تجزیه و تحلیل ریز ساختار ناخالصی در سکه های زرین ایلخانی (مطالعه موردی سه عدد سکه زرین ابوسعید بهادر) (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
سکه های طلا از مهم ترین مواد باستان شناختی است که از دوران تاریخی در مناطق مختلف ایران ضرب شده اند. با مطالعات روشمند ساختار بیرونی و درونی سکه ها، علاوه بر احراز هویت تاریخی و تعیین اصالت، در زمینه ی کاربرد رویکردهای تحلیلی در رفع ابهامات اقتصادی، فرهنگی، اجتماعی و سیاسی دوره های مختلف تاریخی اهمیت فراوانی دارد. در این پژوهش، سه عدد سکه ی طلا از ضرابخانه های مختلف از مجموعه سکه های زرین سلطان ابوسعید بهادر، فرمانروای ایلخانی، موجود در مخزن موزه ملی مورد مطالعه باستان شناختی و باستان سنجی قرار گرفت. در گام نخست، با هدف دسترسی به مستندات احراز هویت و شناسایی عناصر تشکیل دهنده سطح بیرونی، مراحل مستندنگاری و خوانش نقوش و خط نگاره ها و توزین و اندازه گیری قطر سکه ها انجام شد. در گام بعدی و در مهم ترین مرحله پژوهش، به منظور شناسایی ساختار درونی سکه های مورد مطالعه، آنالیز عنصری فلز سکه به منظور شناسایی ساختار متالورژیکی سکه ها انجام شد. در این مرحله بر روی نمونه ها آزمایش غیرمخرب پیکسی انجام شد. این آزمایش روشی غیرمخرب با حساسیت تحلیلی بالا و همچنین ابزاری علمی، دقیق و کاربردی برای تجزیه وتحلیل سکه های تاریخی می باشد. آنالیز با کاربرد شتاب دهنده و اندوگراف پژوهشکده فیزیک و شتابگرها در آزمایشگاه انرژی اتمی ایران انجام شد. پس از دستیابی به داده های ریزساختار اصلی، از آن جا که درصد ناخالصی نقش مهمی در تعیین عیار سکه های طلا دارد، بنابراین با هدف تعیین میزان خلوص، با تمرکز بر داده های ریزساختار ناخالصی، درجه خلوص و تغییرات عیاری در هر سه سکه با کاربرد روش آمار تحلیلی- استنباطی و بهره گیری از نرم افزار SPSS مدل واریانس یک طرفه داده ها استخراج و به منظور دقت بالا در نتایج حاصله، تفاوت در شاخص های توصیفی با انجام آزمون توکی داده های به دست آمده آزمایش گردید.Analysis of the microstructure and impurity in Ilkhani gold coins(case study of three gold of abu saeed bahadur)
Coins are among the most significant archaeological and historical data, which-beyond their economic value-can play a crucial role in resolving historical ambiguities, understanding economic conditions, political structures, and even trade and cultural relations of the studied period. Through systematic analysis, coins also provide precise scientific information regarding production processes and the technological capabilities embedded in their structure. Among these, gold coins hold a special status due to their high material value, durability, and resistance to corrosion.
During the Ilkhanid period-one of the most pivotal historical eras in Iran-this study aims to conduct detailed and systematic field, laboratory, and archaeometric investigations on three selected samples from a collection of 105 gold coins attributed to Sultan Abu Sa'id Bahadur, discovered in the Jameh Mosque of Tabriz and currently housed in the National Museum of Iran. To authenticate the historical identity of the samples, the external surface of the coins was first examined through documentation procedures including weighing, dimensional measurements, and photography. Iconographic and epigraphic readings were conducted to identify minting details and inscriptions. The coins under study date back to the reign of Abu Sa'id Bahadur (716-736 AH), with minting dates ranging from 724 to 729 AH. Weight measurements revealed that the coins deviate from the standard weight norms of the period. Surface analysis showed that the coins fall into the category of geometrically patterned coins. Two samples (Registry Nos. 12530 and 12546) feature common circular and square-in-circle motifs. The third sample (Registry No. 12544) displays an innovative design with a Quranic verse (Surah 2:137) inscribed around the edge, framed in a mihrab-like structure, along with the names of the four Sunni caliphs-emphasizing religious themes. The reverse side features an octagonal geometric pattern filled with Quranic phrases, with inscriptions referring to victory over enemies. Table 1 presents detailed information on the minting location, date, weight, imagery, and design of the three studied coins. In the second phase, elemental analysis was conducted to obtain microstructural and chemical composition data. Given the importance of non-destructive laboratory methods for identifying the elemental structure of coin metals, PIXE (Proton-Induced X-ray Emission) was employed. This powerful technique enables the detection of major and trace elements as well as impurities. PIXE allows for high-resolution analysis of microstructures and is capable of identifying a wide range of elements from sodium to uranium under optimal conditions. However, like XRF, its main limitation is surface -level analysis.
Since impurity levels significantly affect the purity grade of gold coins, the elemental composition of the samples was analyzed, and the results were interpreted based on the concentration of metallic impurities. Statistical analysis focused on purity variations across coins from three different mints. PIXE utilizes micron-scale proton beams for high-precision, multi-elemental analysis. Under suitable conditions, the minimum detectable concentration ranges from 0.01 ppm to 11 ppm. Although PIXE offers deeper analytical penetration (up to several millimeters with high-energy protons), its standard depth (~70 microns) is generally less than that of XRF (~100 microns). Corrosion and sample heterogeneity may introduce uncertainty in elemental analysis, especially in copper or bronze coins.
The three coin samples were analyzed using the accelerator and endograph facilities at the Physics and Accelerator Research Center of the Atomic Energy Organization of Iran. The elemental composition of major and minor elements-including Fe, Ni, Cu, Ag, Au, Al, Si, K, Ca, and Ti-was determined with a precision range of 10-100 ppm. Based on the obtained data, the primary microstructure, purity level, and the highest impurity concentrations among the samples were identified. Following the acquisition of analytical data, quantitative analysis of major and minor elements, microstructures, and impurities was performed. Impurity elements were statistically processed using SPSS software through descriptive and inferential methods. To ensure high accuracy, differences in descriptive indices were evaluated using post-hoc tests such as Tukey’s test. The final results are based on impurity concentration data and provide valuable insights into the metallurgical composition and purity of the studied coins.
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