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Journal of Sistan and Baluchistan Studies

Journal of Sistan and Baluchistan Studies

BENEATH THE ANCIENT PATINA; INSIGHTS INTO THE CHARACTERIZING AND ARCHAEOMETALLURGY OF SOME BRONZE AGE COPPER-ARSENIC ARTIFACTS FROM SHAHR-I SOKHTA (SOUTHEAST IRAN)

Document Type : Original Research Article

Authors
1 Department of Conservation of Historical Objects and Archaeometry, Faculty of Conservation and Restoration, Art University of Isfahan, Isfahan, Iran.
2 SESAME Synchrotron, King Hussein Bin Talal St / Box 7, Allan, 19252, Jordan.
Abstract
Shahr-i Sokhta, one of the prominent Bronze Age sites located in the Sistan and Baluchistan province of eastern Iran, houses a valuable collection of metal artifacts. This study investigates the corrosion characteristics and mechanisms affecting copper-arsenic bronze artifacts recovered from both the residential area and cemetery of Shahr-i Sokhta. The main goal is to consider to identify the nature, chemical composition, and physical properties of the corrosion products (patinas) on the surfaces of these artifacts to better understand their archaeometallurgical characterization. The research aims to understand what are the chemical and structural characteristics of the corrosion products, and how do these relate to the metallurgical aspects of the artifacts . Additionally we aim to uncover, what are the mechanisms that govern the corrosion process, and what is their role in determining and identifying manufacturing technology in this regard? In order identify the answers to these questions, the samples were analyzed using optical microscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX), and elemental mapping to analyze their structure and chemical composition. Additionally, synchrotron-based X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were applied to identify the corrosion compounds and assess their relationship with the burial soil conditions. The findings of the study demonstrate that the metal artifacts from Shahr-i Sokhta are predominantly composed of Sn–As–Cu alloys, characterized by a relatively low arsenic concentration, averaging approximately 2.77 wt%. Corrosion morphologies suggest internal degradation processes. Soil analysis revealed that the presence of apatite facilitates the migration of arsenic ions. Moreover, the detection of sinnerite, a copper sulfosalt, on the artifact surfaces indicates reductive conditions within the burial environment. These findings contribute to a deeper understanding of the archaeometallurgy and conservation challenges associated with copper-arsenic bronzes at this significant Bronze Age site.
Keywords

چکیده: شهر سوخته، یکی از محوطه‌های شاخص عصر مفرغ در استان سیستان و بلوچستان در شرق ایران، مجموعه‌ای ارزشمند از مصنوعات فلزی را در خود جای داده است. این پژوهش به بررسی ویژگی‌ها و سازوکارهای خوردگی در مصنوعات مفرغی مس ـ آرسنیک به‌دست‌آمده از بخش‌های مسکونی و گورستان شهر سوخته می‌پردازد. هدف اصلی، شناسایی ماهیت، ترکیب شیمیایی و ویژگی‌های فیزیکی محصولات خوردگی (پتینه‌ها) بر سطح این آثار به‌منظور درک بهتر از ویژگی‌های باستان‌فلزشناسی آنهاست. در این راستا، پژوهش به دنبال پاسخ به این پرسش‌هاست که ترکیب و ساختار شیمیایی محصولات خوردگی چگونه‌اند و این ویژگی‌ها چه نسبتی با جنبه‌های فلزشناسی مصنوعات دارند؟ افزون بر این، پژوهش تلاش دارد سازوکارهای مؤثر در فرایند خوردگی را آشکار سازد و نقش آنها را در تعیین و شناسایی فناوری ساخت این اشیاء تبیین کند. برای پاسخ به این پرسش‌ها، نمونه‌ها با روش‌های میکروسکوپی نوری، میکروسکوپ الکترونی روبشی مجهز به طیف‌سنجی پرتو ایکس (SEM-EDX) و نقشه‌برداری عنصری، از نظر ساختار و ترکیب شیمیایی مورد تجزیه و تحلیل قرار گرفتند. همچنین از روش‌های پراش پرتو ایکس (XRD) و فلورسانس پرتو ایکس (XRF) مبتنی بر سنکروترون برای شناسایی ترکیبات خوردگی و بررسی ارتباط آنها با شرایط خاک تدفینی استفاده شد. یافته‌های پژوهش نشان می‌دهد که مصنوعات فلزی شهر سوخته عمدتاً از آلیاژهای Sn–As–Cu تشکیل شده‌اند که دارای غلظت نسبتاً پایین آرسنیک، با میانگین حدود ۷۷/۲ درصد وزنی، هستند. الگوهای خوردگی نشان‌دهنده وجود فرایندهای تخریب درونی‌اند. تحلیل خاک پیرامون اشیاء بیانگر آن است که حضور آپاتیت، مهاجرت یون‌های آرسنیک را تسهیل می‌کند. همچنین، شناسایی سینریت (یکی از سولفوسالت‌های مس) بر سطح آثار، بیانگر شرایط کاهنده در محیط تدفینی است. این نتایج، درک عمیق‌تری از باستان‌فلزشناسی و چالش‌های حفاظتی مربوط به مفرغ‌های مس ـ آرسنیک در این محوطه مهم عصر مفرغ ارائه می‌دهد.

کلیدواژه: مفرغ‌های مس ـ آرسنیک، پتینه، خوردگی، شهر سوخته، ویژگی‌های باستان‌فلزشناسی.

 

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Volume 6, Issue 1
June 2026
Pages 35-52

  • Receive Date 15 July 2025
  • Revise Date 14 August 2025
  • Accept Date 12 September 2025
  • Publish Date 01 June 2026