دانشگاه اصفهان پترولوژی 2228-5210 17 2 2026 06 22 Geochemical investigation and genesis of Cu-(Ag) mineralization in the Hendou-Abad prospect (NE Isfahan) بررسی زمین‌شیمیایی و پیدایش کانه‏‌زایی مس- نقره در محدودة هندوآباد (شمال‏‌‌خاوری اصفهان) 45 70 30407 10.22108/ijp.2026.148346.1383 FA مریم صالحی دانشجوی دکتری، گروه زمین‏‌شناسی اقتصادی، دانشگاه تربیت مدرس، تهران، ایران زهرا اعلمی‌نیا دانشیار، گروه زمین‏‌شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران شهره حسن پور دانشیار، گروه زمین‌شناسی، دانشگاه پیام نور، تهران، ایران Journal Article 2026 02 14 <strong>Introduction</strong><br />The Hendou-Abad Cu(-Ag) deposit is located in the central part of the Urumieh-Dokhtar magmatic arc, approximately 110 km northeast of Isfahan, Iran. The deposit is hosted by upper Eocene volcanic rocks composed mainly of andesitic basalt, andesite, and subordinate trachyandesite and trachybasalt. Although copper mineralization in the area had previously been recognized, its geological controls, fluid evolution, and genetic characteristics had not been comprehensively investigated. This study integrates geological, mineralogical, geochemical, and fluid inclusion data to characterize the ore-forming processes and evaluate the relationship between the deposit and manto‑type copper systems.<br /><strong>Methodology</strong><br />Field investigations, sampling, petrographic studies, XRD analyses, whole‑rock geochemistry, electron probe microanalysis (EPMA), and fluid inclusion microthermometry were conducted. Fifty‑seven representative samples were collected from mineralized and altered zones. Petrographic observations were used to determine mineral assemblages and paragenetic relationships, whereas XRD analyses identified alteration minerals. Whole‑rock geochemistry and EPMA were employed to investigate elemental distributions and ore mineral chemistry. Fluid inclusion studies on quartz, epidote, and calcite veins provided information on the evolution of temperature and salinity of the ore‑forming fluids.<br /><strong>Geology and Mineralization</strong><br />The oldest exposed rocks in the area are upper Eocene volcanic units consisting predominantly of andesitic basalt and andesite, with minor trachyandesite and trachybasalt. These rocks host the Cu(-Ag) mineralization and are intruded by mafic to intermediate dikes. Regional strike-slip fault systems, particularly the Kachomesqal and Zafarghand fault zones, acted as the principal pathways for hydrothermal fluid circulation.<br />Mineralization occurs as veins, veinlets, stockworks, disseminations, cavity fillings, and replacement bodies. Three distinct breccia types are recognized: red, green, and white breccias. The red breccia contains rounded volcanic fragments cemented by a quartz‑calcite‑iron oxide matrix, whereas the white breccia consists of volcanic and red breccia fragments enclosed within a siliceous matrix. The green breccia is characterized by angular to sub-rounded fragments within an epidote-calcite-quartz matrix.<br />Primary ore minerals include chalcocite, chalcopyrite, bornite, pyrite, and minor galena. Electron microprobe analyses also identified tetrahedrite, electrum, native gold, digenite, and accessory Ag‑bearing phases. Chalcocite, chalcopyrite, and bornite constitute the dominant copper sulfides. The average grades of copper and silver in mineralized samples are approximately 2.7 wt.% Cu and 62 ppm Ag, respectively.<br />Hydrothermal alteration is closely associated with mineralization. A pervasive propylitic assemblage consisting of epidote, chlorite, calcite, tremolite-actinolite, and prehnite is particularly developed within the red breccias. In contrast, epidote-chlorite alteration is spatially associated with copper-bearing veins in the green and white breccias. Away from the mineralized zones, this alteration gradually changes into zeolite-bearing assemblages.<br /><strong>Discussion</strong><br />Petrographic observations, mineral chemistry, and fluid inclusion data indicate that mineralization developed through three successive stages. The first stage is represented by disseminated pyrite and minor chalcopyrite associated with pervasive propylitic alteration and Type I quartz within the red breccias. Fluid inclusions hosted by Type I quartz exhibit homogenization temperatures of 218–275°C and salinities ranging from 12.5 to 16.8 wt.% NaCl equivalent, indicating formation from relatively hot and moderately saline hydrothermal fluids.<br />The second stage represents the principal Cu-Ag mineralization event and is responsible for most of the economic metal accumulation. Mineralization occurs as veins, veinlets, stockworks, and replacement bodies controlled primarily by E–W-trending structures. Ore minerals include chalcocite, bornite, chalcopyrite, tetrahedrite, electrum, native gold, and galena. This stage is associated with Type II epidote, Type II quartz, and Type II calcite. Fluid inclusion studies indicate homogenization temperatures between 95 and 237°C and salinities ranging from 2.90 to 12.96 wt.% NaCl equivalent. These lower temperatures and salinities indicate progressive cooling and dilution of hydrothermal fluids by meteoric water. Most copper and silver precipitation occurred during this stage.<br />The third mineralization stage is characterized by low-temperature hydrothermal activity and chalcedonic quartz-calcite veinlets. This stage contributed little to the overall metal budget and is therefore economically insignificant.<br />Whole-rock geochemical analyses reveal enrichment of Cu, Ag, Pb, Sr, and sulfur and depletion of Ba and Zn relative to host rocks. Strong positive correlations between Cu and Ag indicate a close genetic relationship between silver and copper sulfides. EPMA data show that silver is present in most copper sulfides but is preferentially concentrated in secondary sulfides. The highest silver concentrations were recorded in covellite, reaching approximately 0.7–1.08 wt.%.<br />Supergene weathering subsequently modified the deposit and produced an enriched Cu-Ag zone. Oxidation and leaching of primary sulfides generated secondary chalcocite, covellite, Ag-bearing digenite, native copper, cuprite, tenorite, malachite, and azurite, significantly enhancing copper and silver grades.<br /><strong>Conclusions</strong><br />The Hendou-Abad Cu(-Ag) deposit formed within upper Eocene volcanic rocks under strong structural control exerted by regional fault systems. Three successive mineralization stages are recognized, with the second stage representing the principal Cu-Ag event. Hydrothermal alteration evolved from widespread propylitic assemblages in the red breccias to epidote-chlorite alteration in the green and white breccias, grading outward into zeolite alteration. Fluid inclusion data demonstrate a progressive decrease in temperature and salinity from the first to the third stage, indicating increasing dilution by meteoric water. Chalcocite, chalcopyrite, and bornite constitute the primary copper ore minerals, whereas supergene processes generated secondary sulfides enriched in silver, particularly covellite. The geological setting, alteration characteristics, ore mineralogy, geochemical signatures, structural controls, and microthermometric data collectively indicate that the Hendou-Abad deposit shares strong similarities with manto-type copper deposits and represents an important example of volcanic-hosted Cu(-Ag) mineralization in the Urumieh-Dokhtar magmatic arc. کانسار مس (-نقره) هندوآباد در بخش مرکزی کمان ماگمایی ارومیه‑دختر و درون سنگ‏‌های آتشفشانی ائوسن بالایی با ترکیب آندزی‏‌بازالت، آندزیت و تراکی‏‌آندزیت جای گرفته است. کانه‏‌زایی اولیه مس در سه مرحله و به‌ترتیب مرتبط با برش‏‌های سرخ، سبز و سفید رنگ توسعه یافته است. افزون‌بر دگرسانی پروپلیتیک فراگیر همراه با برش‏‌های سرخ، دگرسانی اپیدوت‑کلریت همراه با برش‏‌های سبز و سفید رنگ، کانه‏‌زایی را همراهی می‏‌کند و با دورشدن از پهنة معدنی با دگرسانی زئولیت جایگزین می‏‌شود. کالکوسیت، کالکوپیریت و بورنیت، کانه‏‏‌های اولیه مس هستند. میانگین عیار مس و نقره در نمونه‏‌های کانه‏‌دار به‏‏‌ترتیب 7/2 درصد و ۶۲ گرم در تن به‌دست آمده است. بررسی‌های ریزکاو الکترونی نشان می‏‌دهد نقره بیشتر با سولفیدهای ثانویه مس همراهی می‏‌کند و بیشترین غلظت آن در کانی کوولیت اندازه‏‌گیری شده است. بر پایة ریزدماسنجی میانبارهای سیال، کوارتز نوع I همراه با مرحلة نخست کانه‏‌زایی دمای همگن‏‌شدگی ۲۱۸‑۲۷۵ درجة سانتیگراد و شوری 5/12 تا 8/16 درصدوزنی معادل نمک طعام دارد. در برابر، کانی‏‌های اپیدوت نوع II، کوارتز نوع II و کلسیت‏‌های نوع II و III همراه با مرحلة دوم کانه‏‌زایی مس، دمای همگن‏‌شدگی ۹۵‑۲۳۷ درجة سانتیگراد و شوری 9/2 تا 96/12 درصدوزنی نمک طعام را نشان می‏‌دهند و بخش بزرگی از فلززایی مس‑نقره در این مرحله روی داده است. مرحلة سوم کانه‏‌زایی اهمیت اقتصادی چندانی ندارد. فرایندهای برون‏‌زاد با رخداد کانه‏‌زایی ثانویه، پهنة غنی‏‌شدة مس‑نقره هندوآباد را پدید آورده‏‌اند. بر پایة شواهد زمین‏‌شناسی، دگرسانی، کانی‏‌شناسی و ریزدماسنجی، کانسار هندوآباد شباهت‏‌های چشمگیری با کانسارهای مس نوع مانتو نشان می‏‌دهد. https://ijp.ui.ac.ir/article_30407_9dfe2ca98dfa8fc59149c90a6e137ee4.pdf