كليدواژه :
اسكارن رسوبي , ژئوشيمي , كانه زايي آهن , كردستان , ژنز كانسار مگنتيت ميمون آباد - جنوب باختر دهگلان
چكيده فارسي :
كانسار آهن ميمون آباد در توالي سنگ هاي آتشفشاني- رسوبي ژوراسيك و توده هاي نفوذي ژوراسيك-كرتاسه در شمال زون سنندج-سيرجان رخنمون دارد. كاني سازي آهن بيشتر به صورت مگنتيت است كه به اشكال عدسي ، رگه اي، رگچه اي و نواري است. اين كانسار داراي بافت پراكنده، توده اي، جانشيني و شبكه اي است. كاني هاي همراه بيشتر آمفيبول، اكتينوليت، اپيدوت و كوارتز هستند كه در بخش هايي با كاني هاي رسي و كلسيت همراهند. تغييرات اكسيد آهن در كانسنگ بين 30 تا 90 درصد است. عنصر آهن با گوگرد همبستگي مثبت و با تيتانيم، منيزيم، منگنز همبستگي منفي نشان مي دهد. واناديم از 17 تا 107 گرم در تن متغير است. كاهش مقدار CrوV در اين كانسار، منشا ماگمايي را براي آن مردود مي سازد. مجموع مقادير عناصر نادر خاكي در اين كانسار بين 26 تا 283 گرم در تن است. غني شدگي عناصر كمياب سبك نسبت به عناصر كمياب سنگين در كانسار نشانه تفريق است. براساس مقايسه پراكندگي REE، كانسار آهن ميمون آباد شبيه كانسارهاي آهن رسوبي است. تغييرات عناصر نادر خاكي در مگنتيت نشان دهنده دو منشاء اوليه و ثانوي براي كاني سازي آهن ميمون آباد است. به اين صورت كه آهن ابتدا به شكل ميان لايه در سنگ هاي رسوبي- آتشفشاني ژوراسيك تشكيل شده و توسط سيالات داغ حاصل از توده نفوذي، جابه جا شده و در افق هاي بالاتر تجمع نموده است. حضور اپيدوت و آكتينوليت فراوان كه گاهي با گارنت نيز همراه است نشانه ي يك فاز پيرو متاسوماتيسم مي باشد.
چكيده لاتين :
IntroductionKurdistan province has many iron mines, including: Saghez (Saheb and Hassan-salar), West Marivan (Asanawa), West Divandareh (Allijan, Tawakalan, Zafarabad), North Bijar (Shahrak and Sharifkandi), South Dehgolan(Mimounabad) and East Qorveh (Galalli, Khosroabad, Charmalah, Hezarkhani, Meymanatabad and Babaali). The Meymon-Abad Fe mineralization is one of the important mineralizations of Hamedan-Dehgolan zone.Materials and Methods In this research some samples of magnetite mineralization were taken (6 samples) for ICP-MS (GSI Lab), thin polish and thin section samples were taken (21 samples) from host rock and mineralization and 20 XRF samples were collected too (GSI Lab). One sample is selected for EPMA (Binaloud Co 20 points) and SEM (GSI 4 magnetite minerals). Overall, 57 samples were analyzed.DiscussionGhorbani (2008) divides Sanandaj-Sirjan zone into three parts from economic, geologic and metallogenic aspects. The southern part stretches from Sirjan to Isfahan. The middle part in terms of mineralization is more important than northern and southern parts. According to Momenzadeh (1976), the zone is mostly of sedimentary origin but other researchers such as Zamanian (2016), Bartai (2013), Rostmi paidar (2009) or Pirbaba ali, Galali suggest hydrothermal and skarn genesis. Meymon-Abad mineralization is located near other Fe mineralization zones in Gorveh which is located at intrusive margins of Soufi-abad. This matter can make a skarn genesis possible. Field and analytical studies show other origins for Fe mineralization in study area.ConclusionConsidering expansion, stratigraphy and gap relations between REE data diagrams in Magnetite mineralization and intrusive rocks, it showed limited similarities between Fe mineralization and intrusive rocks. There is limited relation between Fe mineralization in Meymon-Abad and skarn and hydrothermal deposits and this matter shows other origins for Meymon-Abad deposit, therefore sedimentary genesis is probable. High values of L.O.I in analyzed samples indicate that sedimentary genesis is probable. Micro probe analysis in magnetite minerals indicate C element and this can provide another reason for a sedimentary origin of Fe mineralization. At the margins of Sufi-abad granite rocks, there is evidence of hydrothermal origin for Fe mineralization. Mineral traces of pyrite, actinolite, cholorite, albite, calcite and garnet provide evidences of hydrothermal fluid effect in the study area. At margins of Sufi-abad percent of Fe decreases. So magnetite further from Sufi-abad is less than magnetite near Sufi-abad granite. There are fluctuations in magnetite amounts in amphibolite rocks and we can see mineral emplacement with magnetite. Magnetite has shaped interlayers and impregnated less in the host rock. The geochemical evidences of the magnetite mineral and REE variation on them show primary and secondary origins for mineralization in the Meymon-Abad ore deposit. This means that, primarily the high iron oxide bearing layers were deposited as interlayers between the Jurassic volcano sedimentary rocks and then remobilized by hot hydrothermal fluids originating from cretaceous intrusive bodies to upper horizons and re deposited. Abundant existence of epidote and actinolite, in part with garnet show a pyrometasomatic phase in this area.
