بررسی پتروژنز توده های گرانیتوئیدی کالک آلکالن و آداکیتی منطقه رابر-لاله زار (جنوب شرق کرمان): بهره گیری از مطالعات ژئوشیمیایی و ایزوتوپ های Sr-Nd

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه زمین شناسی دانشکده علوم - دانشگاه لرستان- خرم آباد

2 دانشکده علوم پایه، گروه زمین شناسی، دانشگاه لرستان، خرم آباد، ایران

چکیده

منطقه مورد مطالعه در شمال تا شمال غرب شهرستان رابر در استان کرمان قرار دارد و جزئی از کمربند ماگمایی ارومیه-دختر محسوب می شود. در این منطقه توده‌های نفوذی متعددی با ترکیب غالب دیوریت، گرانودیوریت و گرانیت در واحدهای آتشفشانی رخنمون دارد. سنگ-های مورد مطالعه بر اساس ویژگی های ژئوشیمیایی به دو گروه تقسیم بندی شده اند: 1) گرانیتوئیدهای آداکیتی که با میزان سیلیس (78/66-49/61 درصد وزنی)، Al2O3 (74/17 – 72/15 درصد وزنی)، Sr (ppm 602 -374)، Sr/Y (53-34) و نسبت (La/Yb)N بین 88/16-35/8 و مقادیر اندک Y مشخص می‌شوند. 2) گرانیتوئیدهای کالک‌آلکالن که مهمترین خصوصیات آنها عبارتند از: میزان سیلیس (32/72-07/63 درصدوزنی)، نسبت‌های پایین Sr/Y (22/13-83/3)، مقادیر بالای Y ( ppm6/31-7/21) و Yb ( ppm26/3-29/2)، میزان Sr کمتر بین ppm 297-119 و نسبت 13/11-02/3 = (La/Yb)N پایین‌تر نسبت به گروه آداکیت‌ها با آنومالی منفی Eu [(Eu/Eu*)N= (ave. 0.49)]. سنگ-های آداکیتی احتمالاً از پوسته زیرین مافیک (آمفیبولیت گارنت‌دار) همراه با گارنت + روتیل ± پلاژیوکلاز بعنوان فازهای باقیمانده در محل منبع در عمقی بیشتر از 50 کیلومتر تشکیل شده‌اند و گروه کالک‌آلکالن نیز احتمالاً در اعماق نزدیک‌تر به سطح زمین نسبت به آداکیت‌ها در پوسته میانی-زیرین با ترکیب سنگی غالب آمفیبولیت تشکیل شده‌اند. بررسی نسبت‌های ایزوتوپی اولیه (704871/0 - 705195/087Sr/ 86 Sr ( و تغییرات Nd ἑ از 44/1+ تا 19/3 + همراه با تغییرات سیلیس، نشان‌گر تأثیر آشکار آلایش پوسته‌ای در تکوین ماگمای سازنده این سنگ‌هاست.

کلیدواژه‌ها


عنوان مقاله [English]

Petrogenesis of adakitic and calc-alkaline granitoids in Rabor-Lalehzar region, SE of Kerman: Constraints from geochemical and Sr-Nd isotopes results

نویسندگان [English]

  • mohsen chekani moghadam 1
  • Zahra Tahmasbi 2
  • Ahmad Ahmadi-khalaji 2
1 Department of Geology, Faculty of science, Lorestan University,Khorramabad, Iran
2 Department of Geology, Faculty of Sciences, Lorestan University, Khoramabad, Iran
چکیده [English]

Study area located on N to NW of Rabor city in Kerman province that belong to Uromieh-Dokhtar Magmatic Belt (UDMB). Most of rock lithology in this area including diorite, granodiorite and granite which have been exposed in volcanic sequences. Based on geochemical studies all of rocks in this area classified in two groups: (1) some igneous rocks show adakitic affinity with high SiO2 (61.49–66.78 wt. %), Al2O3 (15.72–17.74 wt. %), Sr (374–602 ppm), Sr/Y (34–53), (La/Yb) N (8.35–16.88) and low Y values. (2) another rock group that distinguished in study area including various granitiods rocks with typical calc-alkaline characteristics that distinct from adakitic types such as: SiO2 (63.07–72.32 wt. %), lower Sr/Y (3.8–13.2) ratio and higher Y (21.7–31.6 ppm) and Yb (2.29–3.26 ppm) contents, and the lowest Sr (119–297 ppm) and (La/Yb)N (3.02–11.13) values relative to adakitic groups, with distinctly negative Eu [(Eu/Eu*)N= (ave. 0.49)] anomalies.The adakitic rocks most probably originated from thickened mafic lower crust (garnet amphibolite) with garnet+ rutile ± plagioclase as residual minerals in the source corresponding to depths of >50 km, and calc-alkaline rocks were probably generated in shallow depth than adakitic groups in mid-lower crust (dominant amphibolite) correlating to depths of

کلیدواژه‌ها [English]

  • Lalehzar granitoids
  • Uromieh-Dokhtar zone
  • adakitic rocks
  • Subduction
  • Lower Crust

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