نوع مقاله : مقالات پژوهشی
نویسندگان
1 دانشگاه شهید باهنر کرمان
2 دانشگاه جیرفت
چکیده
ارتباط نزدیک و متقابلی بین موقعیت ژئومرفیک و نحوه ی تشکیل و تکامل خاک وجود دارد که مطالعات کانی شناسی به عنوان یکی از مهمترین ویژگی های خاک نسبت به توپوگرافی تغییر می کند. این پژوهش با هدف بررسی کانی شناسی رسی خاک های منطقه جبالبارز- جیرفت در سطوح مختلف ژئومرفیک صورت پذیرفت. اشکال اراضی تپه، پدیمنت سنگی، پدیمنت پوشیده و دشت آبرفتی دامنه ای در منطقه شناسایی گردیدند و شکل اراضی تپه بر اساس میزان پایداری، به سطوح ژئومرفیک مختلف تقسیم گردید. کانی های رسی ایلیت، اسمکتیت، کلریت و کائولینیت با استفاده از پراش سنج پرتوی X (XRD) شناسایی شدند. کانی اسمکتیت کانی غالب در خاک های سطوح ژئومرفیک پایدار تپه و پدیمنت پوشیده بود که به دلیل داشتن سطح پایدار و رطوبت بیشتر در زمان گذشته و حال، این کانی از تغییر شکل کانی ایلیت و کلریت تشکیل شده است. همچنین کانی کلریت در سطح پایدار پدیمنت پوشیده مشاهده نشد که با توجه به افزایش مقدار نسبی کانی اسمکتیت در این سطح، نشان از تغییر شکل کانی کلریت به کانی اسمکتیت است. وجود کانی های کلریت، ایلیت مربوط به مواد مادری منطقه می باشد که البته بررسی ماده مادری منطقه مورد مطالعه این نکته را ثابت کرد. از طرفی منشأ کانی کائولینیت در اقلیم خشک این منطقه خاکساز نبوده و با توجه به مشاهده آن در مواد مادری، دارای منشأ توارثی می باشد. نتایج تحقیق، نمایان گر نقش مهم ژئومرفولوژی در کانی شناسی رسی خاکهای منطقه ی مطالعاتی می باشد.
کلیدواژه‌ها
عنوان مقاله [English]
Clay Mineralogy Studies of Soils Located on Different Geomorphic Surfaces in Jabalbarez-Jiroft Area
نویسندگان [English]
- naser boroumand 1
- saleh sanjari 2
1 Shahid Bahonar University of Kerman
2 University of Jiroft
چکیده [English]
Introduction: Soil and geomorphology are closely related to each other. That is why considering geomorphic concepts in soil genesis and classification studies may cause a better understanding of soil genesis processes. Paleosols with argillic horizons were investigated on stable pediment surfaces in Jiroft area, central Iran, by Sanjari et al. (2011). They found that secondary gypsum and calcium carbonate were accumulated in mantled pediments, but moving down the slope toward lowlands, salts more soluble than gypsum have been accumulated.
Clay mineralogy in soil researches helps to better studying soil genesis and development. A quantitative and qualitative study of clay minerals together with their structural composition provides valuable data on the absorption, fixation, and desorption of different cations in soils. Smectite, chlorite, illite, vermiculite, kaolinite, palygorskite, and sepiolite were reported as dominant clay minerals found in arid and semi-arid areas. The objectives of the present study are to evaluate the clay mineralogy of Jabalbarez-Jiroft soils on different geomorphic surfaces.
Materials and Methods: The study area was located in Jabalbarez, 200 Km south Kerman, Central Iran. Fig. 1 showed the exact location of study area. Soil temperature and moisture regimes of the area were thermic and aridic, respectively. Hill, rock pediment, mantled pediment and piedmont alluvial plain landforms were identified, using aerial photo interpretation, topography and geological map observation, in addition to detailed field works. Air-dried soil samples were crushed and passed through a 2-mm sieve. Routine physicochemical analyses wereperformed on the samples. Undisturbed soil samples from the Bt horizon of pedons 4, 5 and 6 were chosen for micromorphology investigations. Beside, eight samples including A and C2 horizons of pedon 1, A and Bt horizon of pedon 3, Bt and Bw horizons of pedon 4, and Bt and C horizon of pedon 5 were selected for clay mineralogy.
Results and Discussion: Argillic horizon found in mantled pediment and piedmont alluvial plain surfaces and stable hill, respectively. In thin horizons coating of clay were observed. Pedofeatures formed in this geomorphic surface, seemed to have been buried in the soil, due to the favorable conditions in terms of the time factor and the presence of moisture in the past. Fig. 2 showed clay coatings in the Bt horizon of pedons 4,5 and 6. The presence of argillic horizons in the arid climate of the research area is attributed to a more humid paleoclimate, which was also reported by Farpoor et al. (2002), Khademi and Mermut (2003), and Sanjari et al. (2011) in Rafsanjan, Isfahan and Jiroft, central Iran, respectively. Clay minerals illite, smectite, chlorite and kaolinite were identified by using X-ray diffractometer. Similar results were also obtained by Sanjari et al. (2011) in the Jiroft area. Kaolinite and illite in soils of arid and semi-arid environments of Iran have been reported with an inherited origin (Khormali and Abtahi, 2003; Sanjari et al., 2011). As the environmental conditions are not favorable for the pedogenic formation of such minerals in soils of this study area , it is proposed that they might be inherited from their parent material. Just as previously stated by other researchers that the origin of the kaolinite minerals in the dry climate regionsis due to itsinheritance from parent materials (Farpoor et al., 2002; Khormali and Abtahi, 2003). The dominant of smectite minerals in soils on stable geomorphic surfaces ofhills and mantled pediment can be cause of stable level and more moisture content in the past and the present, which may be resulted to smectite formation from illite and chlorite transformation. Also, chlorite minerals on stable surface of mantled pediment were not observed. High amount of leaching, low pH level (
کلیدواژه‌ها [English]
- Geomorphic surfaces
- Jabalbarez
- Smectite
- XRD
)
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