دولومیتی شدن و کانی‌زایی تبخیری‌های سازند ساچون در برش الگو (جنوب شرق شیراز)

شب افروز, روح اله; محبوبی, اسداله; موسوی حرمی, رضا

دولومیتی شدن و کانی‌زایی تبخیری‌های سازند ساچون در برش الگو (جنوب شرق شیراز)

نویسندگان

دانشگاه فردوسی مشهد

چکیده

سازند ساچون (پالئوسن-ائوسن پایینی) متشکل از کربناتها و تبخیریهایی است که در شرایط دریایی کم عمق و ساحلی سبخا نهشته شدهاند. سازند ساچون در ناحیه مورد بررسی از سه بخش تبخیری زیرین، سنگ آهک‌ بیوکلاستی میانی و تبخیری بالایی تشکیل شده است. واحد تبخیری زیرین و بالایی بیشتر از ژیپسهای ثانویه حاصل از دیاژنز انیدریت- ژیپس تشکیل شده است. ژیپسهای ثانویه بیشتر دارای بافت آلاباستری و پورفیروبلاستی به همراه آثار باقیمانده از بلورهای انیدریت هستند. بررسی سنگشناختی نمونههای بخش میانی سازند ساچون در این منطقه نشان میدهد که مهمترین فرایندهای تاثیر گذار، دولومیتی شدن و کانیزایی تبخیری است. بر مبنای بررسیهای سنگشناختی و ژئوشیمیائی چهار نوع دولومیت اولیه تا مراحل دفنی کم عمق شامل دولومیت خیلی ریز تا ریز (نوع یک)، نئومورفیک (نوع دوم)، لوزی رخهای شکلدار و مسطح در اندازه ریز تا متوسط (نوع سوم) و دولومیت پر کننده حفرهها و شکستگیها (نوع چهارم) از یکدیگر تفکیک شدهاند.

کلیدواژه‌ها

عنوان مقاله [English]

Dolomitization and evaporate mineralization of Sachun Formation at type locality (SE Shiraz)

چکیده [English]

The Sachun Formation (Paleocene-Lower Eocene) is mainly composed of carbonates and evaporates that were deposited in shallow-marine evaporitic mudflat environments. The Sachun Formation in the study area has been divided into three units including: lower evaporate; middle bioclastic limestone and upper evaporate. It is mainly composed of diagenetic gypsum, which originated from dehydration of anhydrite precursor. This gypsum in the Sachun Formation generally displays alabastrine and porphyroblastic textures with corroded anhydrite relics. Petrological studies reveal that the most important diagenetic processes affected the middle Part of the Sachun Formation are dolomitization and evaporate mineralization. Four types of dolomite, ranging from early to burial diagenetic environments, were identified. These are including very fine-to-fine crystalline (D1), neomorphic dolomite (D2), fine-to-medium crystalline euhedral to subhedral dolomite (D3) and pore- and fracture-filling dolomite (D4).

کلیدواژه‌ها [English]

gypsum
anhydrite
alabastrine
porphyroblastic
dolomite
Sachun Formation

مراجع

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