توزیع اندازه بلوری گارنت و زمین شیمی گارنت آمفیبولیت هال هال، شمال چالدران - گوشه شمالغربی ایران

گارنت آمفیبولیت های هال هال چالدران از اجزاء آمیزه رنگی مزوزوئیک، از نظر زمین شیمی و نیز توزیع ابعاد بلوری (csd) بررسی شدند. این سنگ ها سرشار از گارنت (آهن و منگنزدار) و آمفیبول سبز/ آبی بوده و کمتر دارای پلاژیوکلاز، کلریت، اپیدوت و کانی های تیره با بافت پورفیروبلاستی و سوگیرش ناشی از دگرگونی ناحیه ای می باشند. این سنگ ها از نوع ارتوآمفیبولیت با سنگ مادر بازالت تولئیتی بوده که در یک محیط درون صفحه ای همراه با آغشتگی شدید با اجزاء پوسته ای تشکیل شده است. گارنت با فراوانی قابل توجه (ناشی از دسترسی به مواد مناسب)، الگوی csd خطی با شیب 3 برای نمونه های دانه درشت تر تا 7 برای سنگهای دانه ریزتر دارد. نسبت نرخ هسته بندی به رشد برای این کانی ها 4 تا 7 برابر بوده است. هسته های متعدد در نتیجه درجه بالای خروج از حالت تعادل در سنگ تشکیل شده و ریخت شناسی منظم بلورها حاکی از تبلور تحت شرایط کنترل بین دانه ای (و نه انتشار سیال) است

crystal size distribution of garnet and geochemistry of hal hal chaldoran garnet amphibolites-northwest corner of iran

garnet has full resistance to weathering and regrowth on the nucleus of previous garnets is common during metamorphic conditions (manzotti and ballevre, 2013). four major processes have role in nucleation and growth of porphyroblasts, are: 1- dissolution of the source material providing the necessary nutrients. 2- accumulation of necessary materials in different places and /or from different sources and transitions from intergranular space to nucleation sites. 3- atomic-scale nucleation where chemical components result from the transfer of materials and possibly the local reactant phases are deformed and transformed into a cumulative product phase in sufficient dimensions and suitable and thermodynamically stable. 4- sedimentation and further deposition of materials on existing surfaces, is called crystal growth (lanari and engi, 2017). the overstepping of a reaction is very important. even if a product phase is thermodynamically and theoretically a stable phase, it is possible that the nucleation of it is failed (waters and lovegrove, 2002). microstructural properties may accelerate nucleation by increasing the free energy, locally. for example, at the hinges of microfolds or at the border of grains, cracks and fissures (gaidies et al., 2011). scientists believe that garnet growth at the intersection of ternary grains much faster than the boundary of a dual grain (spear and daniel, 2001).2- material and methodsto study the garnet of hall hall chaldoran amphibolites, dozens of random samples were taken from the area and among them, 20 thin sections were examined. the halves of samples are analyzed at the tehran zar-azma laboratory by xrd method. three of them graphical results are brought at the paper. also 16 samples are analyzed in xrf to earn the major oxide elements and icp to get trace and rare earth elements of the rocks. the polished surface of the thin sections is put down image processing by digimizer software and the results are corrected by csd correction (higgins, 2006).3- results and discussionthe major phases existed in the rocks are almanden-manganoan garnet and quartz. the minor phases are hornblende, albite, pumpleiite, muscovite, illite, chlorite and chalcopyrite. it should be noted that the samples are ortho-amphibolitic with tholeiitic basalt parent. the ree pattern of the rocks, normalized to chondrite, is concave with decrease in mree special in eu and rise again in hree with final fall in lu and y. such pattern seconder tholeiitic basalt prohtolite for these rocks (storkey et al., 2005). the slope of the csd curves that equivalent with -1/gt is -3 to -7. the linear csd pattern means to uniform flow of energy into the system and constant degree of overstepping degree in the rocks during regional metamorphism. intercept value of regression line of the illustrated csd curve which is equivalent to j/g factor, is 4 to 7.4- conclusionwe illustrate the csd pattern for garnet crystals of hal hal amphibolites and consideration and data analysis, these results was obtained: garnet crystals are assign the quarter to half of modal volume of the rocks which is explained suitable chemical composition of the rocks for crystal growth and appropriate of the other factors such as transportation mechanism, sufficient overstepping due to receiving heat flux and the small number of nuclei leading to significant mineral growth.