ارزیابی انحلال‌پذیری و توسعه کارست در افق‌های مختلف مقطع تیپ سازند ایلام

نویسندگان

1 دانشجوی دکترا، گروه زمین‌شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران

2 استاد گروه زمین‌شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران

3 استاد گروه زمین‌شناسی، دانشکده علوم، دانشگاه بوعلی‌سینا، همدان، ایران

چکیده

کارست در سنگ‌آهک‌ها به دلیل قابلیت انحلال‌پذیری زیاد به ‌آسانی توسعه پیدا می‌کند. فراوانی سنگ‌های آهکی سبب شده تا در پروژه‌های مختلف مهندسی با این نوع سنگ‌ها مواجه باشند. سازند ایلام از جمله سازندهایی است که در ارتفاعات زاگرس گسترش زیادی  دارد و در برش نمونه شامل 195 متر سنگ‌آهک کرم‌رنگ است. با توجه به گستردگی این سازند پروژه‌های زیادی بر روی این سازند اجرا شده  و در حفاری‌های نفتی هم با این سازند برخورد دارند. مرز پایینی آن با سازند سورگاه و مرز بالایی آن با سازند گورپی به‌صورت پیوسته است. در این پژوهش با استفاده از مطالعات سنگ‌شناسی و تعیین خصوصیات فیزیکی و مکانیکی نمونه‌های سنگ‌آهک سازند ایلام در مقطع تیپ، انحلال‌پذیری و گسترش کارست بررسی گردیده است. به‌منظور ارزیابی انحلال‌پذیری سازند ایلام، از افق‌های مختلف سازند نمونه‌برداری انجام شد و  پس از آماده‌سازی نمونه‌ها، ترکیب شیمیایی، ویژگی‌های مهندسی و انحلال‌پذیری آن‌ها مورد ارزیابی قرار گرفت. نتایج XRD نشان‌ می‌دهد که کانی‌شناسی نمونه‌های مورد مطالعه شامل: کوارتز، کربنات کلسیم، کانی‌های رسی و مقدار اندکی دولومیت در نمونه‌ها می‌باشد. نتایج XRF نمونه‌ها نشان می‌دهد که عمده اکسیدهای تشکیل‌دهندهCaO ، SiO2، Al2O3، Fe2O3  و MgO می‌باشد. همچنین براساس آزمایش کلسیمتری و XRF موجود افق‌های E و F بیشترین مقدار کربنات  کلسیم را دارا است و تفاوت انحلال‌پذیری در افق‌های مختلف سازند را نشان می‌دهد به این صورت که افق F بیشترین ثابت سرعت انحلال را دارد. پدیده‌های کارستی همچون فروچاله، کارن، حفرات انحلالی، کانیون، غار، جاماها، تنگه و کارن چاله باران در منطقه و سازند مورد مطالعه وجود دارد.

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation of solubility and karst development in type section of Ilam Formation

نویسندگان [English]

  • M. Amiri 1
  • Gh. R. Lashkaripour 2
  • N. Hafezi Moghaddas 2
  • M. H. Ghobadi 3
1 Ph. D. student, Dept., of Geology, Faculty of Science, Ferdowsi University, Mashhad, Iran
2 Prof., Dept., of Geology, Faculty of Science, Ferdowsi University, Mashhad, Iran
3 Prof., Dept., of Geology, Faculty of Science, Bu Ali Sina University, Hamadan, Iran
چکیده [English]

Karstification develops in limestones easily due to high solubility. The abundance of limestone has caused them to face this type of rock in different engineering projects. The Ilam Formation is exposed in the Zagros mountains and this Formation contains 195 meters of cream-colored limestone in the type section. Due to the extent of this formation, many projects have been executed on this formation, and they also encounter this formation in oil drilling. Its lower and upper Boundaries are continuous with Surgah Formation and Gurpi Formations, respectively. In this research, lithological studies and determining the physical and mechanical properties of limestone samples of Ilam formation in type section, the solubility and karst development have been investigated.  In order to evaluate the solubility of the Ilam Formation, samples were taken from different horizons of the formation and transferred to the geological engineering laboratory for the dissolution test, the samples were evaluated for their chemical composition, engineering properties, and solubility after preparation. The results of XRD show that the oxides include silica, calcium carbonate, clay minerals, and a few numbers of dolomite. The results of the XRF samples show that the major constituent oxides are CaO, SiO2, Al2O3, Fe2O3 and MgO. Additionally, based on calcium and XRF tests, horizons E and F contain the highest levels of calcium carbonate and demonstrate variations in solubility across different layers of the formation. Horizon F, in particular, has the highest rate of dissolution. There are karst phenomena such as dissolution sinkholes, Karen, dissolution holes, canyons, caves, James, gorges, and rain hole Karen in the study area.

کلیدواژه‌ها [English]

  • Lithological properties
  • Physical properties
  • Solubility
  • Limestone
  • Ilam Formation
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