بررسی کانه‌زایی آهن کرفس شمال استان همدان با استفاده از داده‌های ژئوشیمیایی و کانی‌شناسی

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه زمین‌شناسی، دانشکده علوم پایه، دانشگاه بوعلی سینا، همدان، ایران

چکیده

اندیس آهن کرفس در 5 کیلومتری شمال روستای کرفس در استان همدان و از نظر زمین­شناسی در زون سنندج سیرجان قرار دارد. سنگ­های منطقه، شامل آندزیت، شیست، فیلیت، اسکارن و آهک است. کانسنگ آهن در تشکیلات آهکی کرتاسه تحتانی تشکیل شده است. کانه اصلی این ذخیره عمدتاً گوتیت و هماتیت، هرکدام با دو نسل می­باشد. در هماتیت بافت­های جانشینی مانند خوردگی، باقیمانده، کلوفرم، جعبه­ای و در گوتیت بافت­های لایه­ای، جانشینی و گل­کلمی تشکیل شده است. کوارتز، کلریت، اپیدوت و سرسیت، کانی­های باطله را در این ذخیره تشکیل می­دهند. در نمودارهای همبستگی رسم شده عناصر Zn، Cu، P، Mn، Mg همبستگی مثبت و عناصر V، Ti، Ni، Co، Si همبستگی منفی با Fe نشان می­دهند. نمودارهای Sr-Y و Co-Ni و محاسبه پارامترهای عناصر REE به همراه رسم الگوی پراکندگی این عناصر و نمودارهای کوواریانس و ضریب همبستگی این عناصر نشان­دهنده منشاء گرمابی مشتق شده از سیستم گرانیتوئیدی بوده و ذخیره پس از تشکیل دچار شستشوی گرمابی مجدد شده است.

کلیدواژه‌ها


عنوان مقاله [English]

Investigation of types and iron mineralization in the Karafs area, north of Hamadan province using geochemical and mineralogical data

نویسندگان [English]

  • Mehrdad Barati
  • Nesa Vakilishojah
  • Akram Ostadhoseeini
Department of Geology, Faculty of Sciences, Bu Ali Sina University, Hamedan, Iran
چکیده [English]

Introduction
Karafs iron index is located 5Km north of the Karafs village in Hamedan province, Iran and geologically in the Sanandaj-Sirjan structural zone. Iron deposits in Sanandaj- Sirjan structural zone have been discussed and their origin is controversial. In this paper, geological, mineralogical, textural and geochemical properties, especially the geochemical behavior of rare earth elements in Karafs iron index are investigated and the mineralization type and its origin are determined.
Materials and methods
During the field studies, 70 samples were taken for petrographic and mineralogical studies. Petrographic and mineralogical studies were performed in the Bu-Ali Sina University mineralogical laboratory. Geochemical study of iron ore was analyzed by ICP-MS at SGE company of Canada. XRD analyzes were performed at Bu-Ali Sina University.
Results and Discussion
Based on field observation,rock units in the area include volcanic rocks, phyllite, schist, skarn and limestone. Iron deposit is formed in lower Cretaceous limestone formation. The Karafs iron index consists of several small goethite-hematite sac-shaped masses which are accompanied by minor magnetite. Goethite and hematite are the main ore minerals. Most hematites formed in the ore are hypogene (first generation). Secondary hematites caused by conversion of magnetite to hematite (second generation) are very rare.
Replacement textures such as corrosion, marginal and island mainland are seen in hematite crystals. Two generations of goethite were observedin microscopic sections. The first generation goethites are macrocrystalline with an internal reflection of yellow brick and are usually amorphous and crushed and in some parts have a flowing state. Second generation goethites are found at the crystal boundaries of hematite and pyrite or fill its joints and fractures.
In the Karafs iron index, magnetite is seen with primary hematite in the form of amorphous crystals, in the size of 25 to 100 microns and with mass texture. Quartz, chlorite, epidote and sericitic are gangue minerals in the area. The correlation diagrams show positive correlation of Mg, Mn, P, Cu, Zn and negative correlation of Si, Co, Ni, Ti, V with Fe. Geochemical studies showed that the Ni / Co ratio is between 0.2 and 7, which is a characteristic of hydrothermal iron ore (Bajwah et al., 1987). Sr-Y diagram indicates that samples are plotted in the granitoid section, which shows that the hydrothermal fluids are derived from granitoid (Belousova et al., 2002). LREE is enriched in all samples. Enrichment of LREE elements related to HREE and Negative Eu anomalies in the deposit related to hydrothermal fluid have been reported in various parts of the world (Marschik and Fontbote, 2001; Galoyan et al., 2009).
Results
Karafs iron index is located 5Km north of the Karafs village in Hamedan province and geologically in the Sanandaj-Sirjan structural zone. Rock units in the area include andesite, phyllite, schist, skarn and limestone. Iron deposit is formed in lower Cretaceous limestone formation. Goethite and hematite are main ore minerals which are accompanied by minor magnetite. The correlation diagrams show positive correlation of Mg, Mn, P, Cu, Zn and negative correlation of Si, Co, Ni, Ti, and V with Fe. Sr-Y and Co-Ni diagrams. Parameters of REE as well dispersion pattern, variance, diagrams and correlation coefficient of elements indicate hydrothermal origin derived from granitoid system and that the deposit has been hydrothermally leaching after the formation.

کلیدواژه‌ها [English]

  • Iron mineralization
  • REE
  • Hydrothermal type
  • Karafs
-آقانباتی، ع.، 1383. زمین­شناسی ایران، انتشارات سازمان زمین­شناسی و اکتشافات معدنی کشور، 603 ص.
-رجب زاده، م.ع.، پروین، ش.، موسوی نسب، ز. و شمسی­پور، ر.، 1391. بررسی کانه­زایی کانسار هماتیتی هنشک در استان فارس با استفاده از داده­های سنگ­شناسی، کانی­شناسی و زمین­شیمیایی، پترولوژی، شماره 11، ص 19-38.
-سپاهی، ع.ا.، اسدی، ن. و سلامی، ص.، 1393. مطالعه پتروژنز، شیمی کانی‌ها و دما- فشارسنجی سنگ‌های دگرگونی مجاورتی حاشیه توده الوند، همدان، مجله پترولوژی، شماره 5، ص 67-86.
-مقدسی، ج.، 1385. مینرالوگرافی، انتشارات دانشگاه پیام نور، 240 ص.
-سازمان زمین­شناسی کشور،1380. نقشه زمین­شناسی1:100000 ورقه رزن.
 
 
 
-Alai-Mahabadi, S. and Foudazi, M., 2003. Geological map of Razan (Scale: 1:100000), Geological Survey of Iran, Tehran.
-Bajwah, Z.U., Secombe, P.K. and Offler, R., 1987. Trace element distribution, Co: Ni ratios and Genesis of the Big Cadiairon–copper deposit, New South Wales, Australia, Mineralium Deposita, v. 22, p. 292-300.
-Barton, M.D., Jensen, E.P. and Ducea, M., 2003. Fluid sources for IOCG (Candelaria، Punta del Cobre) and porphyry Cu-style mineralization، Copiapó batholith, Chile: Geologic and Sr isotopic constraints, Geological Society of America Abstracts with Programs, v. 37, p. 316-341.
-Belousova, E.A., Griffin, W.L., O’Reilly, S.Y. and Fisher, N.I., 2002. Apatite as an indicator mineral for mineral exploration: trace-element compositions and their relationship to host rock type, Journal of Geochemical Exploration, v. 76, p. 45-69.
-Bin, Z., Hong-Fu, Z., Xin-Miao, Z. and Yong-Sheng, H., 2016. Iron isotope fractionation during skarn-type alteration: Implications for metal source in the Han-Xing iron skarn deposit", Ore Geology Reviews, v. 74, p. 139-150.
-Boynton, W.V., 1984. Geochemistry of the rare earth elements: meteorite studies. In: P. Henderson (Editor), Rare earth element geochemistry, Elsevier, California, p. 63-114.
-Einaudi, M.T. and Burt, D.M., 1982. A special issue devoted to skarn deposits, Introduction Terminology, classification and composition of skarn deposits, Economic Geology, v. 74, p. 745-753.
-Esna-Ashari, A., valizadeh, M.V., Soltani, A. and Sepahi, A.A., 2011. Petrology and geochemistry of Aligoodarz granitoid, Western Iran: implications for petrogenetic relation with Boroujerd and Dehno granitoids, geopersia, v. 2, p. 67-81.
-Forst, B.F., 1991. Introduction to oxygen fugacity and its petroogic importance, In Oxide Minerals: petrologic and Magnetic Significance, Reviews Mineral, v. 25, p. 1-10.
-Frietsch, R., 1978. On the magmatic origin of iron ores of the Kiruna type, Economic Geology, v. 73, p. 478-485.
-Galoyan, R.Y., Sosson, M., Corsini, M., Billo, S., Verati, C. and Melkonyan, R., 2009. Geology, geochemistry and 40Ar/39Ar dating of Sevan ophiolites (Lesser Caucasus, Armenia): Evidence for Jurassic back-arc opening and hot spot event between south Armenia and Eurasia, Journal of Asian Earth Sciences, v. 34, p. 135-153.
-Komninou, A. and Sverjensky, D.A., 1996. Geochemical modeling of the formation of an unconformity-type uranium deposit, Economic Geology, v. 91, p. 590-606.
-Kouhestani, H., Ghaderi, M., Zaw, K., Meffre, S. and Emami, M.H., 2012. Geological setting and timing of the Chah Zard breccia-hosted epithermal gold-silver deposit in the Tethyan belt of Iran, Mineralium Deposita, v. 47, p. 425-440.
-Marschik, R. and Fontbote, L., 2001. The Candelaria-Punta Del Cobre iron oxide Cu-Au (-Zn-Ag) deposits, Economic Geology, v. 96, p. 1799-1826.
-Meinert, L.D., 1995. Igneous petrogenesis and skarn deposits, Geological Association of Canada, Spacial paper, v. 40, p. 569-583.
-Ohmoto, H., 2003. Nonredox transformations of magnetite- hematite in hydrothermal systems, Economic Geology, v. 98, p. 157-161.
-Ramdohr, P., 1980. The Ore Minerals and Their Intergrowths, Pergamon Press, 2nd edition, 1207 p.
-Shelley, D., 1993. Igneous and metamorphic rocks under the microscope, London, Chapman and Hall, 630 p.
-Taylor, S.R. and McLennan, S.M., 1985. The continental crust: its composition and evolution, Blackwell, Oxford, 312 p.
-Whitney, D.L. and Evans, B.V., 2010. Abbreviations for names of rock-forming minerals, American Mineralogist, v. 95, p. 185-187.
-Zhixin, H., Wanming, Y. and Haijun, Y., 2012. Rare earth element geochemical constrains on metallogeny of Jiapigou gold belt, Northeast China, Journal of rare earths, v. 30, p. 95-112