پديد آورندگان :
فتاحي، شيرين نويسنده دانشجوي دكترا، گروه زمين‌شناسي، دانشكده علوم طبيعي، دانشگاه تبريز، تبريز، ايران Fatahi, SH , كلاگري، علي اصغر نويسنده استاد، گروه زمين‌شناسي، دانشكده علوم طبيعي، دانشگاه تبريز، تبريز، ايران Calagari, A. A , عابديني، علي نويسنده دانشگاه اروميه- دانشكده علوم- گروه زمين شناسي- دانشيار Abedini, A , باقري، هاشم نويسنده استاديار، گروه زمين‌شناسي، دانشگاه اصفهان، اصفهان، ايران Bagheri, H
كليدواژه :
چاهريسه , دگرساني , Bentonite , Chahreeseh , Mass changes , Tuff breccia , اصفهان , برش توفي , بنتونيت , alteration , تغييرات جرم , Isfehan
چكيده لاتين :
Chahreeseh bentonite deposit is located at ~55 km northeast of Isfahan, structural zone of Central Iran. This deposit has layered and massive form and includes six discrete outcrops. The field observations showed that the ores are genetically related to Oligo-Miocene tuff breccia. The mineralogical studies testified to the presence of minerals such as montmorillonite, saponite, beidellite, cristobalite, anorthite, calcite, dolomite, albite, vermiculite, actinolite, pyrophyllite, quartz, sanidine nontronite, orthoclase, microcline, tridymite, and hematite in rock-forming quantities in the bentonitic samples. Based on the minerals chemistry considerations, the Chahreeseh bentonite deposit can be classified as the Wyoming type. The results of mass change calculations (with assumption of Hf as low-mobile index element) show that progression of bentonitization process at Chahreeseh was accompanied by depletion of elements like Al, Fe, K, Ti, Mn, P, Ba, Co, Zn, Cs, Rb, Y, Zr, Ni, Sr, and Cu, enrichment of U, and leaching-fixation of elements such as Na, Mg, Ca, and Si. The geochemical interpretations revealed that variations of Eu negative anomaly (0.27-0.90) and weak negative to weak positive anomalies of Ce (0.97-1.22) at Chahreeseh have been controlled by the degree of feldspar alteration and changes in the rate of oxidation potential of the environment, respectively. By considering the results obtained from field relations, mineralogy and geochemistry, it seems factors such as physico-chemical conditions of alteration environment, absorption mechanism, difference in degree of alteration intensity of parent materials, the degree of access to fluoride, chloride, and sulfate ligands, incorporation in crystal structure, ionic exchange, physical concentration, and the presence in resistant mineral phases played significant roles in distribution and concentration of elements in this deposit, respectively.
