دانشگاه اصفهانپترولوژی2228-521016320250923Geochemical evidence of dykes in the Salafchegan-Tafresh region as part of Cenozoic magmatism in the central segment of the Urumieh-Dokhtar magmatic arcشواهد زمینشیمیایی دایکهای منطقة سلفچگان-تفرش بهعنوان بخشی از ماگماتیسم سنوزوییک در بخش مرکزی کمان ماگمایی ارومیه – دختر1262965410.22108/ijp.2025.145472.1363FAمرتضیدلاوریدانشیار، گروه زمینشیمی، دانشکده علوم زمین، دانشگاه خوارزمی، تهران، ایرانمهشیدطاعتیدانشجوی کارشناسیارشد، گروه زمینشیمی، دانشکده علوم زمین، دانشگاه خوارزمی، تهران، ایرانامیرعلیطباخ شعبانیدانشیار، گروه زمینشیمی، دانشکده علوم زمین، دانشگاه خوارزمی، تهران، ایرانJournal Article20250529<strong>Introduction</strong><br />Iran constitutes a critical segment of the Alpine-Himalayan orogenic belt, formed through the collision of the Arabian, Indian and Eurasian tectonic plates (Rolland et al., 2002; Stampfli and Hochard, 2009; von Raumer et al., 2003; Yin and Harrison, 2000). The Urmia-Dokhtar magmatic arc (UDMA), extending northwest-southeast across Iran, records Neo-Tethyan subduction and subsequent continental collision (Chiu et al., 2013; Verdel et al., 2011). Magmatism within this arc is predominantly calc-alkaline, with localized adakitic affinities (Delavari et al., 2020; Lechmann et al., 2018; Omrani et al., 2008). The Salafchegan-Tafresh region, situated in the central UDMA, comprises diverse lithological units, including Paleogene to Neogene volcanics and pyroclastics as well as calc-alkaline intrusions dated at 19–22 Ma (Raeisi et al., 2020). These units reflect UDMA magmatism associated with Neo-Tethyan subduction processes. Additionally, the region is intruded by various dykes, exhibiting predominantly intermediate to mafic composition. These dykes are inferred to be of Miocene–Pliocene age, and their geochemical and structural analysis provides critical insights into the region’s tectonic evolution.<br /><strong>Analytical methods</strong><br />Whole-rock geochemical analyses were performed at Zarazma lab company (Tehran, Iran) using inductively coupled plasma-optical emission spectroscopy (ICP-OES) for major elements and inductively coupled plasma-mass spectrometry (ICP-MS) for trace elements. Sample preparation involved fusion with lithium metaborate followed by dissolution in nitric acid. The analytical precision yielded a detection limit of ~0.05 wt.% for major oxides. To analyze trace elements, sample digestion was performed via acid dissolution (HF-HNO₃-HClO₄). Detection limits ranged between 0.05 and 1 ppm. To ensure data accuracy and reproducibility, replicate analyses and international reference standards were employed.<br /><strong>Results and discussion</strong><br /><strong>Petrography</strong><br />The investigated dykes can be categorized into basaltic andesite and andesite. In the basaltic andesite, plagioclase constitutes the dominant mineral phase, accounting for up to 50 vol.% in some samples, and typically occurs as subhedral to euhedral laths within a fine-grained groundmass. Clinopyroxene and amphibole are present as subordinate phases, often exhibiting partial alteration to secondary minerals. The andesite dykes are characterized by a higher relative abundance of plagioclase, which forms the principal framework of the rock. Ferromagnesian minerals (e.g., pyroxene, amphibole) occur in lesser proportions compared to the basaltic andesite group, suggesting either differences in melt composition or crystallization conditions. Opaque minerals, predominantly Fe-Ti oxides, are ubiquitously present as accessory phases in both groups, typically disseminated throughout the groundmass or as inclusions within major silicate phases.<br /><strong>Geochemistry</strong><br />The studied dykes exhibit a compositional range with SiO<sub>2</sub> contents varying between 51.75 and 64.97 wt%. In the Zr/Ti versus Nb/Y diagram, the samples plot within the basaltic andesite and andesite fields, displaying a calc-alkaline affinity. Low Mg#, Ni, and Cr values suggest significant geochemical modification and derivation from evolved melts. Harker diagrams reveal coherent geochemical trends and decreasing trends in TiO₂, Al₂O₃, MnO, MgO, CaO, Sc, and V with increasing SiO<sub>2</sub>. Chondrite-normalized rare earth element (REE) patterns exhibit enrichment in REEs, with light REEs (LREEs) showing the highest enrichment (~52× chondrite), followed by middle REEs (MREEs; ~16×) and heavy REEs (HREEs; ~14×). The Lan/Smₙ (7.6–9.2) and Lan/Ybₙ (10–3.4) ratios indicate LREE enrichment relative to MREEs and HREEs. The Sm<sub>n</sub>/Ybₙ ratio (0.8–1.9) suggests a flat to gently sloping pattern in the MREE-HREE segment, implying limited HREE depletion. Primitive mantle-normalized multi-element diagrams display enrichment in large ion lithophile (LIL) elements (e.g., Rb, K) and depletion in high field strength (HFS) elements (e.g., Nb, Ta).<br /><strong>Petrogenetic Modeling</strong><br />Fractional crystallization modeling was conducted using one sample (TT22) as the parental melt. Trace element modeling indicates that the more evolved compositions can be derived through 20–80% fractional crystallization of plagioclase, clinopyroxene, olivine, and Fe-Ti oxides.<br /><strong>Regional Tectonomagmatic Implications</strong><br />The Urmia-Dokhtar magmatic arc (UDMA) exhibits distinct temporal variations in magmatism. Eocene and Neogene magmatism displays arc-related signatures, sourced from a metasomatized lithospheric mantle. Oligo-Miocene magmatism is alkaline, likely derived from asthenospheric upwelling. The temporal shift in melt composition from calc-alkaline in the Eocene to alkaline in the Oligo-Miocene, followed by a return to calc-alkaline magmatism in the Neogene within the Urmia-Dokhtar magmatic arc, reflects significant changes in subduction dynamics, crustal interactions, and tectonic regime. The Eocene calc-alkaline magmatism is interpreted as a product of arc-related processes in an active subduction zone, driven by the subduction of the Neotethys oceanic plate beneath the Central Iranian continental margin. In such a setting, calc-alkaline melts are typically generated through partial melting of a hydrated mantle wedge, metasomatized by slab-derived fluids (Delavari and Damghani, 2022; Verdel et al., 2011; Verdel, 2009). This magmatism is consistent with a supra-subduction zone extensional regime, where slab rollback facilitated asthenospheric upwelling, enhancing heat transfer to the mantle lithosphere and triggering widespread partial melting. During the Oligo-Miocene, magmatism transitioned to an alkaline affinity. Continued slab rollback may have induced asthenospheric upwelling and decompression melting, generating melts with oceanic island basalt (OIB)-like characteristics with weak to negligible subduction-related fluid signatures. The resurgence of calc-alkaline magmatism in the Neogene suggests a renewed influence of subduction-related processes, possibly linked to a post-collisional setting. Lithospheric thickening, driven by the convergence of the Arabian and Eurasian plates, may have facilitated partial melting of the mantle lithosphere. Regional fault systems played a critical role in controlling the spatial distribution and geometry of magmatic intrusions. These faults served as conduits for magma transport, localizing magmatic activity along their trends.<br /><strong>Conclusion</strong><br />The Salafchegan-Tafresh dykes, exhibiting basaltic andesite to andesite compositions, provide critical insights into the Urmia-Dokhtar magmatic arc's (UDMA) evolution. Geochemical signatures indicate calc-alkaline affinities, LREE enrichment, and LILE/HFSE fractionation, consistent with subduction-modified melts. Fractional crystallization of plagioclase, clinopyroxene, and Fe-Ti oxides explains compositional variations. The temporal shift from Eocene calc-alkaline to Oligo-Miocene alkaline magmatism reflects slab rollback and asthenospheric upwelling, while Neogene calc-alkaline resurgence suggests renewed subduction influence. Regional faults facilitated magma transport, highlighting the interplay between tectonics and magmatism in the UDMA. These findings underscore the complex geodynamic evolution of the Neo-Tethyan subduction-collision system.دایکهای منطقة تفرش-سلفچگان که گویای فرایندهای ماگمایی سنوزوییک در پهنة ماگمایی مرکزی ارومیه-دختر هستند، بیشتر از آندزیت بازالتی و آندزیت تشکیل شدهاند و کانیشناسی رایج آنها شامل پلاژیوکلاز + کلینوپیروکسن ± هورنبلند + اکسیدهای آهن-تیتانیم است. از دیدگاه زمینشیمیایی این سنگها سرشت کالکآلکالن دارند و شواهدی مانند غنیشدگی از LILE (مانند: Rb، Ba و K) و تهیشدگی از HFSE (مانند: Nb، Ta و Ti) با پیدایش آنها در یک کمان ماگمایی قارهای سازگاری دارد. الگوسازی تبلوربخشی بر پایة عنصرهای کمیاب نشان داد مذابهای اولیهتر با درصدهای متفاوت تبلور (20 تا80%) و فازهای جدایشیافتهتری مانند پلاژیوکلاز، کلینوپیروکسن، الیوین و اکسیدهای آهن-تیتانیمدار به ترکیبات تحولیافتهتر تبدیل میشوند. افزونبراین، تغییرات تدریجی شیمیایی عنصرهای کمیاب دایکها گویای تغییر خاستگاه مذاب در گذر زمان از گوشتة سنگکرهای دگرسانشده به گوشتة سستکرهای است. ماگماتیسم ائوسن و نئوژن (5/0Nb/La<؛ 10Nb/U<) ویژگیهای ماگماتیسم کمانی دارد و خاستگاه سنگکرهای آن تحتتأثیر سیالهای فرورانشی بوده است؛ اما ماگماتیسم الیگو-میوسن (1Nb/La>؛ 10Nb/U>) سرشت آلکالن داشته است و از گوشتة سستکرهای خاستگاه گرفته است. این تغییرات ترکیبی تغییرات مهم ژئودینامیکیِ گذار از سازوکار فرورانشیِ پیش از برخورد به شرایط پسابرخوردی را بازتاب میدهند. روند بیشتر دایکهای منطقة سلفچگان- تفرش که همراستا با روند کلی کمان ماگمایی ارومیه- دختر است نیز به احتمال بسیار با زمینساخت کششی سامانة فرورانشی نئوتتیس در یک مقیاس ناحیهای در ارتباط بوده است. https://ijp.ui.ac.ir/article_29654_d0a32be979442585363eaabeedb6d625.pdfدانشگاه اصفهانپترولوژی2228-521016320250923Geology, geochemistry and origin of the Chore Nab IOA-type iron deposit in the Tarom metallogenic belt, northwestern of Iranزمینشناسی، زمینشیمی و خاستگاه کانسار آهن نوع IOA چورهناب در کمربند متالوژنی طارم، شمالباختری ایران27742973110.22108/ijp.2025.144993.1358FAپریساشاه کرمیدانشجوی دکتری، گروه زمینشناسی، دانشکده علوم، دانشگاه لرستان، خرمآباد، ایرانرضازارعی سهامیهاستاد، گروه زمینشناسی، دانشکده علوم، دانشگاه لرستان، خرمآباد، ایرانمحمدابراهیمیدانشیار، گروه زمینشناسی، دانشکده علوم، دانشگاه زنجان، زنجان، ایراناحمداحمدی خلجیدانشیار، گروه زمینشناسی، دانشکده علوم، دانشگاه لرستان، خرمآباد، ایرانرامینساریخانیدانشیار، گروه زمینشناسی، دانشکده علوم، دانشگاه لرستان، خرمآباد، ایرانJournal Article20250426<strong>Introduction</strong><br />The study area, situated 5 km northeast of Zanjan, is a component of the Tarom magmatic subzone within the Tarom-Hashtjin metallogenic province. This province is characterized by a variety of deposit types, including porphyry, skarn-type iron, IOCG, volcanic-sedimentary, and IOA deposits, all located in the Western Alborz magmatic arc (Nabatian et al., 2015; Ghasemi Siani and Ebrahimifard, 2023). Previous research in the Tarom-Hashtjin subzone has largely concentrated on intrusive igneous bodies (Nabatian et al., 2014a, 2014b; Aghazadeh et al., 2015; Saeedi et al., 2018; Ghasemi Siani et al., 2020), with less emphasis on the geochemical and petrological aspects of volcanic rocks. Specific iron deposits identified include skarn types (Qozlu, Arjin, Gozel Darreh- Moghaddasi et al., 2019; Mokhtari et al., 2019; Shafaiepour et al., 2020), iron oxide-apatite types (Zaker, Sorkheh Dizaj, Morvarid - Nabatian et al., 2014a; Nabatian and Ghaderi, 2013), volcanic-sedimentary types (Shah Bolaghi, Hossein Abad, Reyhan- Mokhtari et al., 2019), and placer type (Zarnan - Ebrahimi et al., 2016, 2017). Some studies highlight the influence of intrusive igneous masses on regional mineralization. For instance, Ghasemi Siani et al. (2020) suggest that the internal igneous masses of Tarom provided the necessary heat and chemical composition for hydrothermal fluids responsible for epithermal mineralization. The Eocene-Oligocene Alborz magmatism cycle, particularly in the Tarom-Hashtjin province, yielded diverse intrusive, semi-volcanic, and volcanic-sedimentary rocks, spanning acidic to intermediate compositions and belonging to calc-alkaline, high-potassium calc-alkaline, and shoshonitic series (Ghasemi Siani and Ebrahimifard, 2023).<br />Given the debated origin of iron ore deposits, this study undertakes detailed geological and mineralogical research in the Chore Nab region. It aims to investigate the petrology of igneous and volcanic rocks to ascertain their role in iron mineralization, analyze the textures, structures, mineralogy, formation, and types of iron mineralization, and establish the magmatic series and tectonic setting of the local rock masses. Comprehensive geochemical and rare earth element studies will be conducted using XRF, XRD, ICP-MS, SEM, and EDS analyses.<br /><strong>Regional Geology</strong><br />Chore Nab is located in the central part of Zanjan Province, Iran. The study area, covering approximately 20 km<sup>2</sup>, is located 5 km northeast of Zanjan city, with geographical coordinates of 36° 41′ 10′′ to 36° 43′ 40′′ N and 48° 32′ 25′′ to 48° 35′ 19′′ E. According to Tarom’s 1:100,000 geological map, several rock units with outcrops are present in the study area. These rocks are Eocene volcanic and pyroclastic rocks, including basalt, dacite, andesite basalt, andesite, sandstone and green tuff in the lower part(unit E<sup>5</sup>k.a), light green tuff breccia and lapilli tuff(E<sup>6</sup>k.a) and andesitic lavas with tuff breccia, green tuff, sandstone, and mudstone(unit E<sup>8</sup>k.a) The Late Eocene granitoid rocks have a lithological composition of quartz monzodiorite, quartz monzonite, quartz syenite(unit Qm), and microquartz diorite porphyry(unit P). Quaternary deposits consist of old alluvial terraces (unit Q<sub>1</sub><sup>t</sup>) and new alluvial terraces (unit Q<sub>2</sub><sup>t</sup>).<br /><strong>Analytical methods</strong><br />Field sampling of rock units was performed, resulting in 50 collected samples. From these, 36 thin sections and 22 polished thin sections were prepared for petrographic, mineralogical, and alteration studies at Bu-Ali Sina University. Following this, 14 samples were chosen for chemical analysis. Zar Azma Company in Tehran conducted ICP-MS analysis for rare earth and trace elements, and XRF analysis for major and minor element oxides on these 14 samples. Additionally, SEM and EDS analyses were performed on ten mineral samples, and eight samples were selected for X-ray diffraction studies at Lorestan University.<br /><strong>Petrography</strong><br />Rocks in the area are classified into volcanic rocks (basalt, andesite, dacite), intrusive masses (monzonite, quartz monzodiorite), and Quaternary sediments. Volcanic rocks primarily display porphyritic and glomeroporphyritic textures, while granitoid intrusives are predominantly granular, with some anti-rapakivi and granophyric textures. Exsolution texture in pyroxenes and sieve texture in plagioclases were noted. Main minerals are plagioclase and pyroxene in volcanics, and quartz, alkali feldspar, and plagioclase in intrusives. Amphibole, epidote, and chlorite are common mafic minerals; apatite and monazite are minor. Laboratory studies reveal extensive mineralization and alteration in volcanic rocks. Magnetite mineralization appears as massive and dispersed grains, accompanied by secondary hematite, limonite, goethite, and copper minerals (malachite, chalcocite). Field studies confirmed significant limonite and goethite alteration.<br /> <br /><strong>Geochemistry</strong><br />For geochemical analysis, 14 minimally altered rock samples from the study area underwent whole-rock analysis using XRF and ICP-MS. Intrusive masses plot as quartz monzodiorite and monzodiorite on the SiO2 versus (Na<sub>2</sub>O + K<sub>2</sub>O) diagram. Volcanic masses appear as andesite-basalt, andesite, trachyandesite, and subalkaline basalt on the Nb/Y versus Zr/TiO2 diagram, and as andesite, andesite-basalt, trachyandesite, and basalt on the Nb/Y versus Zr/Ti diagram. The trace element Co versus Th diagram, along with the AFM diagram, indicate all samples are calc-alkaline. On the SiO2 versus K2O diagram, samples fall within the high-potassium calc-alkaline range. All samples are meta-aluminous based on the A/CNK versus A/NK diagram. Negative Ti and Nb anomalies suggest subduction-related magmatism and crustal involvement. Studied samples are enriched in LREE relative to HREE, showing a high LREE/HREE ratio and a subtle negative Eu anomaly.<br /><strong>Discussion and Conclusion</strong><br />Eocene igneous rocks in the Chore Nab region are linked to iron mineralization. The Chore Nab mine specifically features iron oxide-apatite mineralization in lenses, veins, and as disseminations within intrusive and, to a lesser extent, volcanic-sedimentary rocks. The region’s rocks are high-potassium calc-alkaline and meta-aluminous, with granitoids being Type I. Intrusive masses formed in an active continental margin setting during collision, while granitoids are associated with volcanic arcs. Volcanic masses are found in orogenic environments related to continental arcs. Geochemical diagrams (Th/Ta versus Ta/Yb, Th/Ta versus Yb, Nb versus Y) place the intrusive masses within active continental margin and volcanic arc settings, respectively. Geochemically, the mineralization falls within the range of iron apatite and titaniferous iron deposits based on Ni, V, Ti, and Fe content.<br /><strong>Acknowledgements</strong><br />The authors sincerely appreciate the esteemed editor and referees for their invaluable scientific advice and insightful comments, which significantly enriched this article.معدن آﻫﻦ چورهناب از ذخایر دارای کانهزایی آﻫﻦ در ﮐﻤﺮﺑﻨﺪ ﻓﻠﺰزاﯾﯽ ﻃﺎرم اﺳﺖ که با ذخیرة احتمالی 250.000 تن کانسنگ و عیار متوسط 36 درصد آهن، در نزدیکی روستای چورهناب و شمالخاوری شهر زنجان جای دارد. در این منطقه سنگهای آذرین ائوسن رخنمون گستردهای دارند و با کانهزایی آهن همراه هستند. در شمال و خاور شهر زنجان سنگهای آتشفشانی- آذرآواری ائوسن شامل جریانهای گدازه بازالتی، آندزیت-بازالت، آندزیت، تراکیآندزیت و داسیت همراه با سنگهای آذرآواری شامل توف و برش آتشفشانی رخنمون دارند. سنگهای آذرین درونی ائوسن پایانی شامل گرانیت، مونزونیت، کوارتزمونزونیت، کوارتزمونزودیوریت و مونزودیوریت درون مجموعه آتشفشانی- آذرآواری ائوسن که قدیمیترین سنگهای دارای رخنمون در منطقه هستند، نفوذ کردهاند. واحدهای سنگی منطقة بررسیشده سرشت ﮐﺎﻟﮏآﻟﮑﺎﻟﻦ ﭘﺘﺎﺳﯿﻢ ﺑﺎﻻ و از نوع ﻣﺘاآﻟﻮﻣﯿﻦ دارند. شاخص اشباعشدگی از آلومینیم، معیار خوبی برای تفکیک گرانیتوییدهای پرآلومین (A/CNK>1) از گرانیتوییدهای متاآلومین (A/CNK˂1) بهشمار میرود. بر پایة این شاخص گرانیتوییدهای منطقة چورهناب در نمودار A/NK در برابر A/CNK (97/0) در گسترة متاآلومین جای دارد و از نوع I ﻫﺴﺘﻨﺪ. نمودار SiO₂-Zr نیز همخوانی خوبی با ردهبندی I-type نشان میدهد، که صحت ردهبندی را تأیید میکند. همة مقدارهای بهدستآمده برای نسبت Zr-SiO₂ بسیار کم هستند (کمتر از 1 و حتی کمتر از 5/0) که این مقدارها با گرانیتهای نوع I همخوانی دارند. ﮐﺎﻧﻪزاﯾﯽ اﮐﺴﯿﺪ آﻫﻦ در ﮐﺎﻧﺴﺎر چورهناب ﺑﻪﺻﻮرت ﻋﺪﺳﯽ و رﮔﻪ-رﮔﭽﻪﻫﺎی اﮐﺴﯿﺪ آﻫﻦ-آﭘﺎﺗﯿﺖ درون ﺗﻮدة آذرین درونی و ﺑﻪ ﻣﻘﺪار ﮐﻢ درون ﺳﻨﮓﻫﺎی آﺗﺸﻔﺸﺎﻧﯽ اﺋﻮﺳﻦ و در نزدیکی ﺗﻮدههای آذرین درونی رخ داده اﺳﺖ. کانیسازی در منطقة بررسیشده بیشتر به دو صورت روی داده است که نوع نخستین آن شامل کانیسازی مگنتیت، آپاتیت، اکتینولیت، کالکوپیریت و پیریت است و نوع ثانویه شامل کانیسازی گوتیت، لیمونیت، هماتیت، اسپیکولاریت، کوولیت، کالکوسیت و مالاکیت است. ﺗﻮدهﻫﺎی آذرین درونی در ﻣﺤﯿﻂ ﺗﮑﺘﻮﻧﻮﻣﺎﮔﻤﺎﯾﯽ حاشیة ﻓﻌﺎل ﻗﺎرهای و همزمان با ﺑﺮﺧﻮرد پدید آمدهاﻧﺪ و گرانیتوییدهای منطقه به لحاظ جایگاه تکتونوماگمایی متعلق به کمانهای آتشفشانی (VAG) هستند. سنگهای آتشفشانی نیز بیشتر به محیط تکتونوماگمایی کوهزایی و کمانهای قارهای وابسته هستندhttps://ijp.ui.ac.ir/article_29731_1b77a43fb886516080724bd9c887e87e.pdfدانشگاه اصفهانپترولوژی2228-521016320250923Petrology and geochemistry of volcanic and subvolcanic rocks in the south of Asagi igneous complex, northwest of Zahedan, Sistan Suture Zoneسنگشناسی و زمینشیمی سنگهای آتشفشانی و نیمهآتشفشانی در جنوب مجموعة آذرین آساگی، شمالباختری زاهدان، پهنة زمیندرز سیستان751002988010.22108/ijp.2025.146089.1367FAمحمدبامریاستاد، گروه زمینشناسی، دانشکده علوم پایه، دانشگاه سیستان و بلوچستان، زاهدان، ایرانریحانهعباسیدانشآموختة کارشناسی ارشد، گروه زمینشناسی، دانشکده علوم پایه، دانشگاه سیستان و بلوچستان، زاهدان، ایرانعبدالرضاپرتابیاندانشیار، گروه زمینشناسی، دانشکده علوم پایه، دانشگاه سیستان و بلوچستان، زاهدان، ایرانJournal Article20250724<strong>Introduction</strong><br />The Asagi igneous complex is located in the northwest of Zahedan city (Figure 1A) and is part of a southeast–northwest trending magmatic belt. The igneous rocks of this belt were formed during at least two distinct periods. In the first period, Oligocene igneous rocks occur as extrusive (lava and pyroclastic), intrusive, and subvolcanic bodies that are mostly potassic. In the second period, Pliocene igneous rocks appear as sodic extrusive lavas (Camp and Griffis, 1982; Piri, 2018; Boomeri et al., 2020, 2022; Moradi et al., 2016; Nazari et al., 2022). Based on these studies, the Oligocene rocks belong to alkaline, calc-alkaline, high-potassium calc-alkaline, and shoshonitic magmatic series. These rocks are attributed to subduction-related and post -collisional tectonic settings.<br />The aim of this paper is to investigate the geology, petrography, and geochemistry of volcanic and subvolcanic rocks in the southern part of the Asagi igneous complex. It also explores the tectonic setting and magma origin.<br /><strong>Geology</strong><br />The Asagi igneous complex lies within the Sistan Suture Zone (Figure 1B), situated between the Lut and Afghan blocks. This zone includes two ophiolite complexes—Neh in the west and Ratuk in the east —separated by the Sefid-Abeh sedimentary basin (Tirrul et al., 1983). The Neh and Ratuk complexes contain Upper Cretaceous ophiolites and locally metamorphosed flysch-type sedimentary rocks of Upper Cretaceous to Eocene age. These complexes are commonly intruded by Cenozoic igneous rocks. The Sefid-Abeh basin consists of clastic rocks and limestone deposited in shallow to deep marine environments, with a thickness of approximately eight kilometers (Tirrul et al., 1983). This basin also hosts numerous intrusive and extrusive igneous bodies, indicating multiple magmatic phases during the Cenozoic (Camp and Griffis, 1982; Boomeri et al., 2021; Nazari et al., 2022). Strike-slip faults have played a key role in controlling magmatism in the region (Bagheri and Damani Gol, 2020). The study area is located within the Sefid -Abeh basin, where small outcrops of ophiolitic and sedimentary rocks are intruded by larger outcrops of basic to acidic volcanic and subvolcanic rocks, most of which have undergone hydrothermal alteration (Figures 2 and 3).<br /><strong>Research Method</strong><br />Twenty-four thin sections were prepared from collected samples for petrographic analysis. Thirteen relatively unaltered samples were selected for geochemical analysis of major, minor, and rare earth elements. Major and some minor elements were measured using X-ray fluorescence (XRF) at Tarbiat Modares University, while rare earth and trace elements were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) at Novin Shimiyar Laboratory in Tehran.<br /><strong>Petrography</strong><br />Petrographic studies (Figure 4) reveal that the igneous rocks in the study area include andesite, andesiticbasalt, dacite, trachyte, quartz monzonite, and diorite porphyry. These rocks predominantly exhibit porphyritic textures. The main minerals are plagioclase (with or without quartz), orthoclase, hornblende, biotite, and augite. Secondary, opaque, and accessory minerals are present in most samples. Some primary minerals show disequilibrium textures, such as resorption and zoning. Secondary minerals include calcite, quartz, sericite, and clay minerals, occasionally accompanied by chlorite, epidote, orthoclase, and biotite. Opaque minerals mainly consist of pyrite, hematite, magnetite, and iron hydroxides.<br /><strong>Geochemistry</strong><br />The SiO₂ content in the studied rocks ranges from 53.66 to 66.34 wt.% (Table 1). In Harker diagrams, SiO₂ shows a negative correlation with P₂O₅, TiO₂, CaO, MgO, Fe₂O₃, and Al₂O₃, and a positive correlation with K₂O (Figure 5). These trends likely reflect magma differentiation and fractionation processes (Rollinson, 1993). The correlation between SiO₂ and Na₂O is weak, possibly due to weathering and hydrothermal alteration effects.<br />The rocks belong to alkaline and subalkaline magmatic series (Figure 7B). Alkaline samples are potassium-rich and fall within the shoshonitic series (Figure 8), while subalkaline samples are mainly high -K calc- alkaline. Overall, the samples are classified as high -potassium calc-alkaline and shoshonitic.<br />Geochemically, the rocks exhibit high Sr/Y (>40) and (La/Yb)<sub>N</sub> (>20) ratios, low Y (<18 ppm) and Yb (<1.9 ppm), and high Sr (>400 ppm), along with very low HFSE (Nb, Ta, Ti)—features characteristic of adakitic rocks (Castillo, 2006).<br /><strong>Discussion and Conclusions</strong><br />Shoshonitic, adakitic, high -K calc-alkaline, and calc-alkaline rocks are typically associated with convergent plate boundaries, including continental margins, island arcs, and collision/post-collision zones (Morrison, 1980; Torabi, 2011). Low-K adakites are commonly found in active subduction zones.<br />Tectonic discrimination diagrams confirm that the studied volcanic and subvolcanic rocks are related to convergent plate settings (Figure 9), specifically continental margins. Primitive mantle -normalized diagrams show enrichment in LILE relative to HFSE (Figure 10). Spider diagrams reveal positive anomalies in Cs, Pb, Th, U, and K, and negative anomalies in Rb, Nb, Ti, and P. Chondrite-normalized REE diagrams indicate enrichment in LREE over HREE, with weak negative Eu anomalies in all samples. These geochemical features are typical of high-K calc-alkaline, adakitic, and shoshonitic magmas formed in subduction-related continental margins (Wilson, 1989; Rollinson, 1993; Tatsumi and Eggins, 1995). The magmas are likely contaminated by crustal material (Wilson, 1989) and derived from an enriched mantle source (Figures 12A and B). The host rocks are garnet lherzolites enriched in phlogopite, with partial melting rates below 20 % (Figure 13). Although the geochemical signatures resemble those of magmas formed in continental margin subduction zones, considering the age, it is likely that these rocks formed in a post-collisional tectonic setting within a supra-subduction zone.<br /><strong>Acknowledgement</strong><br />We thank the reviewers for their valuable comments on an earlier draft of this paperمجموعة آذرین آساگی در شمالباختری زاهدان در پهنة زمیندرز سیستان جای دارد. قدیمیترین سنگهای رایج در این پهنه واحدهای سنگی مرتبط با توالی افیولیتی کرتاسه هستند. واحدهای سنگیِ رخسارة فلیشی نیز فراوانترین سنگهای آن بهشمار میروند. در جنوب مجموعة آذرین آساگی، سنگهای آذرین الیگوسن بهصورت درونی، نیمهدرونی، بیرونی و دایک در فلیشهای ائوسن نفوذ کردهاند. پیدایش سنگهای یادشده در کنترل گسلهای راستالغز بوده است. بر پایة سنگنگاری ، سنگهای آذرین بازالتآندزیتی، آندزیت، داسیت، تراکیت، کوارتز مونزونیت پورفیری و دیوریت پورفیری هستند. بافت این سنگها بیشتر پورفیری، میکرولیتیک پورفیری، جریانی، برشی و بهندرت گرانولار است. پلاژیوکلاز فراوانترین کانی سازندة این سنگهاست که همراه با یا بدون پتاسیم فلدسپار، بیوتیت، هورنبلند و کلینوپیروکسن یافت میشود. سنگهای بررسیشده، ویژگیهای کانیشناسی، سنگشناسی و زمینشیمیایی سنگهای کالکآلکالن پتاسیم بالا، شوشونیتی، آداکیتی و شبهآداکیتیِ جایگاههای همگرا را نشان میدهند. سنگهای آذرین بررسیشده مقدار Sr/Y و La/Yb کمابیش بالا و Y و Yb کمی دارند. این ویژگی آنها همانندِ سنگهای آداکیتی است. الگوی نمودار عنکبوتی و عنصرهای خاکی کمیاب سنگهای بررسیشده که بهترتیب به ترکیب گوشتة اولیه و کندریت بهنجار شدهاند نشاندهندة غنیشدگی LILE وLREE نسبت به HFSE و HREE است که با ویژگیهای هم آداکیتهای پتاسیمدار و هم شوشونیتهای پهنههای فرورانش حاشیة قاره و پس از برخورد قابل مقایسه هستند. ماگمای سنگهای بررسیشده از گوشتة غنیشده و دگرنهاد با ترکیب گارنت-لرزولیتی خاستگاه گرفته است. بیشتر سنگهای خاستگاه ویژگیهای زمینشیمیایی گوشته سنگکرهای دارند. https://ijp.ui.ac.ir/article_29880_f371874837c9b4200c24f27d8fb5a300.pdfدانشگاه اصفهانپترولوژی2228-521016320250923Kuroko-type Pb-Zn sulfide deposit at Chah Gaz region, Sanandaj-Sirjan Zone, Kerman Provinceکانسار سولفیدی سرب-روی نوع کوروکو در منطقة چاهگز، پهنة سنندج-سیرجان، استان کرمان1011202988310.22108/ijp.2025.146146.1368FAاعظمزاهدیاستادیار، گروه زمینشناسی، دانشکده علوم، مجتمع آموزش عالی گناباد، گناباد، ایرانمهردادکریمیاستادیار، گروه زمینشناسی، دانشگاه آزاد اسلامی واحد شیراز، شیراز، ایران0000-0002-5954-450XJournal Article20250728<strong>Introduction</strong>
The Chah Gaz Pb-Zn ore deposit is an inactive mineralization located approximately 70 km southwest of Shahr-e Babak in Kerman Province, Iran. It lies within the geologically significant Sanandaj-Sirjan zone, a region renowned for its massive sulfide deposits and thus the focus of extensive previous research (Mousivand et al., 2007; Badrzadeh, 2009; Mousivand, 2011). Numerous consulting engineering companies have studied the Chah Gaz deposit in the past, primarily with an exploratory focus (Sabzehei and Afrooz, 1989; Kavoshgaran Co., 1990; Tehran Padir Co., 1991; Minook Co., 1993; Sabzehei et al., 1993). The most recent scientific research by Mousivand (2011) indicated that, based on a brine pool model, the Chah Gaz deposit closely resembles the siliciclastic felsic type or Bathurst-type deposits, such as those in the Bathurst mining district in Canada and the Iberian Pyrite Belt in Spain and Portugal. The deposit also shows strong geological similarities to volcano-sedimentary volcanogenic Kuroko deposits (Soleimani Alh-Dadi, 2017). Kuroko-type volcanogenic massive sulfide (VMS) deposits are significant submarine hydrothermal mineralizations formed in back-arc basins, associated with bimodal volcanic activity. They are key sources of base metals such as copper and zinc, characterized by low- to medium-temperature hydrothermal fluids and bimodal magmatism. These genetic features are essential for identifying exploration targets and understanding metallogenic processes in extensional tectonic settings (Ohmoto, 1996).
The principal objectives of this study were to investigate the genesis of the deposit through an integrated approach, including geochemistry, petrography, trace element distribution, and fluid inclusion studies. Additionally, the Chah Gaz deposit is compared to global massive sulfide analogues based on key characteristics such as host rock sequences, mineral paragenesis, and tectono-magmatic setting.
<strong>Method</strong>
The concentrations of 23 trace elements and 14 rare earth elements were determined in the ore and metamorphic host rocks using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), conducted by ZarAzma Mineral Studies. Six ore samples were analyzed for gold content using Fire Assay and ICP methods. Eleven samples of ore and associated alteration rocks were examined via X-ray Diffraction (XRD) to identify major and minor minerals. Temperature-pressure measurements of fluid inclusions were carried out using a Linkam heating-cooling stage model THMSG600, TMS94, with a temperature range of -196 to +600 °C, equipped with a computer-linked simultaneous imaging system for video and slide recording.
<strong>Results and Discussion</strong>
<strong>Regional Geology</strong>
The Chah Gaz Pb-Zn ore deposit is situated southwest of Shahr-e Babak, within the southern Sanandaj-Sirjan structural zone. This area comprises metamorphosed rocks such as slate, schist, metarhyolite, metabasalt, and gneiss. The gneisses are likely metamorphosed Cambrian granites transformed into orthogneisses. These rocks are metamorphosed to the greenschist facies and display diverse structures including boudinage, foliation, and mylonitization. The studied host rocks are mainly weakly to moderately metamorphosed and include semi-gneiss, schist, mineralized mylonite, quartzite, metarhyolite, and metabasalt. The schists exhibit chloritic and sericitic alteration, with chlorite contributing to preferred foliation. Black slates contain mica and quartz minerals with relatively weak foliation. Rhyolites in the area have been tectonically transformed into mylonites, showing secondary mineralization such as sericite and goethite veinlets, identified by XRD due to their fine grain size.
<strong>Mineralization</strong>
Both hypogene and supergene mineralization are present. Hypogene minerals include sphalerite, galena, pyrite, and chalcopyrite, while supergene minerals comprise covellite, chalcocite, smithsonite, cerussite, malachite, and iron oxides, especially in the oxidized zone. The gangue minerals mainly consist of sericite, quartz, chlorite, feldspar, siderite, ankerite, dolomite, and barite. Pyrite is the most abundant primary sulfide in the hypogene zone, occurring as euhedral, vein, and cataclastic forms, indicating intense deformation and metamorphic processes. Secondary pyrite appears rregular and veinlet-like, with iron oxide inclusions reflecting asynchronous sulfide and oxide phases. Chalcopyrite forms after pyrite as fracture-fillings, while sphalerite is a secondary sulfide enriched in zinc. Covellite is the dominant supergene oxidation mineral, formed by the alteration of chalcopyrite along its fractures. Azurite and malachite are observed in oxidized zones alongside goethite and limonite.
<strong>Geochemistry </strong>
The highest concentrations of major elements in the host rocks are silica, aluminum, iron, potassium, and magnesium. The elevated Al₂O₃ and LOI values in the host rocks are attributed to clay alteration, resulting from the formation of minerals rich in volatile components such as illite, halloysite, montmorillonite, and other hydrated minerals, consistent with XRD results. The highest average concentrations of minor elements include zinc (5.2 wt%), lead (4.1 wt%), copper (1.9 wt%), sulfur (9.5 wt%), calcium (0.06 wt%), and barium (3.6 wt%), indicating the abundance of sulfide minerals such as galena, sphalerite, chalcopyrite, and barite. The anomalous arsenic content in most ore samples suggests the presence of gold in the area. Fire assay analysis of six sulfide ore samples revealed an average gold content of 8 ppm, exceeding the economic threshold. In contrast, the silver content in the sulfide ore is significantly below the economic grade, with an average concentration of 0.003574 wt%, compared to the economic grade of 0.01 wt%. The absence of silver in this deposit may serve as an important indicator for determining the ore deposit type (Santagulda and Hannington, 1996; Tajeddin et al., 2019).
<strong>Conclusion</strong>
The Chah Gaz deposit represents a typical Kuroko-type volcanogenic massive sulfide system formed in a back-arc basin setting, characterized by acidic volcanic host rocks, stratiform to semi-massive sulfide mineralization, and a paragenetic sequence dominated by chalcopyrite, sphalerite, galena, and abundant barite. It contains economically significant lead, zinc, and copper, with gold concentrations reaching up to 8 ppm. The mineralizing fluids exhibit moderate salinities of 10–15 wt% NaCl and are associated with intense sericitic alteration. Unlike previous classifications as Bathurst-type, Chah Gaz differs by its higher gold -to -silver ratio (~1.4), moderate fluid salinity (vs. >25 wt% NaCl in Bathurst), dominance of sulfide minerals over sulfosalts, and a distinctive abundance of barite. These geological, geochemical, and mineralogical features support the reclassification of Chah Gaz as a Kuroko-type massive sulfide deposit.کانسار چاهگز، یک کانسار سولفید تودهای آتشفشانزاد غنی از طلاست که در لبة خاوری پهنة دگرگونی سنندج-سیرجان در جنوبباختری ایران در60 کیلومتری جنوب شهربابک جای دارد. این کانسار در مجموعه سنگهای آتشفشانی- رسوبی دگرگونشده به سن ژوراسیک میانی جای دارد. سنگهای میزبان کانهزایی شامل توف ریولیتی دگرگونشده و متاریولیت هستند. کانهزایی بیشتر به شکل چینهسان در چندین افق در سنگ میزبان دگرگونی رخ داده است و کانیهای سولفیدی کانسار بیشتر شامل کالکوپیریت، پیریت، اسفالریت و گالن هستند. بیشترین فراوانی فلزات پایه مربوط به عنصرهای سرب (wt%1/4)، روی (wt%2/5)، مس (wt%9/1) است. بررسی میانبارهای سیال نشان میدهد کانهزایی در ارتباط با یک سیال دما متوسط (217 تا 290 درجة سانتیگراد) با شوری کم تا متوسط 10 تا 15 درصدوزنی معادل NaCl همراه بوده است. بررسیهای زمینشناسی، کانیشناسی، زمینشیمیایی، دگرسانی و خاستگاه سیالات در منطقة چاهگز نشان داد این کانسار در پی فعالیتهای آتشفشانی زیردریایی در یک پهنة کمانی بهصورت سولفید تودهای آتشفشانزاد نهشته شده است. مقایسه این کانسار با دیگر نهشتههای مشابه جهانی نشان داد بیشترین شباهت را به تیپ کانسارهای سولفید تودهای آتشفشانزاد طلادار نوع کوروکو دارد. بنابراین میتوان نتیجه گرفت چهبسا پتانسیل اکتشافی چشمگیری برای کانسارهای سولفید تودهای آتشفشانزاد در پهنة سنندج سیرجان وجود دارد. https://ijp.ui.ac.ir/article_29883_d460c90aa7a05e3cb38802921d0c0777.pdf