بررسی رفتار گرمایی لیزاردیت‌های طبیعی در فشار اتمسفری، بر اساس تجزیه دستگاهی XRD و DTA-TG

نویسندگان

1 دانشگاه آزاد اسلامی

2 موسسه تحقیقات فرآوری مواد معدنی

3 دانشگاه آزاد اسلامی مشهد

چکیده

تعیین میزان پایداری، تغییرات کانی­شناسی و واکنش­های گرمایی کانی­های سرپانتین، می­تواند در تعیین ساز و کار فرورانش، ماگماتیسم و عمق صفحات فرورونده بسیار راهگشا باشد. طی فرایند فرورانش، واکنش­های گرمایی، باعث آزاد شدن آب کانی­های سرپانتینی می­شود. این امر نقش به سزایی را در فرایندهای آتشفشانی وابسته به فرورانش ایفا می­کند. در این کار پژوهشی، رفتار گرمایی و تغییرات کانی­شناختی کانی لیزاردیت (سرپانتین)، وابسته به منطقه افیولیتی نیریز، در گستره­های گرمایی متفاوت و در فشار جوی، با پراش پرتو X (XRD) و آنالیزهای DTA-TG، مورد بحث و بررسی قرار می­گیرد. بررسی­ها نشان داد که، واکنش­های آبزدایی (Dehydration) لیزاردیت­های طبیعی، که به مدت یک ساعت، در دمای 100 تا 150 درجه سانتیگراد گرما گرفته­اند، واکنش­های هیدورکسیل زدایی (Dehydroxilation) آنها در گستره دمایی 550 تا 690 درجه سانتیگراد صورت می­گیرد. لیزاردیت­های طبیعی تا دمای 550 درجه سانتیگراد پایدار بوده و در دمای600 درجه سانتیگراد به الیوین (فورستریت) تبدیل می­شوند. همچنین در دمای 700 درجه سانتیگراد، پیروکسن (انستاتیت) در نتیجه تجزیه لیزاردیت تشکیل می­شود. بین واکنش­های آب زدایی و تبلور، آمورف شدن، در دمای 600 درجه سانتیگراد رخ داده و باعث تشکیل مقادیر اندکی آب و سیلیس آزاد شده است.

کلیدواژه‌ها


عنوان مقاله [English]

Thermal treatment investigation of natural lizardite at the atmospheric pressure, based on XRD and DTA/TG analysis methods

چکیده [English]

Determination of  stability limits, mineralogical changes and  thermal reaction of serpentine minerals are very important for the  investigation of magmatism, mechanism and depth of  plates of subduction. During the subduction process, serpentine (Lizardite) minerals will release their water due to thermal reactions. This dehydration can play an important role in volcanism processes related to the subduction. In this study, serpentine minerals (Lizardite) collected from the Neyriz Ophiolite Complex (NOC) were dehydrated under the constant atmospheric pressure. These mineralogical changes were determined by X-Ray diffraction and DTA-TG analyses methods. This study shows natural lizardites that heated for about one hour is stable up to 550°C. Dehydration reactions on lizardite started at approximately between 100 to 150°C and dehydroxilation reactions started at approximately 550-690°C. As a result of thermal reaction, the decomposition of lizardite will take place and then changes in to olivine (forsterite).  Crystallization of olivine (forsterite) will start at 600°C. This mineral is stable up to 700oC and then crystallization of enstatite will start at 700°C. During this dehydration and crystallization reaction, amorphous processes will start at 600°C and some amount water and silica will release.

کلیدواژه‌ها [English]

  • lizardite
  • serpentine
  • thermal reaction
  • XRD
  • DTA-TG
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