimated pressure and temperature for the formation of the granitoid, based on Al- Barometry in hornblendes, is about 3.8 Kb and the temperature is relatively low, about 751 celsius degree in granodiorite.