پديد آورندگان :
عليپور, صمد دانشگاه اروميه - دانشكده علوم - گروه زمين‌شناسي , عليپور, وحيده دانشگاه اروميه - دانشكده علوم - گروه زمين‌شناسي , عابديني, علي دانشگاه اروميه - دانشكده علوم - گروه زمين‌شناسي
كليدواژه :
داسيت و دگرساني , زاويه و كائولن , كائولن زاويه , كاني‌شناسي و زمين‌شيمي سنگ كل
چكيده فارسي :
ذخيره ي كايولن زاويه، در فاصله 20 كيلومتري شمال باختر شهرستان چالدران، استان آذربايجان غربي، شمال باختر ايران واقع مي باشد. مشاهدات صحرايي و مطالعات آزمايشگاهي نشان مي دهند كه اين ذخيره محصول دگرساني سنگ هاي آذرين داسيتي پليوسن است. كايولينيت، مونت موريلونيت، موسكويت- ايليت، آلبيت، كوارتز، روتيل، هماتيت و گوتيت فازهاي كانيايي در اين ذخيره هستند. بررسي پارامترهاي زمين شيميايي نظير مقادير TiO2، Ba+Sr و Ce+Y+Laآشكار مي كنند كه تكوين و توسعه اين ذخيره در ارتباط با عملكرد دو فرآيند درونزاد و برونزاد مي باشد. محاسبات تغييرات جرم با فرض Ti به عنوان عنصر شاخص كم تحرك نشان مي دهند كه عناصري نظير Ca،Mg ، Na،P ، Rb، Cs، Sr و Ce در طي فرآيندهاي كايولينيتي شدن شسته شده و عنصر U در سيستم تثبيت شده است. اين در حالي است كه عناصري مانند Si، Al، Fe، K، Mn، Ba، Ta، Nb، Hf، Y، Zr، Ga، V، Co، Ni، Cu و كليه REEs (به استثناي Ce) متحمل دو فرآيند شستشو و تثبيت گشته اند. تلفيق نتايج به دست آمده از بررسي هاي كاني شناسي و زمين شيمي تغييرات جرم حكايت از آن دارند كه رفتار عناصر در طي توسعه اين ذخيره توسط عواملي نظير تغييرات در شيمي محلول هاي مسيول دگرساني (pH و Eh)، حضور در فازهاي كانيايي مقاوم، تغيير در شدت دگرساني و نسبت سيال به سنگ، و حضور كاني هاي ثانويه كه توانايي ميزباني عناصر در ساختارشان را دارند، كنترل شده است. ملاحظات زمين شيميايي بيشتر آشكار مي كنند كه تمركز لانتانيدها در اين ذخيره توسط كاني هاي رسي، هماتيت، گوتيت، روتيل و فسفات هاي ثانويه صورت گرفته است.
چكيده لاتين :
IntroductionThe Zavieh kaolin deposit is located ~20 km northwest of the Chalderan city, West-Azarbaidjan Province, NW Iran. Field observations and laboratory studies indicate that this deposit is a product of alteration of dacite igneous rocks from Pliocene age. In this research, it has been attempted to provide relatively comprehensive information on the mineralogical and geochemical factors controlling the distribution and mobility of major, minor and trace elements (including rare earth elements) and the role of hypogene and/or supergene processes in the development and formation of this deposit.Materials and methods This study was performed in two field and laboratory sections. In the field, surveys have been conducted to identify different rock units. On the basis of the results of these surveys, 50 samples were collected from kaolinss and dacitic igneous rocks were collected. The laboratory stage began by preparing and studying petrography of 4 thin sections of dacitic rocks and performing XRD analysis of 8 kaolin samples at the Geological Survey of Iran and the Binaloud Company. Subsequently, for geochemical studies, 12 samples (10 kaolins and 2 dacitic igneous rocks) were analyzed with ICP-AES and ICP-MS methods, respectively. The values of major, minor, trace and rare earth elements were obtained by the ALS-Chemex Laboratory, Canada. The LOI values of the samples were determined by the company based on the weight difference of the samples before and after heating for one hour at 950 °C.Results and discussionAlteration processes on igneous rocks of Pliocene age in the Zavieh area, northwest of Chaldaran, and the formation and development of a kaolin deposit have been associated with mineralogy of kaolinite, montmorillonite, muscovite-illite albite, quartz, rutile, hematite and goethite. The geochemical parameters such as TiO2, Ba+Sr and Ce+Y+La indicate that during the development and evolution of kaolin deposit, the supergene processes overlapped the hypogene processes. Alteration of feldspar mineral and distribution of muscovite-illite and rutile minerals have played an important role in the mobility and fixation of large ion lithophile elements (LILE) in this deposit. Factors such as changes in pH of solutions responsible for kaolinization, changes in the fluid-to-rock ratio, differences in the degree of alteration, and differences in accessibility of complexing ions along with adsorption and fixation in neomorphic mineral phases were the key parameters controlling the distribution of HFS elements in the kaolin deposit. Degree of plagioclase alteration and preferential adsorption by iron oxides and hydroxides are two critical parameters controlling changes in Eu anomaly values in this deposit. Changes in values of the Ce anomaly also indicate the valuable role of hypogene solutions during the formation and evolution of this deposit.ConclusionScavenging by metal oxides and hydroxides together with pH changes are the most important factors controlling the distribution of the transition trace elements in the kaolin deposit. Changes in the chemistry of alteration solutions are the major contributing factors in the distribution of REEs in the deposit and minerals such as clays, hematite, goethite, rutile, and secondary phosphates have played valuable control role in the distribution of REEs.
