خاستگاه اسکاپولیت در توده نفوذی پنج‌کوه (جنوب‌شرق دامغان)

اسماعیلی, داریوش; شیبی, مریم; کنعانیان, علی

خاستگاه اسکاپولیت در توده نفوذی پنج‌کوه (جنوب‌شرق دامغان)

نویسندگان

دانشگاه تهران

چکیده

مقاله حاضر به بررسی ترکیب کانیشناسی و نحوه تشکیل بلورهای اسکاپولیت در ناحیه پنج کوه دامغان می پردازد. بر مبنای شواهد صحرایی و بافتی، دو نوع اسکاپولیت قابل تشخیصاند: نوع اول شامل اسکاپولیتهایی است که در اندازههای ریز تا درشتدانه در بخشهایی از توده نفوذی جایگزین پلاژیوکلازها شدهاند. به نظر میرسد که جریان شارههای گرمابی غنی از NaCl، از عوامل تشکیل این کانی هستند. بلورهای نوع دوم اسکاپولیت بهصورت رگچههای میلیمتری در داخل توده نفوذی و یا نوارهایی با ضخامت بیش از 5٠٠ متر در حاشیه توده نفوذی و حد فاصل آن با گستره کانسار آهن پنج کوه مشاهده می‌شود. رشد این درشت بلورها از طریق نهشت مستقیم از شاره گرمابی در رگه‌هاست. حضور گسترده اسکاپولیت - آلبیت در داخل و بهویژه حدفاصل توده نفوذی با یک دنباله نهشتی- آتشفشانی که میزبان کانسار آهن پنج کوه است،‏ نشان میدهد که تشکیل اسکاپولیت با یک دگرنهادی آلکالی همراه بوده و بخش عمدهای از سدیم و کلر مورد نیاز برای تشکیل این کانی از نهشتههای تبخیری موجود در این دنباله تأمین شده است.

کلیدواژه‌ها

عنوان مقاله [English]

Origin of scapolite in plutonic rocks of Panj â Kuh (south-east of Damghan)

چکیده [English]

The mineralogy and origin of the scapolite crystals of the Panj-Kuh area (S-E Damghan) has been investigated. Based on textural and field observations, two types of scapolite have been identified. Type 1 scapolite consists of fine to coarse grain crystals which are mainly replaced for plagioclase in the pluton body. The type 2 as veinlet and vein ranging in thickness from few milimeters inside the body to about few hundred meters in the margin of the body that present close to the iron ore deposit. It seems that the formation of the first type of scapolites is related to the circulation of NaCl rich fluid around of the intrusive body, and the second type has directly been precipitated from the hydrothermal fluids. The extensive aboundance of scapolite-albite zone in intrusive rocks and specially between body and a volcano-sedimentary sequence suggest that the formation of scapolite was accompanied by an alkali metasomatism which has been derived from the evaporate sediments of that sequences.

کلیدواژه‌ها [English]

mineralogy
scapolite
Panj – Kuh
Damghan
alkali metasomatism

مراجع

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