دانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730618220260823Investigation of Low-Sulfidation Precious Metal Mineralization in the Kahyaz Mineral Prospect (Northeast Isfahan, Iran): Insights from Geological, Mineralogical, Geochemical, and Fluid Inclusion Evidenceبررسی کانه زایی فلزهای گران بهای سولفیداسیون پایین در پتانسیل معدنی کهیاز (شمال شرق اصفهان) با تکیه بر شواهد زمین شناسی، کانه زایی، زمین شیمی و میان بارهای سیال1324861310.22067/econg.2026.1178FAمهینرستمیدانشجوی دکتری، گروه زمینشناسی، دانشکده علوم، دانشگاه بوعلی سینا، همدان، ایران0009-0000-1032-615Xمحمدمعانی جواستاد، گروه زمینشناسی، دانشکده علوم، دانشگاه بوعلی سینا، همدان، ایران0000-0001-7843-419Xعلیشعلهدکتری، شرکت مشاوره‌ای اس.آر.کی، آلماتی، قزاقستانعلی اصغرسپاهی گرواستاد، گروه زمینشناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران؛ گروه زمینشناسی، دانشکده علوم، دانشگاه بوعلی سینا، همدان، ایران0000-0002-3075-8416رضاعلی پوراستادیار، گروه زمینشناسی، دانشکده علوم، دانشگاه بوعلی سینا، همدان، ایرانJournal Article20260605The Kahyaz prospect is located approximately 45 km southeast of Ardestan, Esfahan Province, within the central part of the Saveh-Naein-Jiroft magmatic belt. Gold-bearing siliceous veins are hosted by Oligocene andesitic–trachyandesitic volcanic rocks. The main mineralized vein is approximately 2 km long and has a width of 2–5 m, with gold grades ranging from 0.1 to 2.1 g/t. Electrum is the main gold-bearing mineral, whereas base metal sulfides, including pyrite, chalcopyrite, chalcocite, and covellite, occur as minor minerals. Quartz, calcite, and adularia are the dominant gangue minerals. Colloform, crustiform, vein–veinlet, open-space filling, and bladed textures are characteristic features of the Kahyaz. Geochemical data indicate a positive correlation of Au with Ag and Sb, and negative correlations between Au and As, S, and base metals. Hydrothermal alteration is charachterized by silicic, intermediate argillic, and propylitic alteration zones. Fluid inclusion studies indicate that ore-forming fluids were characterized by moderate to high homogenization temperatures (169–278°C) and low to moderate salinities (2.73–10.29 wt% NaCl eq.). These fluids were affected by mixing and boiling processes. The geological, mineralogical, geochemical, and fluid inclusion characteristics of the Kahyaz prospect are consistent with a low-sulfidation epithermal system.IntroductionThe Kahyaz prospect is located 16 km northwest of Neystanak Village, and 45 km southeast of Ardestan City, Esfahan Province, central Iran. The Kahyaz epithermal gold (Au) prospect was discovered in 2018 by Pars-Olang Company. The exploration program, which included geological mapping and diamond drilling (14 drill holes), was recently conducted by Kowsar Mining and Industries Development Investment Company, resulting in the identification of 300,000 tonnes of mineral resources with an average gold grade of 1.1 ppm Au. Unlike the numerous studies conducted on porphyry and epithermal deposits in the northwestern and southeastern parts of the belt, the central segment of the Saveh-Naein-Jiroft magmatic belt has received relatively little attention. The discovery of new mineralized zones, including the area investigated in this study, in the central Saveh-Naein-Jiroft magmatic belt may indicate the presence of significant mineralization that has so far remained unexplored. Therefore, the geological, mineralization, geochemical, hydrothermal alteration, and fluid inclusion data presented in this study provide a basis for developing an exploration model to identify additional mineral occurrences within the central Saveh–Naein–Jiroft magmatic belt. Materials and methodsPetrographic analyses were performed on approximately 100 thin sections was carried out at Bu-Ali Sina University (Hamedan, Iran) using a ZIESS Axioplan2 transmitted- and reflected light polarizing microscope. Textural imaging of five selected samples was performed using an FEI QEMSCAN® Quanta 650F instrument on polished carbon-coated thin sections at the Faculty of Earth Sciences, University of Geneva, Switzerland. Fifty drill-core samples were analyzed for gold using the fire assay method at Zarrin Felez Kavoshgaran Co. (Najafabad, Iran) and Zarraazma Co. (Tehran, Iran). To determine correlation coefficients, 35 samples were analyzed using ICP-OES at Zarazma Co. For fluid inclusion studies, seven quartz samples associated with gold mineralization were selected from drill cores and surface outcrops. After preparing double-polished sections with a thickness of 300 μm, petrographic and microthermometric analyses were performed at Tarbiat Modares University. Microthermometric measurements were conducted using a Linkam THMS 600 heating–cooling stage equipped with a TP94 temperature controller and an LNP cooling system, mounted on a Zeiss microscope. The analytical system operated over a temperature range of −190 to +600 °C.Results and DiscussionThe Kahyaz mineral prospect, located in northeast Isfahan, Iran, hosts a low-sulfidation epithermal precious-metal system associated with Eocene volcanic and subvolcanic rocks. The host succession consists predominantly of andesite–trachyandesite and rhyolite, which are overlain by Oligocene basaltic andesite and rhyodacite–dacite units. Mineralization is principally confined to a quartz–calcite vein extending for approximately 2 km with a thickness ranging from 2 to 5 m. Quartz is the dominant gangue mineral and the principal host of electrum, whereas calcite and adularia occur as subordinate gangue minerals. Quartz exhibits a wide range of open-space filling textures, including crustiform, comb, colloform, bladed, plumose, cockade, brecciated, and vein-veinlet textures.The hypogene ore assemblage comprises electrum, acanthite, pyrite, chalcopyrite, and manganite, whereas chalcocite, covellite, and goethite constitute the supergene mineral assemblage. Hydrothermal alteration includes propylitic, intermediate argillic, and silicic–carbonate alterations. Based on mineral assemblages and cross-cutting textural relationships, the hydrothermal evolution of the Kahyaz prospect is divided into three stages: (1) pre-ore alteration, (2) ore stage, and (3) post-ore supergene alteration.During the pre-ore stage, propylitic and intermediate argillic alteration developed through interaction of near-neutral hydrothermal fluids with the andesitic–trachyandesitic host rocks, producing alteration zonation from argillic adjacent to the veins to propylitic outward. Illite, illite/smectite, montmorillonite, chlorite, epidote, and calcite constitute the principal alteration mineral assemblages. The ore stage was initiated by precipitation of quartz–calcite veins, followed by hydrothermal boiling.Boiling promoted CO₂ degassing, increased fluid pH, and induced supersaturation of silica and potassium, resulting in the precipitation of quartz and adularia. Simultaneously, the loss of dissolved H₂S destabilized Au–Ag bisulfide complexes, triggering electrum precipitation. Bladed calcite, quartz pseudomorphs after calcite, comb and crustiform textures, together with open-space filling fabrics, provide strong evidence for boiling during mineralization.The post-ore stage is characterized by supergene oxidation and enrichment, leading to the formation of chalcocite, covellite, goethite, jarosite, gypsum, and zeolite-group minerals. Fluid inclusion studies of vein quartz indicate homogenization temperatures of 169–278 °C and salinities of 2.73–10.29 wt.% NaCl equivalent, suggesting mineralization from low- to moderate-salinity hydrothermal fluids. The coexistence of fluid mixing and boiling is interpreted as the principal mechanism responsible for gold deposition. Geological setting, alteration mineralogy, quartz–adularia gangue assemblages, characteristic open-space filling textures, fluid inclusion data, and the scarcity of base-metal sulfides collectively indicate that the Kahyaz prospect represents a low-sulfidation precious-metal system.پتانسیل معدنی کهیاز در 45 کیلومتری جنوب‌شرق شهرستان اردستان در استان اصفهان، در بخش مرکزی کمربند ماگمایی ساوه– نایین– جیرفت قرار دارد. رگه‌های سیلیسی حاوی طلا در واحدهای آتشفشانی آندزیتی- تراکی‌آندزیتی الیگوسن قرار گرفته‌اند. رگه اصلی کانه‌زایی دارای حدود 2 کیلومتر طول و عرض 2 تا 5 متر است. عیار طلا از 1/0 گرم بر تن تا 1/2 گرم بر تن متغیر است. الکتروم، کانی طلادار اصلی است. کانی‌های سولفیدی از جمله پیریت، کالکوپیریت، کالکوسیت، کوولیت به صورت فرعی تشکیل‌شده‌اند. کوارتز، کلسیت و آدولاریا مهم‌ترین کانی‌های باطله هستند. بافت‌های رگه- رگچه‌ای، گل‌کلمی، قشری، پرکننده فضای خالی و تیغه‌ای از جمله بافت‌های شاخص هستند. داده‌های زمین‌شیمیایی نشان‌دهنده همبستگی مثبت طلا با عناصر نقره و آنتیموان است و همبستگی منفی آن با آرسنیک، گوگرد و فلزهای پایه است. دگرسانی گرمابی شامل پروپیلیتیک، آرژیلیک متوسط و سیلیسی است. بررسی میان‌بارهای سیال در کوارتز مربوط به مرحله اول و اصلی کانه زایی نشان می‌دهد که سیالات کانه‌دار دارای دمای متوسط تا بالا (169 تا 278 درجه سانتی‌گراد) و شوری پایین تا متوسط (73/2 تا 29/10 درصد وزنی معادل نمک طعام) هستند که تحت‌تأثیر فرایندهای اختلاط و جوشش قرار گرفته‌اند. کانه‌زایی در کهیاز با کانه‌زایی در سامانه‌های سولفیداسیون پایین مطابقت دارد.https://econg.um.ac.ir/article_48613_0a4096345f092c37b8a29da4d03133f4.pdfدانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730618220260823Mineral Chemistry and Crystal Size Distribution of Plagioclases in the Monzonitic Intrusive Body of the Seridune Porphyry Copper Deposit, Iran: Emphasis on Processes Controlling Magma Evolutionشیمی کانی و توزیع اندازه بلور پلاژیوکلازها در توده نفوذی مونزونیتی کانسار مس پورفیری سریدون، ایران: با تأکید بر فرایندهای کنترل کننده تکامل ماگما33594853610.22067/econg.2026.1165FAمهدیهبامروتدانشجوی دکتری، گروه زمینشناسی، دانشکده علوم، دانشگاه شهید باهنر کرمان، کرمان، ایران0009-0001-3917-3334سارادرگاهیدانشیار، گروه زمینشناسی، دانشکده علوم، دانشگاه شهید باهنر کرمان، کرمان، ایران0000-0002-6882-2276محسنآرویناستاد، گروه زمینشناسی، دانشکده علوم، دانشگاه شهید باهنر کرمان، کرمان، ایران0000-0003-4928-1176علیرضاشاکراستادیار، گروه زمینشناسی، دانشکده علوم، دانشگاه شهید باهنر کرمان، کرمان، ایران0009-0004-4775-9011جیمی جیویلکینسوناستاد، گروه علوم‌زمین و مهندسی، دانشکده مهندسی، دانشگاه امپریال کالج لندن، لندن، بریتانیا0000-0002-7706-6003ادگار ایکورتس-کالدرونپژوهشگر، مرکز تصویربرداری و تحلیل، موزه تاریخ طبیعی، لندن، بریتانیا0000-0002-5690-6907مجیدامین زادهرئیس بخش زمینشناسی و زهکشی، مجتمع مس سرچشمه، شرکت صنایع ملی مس ایران0009-0006-7857-9755Journal Article20251121The Seridune porphyry copper deposit is located in the central part of the Kerman porphyry copper belt, Iran, three kilometers northeast of the Sarcheshmeh copper mine. This research focuses on reconstructing magmatic crystallization processes through a qualitative and quantitative study of plagioclase crystals in the monzonitic intrusive body of the Seridune porphyry copper deposit using petrology, mineral chemistry, and crystal size distribution studies. This unit rock, which ranges in composition from monzonite to quartz monzonite, comprises plagioclase, quartz, alkali feldspar, biotite, amphibole, as well as accessory minerals such as magnetite, apatite and zircon. The composition of the plagioclase crystals studied varies from labradorite to albite (An3.0-55.0Ab44.1-94.5Or0.0-17.7, n= 89). Based on crystal size distribution (CSD) studies, the semi-logarithmic patterns of the the studied plagioclase crystals indicate multi-stage crystallization of magma at varying depths. Also, the presence of sieve texture, oscillatory zoning, and CSD data indicate decompression and injection of mafic pulses in a dynamic system. Assuming a constant growth rate and nucleation density (n0), the nucleation rate of plagioclase crystals was determined to be between 64Î10-11mm-3/s-1 and 66Î10-11 mm-3/s-1. Also, based on the 3D crystal size distribution data and using a growth rate (G=10-10), the residence time of plagioclase crystals was calculated to be between 56 and 63 years. The calculated residence time, along with excess aluminum in the plagioclase crystals are consistent with the emplacement of the magma at shallow crustal levels and its high potential for the exsolution of fluids; although the monzonite body is not considered to be the responsible phase for mineralization in the Seridune porphyry copper deposit.IntroductionThe Urumieh–Dokhtar Magmatic Assemblage (UDMA) in the Kerman province contains numerous porphyry copper deposits, known collectively as the Kerman porphyry copper belt (KPCB; Fig. 1A) (Ghorbani, 2013). This belt, the primary source of copper ore in Iran, is primarily composed of folded and faulted early Tertiary volcano-sedimentary rocks (Aghazadeh et al., 2015(. The Seridune porphyry copper deposit (SPCD) is located in the central KPCB within the UDMA (Fig. 1A). It is hosted by Eocene volcanic rocks cut by hypabyssal felsic intrusions and all of the rock units have undergone variably intense hydrothermal alteration (Barzgar, 2007). Phyllic, argillic and advanced argillic alterations are widely exposed at the surface, whereas potassic alteration is concentrated at depth and is only accessible through drill core samples.Porphyry copper deposits form under the influence of dynamic processes governing a magma reservoir within the crust. These processes influence the magma's potential for metal enrichment and fluid dynamics (Park et al., 2021). Consequently, examining the physical and chemical evolution of minerals in igneous rocks is crucial for understanding the processes and dynamics of magmatic systems (Blundy and Cashman, 2008; Ellis et al., 2023) that lead to the formation of these deposits. Magmatic processes such as fractional melting, partial melting, fractional crystallization, and magma mixing (Higgins et al., 2015), which directly affect crystal nucleation and growth, are important petrological processes (Deb and Bhattacharyya, 2018). These processes do not change the bulk-rock chemical composition. Then, they cannot be constrained through chemical and isotopic studies of rocks (Higgins and Roberge, 2007). Instead, these processes have to be investigated through textural studies of rocks and crystal-scale mineral chemistry. Crystal size distribution (CSD) is a quantitative petrographic method which can provide important insights into the conditions within magma reservoirs or crystal mushes, including the rates of nucleation and growth, fractionation, coarsening, and mixing processes (Ngonge et al., 2013; Klein et al., 2017). This research aims to constrain the magmatic processes that governed the evolution of the monzonitic intrusive body in the Seridune porphyry copper deposit. This aim is achieved through the integration of petrographic observations with the determination of three-dimensional crystal shapes, Crystal Size Distribution analysis, and mineral chemistry of plagioclase crystals. This implications of the quantitative textural analyses on the studied samples are that they enable a more comprehensive understanding of the kinetic evolutionary history and the different processes—such as magma mixing and textural coarsening—that contributed to the formation of this intrusive body.Material and methodsTo identify the rock units and structures in the Seridune area, extensive field studies were conducted. For the present study, samples from the monzonite body of the Seridune porphyry copper deposit (Fig. 1B) exhibiting the least alteration were selected for preparation into polished thin sections. These sections were examined using a polarizing microscope to identify plagioclase crystals suitable for chemical microanalysis. Plagioclase compositions were determined using a JEOL 8530 F electron probe microanalyzer (EPMA) equipped with five tunable Wavelength Dispersive Spectrometers (WDS) hosted at the Imaging and Analysis Centre in the Natural History Museum, London. Operating conditions were 15 kV acceleration voltage, 20 nA beam current and a defocused beam of 10 μm diameter. On-peak counting times were set to 20 - 30 s for all elements and the background was acquired before and after the peak position for 10 - 15 s. Sodium, and potassium were analyzed first to reduce alkali migration due to prolonged electron dose. Standards were albite for Si kα and Na kα, corundum for Al kα, wollastonite for Ca kα, anorthoclase for K kα, fayalite for Fe kα, forsterite for Mg kα, celestine for Sr kα, barite for Ba kα, rutile for Ti kα and Mn-titanate for Mn kα. An internal secondary standard, plagioclase from the Isle of Rhum, was measured along with the unknowns to test the standardization and assess reproducibility. Oxygen was calculated by cation stoichiometry and included in the matrix correction. (Moy et al., 2023). Matrix correction was performed using the Phi-Rho-Z method, with mass absorption coefficients obtained from the FFAST (NIST version 2.1; Chantler et al., 2005). According to Armstrong (1998), the specific Phi-Rho-Z algorithm employed was the Armstrong/Brown/Scott-Love model.Quantitative measurements of crystal sizes were conducted on two representative, least-altered samples using a polarizing microscope. Digital images were captured, and image processing was performed using Adobe Photoshop (Adobe Creative Cloud version) to isolate plagioclase crystals in binary images. The long axis, short axis, area, and centroid of the crystals were measured using ImageJ software. The ShapeCalc spreadsheet program was then employed to convert two-dimensional data to three-dimensional data, allowing for the calculation of crystal dimensions based on the ratios of the short (S), intermediate (I), and long (L) axes. Finally, Crystal Size Distribution (CSD) plots were generated for each sample using CSD Correction 1.40 software.The residence time of the crystals for each sample was determined using the slopes from the CSD plots. This calculation was performed using the formula Tr = (-1/GÎm) / 31536000, where Tr is the residence time in years, m is the slope of the crystal population trend line, and G refers to the crystal growth rate in mm/s. The selected G value was based on the suggested value for intrusive magma (G = 10-10 mm/s, Cashman, 1993) and 31536000 is the conversion factor from seconds to years.ResultsSample petrographyThe Seridune Monzonite exhibits a porphyritic texture characterized by phenocrysts of plagioclase, alkali feldspar, quartz and biotite set in a microcrystalline groundmass. Secondary minerals resulting from hydrothermal alteration include biotite, alkali feldspar, chlorite, sericite and clay minerals.Plagioclase is the most abundant mineral in the Seridune Monzonite. It occurs both as subhedral to euhedral phenocrysts and microcrystals in the groundmass. Phenocrysts display polysynthetic and Carlsbad-albite twinning, along with oscillatory zoning. In some occurrences, these phenocrysts have even grown intergrown in a cruciform shape. It has commonly been replaced by sericite (Fig. 2B). This alteration is focused on the rim of the phenocrysts and the central parts of plagioclase microlites within the groundmass. Furthermore, these phenocrysts are occasionally crosscut by late-stage veinlets containing quartz, opaque minerals, and anhydrite. This crosscutting phenomenon is definitive evidence that the fluids bearing quartz, opaque minerals, and anhydrite are younger than the time of plagioclase crystallization, and it emphasizes the secondary permeability of the system (Sillitoe, 2000; Sillitoe, 2010).Plagioclase compositionThe results of 7 plagioclase EPMA analyses from two samples, together with the calculated (Wt.%) of anorthite, albite and orthoclase are presented in Table 1. The studied plagioclase crystals have a compositional range from labradorite to albite (An3.0-55.0Ab44.1-94.5Or0.0-17.7) (Fig. 3A). Some of these crystals show oscillatory zoning.Crystal size/shape analysisThe crystals shapes were determined by applying Zingg's diagram (Zingg, 1935). This classification scheme categorizes crystals into four categories: tabular, bladed, prolate (acicular) and spherical (equant), based on the ratios of their short, intermediate, and long axes. In the Seridune monzonite samples, plagioclase crystals are predominantly tabular and bladed in shape (Fig. 7B).DiscussionSome of these crystals exhibit oscillatory zoning, indicating that fractional crystallization and magma mixing play significant roles in influencing the evolving magmatic composition within the magma chamber (Kumar and Ashok, 2024; Ou et al., 2024). The plagioclase crystals are tabular and bladed in shape. This morphological variation is likely due to the thermodynamic conditions governing the crystallization process. The deformation of plagioclase crystals in the studied samples resulted from changes in undercooling, chemical potential gradients, and material diffusion. The non-liner trend observed in in the CSD plots for plagioclase crystals suggests multi-stage cooling process for the crystals (Fig. 8). The initial stage is marked by plagioclase phenocrysts with few nuclei, whereas in the following stage, they develop as microcrystalline formed under a high nucleation rate. The nonlinear CSD trends may show the multi-stage crystallization process of magma, magma mixing, and Ostwald Ripening (textural coarsening) processes, as well as modifications in the crystallization course due to changing environments and magma chambers at different depths. The observation of a porphyritic texture with a microlithic groundmass in the Seridune Monzonite, along with features such as oscillatory zoning and sieve texture, indicates multi-stage crystallization at varying depths. The process textural coarsening take place only when a crystal is kept at a temperature near to its liquidus for a prolonged period. Under such conditions, the nucleation rate approaches, while crystals larger than the critical size exhibit a high growth rate. According to Yang (2012), this does not necessarily imply that the temperature remains constant. The nucleation rate and residence time determined for the studied monzonitic intrusive body indicate a high nucleation rate and short residence time for the samples. Based on the Ca+Na+K versus Si+Al diagram, plagioclase crystals in the monzonitic body show a trend similar to those observed in the mineralizing magmatic systems and hydrous porphyries (Williamson et al., 2016). This trend, coupled with the calculated Al* values, reflects magmatic conditions favorable for porphyry-style mineralization; Although, despite these favorable indicators, this body itself is not considered the responsible phase for mineralization in the Seridune deposit. AcknowledgementThe authors gratefully acknowledge the financial and logistical support provided by the Vice Chancellor for Research at Shahid Bahonar University of Kerman and National Iranian Copper Industries Company (NICICO). Sincere thanks are also extended to the editor and anonymous reviewers of the Journal of Economic Geology for their constructive comments and valuable suggestions, which helped improve this manuscript.کانسار مس پورفیری سریدون، در بخش میانی کمربند مس پورفیری کرمان و سه کیلومتری شمال‌شرقی معدن مس سرچشمه واقع‌شده است. این پژوهش، با توجه به نقش پلاژیوکلاز در بازسازی فرایندهای تبلور ماگما، بررسی کیفی و کمی بلورهای پلاژیوکلاز توده مونزونیتی کانسار مس سریدون با بهره‌گیری از بررسی‌های سنگ‌شناسی، شیمی‌کانی و پراکندگی اندازه متمرکز است. این واحد سنگی که از نظر ترکیب از مونزونیت تا کوارتز مونزونیت متغیر است، شامل کانی‌های اصلی پلاژیوکلاز، کوارتز، فلدسپار پتاسیم، بیوتیت،آمفیبول و همچنین کانی‌های فرعی کدر اغلب از نوع مگنتیت، آپاتیت و زیرکن است. ترکیب بلورهای پلاژیوکلاز مورد بررسی از لابرادوریت تا آلبیت (An3.0-55.0Ab44.1-94.5Or0.0-17.7, n= 80) متغیر است. بر اساس بررسی‌های پراکندگی اندازه بلور، الگوهای نیمه لگاریتمی بلورهای پلاژیوکلاز مورد بررسی نشان‌دهنده تبلور چند مرحله‌ای ماگما در اعماق مختلف است. همچنین، وجود بافت غربالی، منطقه‌بندی نوسانی و نتایج پراکندگی اندازه بلور نشان‌دهنده کاهش فشار و تزریق پالس‌های مافیک در یک سامانه پویاست. با فرض نرخ رشد ثابت و چگالی هسته (n0)، نرخ هسته‌بندی بلورهای پلاژیوکلاز بین 1-/s3-mm 11- 10 Î 66 تا 1-/s3-mm 10-11 Î64 تعیین‌شد. همچنین، بر اساس داده‌های توزیع اندازه بلورهای سه‌بعدی و با استفاده از نرخ رشد 10- 10، زمان اقامت بلورهای پلاژیوکلازها بین 56 تا 63 سال برآورد شد. زمان اقامت محاسبه‌شده و آلومینیم اضافی بلورهای پلاژیوکلاز مورد بررسی با جای‌گیری ماگما در سطوح کم‌عمق‌تر و پتانسیل بالای آن برای آزادسازی سیالات همخوانی دارد؛ هرچند توده مونزونیتی فاز مسئول کانه‌زایی در کانسار مس پورفیری سریدون محسوب نمی‌شود.https://econg.um.ac.ir/article_48536_44b4034e6b33988e2b4539a0783215b9.pdfدانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730618220260823Origin and Genesis of the Color of Variscite in the Koushk Zn-Pb Deposit, Yazd Province: Evidence from Mineralogy, Geochemistry, and Fluid Inclusionsپیدایش و منشأ رنگ کانی واریسکیت در کانسار روی و سرب کوشک (استان یزد): شواهدی از کانی شناسی، زمین شیمی و میان بارهای سیال611034853510.22067/econg.2026.1173FAکیامرثحسینیدانشجوی دکتری، دانشکده منابع معدنی و آب‌های زیرزمینی، دانشگاه شهید بهشتی، تهران ایران0000-0002-2796-8340محمدیزدیاستاد، گروه زمینشناسی، گروه منابع معدنی و آب‌های زیرزمینی، دانشگاه شهید بهشتی، تهران، ایران0000-0002-7948-0478حسینعزیزیاستاد، گروه معدن، دانشکده مهندسی، دانشگاه کردستان، سنندج، ایران0000-0001-5686-4340Journal Article20260512The Koushk Zn-Pb deposit in Central Iran is considered the largest mineral potential for variscite mineralization. Macroscopic and microscopic observations indicated minor variscite mineralization occurring in veinlet-vein form and as disseminations, associated with massive and layered ore zones, as well as extensive mineralization related to zinc- and lead-barren marginal shales, dioritic sills, and late carbonate ± quartz veinlets. Textural features and chemical characteristics indicated that variscite formed through multi-stage phosphatization of Al-rich shales with minor silica. XRD data reveal variscite and strengite as the dominant phases. Other phosphates such as phosphosiderite, metavariscite, and crandallite were also identified, occurring as intergrowth mixtures with variscite. Color variations in the Koushk variscites are attributed to intergrowth with other phosphates, sulfates, or silicates; electronic transitions; crystal field transitions of chromophore elements; structural defects; and the arrangement of water molecules within the variscite structure. The highest intensity Raman peak observed in the spiderweb variscites occurs at approximately 1033 cm⁻¹, whereas in the simple green variscites and soapy variscites (pale green-blue to white), the strongest peak appears at around 1022 cm⁻¹. Three additional peaks with lower intensities are also present, all corresponding to the symmetric stretching vibrations of the phosphate (PO₄) group in minerals of the variscite–metavariscite group. The REE+Y patterns, LREE enrichment, and negative Ce anomaly indicate low-temperature hydrothermal fluids with a composition approaching seawater. Microthermometric studies of fluid inclusions reveal that fluid mixing and temperature decrease played a significant role in variscite mineralization, with formation temperatures ranging from 110 to 340 °C.IntroductionThe Kushk zinc-lead deposit is the most important variscite mineral mass in Central Iran. Variscite a relatively common mineral that forms as a result of phosphate-bearing surface solutions reacting with aluminum-rich rocks (Calas et al., 2005). First described in 1837 from a source close to Variscia, the former name of the Vogtland region in northeastern Germany, its chemical formula was determined in 1896 (Willing et al., 2008). Variscite was used in Neolithic jewelry and is found in many archaeological sites (e.g., Ervedosa, Portugal; Pannecé, France; and Sardinia, Italy; see Calas et al., 2005; Querré et al., 2019; Willing et al., 2008). Variscite is a member of the hydrous aluminum phosphate group, Al(PO4)·2H2O, while strengite is part of the iron phosphate group, Fe3+(PO4)·2H2O. Both are orthorhombic phosphate members of the variscite mineral group, while mansfieldite, scorodite, and yanomamite are the arsenate isostructural members of this group. The general chemical formula of variscite group minerals is A(XO4)·2H2O, where A = Al, Fe3+, In and X = P, As.Regional GeologyThe 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 in Central Iran (Fig. 1). Two major stratigraphic sequences have been recognized in the area (Fig. 2): (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 are hosting 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 MethodsIn this study, 35 variscite samples were collected from ore-bearing rocks across different geological sections. Petrographic and mineralogical investigations were carried out on 23 thin and polished-thin sections using transmitted and reflected light microscopy at Shahid Beheshti University, Iran. In addition, 7 samples representing different generations of variscite were analyzed by using scanning electron microscopy (SEM) at Aria Electron Optics Company, Iran. To complement the mineralogical data, one variscite sample was analyzed via XRD at Kansaran Binalud Company, and three variscite samples of varying colors were examined using Raman spectroscopy at Shahid Beheshti University. For geochemical studies, a deep-green variscite sample was analyzed at 10 points using a CAMECA SXFive X‑ray Probe Microanalysis (XPMA) (France) at Kansaran Binaloud Company, Iran. Furthermore, 6 samples were analyzed by ICP-MS using a PerkinElmer NexION 300 instrument at Zarazma Laboratory, Iran. 10 samples were analyzed by XRF at Tarbiat Modares University of Iran. Petrographic examination and microthermometric studies of fluid inclusions were performed on 2 quartz and calcite samples associated with variscite mineralization in the marginal zone, using a Linkam THMCG 600 heating–freezing stage at the Microthermometry Laboratory of Tarbiat Modares University, Iran. ResultsMacroscopic and microscopic observations indicate that variscite mineralization occurring as veins, veinlets, and disseminated form associated with the massive and stratiform sulfide ore zone, as well as extensive mineralization related to the marginal zone and microdioritic sills. These variscites occur intergrown with strengite and minor amounts of other minerals belonging to the variscite and metavariscite groups. The color variations in these variscites are attributed to intergrowths with other phosphates, sulfates, or silicates, electronic transitions, crystal field transitions in chromophore elements, structural defects, and the arrangement of water molecules within the variscite structure. These factors may lead to significant fluctuations in both the green hues and the apparently low Cr³⁺ content. In the variscites from the Koushk Zn–Pb deposit, the Cr³⁺ content is low compared to that of similar worldwide variscites. However, our samples containing higher amounts of Cr³⁺ exhibit a more intense and deeper green color. The highest Raman spectral peak intensity show that spiderweb variscites occurs at approximately 1033 cm⁻¹, whereas in the simple green variscites and the soapy variscites (pale greenish-blue to white), the most intense peak occurs at around 1022 cm⁻¹. In addition, three lower-intensity peaks are present, all of which are attributed to the symmetric stretching vibrations of the phosphate (PO4) group in minerals of the variscite and meta-variscite groups. The Raman spectra of variscite from the Koushk Zn–Pb deposit and Tajikistan show a remarkable overlap. The ΣREE values in the variscite ore are negligible. The REE+Y pattern, characterized by LREE enrichment and a negative Ce anomaly which is similar to that of seawater. Such evidence may indicate the involvement of low-temperature hydrothermal fluids, which is further supported by micro-thermometric studies of fluid inclusions, confirming the corresponding temperature range. DiscussionIn the Koushk deposit, aluminum was derived from the weathering of the host rock, whereas phosphate originated from the leaching of ancient sedimentary phosphorites or phosphorites contemporaneous with the carbonate rocks of the Soltanieh Formation, Ediacaran deposits, or evaporitic and phosphatic crustal units in Central Iran by magmatic and hydrothermal fluids related to the intrusion of granitoid bodies (Hosseini and Rajabzadeh, 2022). The interaction of aluminum-rich and phosphate-bearing hydrothermal fluids resulted in variscite mineralization. In the Koushk Zn–Pb deposit, variscite commonly displays a wide range of green hues, including bluish green, olive green, moss green, and pale bluish white. These color variations are not dependent on depth. The color variation in variscite is, in part, attributed to intergrowth with phosphates, silicates, sulfates, and oxides. SEM–BSE, EDS, and XRD studies confirm this interpretation. On the other hand, color variations in minerals are associated with various mechanisms, such as electronic transitions (Nassau, 1978), crystal field transitions in chromophores (Burns, 1993) such as Cr, Mn, Fe, Co, Ni, Cu, and V, charge transfer between elements (Mattson and Rossman, 1987; Bill and Calas, 1978), as well as color centers caused by structural defects in the crystal lattice and variations in the concentration of Cr³⁺ and V⁴⁺ (Krambrock et al., 2007). Therefore, the green color of variscite is related not only to the presence of combined structural impurities but also to crystal defects and the arrangement of water molecules within the variscite structure, which has led to the formation of different variscite polymorphs. Furthermore, color variations are attributed to metasomatic replacement processes and the development of zoning within the primary microcrystalline and porous minerals, driven by successive pulses of late-stage fluids (Díaz-Acha et al., 2022). Consequently, the color changes gradually along the veins and nodules. Some variscite samples from Koushk area exhibit a progressive color transition from a gray phosphosiderite core to a pale green unit (consisting of phosphosiderite-dominated mixtures with variscite) and, ultimately, to dark green margins dominated by variscite. The diversity in microscopic textures and ore geochemistry points to multistage mineralization and reflects dissolution–reprecipitation processes controlled by the prevailing physicochemical conditions during formation.AcknowledgementsThe authors appreciate Shahid Beheshti University Research Council that supported this work. The Director General and personal of the Koushk Mine Company are acknowledged for their assistance in the field works.کانسار کوشک در مرکز ایران به عنوان یکی از بزرگ‌ترین پتانسیل‌های معدنی کانی واریسکیت به شمار می‌رود. مشاهدات ماکروسکوپی و میکروسکوپی بیانگر کانی‌زایی ناچیز واریسکیت به صورت رگه- رگچه‌ای، انتشاری، مرتبط با زون کانسنگ توده‌ای و لایه‌ای و کانی‌زایی گسترده مرتبط با شیل‌های بدون کانی‌زایی روی و سرب در زون حاشیه‌ای، سیل‌های دیوریتی و همراه رگچه‌های تأخیری کربناتی ± کوارتز است. بافت‌ها و ویژگی‌های شیمیایی بیانگر تشکیل واریسکیت از طریق فسفاته‌شدن چند مرحله‌ای شیل‌های غنی از آلومینیم با سیلیس جزئی است. بررسی های پراش پرتو ایکس بیانگر وجود فازهای غالب واریسکیت و استرنگیت هستند. فسفات‌های دیگری مانند فسفوسیدریت، متاواریسکیت و کراندالیت نیز شناسایی شدند که به صورت درهم‌رشدی با واریسکیت دیده می‌شود. تغییرات رنگ در واریسکیت‌های کوشک، ناشی از درهم‌رشدی با دیگر فسفات‌ها، سولفات‌ها، یا سیلیکات‌ها،گذارهای الکترونی، گذارهای میدان بلوری در عناصر رنگ‌زا، نقص ساختار بلوری و نحوه آرایش ملکول‌های آب در ساختار واریسکیت است. بیشترین شدت پیک طیف‌های رامان مشاهده‌شده در واریسکیت‌های تار عنکبوتی در حدود ۱۰33 سانتی‌متر معکوس (cm⁻¹) است. در واریسکیت‌های سبز ساده و واریسکیت‌های صابونی (سبز- آبی کم‌رنگ تا سفید) بیشترین شدت پیک در حدود ۱۰22 سانتی‌متر معکوس (cm⁻¹) است و سه پیک با شدت کمتر وجود دارد که همگی به دلیل ارتعاش‌های کششی متقارن گروه فسفات (PO4)، در مواد معدنی گروه واریسکیت و متاواریسکیت هستند. الگوی REE+Y، غنی‌شدگی LREES و ناهنجاریی منفی Ce، روند دمای پایین سیالات گرمابی تا شبیه آب دریا را پوشش می‌دهند. بررسی ریزدماسنجی میان‌بارهای سیال بیانگر نقش اختلاط سیالات و کاهش دما و بازه دمایی 110 تا 340 درجه سانتی‌گراد در کانی‌زایی واریسکیت است.https://econg.um.ac.ir/article_48535_1e0f51c74e9604461da8103a7fadd754.pdfدانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730618220260823Geology, alteration, mineralization, geochemistry and fluid inclusion microthermometry in the Kaviran prospect area, northwest of Dehsalm (center a Lut Block)زمینشناسی، دگرسانی، کانه نگاری، زمین شیمی و ریزدماسنجی میان بارهای سیال در محدوده اکتشافی کویران، شمال غرب دهسلم (مرکز بلوک لوت)1051304872210.22067/econg.2026.1179FAمحمودپورخسرودانشجوی دکتری، گروه زمینشناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران0009-0004-1128-4667محمدحسنکریم پوراستاد، گروه زمینشناسی و گروه پژوهشی اکتشاف ذخایر معدنی شرق ایران، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران؛ گروه علوم زمین، دانشگاه کلرادو، CB-399، بولدر، Co-80309، امریکا0000-0002-8708-562Xسیدمسعودهماماستاد، گروه زمینشناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران0000-0003-0076-9832فاطمهسپیدبراستادیار، گروه زمینشناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران0000-0002-4604-2244Journal Article20260608The Lut Block in the eastern Iran hosts numerous magmatic-hydrothermal mineral systems and represents one of the most prospective metallogenic provinces of the Iranian Plateau. The Kaviran prospect area, located in the northwest of Dehsalm, and is characterized by widespread hydrothermal alteration, and structurally controlled gold mineralization. Despite several exploration campaigns in the region, the genetic characteristics and mineralizing processes of the Kaviran system have not been comprehensively investigated. Therefore, this study integrates geological mapping, petrography, alteration mineralogy, XRD Analysis, geochemical investigations, and fluid inclusion microthermometry to constrain the ore- forming processes and metallogenic setting of the deposit.IntroductionThe Lut Block in the eastern Iran represents one of the most important metallogenic provinces of the Iranian Plateau and hosts numerous porphyry and epithermal mineral systems formed during extensive Eocene- Oligocene magmatic activity (Sillitoe, 2010; Richards, 2015). Hydrothermal gold mineralization in this region is commonly associated with volcanic–subvolcanic complexes and structurally controlled fluid pathways. The Kaviran prospect, located the northwest of Dehsalm in the central Lut Block, exhibits widespread hydrothermal alteration, silicification, pyritization, and gold-bearing quartz veins. Despite its exploration significance, the ore-forming processes and physicochemical evolution of the hydrothermal system have not been fully constrained.The present study integrates field geology, petrography, alteration mineralogy, XRD Analysis, geochemical investigations, and fluid inclusion microthermometry to characterize the mineralization system and determine the genetic relationship among hydrothermal alteration, ore deposit, and magmatic activity.Materials and MethodsGeological mapping and detailed field investigations were conducted throughout the prospect area. Representative samples were collected from mineralized veins, alteration zones, and host rocks for petrographic and mineralogical studies. X-ray diffraction (XRD) Analysis were carried out to identify alteration minerals, particularly within advanced argillic assemblages. Geochemical data were evaluated to investigate metal associations and element distribution patterns. In addition, microthermometric measurements were performed on primary fluid inclusions hosted by quartz and calcite to estimate the temperature, salinity, and evolution of ore-forming fluids following the procedures described by Bodnar et al., 2014.ResultsHydrothermal alteration in the Kaviran prospect comprises silicic, advanced argillic, argillic, sericitic–carbonate, and propylitic assemblages. The alteration pattern is characterized by intensely silicified cores surrounded by progressively weaker alteration zones. Field observations revealed the occurrence of vuggy silica, one of the most diagnostic features of high-sulfidation systems (Sillitoe and Hedenquist, 2003; Arribas, 1995). Furthermore, XRD Analysis confirmed the presence of pyrophyllite within the advanced argillic zone, indicating alteration under acidic hydrothermal conditions.Mineralization occurs as veins, veinlets, stockworks, and disseminations. Pyrite is the dominant sulfide mineral and is accompanied by chalcopyrite and bornite. Secondary minerals include hematite, goethite, and covellite. Extensive pyritization and silicification are closely associated with gold-bearing structures and hydrothermal alteration zones.Geochemical investigations indicate significant Au enrichment associated with Cu, Ag, Mo, Pb, Zn, and As anomalies. Positive correlations among Au, Cu, and Mo suggest a contribution from magmatic-hydrothermal fluids and imply a possible genetic link to a deeper porphyry system.Microthermometric studies of 168 primary fluid inclusions revealed homogenization temperatures ranging from 112 to 320°C and salinities between 1.74 and 23.1 wt.% NaCl equivalent. Coexistence of liquid-rich inclusions (LV), vapor-rich inclusions (VL), and vapor-only inclusions (V) provides strong evidence for fluid boiling during ore formation. The distribution of temperature and salinity data suggests mixing between magmatic and meteoric fluids during hydrothermal evolution.DiscussionSeveral geological and mineralogical features support the interpretation of the Kaviran hydrothermal system as a high-sulfidation deposit. These features include advanced argillic alteration, widespread silicification, the occurrence of vuggy silica, the presence of pyrophyllite, and extensive pyritization. Such features are widely recognized as characteristic indicators of high-sulfidation environments generated by acidic magmatic fluids above shallow intrusive centers (Hedenquist et al., 2000; Sillitoe and Hedenquist, 2003; Simmons et al., 2005).Fluid inclusion data indicate that ore mineralization occurred in a shallow hydrothermal environment at relatively low pressures. The coexistence of vapor-rich and liquid-rich inclusions demonstrates that boiling played a significant role in destabilizing metal complexes and triggering gold precipitation. Boiling is considered an effective mechanism for precious-metal deposition in epithermal systems (Bodnar et al., 2014., Moncada et al., 2012).Mixing between ascending magmatic fluids and cooler meteoric waters appears to have been another important factor controlling mineralization. Dilution of hydrothermal fluids likely caused changes in fluid chemistry, temperature, and sulfur activity, thereby enhancing metal deposition. Similar processes have been documented in numerous epithermal systems worldwide (Rottier et al., 2021; Yasami et al., 2025).The geochemical association of Au with Cu and Mo, together with the presence of dioritic to quartz monzodioritic porphyry intrusions, suggests that the Kaviran hydrothermal system may represent the upper expression of a larger magmatic-hydrothermal complex. High-sulfidation epithermal deposits commonly occur above porphyry systems and may constitute their shallow-level equivalents (Sillitoe, 2010; Richards, 2015). Therefore, the possibility of a concealed porphyry center beneath the prospect should be considered in future exploration programs.ConclusionsIntegrated geological, mineralogical, geochemical, XRD, and fluid inclusion evidences indicates that the Kaviran prospect represents a high-sulfidation gold system developed in association with the Eocene magmatism in the central Lut Block. Advanced argillic alteration, vuggy silica, pyrophyllite-bearing assemblages, intense silicification, and widespread pyritization collectively support this interpretation. Fluid inclusion studies reveal that ore-forming fluid have temperatures of 112–320°C and salinities of 1.74–23.1 wt.% NaCl equivalent, indicating the involvement of low- to moderate-salinity hydrothermal fluids. Boiling has caused a drop in pressure and reduced solubility or instability of metal-bearing complexes such as gold, and fluid mixing can cause changes in fluid chemistry or changes in sulfur fugacity. The association of Au with Cu and Mo anomalies further suggests a probable genetic linkage between the high-sulfidation mineralization and a concealed porphyry system at depth. Consequently, the Kaviran prospect represents a promising exploration target for both high-sulfidation gold and porphyry-style mineralization within the central Lut Block.محدوده اکتشافی کویران در شمال‌غرب دهسلم و در بخش مرکزی بلوک لوت واقع‌شده است. سنگ‌های میزبان کانه‌زایی شامل واحدهای آتشفشانی و آذرآواری ائوسن هستند که توسط توده‌های نیمه‌عمیق دیوریتی تا کوارتزمونزودیوریتی پورفیری قطع شده‌اند. کانه‌زایی اغلب به صورت رگه‌ای، رگچه‌ای، استوک‌ورکی و افشان رخ‌داده و شامل پیریت، کالکوپیریت و بورنیت است. دگرسانی‌های گرمابی شامل سیلیسی، آرژیلیک پیشرفته، آرژیلیک، سریسیتی- کربناته و پروپیلیتیک هستند. وجود واگی سیلیکا و شناسایی پیروفیلیت در نتایجXRD، شرایط اسیدی و توسعه دگرسانی آرژیلیک پیشرفته را در سامانه کانه‌ساز تأیید می‌کند. نتایج بررسی‌های میان‌بارهای سیال نشان می‌دهد که دمای همگن‌شدگی میان‌بارهای اولیه بین 112 تا 320 درجه سانتی‌گراد و شوری آنها بین 74/1 تا 1/23 درصد وزنی معادل NaCl متغیر است. حضور هم‌زمان میان‌بارهای غنی از مایع، غنی از بخار و تک‌فازی گازی بیانگر وقوع فرایند جوشش در هنگام کانه‌زایی است. پراکندگی داده‌های دما- شوری نیز نشان‌دهنده اختلاط سیالات ماگمایی و جوی در طی تکامل سامانه گرمابی است. همراهی ناهنجاری‌های طلا با مس و مولیبدن و همچنین حضور دگرسانی آرژیلیک پیشرفته، واگی سیلیکا و پیروفیلیت نشان می‌دهد که کانه‌زایی کویران در یک سامانه سولفیداسیون بالا تشکیل‌شده است و احتمالاً با یک سامانه پورفیری مدفون در عمق ارتباط ژنتیکی دارد.https://econg.um.ac.ir/article_48722_3498327ae8564a1191c4243b38616bf7.pdfدانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730618220260823Supergene mineralization related to fault planes and fractures at the Kushk Zn-Pb ore deposit, central Iranکانی زایی برون زاد مرتبط با پهنه های گسلی و شکستگی ها در کانسار روی و سرب کوشک، ایران مرکزی1311724881110.22067/econg.2026.1169FAغلامرضامیرزابابائیدکتری، گروه زمینشناسی معدنی و آب، دانشکده علوم زمین، دانشگاه شهید بهشتی تهران، تهران، ایران0000-0003-0147-899Xمحمدیزدیاستاد، گروه زمینشناسی معدنی و آب، دانشکده علوم زمین، دانشگاه شهید بهشتی تهران، تهران، ایران0000-0002-7948-0478محمدگوهری انارکیکارشناسی ارشد، گروه زمینشناسی، دانشکده علوم، دانشگاه اصفهان، اصفهان، ایرانمیناملک محمدیدانشجوی دکتری، گروه زمینشناسی معدنی و آب، دانشکده علوم زمین، دانشگاه شهید بهشتی تهران، تهران، ایرانJournal Article20260217The Kushk Zn-Pb ore deposit is located in the Posht e Badam block of the central Iranian tectono-magmatic zone, and 160 Km east of Yazd city. In this research, the role of structural factors specially faults on post-sulfide mineralization at the Kushk ore deposit is investigated. The dominant basement rocks of the Kushk volcano-sedimentary basin include the Tashk formation, volcanic units, shales and sandstones of the Rizu series and the Aqda limestone. The important structural factors in this research include post-mineralization fault systems. The pre-mineralization structures are thought to be related to a compressional structural regime coincide with the Pan African orogeny. Syn-mineralization structures, following the Pan African orogeny, and coinciding with an extensional tectonic regime, resulted in Zn-Pb sulfide mineralization. The post mineralization faults, following the formation of the Kushk ore deposit, resulted in fracturing the sulfide ore into three stages including: 1) a folding related faulting resulting in appearing the Kushk fault, 2) a dextral movement characterized by the new activation of the Kushk fault and also appearing the Zardu and Pahnu fault systems, and 3) a final sinistral movement evidenced by Konj fault system. The formation of some supergene minerals, including carbonates, sulfates, phosphates, clays, oxides, and silica, occurred along fault surfaces related to the reactivation of post-sulfide structural features.IntroductionIn this research, the role some post sulfide ore structural systems on the formation and development of some secondary ore formation features at the Kushk ore deposit is investigated. The relationships between structural factors and mineralization have been the subject of debate in the past (Kutina, 1983; Mirzababaei., 2011; Mirzababaei et al., 2016; Karimpour and Sadeghi., 2018; Karimpour et al., 2019). The Kushk Zn-Pb ore deposit, located in central Iranian tectono-magmatic zone, 160 Km east of Yazd city, is one of the world class base metals ore systems. There is a general consensus concerning the typology of the ore system generation, with the exception of some differences. With this framework, however, the structural framework of the Kushk ore deposit is still open to investigate. This research makes a case for re-examining the structural reactivations and importance of post mineralization structural factors in generation of some supergene mineral phases at the Kushk ore system in the context of regional tectonics through post-mineralization deformation history to formation of post mineralization secondary mineral phases.Materials and methods The geological report of the Rio Tinto company (RTZ, 1972) was the basic structural report of the Kushk area which is limited to the ore bodies. Since 2020, the stratigraphical and structural investigations were operated at the department of geology of the Kushk mine. The investigations discussed carried out on structural elements of the area as dip and strike measurements, continuity of fault systems, intersecting with stratigraphical units. The data interpretation was carried out in Arc GIS and Leapfrog software. Following the structural interpretations, selected samples from the newly formed mineralogical phases on fault surfaces were taken to laboratories. 19 Representative samples were taken to analyze by XRD at the Kansaran Binaloud research group. XRD methodology was carried out and the instrument was equipped with a voltage of 40 kv and a nickel filament. Similarly, 5 representative samples were selected to take SEM photomicrographs at the geological survey of Iran. SEM was performed using ZEISS system equipped with an accelerating voltage of 25 kv. Moreover, we also used some thin polished sections formerly prepared for investigation of the ore bodies occurrences in both layered and massive parts of the Kushk ore system. Results and discussionStructural analysis of the field-based investigation provides a method of assessing the structural significance in metallogeny. Structural features (all groups of pre-, syn-, and post-mineralization faults), in the Kushk Zn-Pb ore deposit in central Iran, have not been systematically investigated and the role of post-sulfide structural reactivation remains poorly understood. The main aims of this paper are to: 1) drawing a structural framework for the Kushk ore deposit; 2) investigate the role of post-sulfide structural factors in remobilization of elements from the hypogene ore to the structure bound supergene environment and 3) characterize the mineralogical features of the structurally controlled supergene mineral phases. In general, structural factors of the Kushk Zn-Pb ore deposit can be classifieds into three main categories: 1) faults formed prior to the development of the mineralization basin, 2) deep-rooted syn-mineralization fault systems, and 3) post sulfide mineralization fault systems. Except for a few cases (and just in theoretical models), almost all the structural factors debated in that Kushk Zn-Pb ore deposit, fall into the post mineralization category. The first structural groups are those coincided with the Pan African compressive tectonic regime. This orogeny was one of the most important tectonic processes affected the central Iranian litho-tectonic zone in the upper Neoproterozoic. On theoretical map of paleo-tectonics of Iran, Nadimi (2007), offers a tentative explanation of the large-scale geological processes responsible for the development of compressional environments. We believe, based on this research, that the pre-mineralization faults are connected to paleo-structural zones formed during the Pan African orogeny that lately, by contrast, ruptured and formed syn-mineralization faulted environment in younger tensional environments. The second group of faults, formed presumably, a fertile metallogenic environment for Zn-Pb sulfide mineralization in the Kushk ore deposit. Sulfide ore minerals in the Kushk ore deposit, volumetrically, include pyrite, sphalerite and galena. Theoretical modelling of these structures is given in Rajabi et al (2020). The third group of The third group comprises fault systems and faulted zones which are characterized by structural discontinuities within the layered to massive sulfide ore bodies in the mine blocks, structural displacement along the stratigraphic units hosting the ore bodies and in the overlying horizons, and the development of post-sulfide mineral phases, including carbonates, sulfates, phosphates, clays, oxides, and silica. The formation of these minerals is enhanced with CO₂ effervescence and degassing along the fault zones. Rarely, post-ore sulfide mineralization is also observed, represented by the formation of sphalerite hosted by phosphate minerals.ConclusionThe mechanisms involved in appearing and formation of the post-mineralization faults in the Kushk ore deposit are investigated in the context of the regional structural geology of the study area. These structures mainly comprise fault systems that formed following the reactivation of stratigraphic blocks during the main post-mineralization phase of folding in the area. These structural forms resulted in remobilization of the former mineral mass along fault planes and the subsequent precipitation of newly formed post-sulfide mineral phases including carbonates, sulfates, phosphates, clays, oxides, silica and locally, post-ore sulfide mineralization, within low-pressure zones as veins, veinlets and open space fillings. The structural assessment and mineral chemistry of the newly formed minerals indicate that CO₂ effervescence and degassing within low-pressure zones along faults played a critical role in the formation of post-sulfide mineral phases.کانسار روی و سرب کوشک در بلوک پشت‌بادام از زون تکتونوماگمایی ایران مرکزی و در 160 کیلومتری شرق یزد قرار دارد. در این پژوهش به بررسی نقش عوامل ساختاری به ویژه گسل‌ها بر کانه‌زایی پساسولفیدی در کانسار کوشک، پرداخته می‌شود. سنگ بستر غالب حوضه آتشفشانی- رسوبی کوشک شامل سازند تاشک، واحدهای آتشفشانی، شیل و ماسه‌سنگ‌های سری ریزو و آهک عقدا است. عوامل ساختاری مهم در این پژوهش شامل سامانه‌های گسلی پساکانه‌زایی هستند. ساختارهای پیشاکانه‌زایی مرتبط با یک رژیم ساختاری فشاری منطبق بر کوه‌زایی پان‌آفریکن در نظر گرفته می‌شوند. ساختارهای گسلی هم‌زمان با کانه‌زایی، پس از کوه‌زاد پان‌آفریکن و منطبق بر یک رژیم زمین‌ساختی کششی، به کانه‌زایی سولفیدی روی و سرب منجر شده‌اند. سامانه‌های گسلی پساکانه‌زایی پس از تشکیل کانسار، به ایجاد شکستگی در کانسنگ سولفیدی در سه مرحله منجر‌شده است. حرکت گسلی اول در ارتباط با چین‌خوردگی حوضه کوشک بوده و به تشکیل گسل کوشک منجر‌شده است. حرکت گسلی دوم راست‌گرد بوده و با عملکرد مجدد گسل کوشک و سامانه‌های گسلی زردو و پهنو مشخص می‌شود. حرکت ساختاری نهایی نیز چپ‌گرد بوده و با فعالیت گسلی کنج، محرز است. تشکیل برخی از کانی‌های برون‌زاد از جمله کربنات‌ها، سولفات‌ها، فسفات‌ها، رس‌ها، اکسیدها و سیلیس در سطوح ساختارهای گسلی مرتبط با تجدید فعالیت‌های ساختاری پساسولفیدزایی صورت‌گرفته است.https://econg.um.ac.ir/article_48811_e66d9dab8705f19bd91b48f1a6bc5487.pdfدانشگاه فردوسی مشهدزمین شناسی اقتصادی2008-730618220260823Assessment of Gold Mineralization Potential along the Khonsar–Aligudarz belt, with Emphasis on the Darreh Sari Area, Using Factor Analysis and Geological Evidenceارزیابی پتانسیل کانه زایی طلا در محور خوانسار- الیگودرز با تأکید بر منطقه دره ساری، با استفاده از تحلیل عاملی و شواهد زمین شناسی1731974884010.22067/econg.2026.1182FAمیناشاهیندانشجوی دکتری، گروه زمینشناسی، دانشکده علوم، دانشگاه اصفهان، اصفهان، ایران0009-0000-0379-9805زهرااعلمی نیادانشیار، گروه زمین شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران0000-0002-0018-2428زهرهحسین زادهاستادیار، گروه مهندسی معدن، دانشکده مهندسی معدن و مواد، دانشگاه صنعتی همدان، همدان، ایران0000-0002-8476-4440سید محسنطباطبایی منشاستاد، گروه زمینشناسی، دانشکده علوم، دانشگاه اصفهان، اصفهان، ایران0000-0003-4050-5073پوریامحمودیدکتری، شرکت تهیه و تولید مواد معدنی ایران (ایمپاسکو)، تهران، ایرانJournal Article20260728Assessment of gold mineralization potential in metamorphic terrains requires the application of effective analytical approaches because geochemical patterns are simultaneously influenced by lithological variability, hydrothermal alteration, and structural complexity. In this study, the gold mineralization potential along the Khonsar-Aligudarz belt was evaluated by integrating factor analysis with geological evidence. For this purpose, stream-sediment data from the Golpayegan and Aligudarz 1:100000 geochemical sheets were processed, and inter-element relationships were investigated. The results indicate that factor analysis successfully separated the component related to gold mineralization from the regional lithological background and delineated areas with the highest mineralization potential. Validation of the results through field investigations, petrographic studies, and mineralogical examinations in the Darreh Sari area confirmed the presence of NW-SE trending quartz–hematite–bearing vein-veinlets containing pyrite, pyrrhotite, arsenopyrite, marcasite, chalcopyrite, sphalerite, and galena, as well as iron-, manganese-, and copper-oxide minerals, including hematite, goethite, and, less commonly, magnetite, pyrolusite, and malachite, within Triassic–Jurassic schists and metapelites. The close correspondence between the geochemical anomalies and shear zones and quartz veins indicates that these structures played a major role in channeling mineralizing fluids and concentrating gold. The results of this study indicate that integrating factor analysis with geological information provides an effective approach for reducing uncertainty in regional exploration and prioritizing gold exploration targets in the central Sanandaj–Sirjan Zone and other comparable metamorphic environments.IntroductionGold, as one of the most important strategic and economic metals, forms within a wide range of hydrothermal and orogenic systems, and delineating prospective zones for its occurrence remains a central objective of mineral exploration. In the central Sanandaj–Sirjan Zone, between Khonsar and Aligudarz, several gold occurrences (e.g., Darreh Sari, Hasan Abad, Reza Abad, Hossein Abad, Koucheri, and Sefidsang) have been documented within Triassic–Jurassic schists and metapelites, typically as quartz vein-veinlets with iron and base-metal sulfides and associated silicification, chloritization, carbonatization, and oxidation. Structural control by brittle–ductile shear zones, combined with hydrothermal fluid–rock interaction, has played a fundamental role in concentrating gold and base metals in this belt. Despite reasonable knowledge of these occurrences' geology and mineralogy, regional evaluation of geochemical dispersion patterns remains challenging, since differential element behavior during weathering and transport produces complex, overlapping anomalies that single-element interpretation cannot reliably resolve.Stream sediment geochemistry is among the most effective, economical regional exploration methods for detecting concealed mineralization, though its performance depends heavily on data processing. Conventional univariate threshold methods generally fail to reveal complex inter-element relationships or separate signals from different mineralizing systems, whereas multivariate statistics, particularly factor analysis, overcome this limitation by extracting independent geochemical factors and hidden correlations, distinguishing gold-related components from lithological background or polymetallic systems and improving the accuracy of potential maps. Within this framework, the Darreh Sari area, southwest of Golpayegan and southeast of Aligudarz, was delineated as a gold anomaly from stream sediment data; subsequent field work confirmed quartz–hematite veins- veinlets within Triassic–Jurassic schists accompanied by iron and base-metal sulfides, indicating a gold-bearing hydrothermal system. This study integrates stream sediment geochemistry, factor analysis, and field, petrographic, and mineragraphic evidence to evaluate gold potential along the Khonsar–Aligudarz axis, providing a practical framework for targeted exploration in comparable metamorphic terrains. Geological settingThe study area lies in the central Sanandaj–Sirjan metamorphic-structural zone, one of Iran's principal metamorphic-magmatic and metallogenic belts, whose evolution is generally attributed to Paleo-Tethys closure and prolonged Neo-Tethyan subduction beneath Central Iran from the Late Triassic to the Cenozoic, accompanied by magmatism, regional metamorphism, and polyphase deformation; an alternative model instead links part of the Mesozoic magmatism to intracontinental rifting. The belt mainly comprises Mesozoic sedimentary–volcanic sequences metamorphosed under greenschist- to amphibolite-facies conditions, producing slate, phyllite, quartzite, schist, amphibolite, and gneiss. In the central sector, Triassic–Jurassic phyllite–schist sequences are cut by numerous shear zones and faults that, with hydrothermal circulation and quartz veining, principally control mineralization.Materials and methodsGeochemical data from 947 stream sediment samples covering ~1,419 km2 across the Golpayegan and Aligudarz 1:100000 sheets (Mohajjel and Eftekhar Nezhad, 1992; Soheili et al., 1992), previously analyzed by inductively coupled plasma spectrometry and archived by the Geological Survey and Mineral Exploration Organization of Iran, were used. Concentrations of Cu, Pb, Zn, Ba, B, Co, Cr, Mn, Ni, Sc, Sr, V, and Y were evaluated via descriptive statistics, frequency and box plots, and factor analysis with varimax rotation on standardized data to extract mineralization-related factors and construct factor-score maps. The previously undocumented Darreh Sari anomaly was investigated over two field campaigns documenting mineralized outcrops, and alteration zones, sampled for petrographic and mineragraphic study; five rock-chip samples from two gold-bearing veins were analyzed for gold grade by Fire Assay. ResultsStream Sediment Geochemistry Results Stream sediment concentrations show wide ranges reflecting catchment-scale geochemical heterogeneity. Co and Ni display the most uniform distributions, consistent with lithological control, whereas B (CV = 73.4%) and Mn (CV = 94.1%) show the greatest dispersion, reflecting hydrothermal alteration or oxide concentration; Pb shows the highest variability among base metals (CV = 59.3%), suggesting local sulfide enrichment. Factor analysis extracted six factors: lithological (Sc–Y–V), mafic (Ni–Cr–Co), mineralization (Pb–Zn–Mn), alteration (B–Ba), carbonate (Sr), and magmatic-hydrothermal (Cu). The mineralization factor-score map shows pronounced anomalies at the Reza Abad, Hasan Abad, and Takht-e Khosrow occurrences, plus a distinct NW–SE-trending anomaly at Darreh Sari matching the vein orientation; all anomalies are confined to the Triassic–Jurassic greenschist unit, confirming its role in mineralization.At Darreh Sari, local geology comprises Precambrian mica schists with metarhyolite intercalations, Triassic–Jurassic units (marble, black shale, slate, phyllite, schist), granodioritic intrusions, and Quaternary deposits. The intensely fractured, thrust-bounded metamorphic units favored quartz-vein emplacement, while carbonaceous black shales likely supplied sulfur and gold. Gold occurs mainly as two NW–SE-trending silicic veins (~990 m long, ~2 m wide) parallel to host-rock schistosity, locally cut by younger veinlets indicating post-mineralization reactivation. Fire Assay of five samples yielded gold grades of 87, 1051, 2591, and 5256 mg/t east to west along the main vein and 557 mg/t in a subsidiary vein, with the highest grades in the west matching the strongest anomaly and confirming economic mineralization. Mineragraphic study shows abundant multi-generation pyrite and pyrrhotite, accessory arsenopyrite, marcasite, chalcopyrite, sphalerite, and galena as intergrowths and cavity fillings, subordinate early-stage magnetite, and colloform marcasite, consistent with a hydrothermal quartz-vein system corroborating the geochemical model.DiscussionGold mineralization at Darreh Sari developed within a Sanandaj–Sirjan segment shaped by Neo-Tethyan convergence, regional metamorphism, and crustal-scale shear zones. Factor analysis effectively separated lithological background (Factors 1, 2) from mineralization-related components (Factors 3, 6), which form discrete anomalies independent of lithological boundaries and spatially linked to alteration, confirming the superiority of multivariate over single-element interpretation in structurally complex terrains. The close correspondence between anomalies, shear zones, and quartz veins indicates that brittle–ductile structures were the primary conduits for mineralizing fluids, consistent with structural controls documented for the Muteh gold belt and other orogenic systems of the zone. The paragenetic sequence, pyrite and pyrrhotite followed by base-metal sulfides, reflects progressive evolution of a multistage hydrothermal system consistent with orogenic gold models. Carbon-rich host rocks likely contributed sulfur, CO2, and metals through devolatilization, consistent with models in which organic matter scavenges, transports, and helps precipitate gold via fluid reduction. Surface hematitic staining likely reflects supergene oxidation, yet the coherent anomalies indicate the primary hydrothermal signal survived weathering. These results confirm that multivariate analysis of stream sediment data reveals hydrothermal signals in complex terrains, and that integrating it with structural and remote-sensing data effectively reduces exploration uncertainty and prioritizes drilling targets. ConclusionThis study demonstrates that factor analysis of stream sediment geochemical data, integrated with geological and mineragraphic evidence, effectively identifies gold-related anomalies in the Darreh Sari area and along the Khonsar–Aligudarz belt. Separating lithological components from hydrothermal signals enabled recognition of genuine mineralization-related anomalies, whose strong correspondence with NW–SE-trending shear zones, quartz veins, and Triassic–Jurassic metamorphic units confirm the key role of structural controls in channeling fluids and concentrating gold. Consistency between geochemical and field/mineragraphic observations validates a structurally controlled hydrothermal model, offering an efficient framework for prioritizing exploration targets and reducing uncertainty in early-stage gold exploration across comparable settings of the Sanandaj–Sirjan Zone.ارزیابی پتانسیل کانه‌زایی طلا در مناطق دگرگونی به دلیل تأثیر هم‌زمان تنوع سنگ‌شناسی، دگرسانی‌های گرمابی و پیچیدگی‌های ساختاری بر الگوهای زمین‌شیمیایی، نیازمند به‌کارگیری روش‌های تحلیلی کارآمد است. در این پژوهش، پتانسیل کانه‌زایی طلا در محور خوانسار- الیگودرز با تلفیق تحلیل عاملی و شواهد زمینشناسی مورد ارزیابی قرار‌گرفته است. برای این منظور، داده‌های رسوب آبراهه‌ای مربوط به برگه‌های زمین‌شیمیایی ۱:۱۰۰۰۰۰ گلپایگان و الیگودرز پردازش‌شده و روابط بین عناصر مورد بررسی قرار‌گرفته است. نتایج نشان می‌دهد که تحلیل عاملی توانسته است مؤلفه مرتبط با کانه‌زایی طلا را از زمینه‌ی سنگ‌شناسی منطقه به خوبی تفکیک‌کرده و پهنه‌های دارای بیشترین پتانسیل کانه‌زایی را مشخص‌کند. اعتبارسنجی نتایج از طریق بررسی‌های صحرایی، سنگ‌نگاری و کانی‌شناسی در محدوده دره‌ساری، وجود رگه- رگچه‌های کوارتز- هماتیت‌دار با روند شمال‌غربی- جنوب‌شرقی، حاوی کانی‌های پیریت، پیروتیت، آرسنوپیریت، مارکازیت، کالکوپیریت، اسفالریت و گالن و همچنین کانی‌های اکسیدی آهن، منگنز و مس شامل هماتیت، گوتیت و به ندرت مگنتیت، پیرولوزیت و مالاکیت را در شیست‌ها و متاپلیت‌های تریاس- ژوراسیک تأیید می‌کند. انطباق مناسب بی‌هنجاری‌های زمین‌شیمیایی با پهنه‌های برشی و رگه‌های کوارتزی نشان می‌دهد که این ساختارها نقش اصلی را در هدایت سیالات کانه‌زا و تمرکز طلا ایفا کرده‌اند. نتایج این پژوهش بیانگر آن است که تلفیق تحلیل عاملی با اطلاعات زمینشناسی، رویکردی مؤثر برای کاهش عدم قطعیت در اکتشاف ناحیه‌ای و اولویت‌بندی اهداف اکتشافی طلا در بخش میانی پهنه‌ی سنندج- سیرجان و سایر محیط‌های دگرگونی مشابه را فراهم می‌آورد.https://econg.um.ac.ir/article_48840_dcda4faf1ee68fd824f9bdefc41b8e19.pdf