نوع مقاله : مقاله پژوهشی
نویسندگان
1 کارشناس ارشد باستان شناسی، مدیر پایگاه میراث فرهنگی محوطۀ تاریخی سیروان، ایلام، ایران
2 استادیار گروه مرمت اشیاء تاریخی فرهنگی، دانشگاه هنر، تهران، ایران
3 دکترای باستان شناسی، ایران.
4 استادیار پژوهشکدۀ پژوهشکدۀ حفاظت و مرمت، پژوهشگاه میراث فرهنگی و گردشگری، تهران، ایران.
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسندگان [English]
According to experts, Sirvan historical site in Ilam province belongs to the Sassanid period or the early Islamic centuries. Despite the archaeological importance of this site, unfortunately, methodical and broad archaeological and archaeometical activities have not been performed. To the systematic investigation of samples obtained from the initial excavations for geoarchaeological studies, 14 potsherds from this site were examined. Concerning this question that what are the main geochemical properties, structural similarities, and differences between these specimens, experimental analysis was done. In order to the elemental and mineralogical description of samples, estimating their firing temperature, and preparing a model for classification of them, chemical composition and mineralogical phases of samples were characterized through X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis. The standard deviations of the amount of silicon, aluminum, iron, calcium, and magnesium oxides were calculated at 11.527, 3.290, 2.705, 5.887, and 2.087, respectively. High dispersion of the quantity of elements especially for Si and Ca reveals that these samples belong to different workshops, regions, or historical periods with variation in sources and amounts of raw materials and processing steps. in the same geographical area. Moreover, any special model for classification of samples not found, except samples no. S8 and S9 that have similarity in their chemical and mineralogical composition. In addition, the three samples S12, S13, and S14 have completely different chemical and mineralogical characterization and are probably to be imported products. Also in samples with a high amount of the calcium oxide (more than 6%), probably local limestones were used as temper. In general, these samples can be considered as local production (except for the three examples mentioned. Concerning not identifying the clay minerals and presence of calcite (likely primary), diopside, and gehlenite (as firing products), the firing temperature of these samples was estimated between 850 - 900.
Keywords: Ilam, Sirvan Historical Site, Pottery, Structural Analysis, XRD and XRF.
Introduction
The pottery abundance and its sufficiency in describing and interpreting the past cultures and civilizations have made it a significant source of information on regard to the reconstruction of human behavior in archaeological studies (Feinman & Skibo, 1999; Shrotriya, 2007). One aspect of research on pottery from archaeological excavations is the study of the characteristics of pottery in its archaeological context, i.e. paying attention to aspects of its preparing method, production technology, and its function (Sinopoli, 1991, p. 70). Potteries are analyzed through various approaches such as the study of macroscopic properties (shape, color, decorative patterns, etc.) and the study of microscopic properties such as mineralogy, and chemical composition and microstructure. The information obtained from the study of the mineral and chemical composition of pottery leads to recognition of their origin and production technology (Emami and Noghani, 2013).
The historical site of Sirvan in Ilam province is one of the areas that, based on archaeological evidence and references in historical texts and sources, is a city belonging to the Sassanid era and the first centuries of the Islamic period (Alibeygi, 2012). Unfortunately, despite the archaeological importance of Sirvan, extensive archaeological activities and archaeological studies of the artifacts have not taken place in this area.
In this study, for the first time, 14 samples of pottery obtained from archaeological activities (speculation for geological-archaeological studies) of this historical area, to identify the elements and compounds used in them, were experimented through X-ray diffraction (XRD) and X-ray fluorescence (XRF) spectroscopy, to estimate the sintering temperature of the samples. The main questions of this research are:
1: What are the main phases of these samples?
2: According to the identification of raw materials, what will be the basis for classifying these samples?
3: According to the identification of phases in the structure, in what range is the firing temperature of the samples estimated?
Materials and Methods
Based on the variety of specifications and appearance characteristics, samples were classified into two groups of glazed samples (S4, S5, S6, S7, S10, S11, S12, S13, S14) and unglazed samples (S1, S2, S3, S8, S9). To identify the structure of these samples, X-ray Fluorescence Spectroscopy (XRF) (Magix-pro device manufactured by Philips India, and semi-quantitative software of IQ +) was used for elemental analysis and chemical composition detection, and X-ray diffraction (XRD) was used to determine the primary and secondary phases. The XRD device used in this research was a BRUKER device made in Germany, model D4 and DIFFRAC Plus software. The analyzes were performed in the laboratory of the organization of Country Geology and Mineral Explorations.
Discussion
In XRF analysis of samples, silicon, aluminum, calcium, iron, magnesium, are determined as the main elements, sodium and potassium as trace elements, and titanium, manganese, sulfur and strontium as rare elements. The highest weight percentage of compounds belongs to the sum of silicon oxide and aluminum oxide. The percentage of iron oxide in these samples varies between 2.5% to 9.965%. Iron is found in these historical potteries as an impurity of clay minerals or intentionally used by the potter. In relation to the detected calcium oxide, a range of changes can be observed. These samples can be divided into two categories: low calcium (CaO with a weight percentage of less than 6%) and high calcium (CaO with a weight percentage of more than 6%).
According to the results of XRD analysis, the indicator phase in all samples is quartz. The type of feldspar detected in these samples is mainly anorthite and sodium anorthite and in two samples S11 and S14 calcium albite has been identified. Calcite was detected in all samples. Identification of diopside and gehlenite as products of the firing process indicates a temperature above 850 ° C for the firing process (Noghani and Emami, 2017).
Conclusion
Concerning determine the chemical properties and investigating the possibility of systematic classification of specimens obtained from initial excavations from speculation for geoarchaeological studies of the Sirvan historical site, 14 specimens of pottery were tested using XRF and XRD analyzes. According to the weight percentage of the identified compounds, these samples include silicon, aluminum, calcium, iron, and magnesium as main elements, potassium, sodium, and titanium as minor elements, and strontium, manganese, sulfur, and phosphorus as trace elements. Differences in weight percentages of identified elements and their high standard deviation indicate that a great variety is observed in terms of type and amount of raw materials and preparation processes.
The observation of diopside and gehlenite phases along with calcite, and the lack of identification of clay minerals, probably indicate that due to the usage of carbonate soil, the particles of these phases are present as temper in the composition of raw materials and the firing temperature is about 850 or finally 900 ° C, except for the S1 sample, which due to the presence of calcite and dolomite and no detection of diopside or gehlenite, had the firing temperature of less than 850 ° C.
In general, it seems that the samples studied in this research are the product of different pottery production workshops or different historical periods, and the sources of their raw materials have been prepared from various regions in the geographical area of Zagros.
کلیدواژه‌ها [English]
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