دانشگاه اصفهان پترولوژی 2228-5210 17 2 2026 06 22 Origin, Nature, and Crystallization Conditions of the Dacitic Magma Hosting the Koushk Zn-Pb Deposit, NE Bafq: Based on zircon crystal morphology, mineralogical evidence, and whole-rock geochemical خاستگاه، سرشت و شرایط تبلور ماگمای داسیتی میزبان کانسار روی-سرب کوشک، شمال‏‌خاوری بافق: بر پایة ریخت‌شناسی بلورهای زیرکن، شواهد کانی‌شناسی و زمین‌شیمی سنگ کل 1 44 30457 10.22108/ijp.2026.148209.1380 FA کیامرث حسینی دانشجوی دکتری زمین‌شناسی اقتصادی، دانشکده منابع معدنی و آب‌های زیرزمینی، دانشگاه شهید بهشتی، تهران، ایران محمد یزدی استاد، گروه زمین‌شناسی، گروه منابع معدنی و آب‌های زیرزمینی، دانشگاه شهید بهشتی، تهران، ایران حسین عزیزی استاد، گروه معدن، دانشکده مهندسی، دانشگاه کردستان، سنندج، ایران Journal Article 2026 01 31 Introduction The Kushk Pb–Zn deposit in northeastern Bafq, Central Iran, is associated with Neoproterozoic–Early Cambrian magmatism related to the Proto-Tethyan continental arc system. These magmatic processes, accompanied by crustal extension and interaction between mantle-derived magmas and continental crust, played an important role in regional metallogeny. Therefore, investigating the origin and crystallization conditions of the host dacitic magma is crucial for understanding magma evolution and ore-forming processes in the Bafq district. In this study, whole-rock geochemistry together with zircon morphology and internal textures are used to evaluate the magma source, tectonic setting, and magmatic evolution. Because zircon preserves geochemical and crystallization features under different geological conditions, it is widely applied in petrogenetic studies. Regional Geology The Koushk Zn–Pb deposit is situated within the upper part of the Lower Cambrian volcano‑sedimentary sequences, in the central part of the Zarigan–Chahmir Basin (Figure 2). Two major stratigraphic sequences have been recognized in the area (Figure 3): (1) a mineralized sequence comprising the upper interval of the Lower Cambrian volcano‑sedimentary sequences at the base, and (2) an overlying volcano‑sedimentary sequence that includes Lower Paleozoic shales, argillaceous limestone, dolomitic units which host Fe-mineralization, as well as the rhyolitic and tuffaceous rocks (Gibbs, 1976). Rhyolitic and dacitic domes are present in the southeastern part of the deposit, adjacent to the mineralized sequence, as well as to the north and northwest of the deposit. Materials and Methods In this study, 65 samples were collected from the dacitic units hosting the Koushk Zn–Pb deposit. Petrographic and mineralogical investigations were carried out on 47 thin sections using an optical microscope at Shahid Beheshti University, Iran. To evaluate whole‑rock geochemistry, 27 samples of the rhyolites and rhyodacites hosting the Koushk Zn–Pb deposit were analyzed by XRF using a Philips PW 2404 instrument at Tarbiat Modares University, and a separate suite of 9 samples was processed for trace elements by ICP‑MS using a Perkin Elmer NexION 300 instrument at Zarazma Company Laboratory. Zircons were separated using a Wilfley shaking table, a Frantz magnetic separator, and heavy liquids, followed by handpicking under a binocular microscope at the Geological Survey of Iran. Zircon grains selected for CL and BSE‑SEM were mounted in epoxy resin and polished to expose their internal structures. CL images were obtained using a JEOL JXA 8900RL electron microprobe, and BSE‑SEM images were acquired using a Hitachi S3400N scanning electron microscope at Nagoya University, Japan, and Aria Electron Optics Co., Ltd. Discussion Examination of the external and internal morphology of zircon can aid in identifying the origin of magmatic rocks, the degree of aluminum and alkali saturation (Pupin, 1980), and the temperature of the melt (Pupin and Turco, 1972). Temperature and Zr saturation are the main factors governing the relative growth of different prismatic zircon morphologies. Zircons crystallizing from alkali, water-poor, and tholeiitic melts fall within the (101) and (100) fields; those derived from peraluminous melts plot within the (101) field; and in the presence of high-water content in the melt, they occur within the (101) and (110) domains. Based on the above considerations, the examination of zircon crystals associated with the Koushk dacites indicates that they predominantly display prismatic faces (110) and (110) >> (100), along with pyramidal faces (101) and (211) >> (101). The development of prismatic forms (110) and (100) reflects a high-temperature crystallization index, whereas the dominance of the (101) pyramids suggests a high alkalinity index an interpretation that is further supported by the geochemical characteristics of the samples. Moreover, the morphological analysis reveals that some zircon crystals exhibit noticeable variations in their length-to-width ratios, indicating differences in growth dynamics during crystallization. This may be attributed to crystallization rate (Bussy and Cadoppi, 1996) or the possible presence of two zircon generations in these samples. However, based on the detrital zircon dating from the Koushk area, (Mahmoudi, 2022; Vickers-Rich et al., 2017), the presence of a single zircon generation in these samples is confirmed. Therefore, crystallization rate is likely the main factor responsible for the increased length-to-width ratio observed in these zircons. Conclusion These crystals predominantly fall within the P2, P5, S5, and S25 fields, with fewer crystals plotting in the AB5, D, L5, P3, P4, R3, S10 and S20 domains. The minimum zircon crystallization temperatures in the studied dacites, based on zircon morphology and the temperature (I.T) and alkalinity (I.A) indices, are 740°C and 706.6°C, respectively. The temperature of the rhyolitic melt, based on zircon saturation thermometry, ranges from 703.49 to 830.74 °C (Watson and Harrison, 1983) and from 702.94 to 877.49 °C (Boehnke et al., 2013). Whole‑rock geochemical data yield a temperature range of 700 to 780 °C. The data show that rhyolitic magma was supersaturated with respect to Zr from the earliest stages of crystallization making zircon one of the first minerals to form-a temperature interval of 700 to 780 °C is inferred for zircon crystallization in the rhyolitic magma. The presence of zoning within zircon crystals likely reflects a decrease in HREE and an enrichment in LREE, U, Th, and Y in these zones. The presence of narrow and closely spaced zoning in both elongated needle‑like zircons and shorter crystals indicates that the magma remained supersaturated with respect to zircon from the earliest to the latest stages of crystallization. Internal structures of some zircon crystals reveal rounded cores with zoning patterns distinct from their rims, suggesting that these cores acted as non‑reactive mineral relics during partial melting. The zircons within the dacites also exhibit evidence of partial resorption, implying episodic intervals of zircon undersaturation in the melt. Structural and compositional characteristics, crystal growth conditions, zircon age and provenance and metamictization processes, can all contribute to reduced lattice order and, consequently, diminished or absent cathodoluminescence (CL) in zircon crystals. Based on geochemical studies, these rocks originate from crust‑derived melts, and their magmas correspond to A‑type granites, specifically the A2 subtype within the calc‑alkaline series. According to tectonic discrimination diagrams, the dacites are derived from volcanic arc granites. Acknowledgements The authors appreciate Shahid Beheshti University Research Council that supported this work. در این بررسی خاستگاه، سرشت و شرایط تبلور داسیت‌های پورفیری میزبان کانسار روی و سرب کوشک در شمال‏‌خاوری بافق بررسی شدند. برای این منظور ریخت‌شناسی خارجی و ساختار درونی بلورهای زیرکن با استفاده از روش کلاسیک پوپین بررسی شد. بر پایة روش کلاسیک پوپین زیرکن‌ها بیشتر در گسترة P2، P5، S5 و S25 جای دارند و شمار کمتری در بخش‌های AB5،D ، L5،P3 ،P4 ، R3، S10 و S20 جانمایی می‌شوند. همچنین، مقدارهای شاخص دما (I.T) و شاخص آلکالن (I.A) به‏‌ترتیب برابر 740 و 6/706 است. بررسی ساختار درونی زیرکن‌ها نشان‏‌دهندة وجود پهنه‌بندی نوسانی ماگمایی هستند. تصویرهای CL دانه‌های زیرکن، ویژگی‌های رشد ثانویه و وجود مقدارهای ناچیز میانبارهای مذاب را نشان می‌دهند. رخداد انحلال ناهمگن چه‌بسا بازتابی از بازجذب بلور زیرکن به‌علت تحت‌اشباع‌بودن مذاب از زیرکنیم است. ویژگی‌های ساختار بلوری، شرایط فیزیکوشیمیایی، سن و خاستگاه زیرکن و فرایندهای متامیکتی را می‌توان از عوامل کاهش نظم بلوری و به‌دنبال آن، کاهش یا حذف CL در بلورهای زیرکن دانست. افزون‌بر این، بررسی‌های زمین‌شیمیایی نیز تهی‌شدگی از عنصرهای Ta، Nb و Ti و غنی‌شدگی ترکیب سنگ کل در عنصرهای Pb، Th، U، Rb، Cs و Ba را نشان می‌دهند که گویای نقش فرورانش و آلایش پوسته‌ای در پیدایش این سنگ‌ها هستند. همچنین، بر پایـة نمودارهـای متمایزکننـدة رژیم‌های زمین‌ساختی، خاستگاه داسیت‌ها همانند گرانیت‌های کمـان آتشفشـانی (VAG) است. این ویژگی‌ها همانند گونه‌شناسی زیرکن، با ویژگی‌های گرانیت نوع A و زیرگروه A2 وابسته به سری کالک‌آلکالن همخوانی دارند. ناهنجاری منفی Eu همراه با غنی‌شدگی LREE در برابر HREE و نسبت بالای (La/Lu)n نشان‌دهندة اهمیت نقش جدایش بلورین در فرایند تکامل این سنگ‌هاست.

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دانشگاه اصفهان پترولوژی 2228-5210 17 2 2026 06 22 Geochemical investigation and genesis of Cu-(Ag) mineralization in the Hendou-Abad prospect (NE Isfahan) بررسی زمین‌شیمیایی و پیدایش کانه‏‌زایی مس- نقره در محدودة هندوآباد (شمال‏‌‌خاوری اصفهان) 45 70 30407 10.22108/ijp.2026.148346.1383 FA مریم صالحی دانشجوی دکتری، گروه زمین‏‌شناسی اقتصادی، دانشگاه تربیت مدرس، تهران، ایران زهرا اعلمی‌نیا دانشیار، گروه زمین‏‌شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران شهره حسن پور دانشیار، گروه زمین‌شناسی، دانشگاه پیام نور، تهران، ایران Journal Article 2026 02 14 Introduction The Hendou-Abad Cu(-Ag) deposit is located in the central part of the Urumieh-Dokhtar magmatic arc, approximately 110 km northeast of Isfahan, Iran. The deposit is hosted by upper Eocene volcanic rocks composed mainly of andesitic basalt, andesite, and subordinate trachyandesite and trachybasalt. Although copper mineralization in the area had previously been recognized, its geological controls, fluid evolution, and genetic characteristics had not been comprehensively investigated. This study integrates geological, mineralogical, geochemical, and fluid inclusion data to characterize the ore-forming processes and evaluate the relationship between the deposit and manto‑type copper systems. Methodology Field investigations, sampling, petrographic studies, XRD analyses, whole‑rock geochemistry, electron probe microanalysis (EPMA), and fluid inclusion microthermometry were conducted. Fifty‑seven representative samples were collected from mineralized and altered zones. Petrographic observations were used to determine mineral assemblages and paragenetic relationships, whereas XRD analyses identified alteration minerals. Whole‑rock geochemistry and EPMA were employed to investigate elemental distributions and ore mineral chemistry. Fluid inclusion studies on quartz, epidote, and calcite veins provided information on the evolution of temperature and salinity of the ore‑forming fluids. Geology and Mineralization The oldest exposed rocks in the area are upper Eocene volcanic units consisting predominantly of andesitic basalt and andesite, with minor trachyandesite and trachybasalt. These rocks host the Cu(-Ag) mineralization and are intruded by mafic to intermediate dikes. Regional strike-slip fault systems, particularly the Kachomesqal and Zafarghand fault zones, acted as the principal pathways for hydrothermal fluid circulation. Mineralization occurs as veins, veinlets, stockworks, disseminations, cavity fillings, and replacement bodies. Three distinct breccia types are recognized: red, green, and white breccias. The red breccia contains rounded volcanic fragments cemented by a quartz‑calcite‑iron oxide matrix, whereas the white breccia consists of volcanic and red breccia fragments enclosed within a siliceous matrix. The green breccia is characterized by angular to sub-rounded fragments within an epidote-calcite-quartz matrix. Primary ore minerals include chalcocite, chalcopyrite, bornite, pyrite, and minor galena. Electron microprobe analyses also identified tetrahedrite, electrum, native gold, digenite, and accessory Ag‑bearing phases. Chalcocite, chalcopyrite, and bornite constitute the dominant copper sulfides. The average grades of copper and silver in mineralized samples are approximately 2.7 wt.% Cu and 62 ppm Ag, respectively. Hydrothermal alteration is closely associated with mineralization. A pervasive propylitic assemblage consisting of epidote, chlorite, calcite, tremolite-actinolite, and prehnite is particularly developed within the red breccias. In contrast, epidote-chlorite alteration is spatially associated with copper-bearing veins in the green and white breccias. Away from the mineralized zones, this alteration gradually changes into zeolite-bearing assemblages. Discussion Petrographic observations, mineral chemistry, and fluid inclusion data indicate that mineralization developed through three successive stages. The first stage is represented by disseminated pyrite and minor chalcopyrite associated with pervasive propylitic alteration and Type I quartz within the red breccias. Fluid inclusions hosted by Type I quartz exhibit homogenization temperatures of 218–275°C and salinities ranging from 12.5 to 16.8 wt.% NaCl equivalent, indicating formation from relatively hot and moderately saline hydrothermal fluids. The second stage represents the principal Cu-Ag mineralization event and is responsible for most of the economic metal accumulation. Mineralization occurs as veins, veinlets, stockworks, and replacement bodies controlled primarily by E–W-trending structures. Ore minerals include chalcocite, bornite, chalcopyrite, tetrahedrite, electrum, native gold, and galena. This stage is associated with Type II epidote, Type II quartz, and Type II calcite. Fluid inclusion studies indicate homogenization temperatures between 95 and 237°C and salinities ranging from 2.90 to 12.96 wt.% NaCl equivalent. These lower temperatures and salinities indicate progressive cooling and dilution of hydrothermal fluids by meteoric water. Most copper and silver precipitation occurred during this stage. The third mineralization stage is characterized by low-temperature hydrothermal activity and chalcedonic quartz-calcite veinlets. This stage contributed little to the overall metal budget and is therefore economically insignificant. Whole-rock geochemical analyses reveal enrichment of Cu, Ag, Pb, Sr, and sulfur and depletion of Ba and Zn relative to host rocks. Strong positive correlations between Cu and Ag indicate a close genetic relationship between silver and copper sulfides. EPMA data show that silver is present in most copper sulfides but is preferentially concentrated in secondary sulfides. The highest silver concentrations were recorded in covellite, reaching approximately 0.7–1.08 wt.%. Supergene weathering subsequently modified the deposit and produced an enriched Cu-Ag zone. Oxidation and leaching of primary sulfides generated secondary chalcocite, covellite, Ag-bearing digenite, native copper, cuprite, tenorite, malachite, and azurite, significantly enhancing copper and silver grades. Conclusions The Hendou-Abad Cu(-Ag) deposit formed within upper Eocene volcanic rocks under strong structural control exerted by regional fault systems. Three successive mineralization stages are recognized, with the second stage representing the principal Cu-Ag event. Hydrothermal alteration evolved from widespread propylitic assemblages in the red breccias to epidote-chlorite alteration in the green and white breccias, grading outward into zeolite alteration. Fluid inclusion data demonstrate a progressive decrease in temperature and salinity from the first to the third stage, indicating increasing dilution by meteoric water. Chalcocite, chalcopyrite, and bornite constitute the primary copper ore minerals, whereas supergene processes generated secondary sulfides enriched in silver, particularly covellite. The geological setting, alteration characteristics, ore mineralogy, geochemical signatures, structural controls, and microthermometric data collectively indicate that the Hendou-Abad deposit shares strong similarities with manto-type copper deposits and represents an important example of volcanic-hosted Cu(-Ag) mineralization in the Urumieh-Dokhtar magmatic arc. کانسار مس (-نقره) هندوآباد در بخش مرکزی کمان ماگمایی ارومیه‑دختر و درون سنگ‏‌های آتشفشانی ائوسن بالایی با ترکیب آندزی‏‌بازالت، آندزیت و تراکی‏‌آندزیت جای گرفته است. کانه‏‌زایی اولیه مس در سه مرحله و به‌ترتیب مرتبط با برش‏‌های سرخ، سبز و سفید رنگ توسعه یافته است. افزون‌بر دگرسانی پروپلیتیک فراگیر همراه با برش‏‌های سرخ، دگرسانی اپیدوت‑کلریت همراه با برش‏‌های سبز و سفید رنگ، کانه‏‌زایی را همراهی می‏‌کند و با دورشدن از پهنة معدنی با دگرسانی زئولیت جایگزین می‏‌شود. کالکوسیت، کالکوپیریت و بورنیت، کانه‏‏‌های اولیه مس هستند. میانگین عیار مس و نقره در نمونه‏‌های کانه‏‌دار به‏‏‌ترتیب 7/2 درصد و ۶۲ گرم در تن به‌دست آمده است. بررسی‌های ریزکاو الکترونی نشان می‏‌دهد نقره بیشتر با سولفیدهای ثانویه مس همراهی می‏‌کند و بیشترین غلظت آن در کانی کوولیت اندازه‏‌گیری شده است. بر پایة ریزدماسنجی میانبارهای سیال، کوارتز نوع I همراه با مرحلة نخست کانه‏‌زایی دمای همگن‏‌شدگی ۲۱۸‑۲۷۵ درجة سانتیگراد و شوری 5/12 تا 8/16 درصدوزنی معادل نمک طعام دارد. در برابر، کانی‏‌های اپیدوت نوع II، کوارتز نوع II و کلسیت‏‌های نوع II و III همراه با مرحلة دوم کانه‏‌زایی مس، دمای همگن‏‌شدگی ۹۵‑۲۳۷ درجة سانتیگراد و شوری 9/2 تا 96/12 درصدوزنی نمک طعام را نشان می‏‌دهند و بخش بزرگی از فلززایی مس‑نقره در این مرحله روی داده است. مرحلة سوم کانه‏‌زایی اهمیت اقتصادی چندانی ندارد. فرایندهای برون‏‌زاد با رخداد کانه‏‌زایی ثانویه، پهنة غنی‏‌شدة مس‑نقره هندوآباد را پدید آورده‏‌اند. بر پایة شواهد زمین‏‌شناسی، دگرسانی، کانی‏‌شناسی و ریزدماسنجی، کانسار هندوآباد شباهت‏‌های چشمگیری با کانسارهای مس نوع مانتو نشان می‏‌دهد.

https://ijp.ui.ac.ir/article_30407_9dfe2ca98dfa8fc59149c90a6e137ee4.pdf

دانشگاه اصفهان پترولوژی 2228-5210 17 2 2026 06 22 Application of Biotite Chemistry for Discrimination of Origion, Emplacement and Mineralization Potential of Sarbijan–Dalfard Granitoids, NW Jiroft, Kerman, SE Iran کاربرد ترکیب شیمیایی بیوتیت در تشخیص خاستگاه، جایگزینی و پتانسیل کانه‏‌زایی گرانیتوییدهای سربیژن- دلفارد، شمال‌باختری جیرفت، کرمان، جنوب‌خاوری ایران 71 94 30326 10.22108/ijp.2026.148212.1381 FA راضیه رضایی آدریانی دانشجوی دکتری، گروه پترولوژی و زمین‏‌شناسی اقتصادی، دانشکده علوم زمین، دانشگاه صنعتی شاهرود، شاهرود، ایران حبیب اله قاسمی استاد، گروه پترولوژی و زمین‏‌شناسی اقتصادی، گروه پژوهشی ماگمازایی و کانه‏‌زایی در ایران، دانشکده علوم زمین، دانشگاه صنعتی شاهرود، شاهرود، ایران مسعود علی پور اصل دانشیار، گروه پترولوژی و زمین‏‌شناسی اقتصادی، گروه پژوهشی ماگمازایی و کانه‏‌زایی در ایران، دانشکده علوم زمین، دانشگاه صنعتی شاهرود، شاهرود، ایران محسن مباشری دکترا، گروه پژوهشی ماگما‏‌زایی و کانه‏‌زایی در ایران، شرکت مهندسی مشاوره‏‌ای کاواک آرای نوین معدن، کرمان، ایران سیلویا فورناسارو پژوهشگر وابسته، گروه علوم زمین، دانشگاه پیزا، پیزا، ایتالیا Journal Article 2026 01 31 Introduction Urumieh–Dokhtar Magmatic Arc (UDMA) as a part of Zagros orogeny is the most important Cenozoic magmatic belt in Iran (Alavi, 1994; Babazadeh et al., 2024). Lithostratigraphic and age dating evidence indicates that magmatic activity in this belt initiated during Late Cretaceous-Paleocene and continued to Pliocene-Quaternary, with the peak of the magmatism in the Middle-Late Eocene. This was followed by extensive Oligocene-Miocene intrusive magmatism and subsequently renewed during Pliocene–Quaternary by scattered volcanism (Moghadam et al., 2022a, b; Babazadeh et al., 2024). In the southeastern segment of the UDMA, particularly along the Jebal-e-Barez mountains, regional geology and zircon U–Pb geochronology record multiphase, extensive arc related magmaism from the Eocene to the Oligocene-Miocene, locally extending to the Pliocene–Quaternary (Nazarinia et al., 2020; Atapour and Aftabi, 2021; Moghadam et al., 2022a, b; Babazadeh et al., 2024). Peak of the magma emplacement occurred during the Oligocene–Miocene, characterized by intermediate to felsic plutons of the Jebal-e-Barez mountains (Chiu et al., 2013; Babazadeh et al., 2024). Biotite, a major Fe–Mg-bearing constituent of the Jebal-e-Barez intrusive complex, has a substantial capacity for incorporating Ti and Al, making it an effective monitor of crystallization conditions (temperature, pressure, oxygen fugacity), as well as for classification and discrimination of granite tectonic settings and their mineralization potential (Wones and Eugster, 1965; Wones, 1989; Abdel-Rahman, 1994; Henry et al., 2005; Nachit et al., 2005; Jiang et al., 2002; Uchida et al., 2007; Anderson et al., 2008; Villaseca et al., 2017). Most previous studies on the Jebal-e-Barez intrusive complex have relied on whole-rock geochemistry for petrological purposes and economic fertility assessments, whereas mineral chemistry approaches such as biotite chemistry remain sparse. Geology The Sarbijan–Dalfard district, located northwest of Jiroft within the Jebal‑e‑Barez mountain range, represents the southern part of the UDMA. This major volcano‑plutonic complex developed in response to prolonged subduction of the Neotethys oceanic lithosphere beneath the Central Iran block, with magmatic activity persisting from the Late Cretaceous to the Neogene. In the southeastern segment of the UDMA, a compositionally diverse suite of intermediate‑felsic plutonic rocks—including diorite, monzodiorite, quartz diorite, granodiorite, and granite—intrudes the Eocene volcanic and volcano‑sedimentary rocks (Moghadam et al., 2022a, b; Babazadeh et al., 2024). The Jebal‑e‑Barez granitoids exhibit calc‑alkaline to high‑K calc‑alkaline affinities, consistent with an active continental arc setting. Moreover, the Oligocene–Miocene magmatism has been attributed to incipient collisional processes, crustal thickening, and partial melting of the oceanic slab and metasomatized mantle wedge, with variable crustal contamination (Moghadam et al., 2022a, b; Babazadeh et al., 2024). Research Methods Representative specimens from the main lithological units (monzodiorites and granodiorites) were selected for mineral chemical analyses using a JEOL 8200 electron microprobe at the Microprobe Laboratory, University of Milan, Italy. Analyses were conducted at an accelerating voltage of 30 kV, beam currents ranging from 10⁻¹² to 10⁻⁵ A, and a counting time of 80 seconds. Biotite composition was normalized to 22 oxygens, and the Fe³⁺ content was calculated following Droop (1987) assuming charge balance within the biotite structure. Petrography The granitoid bodies of the Sarbijan–Dalfard district show a progressive fractionated series from diorite to granite. The diorites and monzodiorites exhibit coarse‑ to medium‑grained hypidiomorphic textures, characterized by plagioclase as the dominant mineral, alongside biotite and amphibole as the primary mafic phases. Granodiorites predominantly display anhedral granular textures, where plagioclase often shows polysynthetic twinning and evidence of secondary alteration. Granites are typically coarse‑grained and anhedral granular, and show granophyric and myrmekitic textures in alkali‑feldspar‑rich varieties, representing the late‑stage simultaneous crystallization of quartz and feldspar. Discussion Biotite geochemistry in the Sarbijan–Dalfard granitoids provides key constraints on the physicochemical conditions (P, T, fO₂) of magma generation, crystallization, and emplacement, as well as classification (I, S, A), tectonic setting , and mineralization potential. Microprobe analyses of biotites in the Sarbijan–Dalfard granitoids indicate their Mg‑rich magmatic nature, crystallized under relatively high H₂O pressure and oxidizing conditions, reflecting a calc‑alkaline (I‑type) orogenic magma within a subduction‑related continental margin environment. Fe/(Fe+Mg) ratios and Al content indicate limited crustal contribution, while Ti concentrations suggest closure temperatures of 638 to 724°C, close to the crystallization conditions of granodiorite‑granite suites (Luhr et al., 1984; Henry et al., 2005). Total Al content in biotite implies emplacement pressures of 0.98–2.56 kbar, corresponding to depths of 3‑7 km in the upper crust (Uchida et al., 2007). High Mg# contents of biotites and their coexistence with Fe‑Ti oxides further support high fO₂ conditions, consistent with subduction‑related arc magmatism and minimal post‑emplacement re‑equilibration. Conclusion Biotites of the Sarbijan–Dalfard granitoids are Mg‑rich, magmatic, and largely unaltered, recording relatively oxidizing conditions during crystallization, consistent with Fe‑Ti oxide‑bearing calc‑alkaline I‑type magmas of a subduction‑related arc setting. Thermo‑barometry estimates based on Ti and Al‑in‑biotite suggest closure temperature ranges of 630‑725 °C and pressure ranges of 1‑2.5 kbar, indicating emplacement at shallow upper crustal depths. Integration of petrography, biotite chemistry, and thermo‑barometry calculations confirms that these granitoids were generated in an oxidizing, subduction‑related environment, with significant potential for Cu mineralization. Acknowledgments This study forms part of the first author’s PhD dissertation, which was financially supported by the Research Vice‑Presidency of Shahrood University of Technology (SUT). The authors gratefully acknowledge SUT, the staff of the Microprobe Laboratories at the University of Milan, and the esteemed reviewers of the Petrological Journal for their valuable guidance and constructive comments. توده‌های گرانیتوییدی محدودة سربیژن- دلفارد در جبال بارز بخشی از ماگماتیسم الیگوسن- میوسن در جنوب‌خاوری پهنة ارومیه- دختر را تشکیل می‌دهند. این توده‏‌ها از دیوریت، مونزودیوریت، گرانودیوریت و گرانیت ساخته شده‌اند و بافت‌ اصلی دانه‌ای بی‏‌شکل تا نیمه‌شکل‌دار دارند. بیوتیت که مهم‌ترین کانی تیره در بیشتر این توده‏‌هاست خاستگاه اولیه ماگمایی و ترکیب منیزیم‌دار دارد. دماسنجی برپایة تیتانیم درون بیوتیت، دماهای 600 تا 730 درجة سانتیگراد را برای بسته‌شدن سیستم این کانی نشان می‌دهد با شرایط تبلور و جایگزینی ماگماهای گرانیتوییدی کالک‌آلکالن سازگار است. فشارسنجی بر پایة میزان آلومینیم کل درون بیوتیت، نشان‏‌دهندة جایگیری این توده‌های درونی در فشارهای 1 تا 5/2 کیلوبار است که با ژرفای کم پوستة بالایی (ژرفاهای نزدیک به 3 تا 7 کیلومتری) همخوانی دارد. شاخص‌ فوگاسیتة اکسیژن و همیافتی بیوتیت منیزیم‌دار با فازهای اکسید آهن گواهی بر شرایط اکسیدان و تعلق این گرانیتوییدها به سری مگنتیت با پتانسیل کانه‏‌زایی مس هستند. مجموع ویژگی‌های میدانی، سنگ‏‌نگاری و شیمی کانی نشان می‌دهند توده‌های گرانیتوییدی محدودة سربیژن- دلفارد از یک ماگمای گرانیتوییدی کالک‌آلکالن متاآلومین نوعI در یک محیط کمان ماگمایی همزمان با برخورد وابسته به فرورانش در زمان الیگوسن-میوسن پدید آمده‌اند. این نتایج با یافته‏‌های به‌دست‌آمده از الگو‌های پیشنهادی برای ماگماتیسم کمانی در بخش جنوبی پهنة ارومیه-دختر همخوانی دارد.

https://ijp.ui.ac.ir/article_30326_b52ed9692d619ba0bc1c1959187e6a66.pdf

دانشگاه اصفهان پترولوژی 2228-5210 17 2 2026 06 22 Petrogenesis and tectonomagmatic evolution of the Sabzevar ophiolitic complex based on whole rock geochemistry, zircon U–Pb geochronology, and zircon trace element composition in pillow lavas and sheeted dikes of the Sultanabad area بررسی پتروژنز و تحولات تکتونوماگمایی مجموعة افیولیتی سبزوار با استفاده از ژئوشیمی سنگ‌کل، سن سنجی U-Pb و ترکیب عنصرهای کمیاب زیرکن در گدازه‌های بالشی و دایک‌های ورقه‌ای منطقه سلطان‌آباد 95 130 30439 10.22108/ijp.2026.148624.1385 FA سید علی مظهری دانشیار، مرکز پژوهشی علوم جغرافیایی و مطالعات اجتماعی، دانشگاه حکیم سبزواری، سبزوار، ایران دانشیار، هستۀ پژوهشی فلزات سنگین، دانشگاه حکیم سبزواری، سبزوار، ایران فرناندو به آ استاد، گروه زمین شناسی، دانشگاه گرانادا، اسپانیا Journal Article 2026 04 01 Introduction Ophiolitic complexes—fragments of oceanic lithosphere tectonically emplaced onto continental margins—serve as crucial archives for reconstructing the formation and evolution of ancient ocean basins. The Sabzevar ophiolite in northeastern Iran represents one of the most significant remnants of Mesozoic Neotethyan oceanic lithosphere and provides a key window into the tectonic development of the northern Neotethys branch. Previous studies have assigned this ophiolite to diverse tectonic settings, including mid‑ocean ridge, supra‑subduction zone, and back‑arc environments (Khalatbari Jafari et al., 2013a, b; Rezaei et al., 2018; Jafari and Ghasemi, 2023). Nevertheless, the co‑occurrence of contrasting magmatic signatures within its volcanic sequences points to a polyphase magmatic history in a complex geodynamic framework (Omrani et al., 2018; Moghadam et al., 2025). This study investigates the pillow lavas and sheeted dikes exposed in the Sultanabad area, in the eastern sector of the Sabzevar ophiolite. Its primary aims are to characterize the geochemistry, constrain the crystallization ages of the volcanic units via zircon U–Pb geochronology, and assess their tectonomagmatic significance for the evolution of the Sabzevar oceanic basin. Geological Setting The Sabzevar ophiolite, situated in northeastern Iran, constitutes an integral component of the tectonic structure of the Central Iranian microcontinent (Alavi, 1994). It is widely interpreted as a relict of the northern Neotethyan oceanic realm, which formed within the Central Iranian terrane between Central Iran and the Alborz belt during the Mesozoic (Agard et al., 2005). The ophiolitic succession comprises ultramafic mantle rocks, layered ultramafic–mafic cumulates, sheeted dike complexes, pillow basalts, and pelagic sedimentary cover (e.g., Shojaat et al., 2003; Khalatbari Jafari et al., 2013a, b; Moghadam et al., 2025). The Sultanabad area hosts well‑preserved volcanic units, dominated by pillow basalts intercalated with sheeted dikes and minor massive lava flows. These rocks represent the uppermost levels of the oceanic crust. Field relations indicate that the pillow lavas erupted in a submarine setting and were subsequently affected by tectonic deformation during the Neotethyan closure and obduction of the ophiolitic complex onto the continental margin. Materials and Methods Representative samples of pillow basalts and sheeted dikes were collected from the Sultanabad area. Petrographic examination was performed using optical microscopy to characterize mineral assemblages and textural features. Whole‑rock major and trace element concentrations were determined via X‑ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP‑MS). Zircon grains were extracted from selected samples and subjected to U–Pb isotopic dating and trace element analysis using laser ablation‑inductively coupled plasma mass spectrometry (LA‑ICP‑MS). The geochemical data served to classify magma types, constrain magma sources, and discern tectonic affinities. Zircon trace element compositions were additionally examined to offer complementary constraints on magmatic processes and crystallization conditions. Results Petrographic observations reveal that the studied volcanic rocks consist predominantly of plagioclase, clinopyroxene, and secondary alteration minerals. The pillow lavas typically exhibit porphyritic to intersertal textures, whereas the sheeted dikes show fine‑grained to subophitic textures. Whole‑rock geochemical data indicate that the studied samples fall into three main magmatic series: alkaline, calc‑alkaline, and tholeiitic varieties. The alkaline basalts are enriched in incompatible elements and display pronounced LREE enrichment relative to HREE. Their trace element patterns are akin to those of ocean island basalts (OIB). The tholeiitic basalts and sheeted dikes exhibit relatively flat REE patterns and are marked by negative Nb and Ta anomalies, characteristic of magmas generated in supra‑subduction zone settings. Calc‑alkaline basalts show intermediate geochemical signatures between these two groups. Zircon U–Pb geochronology reveals that magmatic activity in the study area took place during the Cretaceous, yielding ages between ~113 and 90 Ma. The alkaline basalts record the oldest ages (~112–110 Ma), while the tholeiitic and calc‑alkaline rocks give slightly younger but overlapping ages of ~113–91 Ma. Trace element compositions of zircon grains show HREE enrichment and LREE depletion, consistent with a magmatic origin. Variations in elemental ratios such as Th/U and Eu/Eu* point to differences in magma composition and crystallization conditions across the studied rock types. Discussion The geochemical signatures of the studied rocks point to the involvement of multiple magma sources in generating the Sultanabad volcanic sequence. The alkaline basalts most likely originated from low‑degree partial melting of a garnet‑bearing enriched mantle source, consistent with an intraplate or seamount‑related affinity. By contrast, the tholeiitic basalts and sheeted dikes appear to have been derived from higher‑degree partial melting of a depleted mantle source metasomatized by slab‑derived fluids. The calc‑alkaline basalts exhibit geochemical features characteristic of subduction‑related magmatism and probably represent melts generated in a mantle wedge modified by slab‑derived fluids. The co‑occurrence of alkaline and supra‑subduction zone magmas within the same volcanic sequence implies that the Sabzevar oceanic basin underwent a complex tectonomagmatic history, encompassing both intraplate and subduction‑related processes. The zircon U–Pb ages obtained in this study show that magmatic activity persisted over a protracted interval during the Middle to Late Cretaceous. This prolonged magmatism likely reflects the progressive evolution of a supra‑subduction zone system linked to the initiation and advancement of subduction within the northern Neotethys. Conclusions Combined whole‑rock geochemistry and zircon U–Pb geochronology provide new constraints on the petrogenesis and tectonic evolution of the volcanic units in the eastern Sabzevar ophiolite. The investigated rocks fall into alkaline, calc‑alkaline, and tholeiitic suites, reflecting the contribution of multiple mantle sources and magmatic pathways. Zircon U–Pb dating restricts magmatism to ca. 113–90 Ma, i.e., the Middle–Late Cretaceous. Geochemical fingerprints suggest that the tholeiitic basalts and sheeted dikes formed in a supra‑subduction zone setting, whereas the alkaline basalts represent within‑plate‑related magmatism subsequently incorporated into the ophiolitic succession. Collectively, the results favor a model whereby the Sabzevar ophiolite developed within a complex supra‑subduction zone system during the evolution and final closure of the northern Neotethys Ocean. در این پژوهش، گدازه‌های بالشی و دایک‌های ورقه‌ای منطقۀ سلطان‌آباد در بخش خاوری مجموعۀ افیولیتی سبزوار با به‌کارگیری داده‌های زمین‌شیمیایی سنگ‌کل، زمین‌زمان‌سنجی U–Pb زیرکن و بررسی عنصرهای کمیاب زیرکن بررسی شدند تا سرشت ماگمایی و چارچوب تکتونوماگمایی پیدایش آنها روشن شود. داده‌های زمین‌شیمیایی نشان می‌دهند سنگ‌های بررسی‌شدة این منطقه دربردارندة سه سری ماگمایی متمایز یعنی آلکالن، کالک‌آلکالن و توله‌ایتی هستند. بازالت‌های آلکالن با غنی‌شدگی در عنصرهای ناسازگار و نسبت‌های بالای عنصرهای خاکی نادر سبک، ویژگی‌هایی همانند بازالت‌های درون‌صفحه‌ای نشان می‌دهند؛ اما نمونه‌های کالک‌آلکالن و توله‌ایتی با تهی‌شدگی از برخی عنصرهای با شدت میدان بالا و الگوهای عنصرهای خاکی نادر کمابیش تخت، با ماگماهای مرتبط با محیط‌های فرورانشی همانندی دارند. زمین‌زمان‌سنجی زیرکن‌ها بازۀ زمانی نزدیک به ۱۱۳ تا ۹۰ میلیون سال پیش را برای تبلور این واحدهای ماگمایی نشان می‌دهد که نشان‌دهندة تداوم فعالیت ماگمایی در کرتاسة میانی تا پسین است. ترکیب عنصرهای کمیاب زیرکن‌ها نیز خاستگاه ماگمایی بلورها را روشن می‌کند و تفاوت در سرشت ماگمای اولیه در میان گروه‌های سنگی گوناگون را آشکارا نشان می‌دهد. تفسیر یکپارچة داده‌های زمین‌شیمی و زمین‌زمان‌سنجی گویای آن است که گدازه‌های توله‌ایتی و دایک‌های ورقه‌ای چه‌بسا در پوستة اقیانوسی وابسته به سامانۀ پیش‌کمان یک کمان آتشفشانی پدید آمده‌اند؛ اما بازالت‌های آلکالن چه‌بسا نمایانگر فعالیت ماگمایی درون‌صفحه‌ای در پهنه‌ای اقیانوسی هستند که بعدها در پی فرایندهای همگرایی و بسته‌شدن نئوتتیس به مجموعۀ افیولیتی افزوده شده‌اند. این یافته‌ها دیدگاه تازه‌ای دربارة پیچیدگی ماگماتیسم و تکامل زمین‌ساختی افیولیت سبزوار در چارچوب ژئودینامیکی نئوتتیس ارائه می‌دهد.

https://ijp.ui.ac.ir/article_30439_30efa2384e5f9207c4cb9df8924f8279.pdf