Mehraj Aghazadeh

Numerical simulations and theoretical analyses predict that forearc ophiolites probably record the end of subduction followed by re-initiation. We report here the results of a field study and new geochronological data that enable identification of the Kermanshah forearc basin, SW Iran. This basin is filled with two terrestrial volcaniclastic successions separated by an Upper Cretaceous reef facies limestone. Early Late Cretaceous ocean island basalts, early Eocene incompatible element-enriched mid-ocean ridge basalts/normal-type mid-ocean ridge basalts and late Eocene arc basalts of the basin indicate that Neotethyan subduction ended during the early Late Cretaceous and then re-initiated during the late Eocene. We suggest that the Neotethyan Ocean between the Iranian and Arabian continents consisted of leading and trailing oceanic plates separated by a mid-ocean ridge (MOR). Subduction of the leading plate generated the Jurassic–Early Cretaceous Sanandaj–Sirjan arc, which was ended ...

Numerical simulations and theoretical analyses predict that forearc ophiolites probably record the end of subduction followed by re-initiation. We report here the results of a field study and new geochronological data that enable identification of the Kermanshah forearc basin, SW Iran. This basin is filled with two terrestrial volcaniclastic successions separated by an Upper Cretaceous reef facies limestone. Early Late Cretaceous ocean island basalts, early Eocene incompatible element-enriched mid-ocean ridge basalts/normal-type mid-ocean ridge basalts and late Eocene arc basalts of the basin indicate that Neotethyan subduction ended during the early Late Cretaceous and then re-initiated during the late Eocene. We suggest that the Neotethyan Ocean between the Iranian and Arabian continents consisted of leading and trailing oceanic plates separated by a mid-ocean ridge (MOR). Subduction of the leading plate generated the Jurassic–Early Cretaceous Sanandaj–Sirjan arc, which was ended ...

Numerical simulations and theoretical analyses predict that forearc ophiolites probably record the end of subduction followed by re-initiation. We report here the results of a field study and new geochronological data that enable identification of the Kermanshah forearc basin, SW Iran. This basin is filled with two terrestrial volcaniclastic successions separated by an Upper Cretaceous reef facies limestone. Early Late Cretaceous ocean island basalts, early Eocene incompatible element-enriched mid-ocean ridge basalts/normal-type mid-ocean ridge basalts and late Eocene arc basalts of the basin indicate that Neotethyan subduction ended during the early Late Cretaceous and then re-initiated during the late Eocene. We suggest that the Neotethyan Ocean between the Iranian and Arabian continents consisted of leading and trailing oceanic plates separated by a mid-ocean ridge (MOR). Subduction of the leading plate generated the Jurassic–Early Cretaceous Sanandaj–Sirjan arc, which was ended by MOR–trench collision. The Zagros late Early Cretaceous forearc ophiolites represent the youngest/hottest segments of the leading plate emplaced during the MOR–trench collision. Subsequently, subduction of the MOR generated the forearc basin and basalts with diverse geochemistry. After c. 60 myr, the cooled trailing plate started to subduct, generating the late Eocene arc basalts. This model has significant implications for investigating and understanding other fossil subduction zones elsewhere in the world. Supplementary material: Supplementary material is available at https://doi.org/10.6084/m9.figshare.c.6086586

Adakitic rocks occur in a variety of tectonic settings and are key to understanding the tectonic evolution and geodynamics of orogenic belts. We investigated latest Oligocene (23.5–22.5 Ma) quartz monzonites and granites from the western segment of the Urumieh–Dokhtar magmatic belt in Iran, which are likely to have formed in response to the early stages of Arabia–Eurasia collision. The studied rocks have the geochemical characteristics of typical adakites, such as high SiO 2 (60.18–68.82 wt%) and Sr (499–793 ppm) contents, low Y (8.90–17.1 ppm) and Yb (0.88–1.58 ppm) contents, and high Sr/Y (26.1‒67.8) and (La/Yb) N (21.9‒32.9) ratios. They have variable K 2 O (3.88–5.09 wt%), MgO (0.44–2.74 wt%; Mg# = 33.7–52.5), Cr (4.27–40.59 ppm), Ni (4.28–35.68 ppm) and Th (9.56–59.59 ppm) contents, and relatively depleted Sr–Nd isotopic compositions [( 87 Sr/ 86 Sr) i  = 0.70450–0.70516; ε Nd ( t ) = 2.1–2.7]. These characteristics indicate that the quartz monzonites were derived from the part...

In this research, zircon Hf isotopic ratios from Sungun, Sar Cheshmeh, Meiduk, Darreh Zar and Bondar Hoza porphyry mineralized intrusions has been studied. The Hf isotopic ratios in the studied porphyry intrusions are similar and the average of zircon eHf values from Sar Cheshmeh, Meiduk, Darreh Zar, Bondar Hanza and Sungun porphyry intrusions are +8.2, +9.3, +9.2, +10 and +8.6, respectively. Also, the averages of zircon TDMC ages from the Sar Cheshmeh, Sungun, Meiduk, Darreh Zar and Bondar Hanza porphyry intrusions are 573, 550, 502, 510 and 464, respectively. The positive and restricted eHf values in the studied porphyry intrusion zircons along with the lack of inherited zircons shows continental crust did not contribute in the evolution of the porphyry magmas. The eHf in the studied zircons is between depleted mantle and lower crust values with a tendency towards the depleted mantle. According to adakitic nature of studied porphyry intrusions, post collisional tectonomagmatic set...

basaltic rocks in Barzand area (Continue to Kousmalyn basaltic rocks in Iran) show parallel trend with Poshtasar basalt and they have older age according to stratigraphy in comparison with Poshtasar basalts. These basalts whit prismatic structure mostly have mugearitic composition and show hyalomicroporphyritic and glomeroporphyritic textures. The main minerals are Ca-rich plagioclase and diopsidic clinopyroxenes. Leucites generally have been altered to analcime. The parent magma of these rocks has a potassic and shoshonitic nature. In multi- element diagrams Ta, Ti and Nb show depletion and LILE, LREE have enrichment that suggests their primary magma have been originated from a subduction related mantle source. According to radiogenic isotopic ratios, mantle source of Barzand basaltic rocks have been drived from a fertilized mantle source during 0.8 to 0.9 billion years ago. According to initial 87Sr/86Sr (0.70499 ± 0.0004) and initial 143Nd/144Nd ratios (0.5127 ± 0.0004) estimated...

The studied area is located in the SE of Heris (Eastern Azerbaijan province) and the Alborz-Azerbaijan structural zone. The Eocene volcanic rocks in the area of under study show various compositions ranging from olivine basalt, hornblende basalt, basaltic andesite and andesite to trachy andesite. The studied basaltic rocks, except for amphibole types, which show calc-alkaline affinity, mainly have shoshonitic and the andesitic rocks are adakitic composition. According to primitive mantle and chondrite normalized spider and REE diagrams, the studied rocks are characterized by LILE and LREE enrichment and pronounced depletion in HFS elements. Based on geochemical data the basaltic rocks have been originated from different degrees partial melting of a heterogeneous lithospheric mantle that metasomatized by subduction agents. The adakitic rocks have been generated from partial melting of thickened potassic mafic lower crust that have been metamorphosed in eclogitic facies.

Abstract The Neotethyan tectonics of the Zagros orogenic belt, SW Iran remains still hotly debated in comparing with its western counterparts. One major issue concerns the timing and nature of the Sanandaj-Sirjan magmatic-metamorphic belt (SSMB), which is made predominantly of metamorphic rocks and Jurassic to Early Cretaceous large plutonic complexes. The Alvand and Qory are two largest plutonic complexes locating in north-central and southern segments, respectively, of the SSMB. Careful LA-ICP-MS U/Pb analyses of the magmatic zircons from the Alvand plutonic complex reveal a smooth spectra, along which the concordant age increase gradually from 120 to 190 Ma; while that of Qory is step-like consisting of two stages, a Jurassic and a late Early Cretaceous ones, respectively. New geochemical data, combined with zircon Lu/Hf results suggest that (1) the Alvand granitoids mostly resulted from a long-lived, successive injection of juvenile-crust-sourced magma batches without obvious fractionation crystallization (FC); but (2) the two stages granitoids of the Qory complex both generated by FC of juvenile-crust-sourced magmas; and (3) the gabbros of the Alvand complex are geochemically of E-MORB-affinity while those of the Qory complex are typical continental arc mafic rocks. Previously published petrological and 40Ar/39Ar data have identified a broken, Jurassic to Early Cretaceous high-pressure metamorphic belt to the southwest of the SSMB, which likely represents the closed, southeastern equivalent of the northern Neotethyan Ocean, north of the Taurides-Anatolia-Armenia block. Thus, the SSMB in Iran, the Kapan belt in Caucasus, and the Serbo-Macedonian belt in northern Turkey form a huge Jurassic to Early Cretaceous continental margin arc system recording northeastwards subduction of the older Northern Neotethyan Ocean beneath Eurasia. The Albian-Cenomanian ophiolites such as Koy, Kermanshah, and Neyriz in Iran represent the eastern counterpart of the younger Southern Neotethyan Ocean, south of the Taurides-Anatolia-Armenia block. During the subduction of the Old Neotethys, an intraplate transform fault likely opened and generated a slab-window beneath the Alvand region, which provided a constant energy source to steadily heat the low crust. This model satisfactorily interprets the unusual geochronological framework and geochemistry of the Alvand complex.

Petrography and chemistry of minerals showing that Eocene alkaline volcanic rocks in southwestern of Germi (Talesh zone, NW Iran) mostly have basaltic composition. Mineralogically these rocks are composed of diopsidic clinopyroxene and labradoritic plagioclase phenocrysts. The microlithic and glassy groundmass composed of sanidine, clinopyroxene, biotite, pargasitic amphibole and magnetite associated with devitrified glass. Clinopyroxenes show relatively high Mg-numbers (0.76-0.93), low AlVI (mostly <0.1), suggesting relatively low-pressure (~5), and water content ~2.5 to less than 10% and high oxygen fugacity (-8.38-11.51) of crystallization condition. High amount existence of magnetite coexisting with amphibole and biotite mineral confirm high fugacity of the host magma. According to clinopyroxene and feldspar thermometry, estimated crystallization temperature varies between 1106˚C to ~1200 ˚C. The clinopyroxene and amphibole mineral composition of studied rocks indicate that t...

Studied volcanic- sedimentary sequence located in the East-Azarbaijan province, north Marand and in the Alborz-Azarbaijan structural zone. The studied sequence composed of alternative sandstone, shale, conglomerate, limestone, felsic volcaniclastics, alkalibasalt and rhyolite which outcropped under Permian sedimentary sequence and on the Devonian sedimentary rocks. Magmatism in the area has a bimodal magmatic characteristic and the basaltic rocks have alkaline affinity. They are characterized by enrichment of LILE over HFSE and show significant OIB-type trace element signatures. On the basis of trace element data, basic rocks generated by low degree partial melting of Garnet-spinel lherzolite mantle source with ocean island basalt characteristics, which fractionated en route to the surface. On the basis of geological and major and trace elements data, the felsic rocks are comparable to A-type granitoids and their trace element ratios are very close to determinate bulk continental cr...

The Khankandi pluton forms part of a group of gabbro–granodiorite intrusions in the Alborz Mountains of NW Iran. A petrographical and geochemical study of this plutonic association reveals the existence of several magmatic cycles with different origins and slight ...

در شمال غرب ایران رخنمون های متعددی از سنگهای لامپروفیری به صورت دایک و سیل حضور دارند. لامپروفیرهای منطقه به دو نوع غنی از میکا و غنی از آمفیبول قابل تقسیم هستند. لامپروفیرهای غنی از آمفیبول شامل فنوکریست های آمفیبول، پسدومورف اولیوین، کلینوپیروکسن در یک زمینه ای از فلدسپار و شیشه آلتره شده هستند. لامپروفیرهای غنی از میکا شامل فنوکریست های میکا، کلینوپیروکسن در یک زمینه ای از فلدسپار و شیشه هستند. ترکیب بلورهای آمفیبول عمدتا کرسوتیتی، میکا ها فلوگوپیتی و کلینوپیروکسن ها از نوع دیوپسید – سالیت هستند. کلینوپیروکسن های لامپروفیرهای غنی از آمفیبول در مقایسه با لامپروفیرهای غنی از میکا حاوی اکسید آلومینیوم بالایی هستند. بر اساس ترکیب کانی ها، ماگمای به وجود آورنده لامپروفیرهای مورد مطالعه میزان فوگاسیته اکسیژن بالایی داشته و این ماگما در شرایط عمق کم دچار تبلور بخشی شده است. بر اساس کانی شناسی لامپروفیرهای غنی از میکا ماهیت کالک آلکالن و از نوع مینت هستند و لامپروفیرهای غنی از آمفیبول ماهیت آلکالن و از نوع کامپتونیت هستند. لامپروفیرهای غنی از میکا از یک گوشته لیتوسفری غنی شده حاوی فلوگو...

توده های مطالعهٍَُِّ شده در پهنه البرز غربی و زیر پهنه طارم قرار دارند. اغلب رخنمون های توده های مورد مطالعه ترکیب مونزونیت و کوارتز مونزونیت دارند و در داخل نهشته های آتشفشانی-رسوبی ائوسن نفوذ نموده اند. این توده ها ماهیت شوشونیتی و متاآلومین دارند. بر اساس مطالعات ژئوشیمیایی، توده های فوق از یک ماگمای غیر اولیه حاصل شده اند که در شرایط پوسته قاره ای دچار تفریق و تحول گردیده اند. در نمودارهای عنکبوتی عادی شده نسبت به گوشته اولیه و عناصر نادر خاکی عادی شده نسبت به کندریت، نمونه های مورد مطالعه از عناصر LREEs و LILEs غنی شدگی و از عناصر HFSEs تهی شدگی نشان می دهند. ماگمای اولیه منشاء توده های مورد مطالعه، از ذوب بخشی 1 الی 5 درصدی منشاء گوشته لیتوسفری متاسوماتیسم شده توسط عوامل فرورانش و با ترکیب اسپینل لرزولیتی حاوی رگه های فلوگوپیت فراوان ایجاد شده است. بر اساس سن سنجی های انجام شده به روش U-Pb (SHRIMP) بر روی بلورهای زیرکن، توده های مورد مطالعه در محدوده زمانی 8/37 الی 9/38 میلیون سال قبل و اشکوب پریابونین ائوسن پایانی در یک محیط بعد از برخورد جایگزین شده اند. کلید واژه: توده های ...

تودۀ بررسی شده در شرق زنجان، با روند شمال غرب-جنوب شرق، برون زد دارد و از نظر ساختاری در پهنۀ البرز-آذربايجان و زيرپهنۀ طارم واقع شده است. اين توده، از نظر ترکیب سنگ شناختی، دامنه ای از مونزوگرانیت، کوارتزمونزونیت، مونزونیت، کوارتزمونزوديوريت و مونزوديوريت دارد و در واقع يک سری مونزونیتی را نشان می دهد. کانی های اصلی تشکیل دهندۀ توده، فلدسپات پتاسیم، پلاژيوکلاز، پیروکسن )اوژيت- ديوپسید( و کوارتز هستند. بافت اصلی توده گرانولار، اينترگرانولار، میکروگرانولار تا میکروگرانولار- پورفیريتی است. به لحاظ ژئوشیمیايی، ماهیت آن متاآلومین و type - I است و به سری ماگمايی کالک آلکالن پتاسیم بالا تا شوشونیتی تعلق دارد. آنکلاوهای موجود در تودۀ نفوذی، از نوع میکروگرانولار مافیک، با ترکیب مونزوديوريتی و کوارتز مونزوديوريتی است، که نسبت به سنگ میزبان خود دانه ريزتر است و بافت میکروگرانولار- پورفیريتی دارد. طبق نتايج به دست آمده از مباحث ژئوشیمی و پتروژنز، ماگمای سنگ های منطقۀ بررسی شده، عمدت ا از ذوب بخشی گوشته لیتوسفری زيرقاره ای متاسوماتیزه شده در اثر سیالات و يا مذاب های بخشی برخاسته از لبۀ فرورانش ...

توده کوارتز مونزونیتی طارم علیا بخشی از توده های نفوذی موجود در پهنه البرز آذربايجان را تشکیل داده و به صورت کشیده و - طويل با روند شمال غرب جنوب شرق رخنمون دارد. ترکیب سنگ شناسی اين توده بهه طهور عمهده متشهکل از مونزوديوريه ت، - مونزونیت،کوارتز مونزونیت و مونزوگرانیت است. مطالعات صحرايی، سنگ شناسی و ژئوشه یمیايی نشهان مه ی دهه د کهه ماگمها ی سازنده اين توده از نوع I ، متاآلومین و شوشونیتی است. شواهد ژئوشیمیايی عناصر نادر خهاک ی و کمیه اب نشهان مه ی دهه د کهه ماگمای اولیه مولد توده از گوشته لیتوسفری متاسوماتیزه شده منشأ گرفته اسهت که ه سهس،، تحهول ماگمها ی اولیه ه مافیه ک، ترم های متوسط و فلسیک را ايجاد کرده است.

در شمال غرب ایران انواع لامپروفیرهای غنی از آمفیبول و غنی از بیوتیت عمدتا به صورت دایک رخنمون دارند و نهشته های قبل از پلیوسن را قطع می کنند. لامپروفیرهای مورد مطالعه در مناطق ارسباران، شبه جزیره اسلامی و رشته ارتفاعات میشو رخنمون دارند. بر اساس مطالعات کانی شناسی و مینرال شیمی لامپروفیرهای غنی از آمفیبول دارای کانی شناسی عمده آمفیبول نوع کرسوتیتی، کلینوپیروکسن نوع دیوپسیددر یک زمینه ای از بلورهای فلدسپار و شیشه قرار دارند. این نوع لامپروفیرها گاهی دارای بلورهای اولیوین و بیوتیت هستند. لامپروفیرهای غنی از میکا دارای کانی های میکا با ترکیب فلوگوپیت و کلینوپیروکسن دیوپسیدی در یک زمینه شیشه ای هستند. بر اساس مجموعه کانیایی، شیمی کانی ها و همچنین ویژگی های ژئوشیمیایی لامپروفیرهای غنی از آمفیبول از نوع آلکالن و ترکیب کامپتونیتی و میکا لامپروفیرها از نوع کالک آلکالن و ترکیب مینت را دارند. در دیاگرام های هارکر لامپروفیرهای آلکالن و کالک آلکالن مورد مطالعه روندهای تحول متمایزی دارند. لامپروفیرهای آلکالن شاخصه های ماگماهای منشاء گرفته از گوشته نوع OIB را نشان می دهند درحالی که لامپروفیرهای ک...

Ali Javad porphyry Cu-Au deposit is located 20 Km north of Ahar city in Arasbaran metallogenic zone which is considered as a part of Alp-Himalayan mineralization belt. Magmatism in this area began in Late Cretaceous, followed by extensive magmatism in Cenozoic and Quaternary periods. Porphyry type mineralization developed in Ali Javad quartz monzonitic porphyry stock and Eo-cene pyroclastic and volcanic country rocks. Ali Javad porphyry intrusion has shoshonitic nature and shows characteristics of volcanic arc granitoids that it is have been emplaced in a post-collision tectonic setting. Alteration zones at the deposit demonstrated zoning which is comparable with Lowel-Guilbert model proposed for quartz-monzonite type porphyry copper deposits. Phyllic, argillic, silicic and propylitic alteration zones were observed at the surface while potassic alteration zone could be observed at depth in drill core samples. Mineralization was recognized both as supergene and hypogene, the latter was as veins, veinlets and disseminations. Dominant hypogene minerals were chalcopyrite, bornite, molybdenite, pyrite and magnetite while chalcocite, covellite and limonite were dominant supergene minerals. Four mineralization zones were observed in the deposit as leached, transitional, supergene and hypogene zones. Average grades were 0.75% for copper and 1.86 ppm for gold with 81.5 Mt proved reserve for copper and 37.8 Mt for gold.

Ali Javad porphyry copper-gold deposit is located in Arasbaran porphyry copper belt at northwestern Iran, some 20 km east of Sungun Mine. Porphyry mineralization at the Ali Javad deposit occurred in post-Oligocene quartz monzonite bodies which intruded in the Eocene volcanic rocks. Mineralization occurred as veins, veinlets and dissemination both as hypogene and supergene type. Several types of veinlets were distinguished during the study of the deposit. Fluid inclusion studies on fluids trapped in quartz which were taken from drill core samples indicated a wide range of homogenization temperature in the veinlets from 138˚C to 565˚C which their salinity demonstrated 33-61 wt% NaCl equivalent. Mineralizing fluids density at the deposit was 0.8-1.2 g/cm 3. Fluid inclusion studies suggested that Ali Javad deposit is an Au-rich porphyry copper deposit ; its fluid inclusion features were comparable with other porphyry deposits.