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Abstract
Due to the long lasting durability of pottery, they remain unchanged and plays an important role in archaeological researches. Aside of its difference usage in archaeological research such as dating, artistic and subsistent and communications and exchanges among people of different regions, is used in technology level. Archaeological site of Tape Kelar Hill, situated near Hasankif city, in Kelardasht, is one of the most important prehistoric sites in southern coast of Caspian Sea, which includes cultural materials from the Late Chalcolithic from the fourth millennium B.C. to the Islamic era. The significance of this site has become twofold considering the previous views issued about prehistoric cultures in western Mazandaran and Gilan provinces. The Early Bronze Age potteries of this site are of Kura-Araxes. These are the most important finds of this site. The main research question of this article pertains to the structure of the pottery in this area in two periods and aims to see whether or not the initiation of Kura-Araxes pottery has resulted from external factors and there is difference between Early and Middle Bronze Ages? In this study, 15 pieces of pottery from Early and Middle Bronze ages were studied via petrography method in order to compare in terms of composition and mineral tissues. Research has shown that the pottery of this site, in spite of experiencing some changes in the tissues, is local production. Therefore, it is rebutted to claim that the pottery of this culture is simulated by indigenous potters.
Keywords: Kura-Araxes, Middle Bronze Ages,Tape Kelar, Petrography.

Introduction
Petrographic study of Kura-Araxes pottery, despite its prevalence outside of Iran, has not received much attention from Iranian archaeologists. The first petrographic study of Kura-Araxes pottery in Iran was also conducted by Western archaeologists. The study of Kura-Araxes pottery in areas far from emergence region of this culture in Iran requires data from sites that had a stratigraphic-chronology continuity that was not available until the excavation of Tapeh Kelar.
In terms of the location of the sites studied by the petrographic method prior to the present study, two general classifications can be proposed: first, the sites that were within the geographical area of the origin of the Kura-Araxes culture, and second, the area- Those who are far away and outside the region of origin and only in the second stage of the development of the Kura-Araxes culture reached this culture.
This classification can be useful in analyzing the existence of trans-regional connections with the Caucasus or northwestern Iran, along with comparing the minerals of Tapeh Kelar pottery with the petrology of Kelardasht region. In this research, the authors have studied Kura-Araxes pottery obtained from the excavations of Tapeh Kelar site based on petrographic method.
This research is based on two questions. The first question of this research is that according to the minerals in Kura-Araxes and Middle Bronze Age pottery, what are the similarities or differences between them? And the second question includes the question that based on the petrographic study of the pottery samples of Tapeh Kelar, which of the ideas on how to spread the Kura-Araxes culture can be considered more logical for the emergence of this culture in the site? Based on visual evidence and cultural materials that show major changes in the transition from the Late Chalcolithic period to the Early Bronze Age, it can be expected that major changes have occurred in the field of process of pottery making and heating.

Discussion
In this study, 15 sample of potsherds obtained from excavations at Tapeh Kelar were selected. Samples were selected from Early Bronze Age (Kura-Araxes) and Middle Bronze Age contexts. Of these, 10 samples belonged to the Early Bronze Age and 5 samples belonged to the Middle Bronze.
10 samples of the Early Bronze Age were selected for the study. Samples can be divided into two main categories based on texture: samples with porphyry (coarse-grained) texture and samples with silty (fine-grained) texture. 9 samples have porphyry and coarse-grained texture and only sample number 4 has silty texture. 5 samples of pottery belong to the Middle Bronze Age. The samples have a dark background and a dark color.
Two types of silty tissue (samples 2, 4 and 5) and porphyry can be seen in the samples. Minerals detected in the samples are: quartz (clear and cloudy), plagioclase, amphibole and pyroxene, iron oxide, mica, Intrusive and extrusive volcanic rocks, silt and shale, chalcedony, agate and nepheline.
In the studied samples, some minerals are interesting. Nephline is rare in Iran. In Iran, due to the scarcity of alumina and other items that required nepheline, this mineral was importef from other countries due to its scarcity. Since the 1960s, several sources of nepheline have been reported in the northwest, such as Kalibar, Razgah, Bozqush, and Azarshahr.
Two other regions, namely the north of Shahroud and the central Alborz region, also have this mineral. In the north and northeast of Shahroud city in the Sultan Meidan area, the presence of nepheline mineral has been reported. However, due to the fact that the spread of Kura-Araxes culture was not to Shahroud city, the existence of Shahroud nepheline mineral has no role in the subject of this article. The third region, which is the central Alborz, is important in two ways: first, this mineral has been reported in it, and second, the Taph Kelar site is also located in the same region. As mentioned, in the geological map of Marzanabad sheet, the existence of nepheline mineral is mentioned.

Conclusion
The results of this study, as well as studies conducted elsewhere; show that each region has a regional diversity that itself indicates the local production of Kura-Araxes pottery. If that Kura-Araxes pottery was produced in one or more workshops in the motherland of the culture and then shipped to other areas, these potteries should not be so different and heterogeneous.
Nevertheless, two points should be considered: First, the studied site (Tapeh Kelar) may not be the oldest Kura-Araxes site in Alborz. In addition, ripple in the stream theory must be considered. The time difference between the region of origin of culture and distant regions has lasted for more than two hundred years.
In this theory, the spread of Kura-Araxes culture has been gradual and in several waves and stages, so it is possible that this expansion, even if it is due to migration from the Caucasus, is different from the Caucasus region in terms of mineralogical structure. This study shows that long-distance and direct exchange in the spread of Kura-Araxes culture to the Kelardasht area is not approved.
For better results, it is necessary to obtain more information, especially in archaeological site that transition from the Late Chalcolithic period to the early Bronze Age is uninterrupted, and also genetic studies on human remains of such sites to genetic changes in the inhabitants of the areas in the transition from the Late Chalcolithic Period to the Early Bronze Age Evaluated.