نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم زمین، دانشکده علوم، دانشگاه کردستان، سنندج، ایران

2 سازمان زمین شناسی غرب کشور، سنندج، ایران

چکیده

غار کرفتو، 67 کیلومتری شمال‏ باختری شهرستان دیواندره در استان کردستان، شامل 4 طبقه است. ‏کف طبقه‏ دوم آن، در تالار خفاش ‏ها، با نهشته‏ های ستبری از گوانو پوشیده شده است. آنالیز SEM-EDX نمونه‏ های گوانو گویای حضور کانی‏ های ثانویه سولفاته (ژیپس، سسنایت)، فسفاته (فسفامیت، بروشیت، تاناراکیت، فرانکوانلیت، وایتلوکیت، لئوکوفسفیت، اسفنیسیدیت، پیروکپروئیت)، و نیتراته (اوره، نیتر)، همراه با میکروارگانیسم ‏ها و کیتین است. وجود این کانی‏ های متفاوت ناشی از تغییر pH (از اسیدی تا قلیایی) و رطوبت (مرطوب و خشک) در حضور میکروارگانیسم‏ ها است. نهشته‌های گوانوی غار کرفتو، به ترتیب از پایین به بالا، در سه شرایط خشک، مرطوب و خشک تشکیل شده‌اند. مقایسه توزیع کانی‌های ثانویه با الگوی تغییرات بی‌هنجاری سریم در طول پروفیل گویای تشکیل کانی تاراناکیت فقط در شرایط مرطوب، و تشکیل کانی‌های وایتلوکیت، اوره، نیتر و سسنایت فقط در شرایط خشک است. بنابراین، آنها می‌توانند کانی‌های شاخص شرایط آب و هوایی باشند ولی کانی‌های دیگر چون در هر دو شرایط مرطوب و خشک تشکیل شده‌اند، نمی‌توانند چنین باشند. واکنش میان محلول تراوشی از گوانو و حرکت محلول از داخل سنگ بستر منجر به فسفاتی شدن و ‏دولومیتی شدن سنگ بستر شده است. فراوانی کیتین در نهشته ‏های گوانوی غار کرفتو نشان می ‏دهد که گوانوها مدفوع خفاش ‏های حشره‌خوار هستند.

کلیدواژه‌ها

موضوعات

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