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زمین شناسی اقتصادی - سال نهم شماره 2 (پاییز و زمستان 1396)
  • سال نهم شماره 2 (پاییز و زمستان 1396)
  • تاریخ انتشار: 1396/09/27
  • تعداد عناوین: 15
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  • پژوهشی
  • محمدحسن کریم پور، آزاده ملکزاده شفارودی، عباس اسماعیلی سویری، سعید شعبانی، جولین الاز، چارلز استرن صفحات 294-267
    ناحیه معدنی ایرانکوه در جنوب اصفهان و در کمربند متالوژنی ملایر- اصفهان در زون سنندج- سیرجان واقع شده است. بر اساس شواهد زمین شناسی، آلتراسیون، شکل و بافت کانی سازی و مجموعه کانیایی، کانی سازی سرب و روی از نوع می سی سی پی است. زمین شناسی منطقه شامل سیلتستون و شیل ژوراسیک و انواع مختلف واحدهای کربناته کرتاسه است. کانی سازی کنترل ساختاری دارد و در سنگ میزبان کربناته (دولستون و سنگ آهک) و کمتر سنگ های آواری به شکل اپی ژنتیک تشکیل شده است. کانه زایی به شکل های برشی، رگه چه ای، پرکننده فضای خالی، لکه ای، پراکنده و جانشینی (در سنگ میزبان کربناته) دیده می شود. مجموعه کانیایی شامل اسفالریت غنی از آهن، گالن، کمی پیریت همراه با باطله های دولومیت غنی از آهن، آنکریت، بیتومن، کلسیت ± کوارتز ± باریت است. همبستگی مثبتی بین نقره و آنتیموان در گالن دیده می شود. نسبت Sb/Bi در کانی گالن بیش از 20 است که شاخصه کانسارهای دما پایین است. دمای تشکیل ایرانکوه (170 تا 260 درجه سانتی گراد) از کانسارهای تیپیک می سی سی پی امریکا (80 تا 120 درجه سانتی گراد) بالاتر است. بر اساس مقایسه ایرانکوه با ذخایر امریکا، دمای تشکیل کانسار رابطه مستقیم با مقدار آهن و رابطه ای معکوسی با مقدار کادمیوم اسفالریت دارد. مقدار آهن در اسفالریت های منطقه به بیش از 5 درصد رسیده و مقدار کادمیوم کمتر از 2000 گرم در تن است. همچنین دولومیت های هیدروترمالی در سنگ میزبان کربناته غنی از آهن هستند و در برخی نقاط آنکریت تشکیل شده است که نشان دهنده محلولی هیدروترمالی غنی از آهن است. در سنگ میزبان آواری، عمده آهن محلول کانه دار با گوگرد واکنش داده و پیریت را تشکیل داده است. در این قسمت ها دولومیت ها کم آهن هستند. شاخصه های کانی شناختی، دمایی و ماهیت غنی از آهن محلول کانه دار منطقه ایرانکوه می تواند به عنوان الگویی برای اکتشاف این نوع کانسارها در ایران و دنیا مدنظر قرار گیرد.
    کلیدواژگان: کانه زایی، شیمی کانی، محلول غنی از آهن، ایرانکوه، اصفهان
  • زهرا اعلمی نیا، هاشم باقری، مریم صالحی صفحات 295-312
    منطقه اکتشافی مورد بررسی در بخش میانی کمان آتشفشانی- ماگمایی ارومیه- دختر و در فاصله 7 کیلومتری باختر ظفرقند، شمال خاور اصفهان قرار دارد. در این منطقه، مجموعه سنگ های آتشفشانی با سن ائوسن بالایی و نفوذی با سن الیگوسن پایینی و جوانتر رخنمون دارند. سنگ های آتشفشانی شامل داسیت، ریوداسیت و آندزیت و سنگ های نفوذی شامل دیوریت، کوارتزدیوریت و میکرودیوریت هستند. هاله های دگرسانی از فیلیک، پتاسیک، پروپلیتیک، سیلیسی و آرژیلیک تشکیل شده است. بررسی های زمین شیمیایی انجام شده، حضور عناصر مس و مولیبدن را در ارتباط با توده های نفوذی دیوریتی نشان می دهند. هاله های زمین شیمیایی عناصر گرانبهای طلا و نقره نیز از الگوی توزیع هاله های مس پیروی می کنند. عناصر آرسنیک و آنتیموان در فاصله دورتری ناهنجاری نشان می دهند. به نظر می رسد ناهنجاری های مشاهده شده در منطقه اکتشافی ظفرقند، منطقه بندی مشابه با کانسارهای پورفیری و اپی ترمال مرتبط باآن دارند. بررسی های زمین فیزیکی عمق توده دیوریتی را بیشتر در جنوب خاور منطقه نشان داده است. کانی سازی اولیه سولفیدی در نزدیک توده های دیوریت و کوارتز دیوریت و در سنگ دیواره داسیتی گسترش یافته است. بررسی های سیالات درگیر انجام شده بر روی رگه های کوارتزی نوع I و II، دو نوع سیال با دو ویژگی متفاوت نشان می دهد که با پیش بینی الگو های زمین شیمیایی عناصر بررسی شده همخوانی دارد. سیال کانیساز همراه با کمپلکس های کلریدی (نوع I) با دمای 328 تا 550 درجه سانتی گراد و شوری 32 تا 43 درصد، منشا ماگمایی دارد و سبب کانی سازی مس- مولیبدن در منطقه شده است؛ در حالی که سیال نوع II با دمای 123 تا 391 درجه سانتی گراد و شوری 15/1 تا 16/5 درصد با رخ داد جوشش و اختلاط با آب های جوی و سردشدگی سبب تشکیل ناهنجاری های عناصر گرانبها شده است. عمده کانی سازی سولفیدی با سیال نوع I همراه بوده و در جنوب خاور منطقه در نزدیکی توده دیوریتی تشکیل شده است. در نهایت، با تلفیق نتایج به دست آمده جنوب خاور منطقه جهت بررسی های بیشتر اکتشافی و حفاری توصیه می شود.
    کلیدواژگان: سیالات درگیر، داده های زمین شیمیایی، ظفرقند، کمان آتشفشانی- ماگمایی ارومیه- دختر
  • علی کنعانیان، فاطمه قهرمانی، فاطمه سرجوقیان، جمشید احمدیان، کاظم کاظمی صفحات 313-334
    توده نفوذی فشارک با سن احتمالی الیگومیوسن، بخش کوچکی از نوار ماگمایی ارومیه- دختر شمرده می شود و شامل دو فاز تزریق گرانودیوریتی و کوارتز دیوریتی است که ترکیب گرانودیوریتی در برخی نواحی به ترکیب گرانیت و تونالیت متمایل شده است. این سنگ ها شامل برون بوم های نسبتا فراوان کوارتز دیوریتی و کوارتز مونزودیوریتی است. این توده نفوذی دارای کانی های اصلی کوارتز، فلدسپار، بیوتیت، آمفیبول و پیروکسن با بافت گرانولار است؛ در صورتی که در برون بوم ها دارای ترکیب کانی شناسی مشابه با توده نفوذی است، ولی بافت میکروگرانولار نشان می دهد. نمودار عناصر کمیاب خاکی عادی سازی شده به کندریت همراه با افزایش میزان Ba و کاهش جزئی Sr با افزایش Rb، بیانگر نقش تفریق فلدسپار در تحولات ماگمایی است. نمودارهای تمایزکننده محیط زمین ساختی همراه با غنی شدگی از عناصر ناسازگار LILE و LREE نسبت به عناصر HFSE و HREE و آنومالی منفی عناصر Nb، Ti و Eu نمایانگر شکل گیری این سنگ ها در مناطق مرتبط با فرورانش در حاشیه فعال قاره ای است. نمودارهای تعیین کننده منشا سنگ ها بیانگر نقش گسترده پوسته قاره ای آمفیبولیتی در شکل گیری توده نفوذی فشارک است.
    کلیدواژگان: توده نفوذی، پتروژنز، محیط زمین ساختی، فشارک، اصفهان، ارومیه- دختر
  • حسین حاجی میرزاجان، آزاده ملکزاده شفارودی، محمدرضا حیدریان شهری، سید مسعود همام صفحات 335-356
    کانسار آهن ده زمان در جنوب غربی استان خراسان رضوی و در شمال شرقی زون زمین ساختی کاشمر- کرمان واقع شده است. زمین شناسی منطقه شامل واحدهای رسوبی- آتشفشانی دگرگون شده و توده های نفوذی گرانیتی به سن پرکامبرین بالایی- کامبرین زیرین است. کانه زایی آهن آپاتیت دار به شکل رگه های مگنتیت± اسپکیولاریت در بخش مرکزی و مگنتیت- اسپکیولاریت در بخش شرقی در سنگ میزبان متاریولیت تا متاریوداسیت تشکیل شده است. کانی های اولیه شامل مگنتیت، اسپکیولاریت، آپاتیت و جزیی کالکوپیریت و کانی های ثانویه مالاکیت و هماتیت است. کلریتی شدن، کربناتی شدن، سیلیسی شدن و بیوتیتی شدن مهمترین آلتراسیون های همراه با رگه ها هستند. عیار آهن بین 56 تا 67 درصد و مقدار FeO بین 29/0 تا 13/20 درصد متغیر است. مقدار FeO رابطه معکوس با اسپکیولاریت در کانسنگ دارد. همچنین مقادیر قابل توجه عناصر نادر خاکی به ویژه عناصر LREE در کانسنگ دیده می شود؛ به طوری که مقدار کل عناصر نادر خاکی اغلب بیش از 100 گرم در تن بوده و به 4827 گرم در تن نیز می رسد. سنگ میزبان، کانی شناسی، ساخت و بافت، آلتراسیون و ژئوشیمی این بخش از کانسار ده زمان شبیه به ذخایر آهن نوع کایروناست.
    اختلاف قابل توجه پذیرفتاری مغناطیسی رگه های آهن آپاتیت دار ( SI5-10×5000 تا SI3-10×2000) و سنگ میزبان آتشفشانی (صفر تا SI 5-10× 70) باعث شده است تا روش مغناطیس سنجی و تلفیق آن با داده های زمین شناسی و کانی سازی بهترین روش برای اکتشاف آهن و عناصر نادر خاکی همراه با آن در منطقه باشد. تغییرات شدت کل میدان مغناطیسی در بخش مرکزی و شرقی به ترتیب 8981 گاما و 15592 گاماست. نقشه RTP قسمت شرقی نشان دهنده وجود ناهنجاری با روند تقریبا شمالی- جنوبی است که گسترش عرضی آن در عمق به بیش از 20 متر می رسد. نقشه های فراسو می رساند که عمق منبع ایجاد کننده ناهنجاری (کانی سازی مکنتیت) تا بیش از 50 متر ادامه دارد. در مرکز این زون به دلیل افزایش میزان اسپکیولاریت در رگه ها، ناهنجاری مغناطیسی پاسخ مناسبی ندارد. بر پایه ناهنجاری های مغناطیسی، زمین شناسی، کانی سازی و شیب رگه ها در سطح تعداد 4 نقطه حفاری برای بخش شرقی پیشنهاد شد. ناهنجاری مغناطیسی در پنجره مرکزی دارای روند شرقی- غربی با عرض کم (حدود 25 متر) است و انطباق خوبی با رخنمون های سطحی دارد. عمق کانی زایی بخش شرقی این زون تا بیش از 50 متر ادامه دارد. حرکت گسل های راست گرد در قسمت میانی این منطقه باعث نبود کانه زایی و نبود پیوستگی ناهنجاری مغناطیسی شده است. بر پایه ناهنجاری های مغناطیسی و شیب رگه ها در سطح، دو نقطه حفاری برای بخش مرکزی پیشنهاد شد.
    کلیدواژگان: متاریولیت تا متاریوداسیت، مگنتیت ± اسپکیولاریت، عناصر نادر خاکی، مغناطیس سنجی، ده زمان
  • شکوه ریاحی، نادر فتحیان پور، سید حسن طباطبایی صفحات 357-374
    اولویت بندی و انتخاب بهترین منطقه برای تمرکز و ادامه عملیات اکتشافی، به گونه ای که نتیجه به دست آمده قابل اطمینان و با خطرپذیری کمتر باشد، یکی از مهمترین چالش ها در اکتشاف مواد معدنی است. بدین منظور سعی می شود از روش های اکتشافی هوشمند و کارآمدتر برای شناسایی مناطق مستعد کانی سازی استفاده شود. در این بررسی از روش های تصمیم گیری چند معیاره تاپسیس و منطق فازی برای پهنه بندی، با استفاده از لایه های اکتشافی دورسنجی، زمین شناسی، ژئوشیمیایی، ژئوفیزیکی و ساختاری به عنوان معیارها و نشانه های کانی سازی مس پورفیری در محدوده معدن مس سرچشمه که شامل مناطق شناخته شده کانی سازی از این نوع است، استفاده شده است. اعتبارسنجی نهایی نشان دهنده برتری محدوده کانسار دره زار است که معدن شناخته شده مس پورفیری به حساب می آید و سایر مناطق نیز بر اساس اهمیت اکتشافی اولویت بندی و مناطق جدیدی از دیدگاه توانایی کانی زایی مس پورفیری نیز معرفی شده اند
    کلیدواژگان: اکتشاف مواد معدنی، منطق فازی، روش تاپسیس، کانی سازی مس پورفیری، مناطق امیدبخش
  • قدرت ترابی، غلام حسین نظری صفحات 375-395
    دایک ها و استوک های لمپروفیری الیگوسن در منطقه کال کافی (ایران مرکزی، غرب بلوک یزد)، سنگ های ولکانیک ائوسن و سایر واحدهای قدیمی تر همچون سنگ آهک های کرتاسه را قطع کرده اند. این لمپروفیرها دارای فنوکریست های هورنبلند (مگنزیوهاستینگزیت)، پیروکسن (دیوپسید) و پلاژیوکلاز (لابرادوریت تا بیتونیت) در یک ماتریکس دانه ریز تا دانه متوسط شامل همان کانی ها و آپاتیت، مگنتیت، اپیدوت و کلریت هستند. زونینگ نوسانی فنوکریست های کلینوپیروکسن و گستره تدریجی مقادیر Al2O3 (34/1 تا 49/5 درصد وزنی) و TiO2 (37/0 تا 83/0 درصد وزنی) آنها، بیانگر تبلور این کانی ها در حین صعود، همراه با تغییرات فشار است. با توجه به نتایج بررسی های پتروگرافی، نوع و ترکیب شیمیایی کانی های سازنده این لمپروفیرها، می توان آنها را اسپسارتیت های کالک آلکالن نامید. نتایج آنالیز عناصر کمیاب فنوکریست های آمفیبول، پیروکسن و پلاژیوکلاز با استفاده از دستگاه LA-ICP-MS نشان می دهد که آمفیبول ها بیشترین و پلاژیوکلازها کمترین مقدار عناصر نادر خاکی را دارند. ترموبارومتری آمفیبول وپیروکسن های موجود در لمپروفیرهای کال کافی به ترتیب دمای میانگین 886 و 1150 درجه سانتی گراد و فشار 5/1تا 0/3 و 2 تا 5 کیلوبار را نشان می دهند. فشارهای به دست آمده اعماق 7 تا 17 کیلومتر را برای تبلور کلینوپیروکسن ها و 6 تا 11 کیلومتر را برای تبلور آمفیبول ها مشخص می کنند. دمای تعادل زوج کانی همزیست آمفیبول – پلاژیوکلاز به طور متوسط 860 درجه سانتی گراد به دست آمده است. ویژگی های ژئوشیمیایی کانی های سازنده لمپروفیرهای کال کافی نشان می دهد که ماگمای سازنده این سنگ ها در محیط تکتونوماگمایی مرتبط با فرورانش ایجاد شده و محصول ذوب یک اسپینل لرزولیت گوشته لیتوسفری بوده است.
    کلیدواژگان: اسپسارتیت، لمپروفیر، کالک آلکالن، الیگوسن، کال کافی، ایران مرکزی
  • امیر علی طباخ شعبانی، مرتضی دلاوری کوشان، مهسا حاجی عبدالرحیم خباز صفحات 397-418
    شمالشرق تهران در محدوده بومهن و رودهن سنگ هایی با ترکیب الیوین بازالت در بین سازند کرج برون زد دارند که در حفرات و شکستگی های آن کانی های زئولیت فیبری شکل تشکیل شده است. بنابراین سن این سنگ ها، ائوسن میانی تا بالایی در نظر گرفته می شود. این سنگ ها دارای بافت های هیالو میکرولیتی پورفیری و گلومروپورفیری هستند که درشت بلورهای آن را پلاژیوکلاز ، کلینوپیروکسن و الیوین ایدنگسیتی شده تشکیل می دهد. نتایج آنالیز الکترون میکروپروب فنو کریست های پلاژیوکلاز ترکیب لابرادوریت تا بیتوونیت و پیروکسن ترکیب اوژیت- دیوپسید را نشان می دهد. دمای تبلور پیروکسن ها بین 1150 تا 1250درجه سانتی گراد و فشار تبلور بین 3 تا 8 کیلوبار تخمین زده می شود .این سنگ ها در نمودارهای تعیین دسته ماگمایی در دسته آلکالن و در نمودارهای تعیین محیط تکتونوماگمایی در جایگاه بازالتهای کمان قارهای قرار میگیرند. نمودار عنکبوتی عناصر کمیاب که نسبت به گوشته اولیه به هنجار شده، غنی شدگی عناصر LILE همچون K و Rb و تهی شدگی عناصر HFSE همچون Nb و Hf را نشان می دهند. غنی شدگی از LILE و تهی شدگی از HFSE از ویژگی های مذاب های کمان های آتشفشانی است. همچنین مشابهت الگوی نمودار عنکبوتی این سنگ ها با آندزیت های بازالتی آند نشانه ماگماتیسم زون های فرورانشی است. علاوه بر این، ترکیب شیمیایی پیروکسن ها نیز مشابه پیروکسن های محیط کمان آتشفشانی است.
    کلیدواژگان: الیوین بازالت، آلکالن، کمان ماگمایی، بومهن- رودهن، البرز مرکزی
  • مرضیه محبوبیان فرد، فرهاد احیاء، امید جاوریانی صفحات 419-438
    کانی سازی آهن در کانسار سنگ آهن- خاک سرخ مامونیه، در توف ها، گدازه های تراکیتی- تراکی آندزیتی و سنگ های آذرآواری به سن پلیوسن رخ داده است. بر اساس بررسی های صحرایی و کانی شناسی، کانسنگ شامل کانه اصلی هماتیت به همراه سیلیکای ریزبلور فراوان به صورت لایه ها و میان لایه های ظریف در ضخامت های مختلف و رنگ های متنوع است. با توجه به پایین بودن میزان Cr و Zr و بالا بودن میزان V، Zn و Sr در کانسار مامونیه، می توان نتیجه گرفت که این کانسار مرتبط با فعالیت های آتشفشانی زیردریایی است. داده های زمین شیمیایی شامل الگوهای REE عادی سازی شده با کندریت به خوبی نشان می دهد که محلول های گرمابی بستر دریا محتمل ترین منبع محلول های کانی ساز هستند. نمودار مجموع عناصر (Cu+ Co+ Ni) در مقابلREE ∑ در کانسار مامونیه نیز بیان کننده نقش محلول های گرمابی مناطق عمیق دریا در ته نشست کانسنگ است. الگوهای REE عادی سازی شده با کندریت، غنی شدگی LREE نسبت به HREE، بی هنجاری مثبت Eu و بی هنجاری منفی Ce ، بیانگر این است که منبع آهن در کانسار مامونیه از پوسته اقیانوسی بوده است. بر اساس شواهد موجود می توان دریافت که کانسار مامونیه در اثر شسته شدن آهن و سیلیکا از سنگ های آتشفشانی زیردریایی به وسیله محلول های گرمابی در زون فرورانش و ته نشست لایه ای تشکیل شده است.
    کلیدواژگان: هماتیت، سیلیکا، عناصر نادرخاکی، سیالات گرمابی
  • زهرا واحدی طبس، سید سعید محمدی، محمدحسین زرین کوب صفحات 439-461
    در 60 کیلومتری جنوب گزیک در شرق استان خراسان جنوبی و در بخش شمالی زمین درز سیستان، برون زدهایی از سنگ های آتشفشانی با ترکیب حدواسط (الیگومیوسن) و بازیک (پلیوکواترنر) بر روی واحدهای مجموعه افیولیتی وجود دارد. بر اساس نتایج تجزیه ریزکاو الکترونی، ترکیب کلینوپیروکسن موجود در الیوین بازالت از نوع دیوپسید و الیوین از نوع کریزولیت باMg# بین 81 تا 82 درصد تعیین شد. داده های ژئو شیمیایی نمونه های سنگ کل بیانگر کالک آلکالن بودن آندزیت ها و ماهیت آلکالن گدازه های بازالتی است. الگوی عناصر کمیاب گدازه ها به ویژه برای آندزیت ها، غنی شدگی عناصر Ba، K، Cs،Sr وTh ، تهی شدگی عناصر P، Nb، Ti و غنی شدگی LREE نسبت به HREE را نشان می دهد. همچنین نتایج آنالیز نقطه ای کانی کلینوپیروکسن در واحد سنگی الیوین بازالت، دسته ماگمایی آلکالن و محیط زمین ساختی درون صفحه ای را برای این سنگ ها تایید می کند. دما- فشارسنجی کلینوپیروکسن در الیوین بازالت ها، دمای حدود 1200 درجه سانتی گراد را برای فشار 6 تا 10 کیلوبار مشخص کرده است.
    کلیدواژگان: کلینوپیروکسن، آندزیت، آلکالی بازالت، راتوک، زمین درز سیستان
  • شهریار محمودی، عذرا محمودی، بهزاد مهرابی صفحات 463-481
    کانسار آهن گل گهر در 55 کیلومتری جنوب غرب شهرستان سیرجان، در پهنه ساختاری سنندج- سیرجان واقع شده است. این کانسار توسط مجموعه ای از سنگ های دگرگونی و آذرین شامل انواع شیست، گنیس، آمفیبولیت، مرمر و گرانیت های میلونیتی در بر گرفته شده است. بررسی های انجام شده قبلی نشان می دهد، فرآیند های آذرین رخ دادهای دگرگونی در تشکیل و جایگزینی این کانسار موثر بوده است. ولی اتفاق نظر در این زمینه وجود ندارد. بررسی های ریز ساختاری، بررسی های ژئوشیمیایی ترکیب سنگ های میزبان، کانی سازی و همچنین تجزیه های شیمیایی نقطه ای انجام شده در این پژوهش، بیانگر تاثیر فرآیند های اسکارن زایی به عنوان عامل اصلی در تشکیل کانسار آهن گل گهر است. همچنین بررسی های ریز ساختاری انجام شده، نشان می دهد که مجموعه سنگی گل گهر تحت تاثیر حداقل سه فاز دگرشکلی و دگرگونی متوالی واقع شده است. این بررسی ها نشان می دهد که کانسار آهن گل گهر طی دو مرحله جایگزین شده است. در مرحله اول، طی یکی از فاز های دگرگونی ناحیه ای پیش رونده قبل از نفوذ توده های گرانیتی تشکیل شده که به عنوان مگنتیت نوع یک معرفی شده است و بخش دوم کانسار با توجه به روند های موازی موجود در کانسار با پهنه برشی و ویژگی های فابریکی نشان می دهد که مگنیت نوع دو، بخشی از کانسار است که طی اسکارن زایی هم زمان با دگرگونی دینامیکی ایجاد شده توسط پهنه برشی بعد از جایگزینی توده آذرین و احتمالا در اثر تحرک و تمرکز دوباره کانسار آهن اولیه جایگزین شده است.
    کلیدواژگان: دگرگونی سنندج سیرجان، کانسار گل گهر، ریزساختار، آهن اسکارنی
  • فائزه نبی لو، بهنام شفیعی بافتی، آرش امینی صفحات 483-507
    معدن کمرپشت واقع در جنوب شرقی دوآب در استان مازندران به صورت چینه کران در سنگ های کربناته بخش بالایی سازند الیکا (تریاس میانی) میزبان شده است. مشاهدات صحرایی نشان داد که بخش های با قابلیت معدن کاری اقتصادی در افق های کربناته سازند الیکا دارای فلوئوریت، باریت و گالن بوده که غالبا در شکستگی های واقع در مناطق گسله و حفرات کارستی رخ داده اند. فلوئوریت های دانه درشت و شکل دار با رنگ های متنوع، حضور قابل ملاحظه باریت به شکل توده ای و رگه ای، گالن ‏فراوان و تماس نزدیک بین زون های کانی سازی در کربنات های میزبان ‏کانسار (سازند الیکا) و شیل های زغالی پیریت دار (قاعده سازند شمشک) به صورت گسله یا به شکل میان لایه از ویژگی های بارز زمین شناسی معدن کمرپشت است. فلوئوریت به شکل توده های منقطع، اما متراکم و حجیم با/یا بدون ‏همراهی گالن اغلب حفرات و فضاهای خالی بین قطعات برشی سنگ آهک دولومیتی پرکرده است و ‏کمتر به شکل دانه پراکنده، رگه چه های ظریف و ژئود رخ داده است. باریت به صورت تجمعات توده ای و حجیم در حفرات انحلالی و کارستی و همچنین رگه هایی رخ داده است که ساخت های شعاعی، برشی و گورخری را شامل می شوند. گالن به صورت رگه چه ای و برشی با اندازه ذرات متوسط تا درشت با یا بدون فلوئوریت در سنگ ‏میزبان اغلب ‏دولومیتی و سیلیسی و همچنین غالبا به صورت رگه-‏ رگه چه ای در درون و یا در حاشیه باریت های توده ای رخ داده است. ساخت ها و بافت های دیده شده در بررسی حاضر نشان داد که کانی سازی فلوئوریت وکانه های همراه در دو مرحله همزاد با دیاژنز و بعد از دیاژنز رخ داده اند. بر پایه این بررسی، کانسنگ های دارای بافت های دانه پراکنده، استیلولایتی، ژئودی و ریز رگه چه ای به عنوان ساخت و بافت های اولیه کانی سازی و همزاد با دیاژنز تفسیر شده اند؛ در حالی که ساخت های شکافه پرکن مانند رگه ای و برشی با بافت های جانشینی، شبکه ای و گورخری که عمده ساخت و بافت های کانی سازی را در معدن کمرپشت شکل داده اند، پس از دیاژنز به دست آمده اند. بازپویایی کانه های دیاژنتیک در نتیجه عملکرد محلول های گرمابی ناشی از کوه زاد سیمرین و افزایش انحلال پذیری و دولومیتی و سیلیسی شدن سنگ میزبان احتمالا فرآیندهای اصلی مسوول در کانی سازی اپی ژنتیک معدن کمرپشت بوده اند.
    کلیدواژگان: معدن کمرپشت، فلوئوریت، سازند الیکا، مازندران
  • مروری
  • حبیب الله بازدار، هادی فتاحی، فریدون قدیمی صفحات 509-544
    علوم زمین به طور عمومی و اکتشاف منابع معدنی به خصوص، به دلیل پیچیدگی هایی که دارد و نیز عوامل تاثیر گذار و دخیل در آن، همواره جزو علومی بوده است که احاطه بر تمام ویژگی های آن یا ناممکن بوده و یا بسیار مشکل است. به دلیل دشوار بودن اندازه گیری دقیق مولفه ها و مرزبندی آنها، در چند سال اخیر سعی شده است برای رفع این نوع مشکل ها و مسائل، از روش های جدید مانند روش های پیشرفته هوش محاسباتی استفاده شود که توانایی بالایی در بسیاری از زمینه های محاسباتی دارند. با توجه به تنوع کارهای تحقیقاتی انجام شده در این زمینه و نبود مقاله مروری جامع، انجام این کار پژوهشی ضروری است. هدف از نگارش این مقاله، مروری جامع بر کاربرد انواع روش های پیشرفته هوش محاسباتی در حیطه اکتشاف منابع معدنی و ایجاد منبع مطالعاتی جامع برای پژوهشگران علاقه مند به این زمینه است. نتایج این تحقیقات همگی نشان می دهند، روش های پیشرفته هوش محاسباتی در مقایسه با سایر روش ها در بررسی اکتشاف منابع معدنی، کارآمدتر، سریعتر، دقیقتر و مقرون به صرفه تر هستند.
    کلیدواژگان: روش های پیشرفته هوش محاسباتی، اکتشاف، منابع معدنی، مدل سازی
  • پژوهشی
  • عاطفه قائدی، عباس مرادیان، حمید احمدی پور صفحات 545-559
    در بخش هایی از جنوب غرب استان کرمان، مثل خاتون آباد در شرق شهربابک و کفه رباط- مروست در غرب شهرستان شهربابک، نهشته هایی از کانی های بورات دیده می شود که غالبا در فروافتادگی های زون سنندج- سیرجان، در زیر قشر نازکی از خاک و به صورت نودول دیده می شوند. بررسی های صحرایی نشان می دهد که در مناطق مورد بررسی، کفه های حاوی بورات ها به وسیله آب راهه هایی تغذیه می شوند که از سنگ های دگرگونی زون سنندج- سیرجان، آمیزه های نائین- بافت و سنگ های آذرین کمربند ماگمایی ارومیه- دختر سرچشمه می گیرند و این سنگ ها می توانند منشا احتمالی بور در این نهشته ها باشند. نتایج بررسی های کانی شناسی به روش XRD نشان داد کانی های بوراته منطقه بیشتر از نوع هیدراته است و شامل یولکسیت، بوراکس، گووریت، ساسولیت، اینیوئیت هستند. داده های ژئوشیمیایی، نشان دهنده فراوانی عنصر بور (B) در این پلایاست. همبستگی خوب بین عناصر بور و کلسیم نشان دهنده تشکیل کانی های بوراته کلسیم دار در مناطق مورد بررسی است.
    کلیدواژگان: پلایای شهر بابک، بورات، یولکسیت، ساسولیت، XRD، ICP- AES
  • سوسن ابراهیمی، سعید علیرضایی، یوانمینگ پن، بهزاد محمدی صفحات 561-586
    ذخیره طلای مسجدداغی در 35 کیلومتری شرق جلفا و در زون ماگمایی البرز- آذربایجان قرار دارد. واحدهای سنگی شامل فلیش، تراکی آندزیت و آندزیت ائوسن و یک توده کوارتز مونزودیوریت پورفیری جوانتر است. کانی سازی به صورت رگه های کوارتز و کوارتز- باریت رخ داده است. پیریت کانی هیپوژن اصلی است و با مقادیری کالکوپیریت، اسفالریت و گالن همراهی می شود. رگه های طلا دار توسط زون های دگرسانی سیلیسی، آرژیلیک پیشرفته، آرژیلیک و پروپیلیتیک احاطه شده اند. داده های میان بارهای سیال کوارتز و اسفالریت مربوط به مرحله کانی سازی، به ترتیب نشانگر دمای همگن شدگی بین 123-298 و 112-218 درجه سانتی گراد و شوری بین 9/1- 8/12 و 9/1- 2/11 درصد وزنیNaCl است. مقادیر δ34S کانی های سولفیدی در دامنه 2/1+ تا 1/1- در هزار قرار دارد. تشکیل آلونیت و کائولینیت در دگرسانی آرژیلیک پیشرفته، کوارتز حفره دار در دگرسانی سیلیسی، همراهی باریت و انیدریت با رگه های کوارتزی و نبود کانی های کربناتی در مسجدداغی شواهدی از ذخیره اپی ترمال سولفید بالاست ؛ اگرچه کانی های سولفید بالای مس (انارژیت و لازونیت) حضور ندارند.
    کلیدواژگان: مسجد داغی، طلای اپی ترمال، پورفیری، ارسباران، ایران
  • فایق هاشمی، فردین موسیوند، مهدی رضایی کهخایی صفحات 587-616
    کانسار باریت- سرب- مس ورندان در جنوب غرب قمصر و درکمان ماگمایی ارومیه- دختر واقع شده است. توالی میزبان کانسار از پایین به بالا شامل سه واحد: 1- واحد توف سیلیسی خاکستری تا سبز، توف برش، توف بلوری و آندزیت، 2- واحد آهک نومولیتی سفید تا خاکستری رنگ، توف آهکی، شیل و مارنو و 3 - واحد توف برش و لیتیک توف بلوری است. کانه زایی در کانسار ورندان به صورت چهار زیرافق کانه دار و در واحد 1 رخ داده است. پنج رخساره متمایز شده در این کانسار شامل: 1- رگه- رگه چه ای، 2- مجموعه های برشی دهانه ای، 3- توده ای، 4- لایه ای- نواری (تناوب نوارهای غنی از باریت و غنی از گالن) و 5- ژاسپر سرخ رنگ هماتیت دار و رسوبات گرمابی- برون دمی آهن و منگنزدار و سولفیدی هستند. بافت ماده معدنی اغلب شامل توده ای، نیمه توده ای، نواری، لامینه، رگه- رگه چه ای و دانه پراکنده است. کانی های اولیه اصلی در ماده معدنی به ترتیب شامل باریت، گالن، کالکوپیریت، پیریت، اسفالریت، تتراهدریت، مگنتیت، پیرولوزیت و بورنیت وکانی های ثانویه شامل مس طبیعی، کوپریت، کوولیت، دیژنیت، گوتیت، مالاکیت و هماتیت هستند. کانی های باطله اغلب شامل کلریت، سریسیت، کوارتز و کلسیت هستند. دگرسانی عمده در سنگ دیواره از نوع کلریتی وکوارتز- سریسیتی است. در کانسار ورندان برای تعیین نوع کانسنگ، نسبت مقدار Cu/Zn به صورت میانگین برای کانسنگ باریتی سولفیدی در زیرافق اول، دوم و سوم به ترتیب برابر80/1، 12/0، 08/11 است که در زیرافق های اول و سوم در محدوده کانسنگ زرد و در زیرافق دوم در محدوده کانسنگ سیاه واقع می شوند. بر اساس بررسی های انجام شده، به نظرمی رسد کانسار ورندان در اثر فعالیت های آتشفشانی- برون دمی زیردریایی در یک حوضه کششی درون کمانی به صورت سولفید توده ای آتشفشان زاد نوع کروکو نهشته شده است.
    کلیدواژگان: باریت- سرب- مس، سولفید توده ای آتشفشان زاد، کروکو، ورندان، ژئوشیمی، کانی شناسی، قمصر
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  • Mohammad Hassan Karimpour, Azadeh Malekzadeh Shafaroudi, Abbas Esmaeili Sevieri, Shabani Saeed, Julien M. Allaz, Charles R. Stern Pages 294-267
    IntroductionThe Irankuh mining district area located at the southern part of the Malayer-Isfahan metallogenic belt, south of Isfahan, consists of several Zn-Pb deposits and occurrences such as Tappehsorkh, Rowmarmar 5, Kolahdarvazeh, Blind ore, and Gushfil deposits as well as Rowmarmar 1-4 and Gushfil 1 prospects. Based on geology, alteration, form and texture of mineralization, and paragenesis assemblages, Pb-Zn mineralization is Mississippi-type deposit (Rastad, 1981; Ghazban et al., 1994; Ghasemi, 1995; Reichert, 2007; Timoori-Asl (2010); Ayati et al., 2013; Hosseini-Dinani et al., 2015). Geology of the area consists of Jurassic siltstone and shale and different types of Cretaceous dolostone and limestone.
    The aim of this research is new geological studies such as revision of old geologic map, study of different types of textures and mineral assemblages within carbonate and clastic host rocks, and chemistry of galena, sphalerite, and dolomite. Finally, we combined these results with isotopic and fluid inclusion data and discussed on ore-fluid conditions.
    Materials and MethodsIn order to achieve the aims of this work, at first field surveying and sampling were done. Then,200 thin and 70 polished thin sections were prepared. Some of the samples were selected for microprobe analysis and galena and sphalerite minerals were analyzed by using JEOL- JAX-8230 analyzer at Colorado University, USA. The chemistry of dolomite and fluid inclusion data are used after Boveiri Konari and Rastad (2016) and stable isotope is used after Ghazban et al. (1994).
    DiscussionThe Irankuh mineralization is hosted by carbonate rocks (dolostone and limestone) and minor clastic rocks as epigenetic. Mineralization has occurred as breccia, veinlet, open space filling, spoted, dessiminated, and replacement (carbonate hosted rock). The mineral assemblages are Fe-rich sphalerite, galena, minor pyrite, Fe- and Mn-rich dolomite, bituminous, ankrite, calcite ± quartz ± barite within carbonate host rocks, whereas Fe-rich sphalerite, galena, pyrite, minor chalcopyrite, low Fe-dolomite, quartz, bituminous, ± barite ± calcite are important primary minerals at clastic host rocks.
    There is positive correlation between Ag and Sb values within galena mineral. Sb/Bi ratio in galena is up to 20, which is an indicator of low temperature deposits (Malakhov, 1968). The Irankuh homogenization temperature (170 to 260 ºC) is higher than that of US Mississippi-type deposits (80 to 120 ºC). Based on comparison of Th and Fe and Cd contents in sphalerite from Irankuh and US deposits (Viets et al., 1992), homogenization temperature of deposit has a positive relation with Fe values and a negative relation with Cd contents in sphalerite. Fe content in Irankuh sphalerite has reached up to 5% and Cd value is lower than 2000 ppm. In addition, carbonate hosted rock hydrothermal dolomites that are Fe-rich and ankrite have formed at some places. The evidence shows that Irankuh ore-fluid is Fe-rich. However, clastic hosted rock hydrothermal dolomites are low-Fe due to reaction of Fe and S resulting in pyrite formation. Based on O isotope (16–19 ‰) value from hydrothermal dolomites (Ghazban et al., 1994), ore-fluid has been derived from continental crust.
    ResultsFe-rich sphalerite and dolomite and ankrite are the most important characteristics of Irankuh mining district. Temperature and Fe-rich nature of ore-fluid and mineralogy signatures of Irankuh area can be used for exploration of this type of mineralization in Iran and the world. The Irankuh mining district is MVT type mineralization.
    AcknowledgementsThe Research Division of the Ferdowsi University of Mashhad, Iran, supported this study (Project No. 40221.3). Thanks to Bama Co. (especially Mr. Eslami) for the collaborations.
    ReferencesAyati, F., Dehghani, H., Mokhtari, A.R. and Mojtahedzadeh, H., 2013. Geochemistry and mineralogy studies of Gushfil Pb-Zn deposit, Irankuh, Isfahan. Analytical and Numerical Methods in Mining Engineering, 6: 83-91 (in Persian).
    Boveiri Konari, M. and Rastad, E., 2016. Nature and origin of dolomitization associated with sulphide mineralization: new insights from the Tappehsorkh Zn-Pb (-Ag-Ba) deposit, Irankuh Mining District, Iran. Geological Journal, DOI: 10.1002/gj.2875
    Ghasemi, A., 1995. Facies analysis and geochemistry of Kolah-Darvazaeh, Goud-Zendan, and Khaneh-Gorgi Pb-Zn deposits from south of Irankuh. M.Sc. thesis, Tarbiat Modares University, Tehran, Iran, 158 pp. (in Persian)
    Ghazban, F., McNutt, R.H. and Schwarcz, H. P., 1994. Genesis of sediment-hosted Zn-Pb-Ba deposits in the Irankuh district, Esfahan area, west-central Iran. Economic Geology, 89: 1262-1278.
    Hosseini-Dinani, H., Aftabi, A., Esmaeili, A. and Rabbani, M., 2015. Composite soil-geochemical halos delineating carbonate-hosted zinc–lead–barium mineralization in the Irankuh district, Isfahan, west-central Iran. Journal of Geochemical Exploration, 156: 114-130.
    Malakhov, A.A., 1968. Bismuth and antimony in galena, indicators of conditions of ore deposition. Geokhimiya, 11: 1283-1296.
    Rastad, E., 1981. Geological, mineralogical and ore facies investigations on the Lower Cretaceous stratabound Zn – Pb – Ba – Cu deposits of the Irankuh mountain range, Isfahan, west central Iran. Ph.D. thesis, Heidelberg University, Heidelberg, Germany, 334 pp.
    Reichert, J., 2007. A metallogenetic model for carbonate-hosted non-sulphide zinc deposits based on observations of Mehdi Abad and Irankuh, Central and Southwestern Iran. Ph.D. thesis, Martin Luther University Halle Wittenberg, Halle, Germany, 152 pp.
    Timoori-Asl, F., 2010. Sedimentology and petrology of Jurassic deposits and Basinal brines studies in formation of Irankuh deposit. M.Sc. thesis, Isfahan University, Isfahan, Iran, 120 pp. (in Persian)
    Viets, J.G., Hopkins, R.T. and Miller, B.M., 1992. Variation in minor and trace metals in sphalerite from Mississippi Valley-type deposits of the Ozark Region: genetic implications. Economic Geology, 87:1897–1905.
    Keywords: Mineralization, Mineral chemistry, Iron-rich fluid, Irankuh, Isfahan
  • Zahra Alaminia, Hashem Bagheri, Maryam Salehi Pages 295-312
    IntroductionUrumieh-Dokhtar Magmatic Arc (UDMA) is a good prospective area for Cu, Cu-Mo and Cu-Au deposits (Fig. 1A and B). The Zafarghand district is located in the central part of the UDMA and the northeastern Isfahan. The present study concerns geological observations, alteration investigations, geochemical data and fluid inclusion studies. The purpose of the research is to identify geochemical anomalies and source of metals in this area. Geochemical anomalies for mineralizing elements and element associations were identified by using statistical analysis methods. Additionally, these results together suggest a site for exploration drilling in this study area.
    Materials and methodsWe collected 186 samples (rock) along multi-cross sections oriented perpendicular to the strike of the South -Ardestan fault (Fig. 2).Trace element concentrations were determined by the ICP-MS technique in Amdel laboratory (Australia). Thin sections and doubly polished sections (100–200 µm thick) from quartz veins were prepared from samples collected from the Zafarghand district in the University of Isfahan. Heating and freezing experiments on fluid inclusions were performed as defined (by Goldstein and Reynolds (1994) on a Linkam THM600 stage.
    ResultsIgneous rocks in the Zafarghand area are dominated by the Eocene and post Eocene acidic-intermediate rocks that include dacite, rhyodacite and andesite associated with diorite, quartz diorite and microdiorite intrusions. The present investigations indicate that all rocks of the Zafarghand district exhibit a variety of alterations. Hydrothermal alterations include phyllic, potassic, silicification, and argillic with widespread propylitic. The mineralization consists of malachite, azurite, hematite, and goethite, rare amounts of magnetite, pyrite, and chalcopyrite. Numerical traditional statistical analysis techniques have been applied to interpret the geochemical data of the study area. These methods are aimed at producing maps resulting from the detecting of anomaly or threshold values from the background (Aitchison, 1986; Sun et al., 2009). Anomalies of Cu, Mo, Au, Ag, Pb, Zn and Sb were determined by Mean 2 standard deviation (Cheng, 2007; Zuo et al., 2009; Chen et al., 2016). Geochemical maps for these elements in rocks and soils (Fig. 4) show significant contrasts in haloes concentrations within the diorite and dacite rocks in the southeast of the study area. The addition of concentrations in rocks is suggested indicating that a district-scale geochemical present is confined to either base metals or precious metals. The obtained fluid inclusion results are compiled in Table 3. Primary fluid inclusions in quartz mostly consist of two-phases and rarely three phases. Homogenization temperatures (Th) in quartz samples represent wide variations from 123° to 550°C. They were classified according to the mode of homogenization into two immiscible types (Fig. 8): These are early inclusions stage with a high Th (between 328° and 550°C) and late stage inclusions with a low Th (between 123° and 390°C). The salinity measured using the equation of Bodnar (1993) for fluid inclusions varies from 1.15 to 43 eqv.wt% NaCl. It was divided into two groups including high salinity (32 to 43 eqv.wt% NaCl) and low salinity (1.15 to 5.16 eqv.wt% NaCl).
    DiscussionThe predictive results obtained by field observations, geochemical and micro thermometric studies are in good agreement with the known deposits. Geochemical anomalies are associated with phyllic and rare silicified altered rocks. The host rocks of anomalies are mainly dacite and diorite, respectively with an Eocene and younger age. District-scale geochemical patterns of several elements (Cu, Mo, Au, Pb, Ag, As, and Sb) in the surface coincide with the southeastern area and can be used to explore for epithermal and/or porphyry-type deposits. Anomalies of Cu and Mo are suitable for targeting Cu-Mo mineralization. Weak anomalies associated with Au concentration should also be combined with other exploration methods to identify mineralization in the Zafarghand district.
    Quartz veins are classified as V1 and V2 (Fig. 3G). Based on the properties of quartz hydrothermal fluids in the Zafarghand district, they are interpreted to have evolved in two-types of fluid fields (Fig. 7):- Stage 1 fluid inclusion: This inclusion included 32 to 43 wt percent NaCl eqv (high salinity) and homogenizing between 328° and 550°C. Primary quartz in stage 1 veins (V1) is poor inclusion and associated with sulfide minerals. It can be represented by fluids trapped during aporphyry- system episode.
    - Stage 2 fluid inclusion. This inclusion typically contains
    Keywords: fluid inclusions, geochemical data, Zafarghand, Urumieh-Dokhtar Magmatic Arc
  • Ali Kananian, Fatemeh Ghahramani, Fatemeh Sarjoughian, Jamshid Ahmadian, Kazem Kazemi Pages 313-334
    IntroductionGranitic rocks are the most abundant rock types in various tectonic settings and they have originated from mantle-derived magmas and/or partial melting of crustal rocks. The Oligo-Miocene Feshark intrusion is situated in the northeast of the city of Isfahan, and a small part of Urumieh–Dokhtar Magmatic Arc is between 52º21' E to 52º26'E and 32º50' N to - 32º53' N. The pluton has intruded into lower Eocene volcanic rocks such as rhyolite, andesite, and dacite and limestone.
    Analytical methodsFifteen representative samples from the Feshark intrusion were selected on the basis of their freshness. The major elements and some trace elements were analyzed by X-ray fluorescence (XRF) at Naruto University in Japan and the trace-element compositions were determined at the ALS Chemex lab.
    ResultsThe Feshark intrusion can be divided into two phases, namely granodiorite with slightly granite and tonalite composition and quartz diorite with various quartz diorite and quartz monzodiorite abundant enclaves according to Middlemost (1994) classification. The quartz diorite show dark grey and are abundant at the western part of the intrusive rocks. Granodiorite are typically of white-light grey in color and change gradually into granite and tonalite. The granodiorite and granite rocks consist of quartz, K-feldspar, plagioclase, biotite, and amphibole, whereas in the quartz diorites the mineral assemblages between different minerals are very similar to those observed in the granodiorite. However, amphibole and plagioclase are more abundant and quartz and K-feldspar modal contents are lower than in the granodiorite whereas pyroxene occurs as rare grains. They are characterized as metaluminous to mildly peraluminous based on alumina saturation index (e.g. Shand, 1943) and are mostly medium-K calc-alkaline in nature (Rickwood, 1989).
    DiscussionIn the Yb vs. La/Yb and Tb/Yb variation diagrams (He et al., 2009), the studied samples show small variations in La/Yb and Tb/Yb ratios, suggesting fractional crystallization. Chondrite-normalized REE patterns (Sun and McDonough, 1989) of all the samples essentially have the same shape with light REE (LREE) enrichment, flat high REE (HREE) and significant negative Eu anomalies. All of the samples exhibit similar trace element abundance patterns, with enrichment in large ion lithophile elements (LILE) and negative anomalies in high field strength elements (HFSE; e.g. Ba, Nb, Ta, P, and Ti) compared to primitive mantle (Sun and McDonough, 1989). The enrichment of LILE and LREE relative to the HFSE and HREE along with Nb, Ta, and Ti anomalies display close similarities to those of magmatic arc granites (Pearce et al., 1984) and also negative Nb–Ti anomalies are thought to be related to the fractionation of Ti-bearing phases (titanite, etc.). Moreover, these are the typical features of arc and / or crustal contamination (Kuster and Harms, 1998), while the negative P anomalies should result from apatite fractionation. The increasing of Ba and slightly decreasing Sr with increasing Rb, indicate that plagioclase fractionation plays an important role in the evolution of the studied intrusion. Tectonic environment discrimination diagrams such as Nb vs. Y, Nb vs. Yb (Pearce et al., 1984) and Th/Yb vs. Ta/Yb (Pearce, 1983) with enrichment in the LILE and LREE relative to HFSE and HREE and negative anomaly in the Nb, Ti and Eu indicate that their initial magma is generated in the subduction zone related to an active continental margin setting. þThe rocks genesis determining diagrams such as Nb vs. Nb/U (Taylor and McLennan, 1985), Ti vs. Ti/Zr (Rudnick et al. 2000), (La/Sm)cn vs. Nb/U (Hofmann et al., 1986), and Sr/Y vs. Y (Sun and McDonough, 1989) show that the magma was probably generated by partial melting of amphibolitic continental crust.
    Keywords: intrusive rock, petrogenesis, tectonic setting, Feshark, Isfahan, Urumieh Dokhtar arc
  • Hossein Hajimirzajan, Azadeh Malekzadeh Shafaroudi, Mohammad Reza Haidarian Shahri, Seyed Masoud Homam Pages 335-356
    IntroductionThe Dehzaman iron deposit is located in the Northeast of Kashmar- Kerman tectonic zone (KKTZ) (Ramezani and Tucker, 2003), southwest of Bardaskan in the Khorasan Razavi province. Mineralization are in two type: 1- Hematite ore (that is extracted for decades) 2- Magnetite ± Specularite and Magnetite - Specularite associated with apatite veins. Metarhyolite- Metarhyodacite units with low magnetic susceptibility are the most important host rocks in the study area. In the present paper, we provide an overview of the geological, alteration and mineralization characteristics, particularly the results of REE Geochemical data and Ground Magnetic data to explore the Magnetite ± Specularite veins. Identification of these characteristics can be used as a model for exploring this type of iron mineralization in the KKTZ specifically and elsewhere.
    Materials and methodsDetailed field work was carried out in the Dehzaman study area. A total of 95 polished blocks and thin sections were prepared and studied from host rock, mineralization and altered zones, and geology, mineralogy and alteration maps were prepared by conventional petrographic and mineralogical methods at the Department of Geology of the Ferdowsi University of Mashhad. In addition, 9 samples from the ore zones (Magnetite ± Specularite and Magnetite – Specularite) were analyzed by ICP-MS for minor and trace elements and REE content at ACME lab, Canada. Also in order to determine the iron ore grade, 7 samples were analyzed by titration methods. Magnetic susceptibility of ore veins and host rocks was measured in order to determine the magnetic susceptibility contrast, and then ground magnetic survey was carried out with Geometrics G856. Total magnetic Intensity was measured at 2223 stations, processed and interpretation maps were prepared. Finally, magnetic anomalies in the eastern and central parts of the study area were interpreted.
    ResultsIn the northeast of KKTZ, the outcrops of Precambrian to Neogene lithological units are observable. Metamorphosed volcano-sedimentary series of the Dehzaman mine area, all belong to the Upper Neoproterozoic- Lower Cambrian and are considered as low-grade regional metamorphism and deformation of high tectonic activity.
    Outcrop Rock units in the Dehzaman area consist of slate-phylite, Recrystallized carbonate units (Dolomite and limestone), Sericite schist, metavolcanic units, Mylonitic granite, Seynogranite. Metavolcanic units consist of Metarhyolite to metarhyodacite with porphyritic textures which hosts iron ore. Mineralization in the Dehzaman area consists of Magnetite and Specularite associated with apatite and lower amounts of chalcopyrite and Malachite.
    The structure of the area plays an important role in iron mineralization (Magnetite ± Specularite and Magnetite – Specularite) which occurs as vein and veinlet and multiple displacement of it are the result of this tectonic activity. Alteration is mainly limited to Magnetite ± Specularite and Magnetite – Specularite mineralized zone and is classified into chlorite, carbonate, silisification, biotite and tourmalinisation. Chip composite result from mineral veins show a high anomaly of REE (10.44 to 4827 ppm). Increase in rare earth elements is directly related to increasing microcrystals or inclusions of apatite in the Dehzaman iron ore. LREE is enriched into MREE and HREE in all samples. The amount of rare earth elements and their normalized pattern in the Dehzaman iron ore are similar with high rare earth elements in iron oxide ores that are usually known as Kiruna type which shows LREE enrichment relative to HREE (Frietsch and Perdahl, 1995).
    The higher magnetic susceptibility of magnetite ± Specularite and apatite-bearing Magnetite- Specularite in the center and east part respectively relative to volcanic host rocks has resulted in direct responses of mineralization from magnetic data. Integration of this data with geology, outcrop mineralization and filed survey delineated the trend, distribution and depth of magnetite mineralization. High anomaly of REE (in apatite) can also help us explore it indirectly from magnetic data. There is a weak magnetic response in mineral veins especially in the east and central parts of the deposit due to an increase of specularite. The result of ground magnetic survey in the eastern part of the veins shows an east-west anomaly in RTP image particularly at places which have no comparable outcrop. The width of mineralization is more than 20 meters in the northern and south eastern parts. Upward continued maps show the depth extension of the anomaly sources, mineralization to a depth of over 50 meters in the north and south of the eastern part. Based on magnetic anomalies and slope of veins, dip toward the east, 4 drilling locations to a maximum depth of 120 meters and at a vertical angle of 80 degrees in the hanging wall of faults associated with north and south magnetic anomalies are proposed in the eastern part of the Dehzaman deposit. Magnetic anomalies in the central part of the Dehzaman deposit show better correlation with surface outcrops because of higher concentration of magnetite in the veins. Anomalies here have an East-West trend with maximum width of 25 m in the central part. Upward continued images indicate that the depth of anomaly sources, mineralization, extend to over 50 meters.
    Anomaly discontinuities in the middle of the central part are due to two faults, located to the right and left of the center, which caused the displacement of mineral zone after mineralization.
    Based on magnetic anomalies and dip of the veins, two drilling locations to a maximum depth of 100 meters and at 80 degree angle are suggested in the eastern and western parts of central Dehzaman deposit.
    AcknowledgementsThis project is sponsored by the Ferdowsi University of Mashhad in connection with a research project dated 5.3.2015 No. 3/36972 that has been done. This research was made possible by the help of Opal Kany Pars Co.
    Keywords: Metarhyolite, Magnetite-Specularite, Ground Magnetic, Dehzaman, Kashmar-Kerman
  • Shokouh Riahi, Nader Fathianpour, Seyed Hassan Tabatabaei Pages 357-374
    IntroductionThe growing demand for base metals such as iron, copper, lead and zinc on the one hand and the diminishing of surficial and shallow resources of these elements on the other hand have forced explorationists to focus on detecting deep deposits of these metals. As a result, the discovery of such deep deposits requires more advanced and sophisticated methods in the course of preliminary prospecting stages. Since the discovery of new deposits is getting to be increasingly difficult, deploying new prospecting technologies that employ more deposit attributes in the course of combining exploratory evidence may reduce the exploration costs with lower uncertainties. In the past two decades, a number of new data mining and integrating approaches capable of incorporating direct and indirect mineralization indicators, based on expert knowledge, data, or a combination of both, have been proposed )Bonham-Carter, 1994(. In the first step, the input exploratory data layers are corrected and validated through applying some statistical pre-processing algorithms such as background and outlier removal methods. In order to detect a mineralization occurrence, it is necessary to find the proper exploratory geological, geochemical and geophysical data layers which have direct or indirect associations with the governing mineralization followed by constructing these models in an appropriate GIS platform (Malkzewski, 1999). Due to the imperfect available data and a number of unknown parameters affecting the mineralization process, the application of conventional GIS integration methods such as Boolean or weighted overlay or even fuzzy logic methods alone may not produce appropriate results, pointing to a need for deploying multi-criteria decision-making methods such as TOPSIS. In the present study, the pre-processed exploratory data including geological, remotely sensed geophysical and geochemical imagery were used to detect favorable mineralization zones through applying the multi-criteria decision-making method. Finally, the selected favorable areas in the metallogenic strip located at the south to the south-east of the Sarcheshmeh porphyry copper deposit are prioritized and introduced for further follow up ground exploration operations.
    MethodologyIn order to solve complex decision-making problems like the problem of mapping favorable porphyry copper mineralization zones under great uncertainties, the TOPSIS method is considered as an appropriate approach offering significant simplicity, flexibility and capability (Ataei., 2010). The TOPSIS method is considered to be an efficient method due to having very high accuracy, speed, sensitivity as well as being easy to implement and interpret the outputted results (Hwang and Yoon, 1981). It has found many applications in important areas of mining industry where there is a need to make decisions under risky conditions and data uncertainties.
    One basic issue in applying decision-making methods in the field of mineral exploration is to rank and propose the best possible candidates among all potentially favorable areas for the next stage of mineral exploration. In this regard, the best favorable areas are selected based on exploratory data layers including favorable lithologies, alterations, structures plus geochemical and geophysical anomalies (Pazand et al., 2012).
    Results and discussionIn the first step, the area located south to the southeast of one the largest porphyry copper deposits in Iran known as Sarcheshmeh was investigated for favorable areas using all available exploratory data as mentioned in the previous section using fuzzy logic integration approach in the GIS environment.
    Evaluating the highly favorable areas presented by the fuzzy logic approach showed great consistency with the already known copper mineralization prospects. Next, the first 20 priorities obtained from the fuzzy logic approach were chosen as the best candidates to be ranked using the TOPSIS multi criteria decision-making method. Among these favorable prospects, the one with the highest coefficient close to the ideal solution of 0.796 was found to be coincident with the Darehzar area that is a well known porphyry copper deposit 12 kilometers south of the Sarcheshmeh deposit.
    The favorable areas numbered 5 and 8 that correspond to well known porphyry copper mineralization prospects called Sereydoon and North Sereydoon were ranked as the second and third priorities with scores of 0.721 and 0.604, respectively. Other favorable areas ranked by the TOPSIS method were also prioritized and presented for further follow up explorations.
    To assess the sensitivity of the results obtained by the TOPSIS method, an amount of 10% of the values of each of the criteria were added and the outputted ranking results were compared to that of the original TOPSIS results. It was concluded that a slight change in the values of the criteria would not have significant impact on the results. However, 10 percent change of each criteria weight would greatly affect the prospects priorities obtained by re-applying the TOPSIS method.
    Keywords: mineral exploration, Fuzzy logic approach, TOPSIS method, porphyry copper mineralization, favorable regions
  • Ghodrat Torabi, Gholam Hossain Nazari Pages 375-395
    IntroductionLamprophyres are mesocratic to melanocratic igneous rocks, usually hypabyssal, with a panidiomorphic texture and abundant mafic phenocrysts of dark mica or amphibole (or both) with or without pyroxene, with or without olivine, set in a matrix of the same minerals, and with alkali-feldspar restricted to the groundmass (Woolley et al., 1996). Lamprophyres are frequently associated with orogenic settings and a mantle modified by dehydration of subducted slab (Gibson et al., 1995).
    Small outcrops of lamprophyres with Paleozoic to Oligocene age are reported from the central parts of Iran (Torabi 2009 and 2010). The primary magmas of these lamprophyres were derived from decompression melting of the mantle induced by a tensional regime of continental crust (Torabi, 2010). Bayat and Torabi (2011) called the western part of the CEIM (Central-East Iranian Microcontinent) (Anarak to Bayazeh) a “Paleozoic lamprophyric province” and suggested that the lamprophyre magmas were formed by subduction of Paleo-Tethys oceanic crust from the Early to late Paleozoic which resulted in the mantle metasomatism and enrichment.
    Lamprophyric dykes and stocks of the Kal-e-kafi area (Central Iran, Northern part of Yazd Block) cross-cut the Eocene volcanic rocks and other older rock units such as Cretaceous limestone. These lamprophyres are mainly composed of hornblende (magnesio-hastingsite), clinopyroxene (diopside) and plagioclase (labradorite to bytownite) as phenocryst, in a matrix of fine to medium grained of the same minerals and orthoclase, apatite, magnetite, chlorite and epidote.
    In this paper that is a report on the first study on the calc-alkaline lamprophyres of Central Iran, the petrography and mineral chemistry of calc-alkaline lamprophyric dykes of the Kal-e-kafi area are discussed.
    Materials and methodsChemical composition of minerals were conducted at Kanazawa University (Kanazawa, Japan) using the wavelength-dispersive electron probe microanalyzer (EPMA) (JEOL JXA-8800R), with 20kV accelerating potential, 20 nA beam current and a counting time of 40 seconds. Natural minerals and synthetic materials were used as standards. The ZAF program was used for data correction. The Fe3 content of minerals was estimated by stoichiometry. The Mg# and Fe# were calculated as [Mg/(Mgᗭ)], and [Fe2(Fe2)] atomic ratio of minerals, respectively.
    Trace element values of phenocrystic clinopyroxene, amphibole and plagioclase were analyzed by LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometry) using an ArF 193 nm Excimer Laser coupled to an Agilent 7500S at the Earth Science Department of the Kanazawa University (Japan). The diameter of the analyzed points was 60 micrometers for clinopyroxene and 120 micrometers for amphibole and plagioclase.
    Mineral abbreviations are adopted from Whitney and Evans (2010).
    Results and DiscussionLamprophyres of the Kal-e-kafi area (Central Iran, West of Yazd Block) are exposed as dykes and stocks which cross-cut the Eocene volcanic rocks and other older rock units such as Cretaceous limestone. Field studies indicate that calc-alkaline lamprophyric dykes of the Kal-e-kafi (east of Anarak) are younger than the other igneous rocks.
    According to the results of petrography and mineral chemistry, the mesocratic lamprophyres of Kal-e-kafi area are calc-alkaline spessartite.
    Unique values of Al2O3 and TiO2 associated with oscillatory zoning of clinopyroxenes reveal the crystallization of clinopyroxenes during ascending of magma.
    Plagioclase phenocrysts are labradorite to bytownite in composition and the plagioclases of matrix are labradorite. Chemical composition diversity of plagioclase indicates the fractional crystallization of these lamprophyres.
    Amphibole thermometry estimate average temperature of 860°C and barometry by Anderson and Smith (1995) shows 1.5 to 3 kbars pressure. Clinopyroxene thermobarometry calculate 1150 °C temperature and pressure between 2 to 5 kbars.
    The geochemical features and thermobarometry of the Kal-e-kafi spessartite minerals suggest that the primary lamprophyric magma was derived from partial melting of a lithospheric mantle spinel lherzolite. Changes in values of pressure, water content, and Oxygen fugacity during magma ascending lead to oscillatory zoning minerals.
    Based on the mineral chemistry, it can be concluded that the Kal-e-kafi lamprophyres were formed in a subduction-related environment by a calc-alkaline magmatism.
    Keywords: Spessartite, Lamprophyre, Calc-alkaline, Oligocene, Kal-e-kafi, Central Iran
  • Amir Ali Tabbakh Shabani, Morteza Delavari Kooshan, Mahsa Hajiabdolrahim Khabbaz Pages 397-418
    IntroductionThe Upper Eocene basic volcanic rocks that have cropped out in Karaj formation in the Boumehen and Roudehen area in the east of Tehran are characterized by fibrous zeolites filling their vesicles, cavities and fractures creating amygdale texture. The study area is located structurally in the Central Alborz orogenic belt. The presence of large volumes of shoshonitic magma during the Middle to Late Eocene in southern–central Alborz implies that partial melting to produce shoshsonitic melts was not a local petrological event. Thus, their ages, formation processes, and interpretations are of regional tectonic significance. In this study, we present a detailed petrography, mineral chemistry, and whole-rock geochemistry of high-K (shoshonitic) basic rocks to understand the petrogenesis and source region and to deduce the nature of the tectonomagmatic regime of the Alborz.
    Materials and methodsIn this study, we present new major and trace element data for a selection of 4 of the least altered samples by a combination of X-ray fluorescence (XRF) and ICP-OES techniques at the Zarazma Mineral Studies Company.
    Mineral analyses were obtained by wavelength dispersive X-ray spectrometry on polished thin sections prepared from each rock sample described above for 12 elements using a Cameca SX-50 electron microprobe at the Istituto di Geologia e Geoingegneria Ambientale, C.N.R., University La Sapienza of Rome, Italy. Typical beam operating conditions were 15 kV and probe current of 15 nA. The accuracy of the analyses is 1% for major and 10% for minor elements. A total of 24 point analyses were collected.
    Results and DiscussionThe extent of alteration in the study rocks varies from slight to severe and shows porphyritic to glomeroporphyritic textures. Pyroxenes are generally subhedral to euhedral and occur as discrete crystals as well as aggregates. Olivine may occur only as relics filled with iddingsite, chlorite and calcite. Plagioclase is subhedral to euhedral and occurs both as pheocrysts and microliths in the glassy groundmass. The plagioclase crystals are variably sassuratised and sometimes replaced by zeolites.
    Microprobe data indicate a restricted range of chemical composition for pyroxene falling in diopside and augite fields of ternary pyroxene classification diagram (Morimoto, 1988). The plagioclase composistions have been plotted in the fields of labradorite and bytownite in the orthoclase–albite–anorthite ternary diagram (Deer et al., 1992). On the F1-F2 tectonic discrimination diagram of Nisbet and Pearce (1977), pyroxene compositions plot mainly in volcanic arc basalt field consistent with their whole rock geochemistry. Thermobarometry based on pyroxene composition (Soesoo, 1997) displays a range of temperatures from 1150 to 1250 0C and pressure from 3 to 8 kbar for its crystallization.
    Whole rock compositions show that the variations of SiO2 contents are narrow (47.08 – 47.47 wt%) and TiO2 (1.1 – 1.24 wt%). Relatively higher contents of K2O show a shoshonitic affinity in the K2O–SiO2 diagram (Peccerillo and Taylor 1976). Trace element and rare earth element (REE) distribution patterns for the basaltic samples normalized to the primitive mantle (McDonough et al., 1992) and chondrite values (Sun and McDonough, 1989) show similar patterns. The samples are all enriched in large-ion lithophile elements (LILEs), such as Rb, Ba, and K, and light rare earth elements (LREEs) ((La/Sm)N= 2.3–3.2) relative to the more immobile elements (e.g., Hf, Ti and Y). The plot of analyzed samples in a series of different tectonic discrimination diagrams shows that the Boumehen-Roudehen alkaline basalts are consistent with characteristics of subduction related (active continental margins) tectonic environments. In addition, enrichment in LILE and depletion in HFSE on spidergram create patterns which are very similar with the pattern of Andean counterparts indicating an arc setting.
    AcknowledgmentsMarcello Serracino is thanked for microprobe analyses. The authors are grateful to Journal Manager and reviewers who critically reviewed the manuscript and made valuable suggestions for its improvement.
    Keywords: Olivine basalt, alkaline, volcanic arc, Central Alborz, Boumehen-Roudehen
  • Marziyeh Mahboubiyan Fard, Farhad Ehya, Omid Javariani Pages 419-438
    IntroductionIron is among the metals whose ore deposits are not confined to a specific geologic period of crustal formation and they have formed in various geologic environments during previous periods (Ghorbani, 2007). About 95% of iron ore deposits have sedimentary origin and have formed due to chemical deposition from ancient sea water. The remaining percent is the result of alteration and magmatic activities (Gutzmer and Beukes, 2009). In sedimentary environments, a large amount of sedimentary iron minerals have formed resulting in different iron facies. Iron oxide facies are of the most important facies (James, 1954). The most important Iranian iron deposits are located in Central Iran, Sanandaj- Sirjan and East Iran zones, and the Kordestan area (Ghorbani, 2007). In the Orumiyeh-Dokhtar Zone, many iron ore deposits have been formed in conjunction with granitic and granodioritic plutons related to Oligocene-Miocene plutonic and volcanic activities (Hoshmandzadeh, 1995). The Mamouniyeh iron ore-terra rossa deposit is located in the Orumiyeh-Dokhtar volcanic zone. Iron mineralization have occurred in trachytic-trachyandesitic lavas and pyroclastic rocks of Pliocene age.
    Materials and methodsA total of 28 rock samples were picked up from ore and host rocks during field observations. Petrographical and mineralogical studies were performed on 15 thin sections of ore and host rocks. XRD studies were performed on 3 ore samples. In order to investigate the geochemistry of the ore, 10 samples were analyzed for major, trace and rare earth elements (REEs) using the ICP-MS method.
    ResultField and mineralogical studies reveal that the ore is composed of hematite along with crypto-crystalline silica as alternating layers of various thickness and color. The existence of alternating layers of hematite and quartz implies that the ore is similar to banded iron formations, but on a smaller scale, related to submarine hydrothermal activities. Silica is found as chert and minor jasper. Some secondary dolomite and calcite, filling the fractures and open spaces are found. Clay minerals are also minor constituents of the ore. The remaining fossils of green-blue algae indicate the conditions of iron deposition and effective biological processes in oxidizing Fe and creation of new oxide minerals in a sedimentary basin. XRD studies show that tetraferriannite, hisingerite, barite, dolomite and calcite are present in addition to dominant hematite and quartz minerals. Hisingerite is formed in sedimentary iron deposits during hydrothermal alteration (Whelan and Goldich., 1961). Tetraferriannite occurs in low grade iron formations (Miyano, 1982). Structurally, the mineralization is controlled by a tectonic zone in which abundant breccias and faults are well found.
    The amount of Fe2O3 ranges between 11.62% and 65.73%, with an average value of 31% Fe2O3. The amounts of Cr (3-95 ppm) and Zr (
    Keywords: Hematite, Silica, Rare Earth Elements, Hydrothermal fluid
  • Zahra Vahedi Tabas, Seyyed Saeid Mohammadi, Mohammad Hossein Zarrinkoub Pages 439-461
    IntroductionBasaltic volcanoes are one of the volcanisms that have occurred in different parts of the world. The study of these lavas is important for petrologists, because they are seen in different tectonic settings and therefore diverse mechanisms affect their formation (Chen et al., 2007). Young volcanic rocks such as Quaternary basalts are one of latest products of magmatism in Iran that are related to deep fractures and active faults in Quaternary (Emami, 2000). The study area is located at 140km east of Birjand at Gazik 1:100000 geological map (Guillou et al., 1981) and have 60̊ 11' to 60̊ 15 '27" eastward longitude and 32̊ 33' 24" to 32̊ 39' 10" northward latitude. On the basis of structural subdivisions of Iran, this area is located in the northern part of the Sistan suture zone (Tirrul et al., 1983). Because of the importance of basaltic rocks in Sistan suture, this research is done with the aim of investigating the petrography and mineralogy of basaltic lavas, the nature of basaltic and intermediate magmatism and finally determination of tectonomagmatic regime.
    Materials and methodsAfter field studies and sampling, 85 thin sections were prepared and carefully studied. Then ten samples with the lowest alteration were analyzed for major elements by inductively coupled plasma (ICP) technologies and trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS), following a lithium metaborate/tetraborate fusion and nitric acid total digestion at the Acme laboratories, Vancouver, Canada. Electron probe micro analyses of clinopyroxene and olivine were done at the Iranian mineral processing research center (IMPRC) by Cameca SX100 machine. X-ray diffraction analysis of minerals was done at the X-ray laboratory of the University of Birjand.
    ResultsIn 60km south of GaziK at the east of the southern Khorasan province and the northern part of the Sistan suture zone, volcanic rocks with intermediate (Oligomiocene) and basic (Quaternary) compositions outcropped above ophiolitic units. Electron probe micro analyzer (EMPA) data indicated that clinopyroxene in basalt is diopside and olivine from chrysolite type with Mg# around 81-82 percent. The whole rocks geochemical data prove calc-alkaline and alkaline nature for andesites and basalts, respectively. Trace element patterns, especially for andesites show enrichment in Ba, K, Cs, Sr and Th, depletion in P, Nb, Ti and enrichment in LREE relative to HREE. Electron probe micro analyses of clinopyroxene in olivine basalt support alkaline nature and within plate tectonic setting for this rock. Thermobarometry of clinopyroxene in olivine basalt record crystallization conditions about 1200 oC and 6-10kbars.
    DiscussionThe origin of intraplate volcanism is diverse and not always well understood. Most intraplate volcanos have been attributed to (i) mantle plumes and hot spots, (ii) continental rift, (iii) back-arc extension and (iv) lithosphere delamination and thinning (Chen et al., 2007). Although volcanism at intraplate settings is less common than along mid-ocean ridges and subduction zones, it is of significant importance for both preventing geological hazards and understanding mantle geochemistry. It is believed that alkaline oceanic island basalts (OIB) are only derived from the asthenospheric mantle (Alici et al., 2002). However, the intracontinental alkaline magmas can be produced by partial melting of metasomatized mantle enriched in LREE and LILE (Upadhyay et al., 2006).
    On the basis of trace element diagrams, Ratouk basaltic rocks placed within plate volcanic zone (WPVZ) and andesitic samples have been located within the active continental margin (ACM).
    The studies that took place about young basaltic volcanism (Alishahi, 2012; Mollashahi et al., 2011; Ghasempour et al., 2011; Pang et al., 2012; Walker et al., 2009) have shown that the mechanisms of their occurrence are similar such that all of them have been formed in intraplate extensional environments and active fault zone and originated from enriched mantle or asthenosphere. Lithospheric thickness maps derived from the speed of shear waves show that the lithosphere is thin in east of Iran and volcanic activity has occurred along strike-slip faults (Walker et al., 2009). Therefore, according to other similar basaltic eruptions that have occurred in the Sistan suture zone, we can say that all of them are from the same origin and as a result of deep fractures within continental plates that provide conditions for the eruption of basaltic magma.
    Andesitic units in the Ratouk area are located within the active continental margin and show similar characteristics to rocks of the Subduction Zone in terms of composition.
    AcknowledgementsThe authors would like to thank reviewers for the constructive comments which greatly contributed to the improvement of the manuscript.
    Keywords: Clinopyroxene, Andesite, Alkali basalt, Ratouk, Sistan suture
  • Shahryar Mahmoudi, Azra Mahmoudi, Behzad Mehrabi Pages 463-481
    IntroductionThe Gol-Gohar iron ore deposit located in 55 km South West of the city of Sirjan, in the Sanandaj-Sirjan structural zone. Sanandaj-Sirjan zone (SSZ) is part of the Alpian-Hymalian orogenic belt and it is located in the west of the central Iran microplate. SSZ represented the metamorphic belt of the Zagros orogeny, that extends for 1500 km from Sirjan in the southeast to Sanandaj in the northwest of Iran (Mohajjel et al, 2003). The Gol-Gohar iron ore deposit is surrounded by a complex of igneous and metamorphic rocks mainly consisting of pelitic schists, basic schists, gneiss, amphibolite, marble, granodiorit, granite and mylonitic granite.
    In the early studies on the genesis of Gol-Gohr iron deposits, it was considered that sedimentary and tectonic processes were more effective in iron ore deposition. Later studies mainly confirmed a magmatic genesis for Gol-Gohar iron ore (Mucke and Golestaneh, 1982). Although some researchers argued that skarnisation process was the main cause of mineralisation (Hallaj and Jacobpor, 1991º Torabian, 2007), still some discussions on Gol-Gohr genesis are underway.
    Materials and methods –Gol-Gohar mine is divided into three blocks and several exploratory boreholes have been drilled down to 200 to 1400m depths in the third block. The representative samples were taken from exploration drill holes and outcrops around the mine. Microscopic observation (Zeiss Aksioscope) in thin and polish sections show that the main ore mineral in the Gol-Gohar deposit is magnetite formed into two types with distinctive optical properties; the milky-gray magnetite (type1) named also “upper ore” and blue to brown magnetite (type2) named also “lower ore” (Mucke and Golestaneh, 1982). Mineralogy and microtectonic study were carried out on 100 thin and 30 polished sections using Zeiss research microscope. For geochemical analyses 20 samples were selected from 3 major exploration drill holes. After whole rock chemical analyses (XRF), four sample from two ore types and metamorphic host rock were examined by EPMA. The analytical examination were carried out in the Iranian Mineral Processing Research Center (IMPRC) using PW2404 Philips XRF and Cameca X-100 EPMA.
    DiscussionBased on microstructural observations of the metamorphic host rocks of the Gol-Gohar deposit, two main deformation phases were recognized which caused two distinctive foliations, S1 and S2. S1 is a continuous foliation with N18W to N24W general trend and average of 45 to 60 degrees slope toward the East. S2 is with 15-30 ° deviation from S1 and N9E to N17E general trend overprinted on the S1. Granite emplacement has caused deformation phases and magnetite crystals (Which Type) just oriented within the first deformation phase (S1). The second deformation phase (S2) is recognized by fish shapes and pressure shadows around the minerals. The preferred orientation of magnetite in S1 and growth with biotite and garnet in the biotite, garnet and staurolite zones suggests that the early stage of mineralization in Gol-Gohar is contemporaneous with progressive metamorphism. Type1 magnetite does not show any margin thermal reactions.
    EPMA analysis of type 2 magnetite indicates a distinctive enrichment of high mobile elements. The distribution and frequency diagram (Celine and Beaudoin, 2011; Tong et al., 2011) shows that skarnisation is the main process in the genesis of the Gol-Gohar iron ore. Also, a comparison of the chemical composition of type 1 and 2 magnetite shows similar values of Ti, Cu, Si and Mg while metamorphic magnetite (type2) specifically show higher concentrations of Al and Mg.
    The metamorphism-related deformation history of the study area based on magnetite fabrics, mineralogy and metamorphic evolution implies a new model for the Gol-Gohar mineralization. Penetrative NS- to NW/SE dipping fabric is represented by S1 foliation hosted type1 magnetite, which was formed in the prevailing NW–SE shortening event during the first stage of regional metamorphism during the late Carboniferous– early Permian time. This shortening event is interpreted to be associated with the collisional event between the Sanandaj-Sirjan and central Iran blocks. The S2 fabric probably is related to the intrusion of Jurassic or younger granite in the area. Type 2 magnetite has been formed during the Skarnification process.
    Keywords: Sanandaj-Sirjan metamorphism, the Gol-Gohar iron ore deposit, Microstructure, Skarn-type iron ore deposit
  • Faezeh Nabiloo, Behnam Shafiei Bafti, Arash Amini Pages 483-507
    IntroductionUpper part of Elika Formation (middle Triassic) in the central Alborz as one of the most important fluorite districts in Iran is the host of some carbonate rock-hosted fluorite deposits such as Kamarposht, Pachi-Miana, Shashroodbar, Era (Alirezaee, 1989; Gorjizad, 1996; Rastad and Shariatmadar, 2001; Rajabi et al., 2013; Vahabzadeh et al., 2013; Zabihitabar and Shafiei, 2015). One of the main active fluorite mines in the central Alborz is Kamarposht which is located at the southeast of DoAb in the Mazandaran province. The Kamarposht mine has 75000 tons of ores and mining there has begun in 2005. The effects and evidences of underground mining in the northern and southern parts of this mine indicate high-grade and coarse-grained ore zones which have fluorite, galena and barite. Until now, basic economic geology studies in the Kamarposht mine including mineralogy, fabric and texture of mineralization for introducing a new fluorite mine in Iran have not been carried out. The present study is based on field observations and macroscopic as well as microscopic studies aimed at identification of morphology and mode of occurrence of the ore body, mineralogy and fabric of mineralization and discussion of as well as presentation of a new genetic model for the Kamarposht mine.
    Materials and methodsFor the present research study, field geology and sampling were carried out to collect 100 samples from various fluorite ore-types and carbonate host rocks. The samples prepared for thin section (n=55) and polished-thin sections (n=22).
    ResultsField observations indicate that economic mineable ore zones of the Kamarposht mine are mainly hosted by dolomitic limestone and silicified carbonate horizons of the Elika Formation. The ore zones have fluorite, barite and galena which are mainly located in fractured and faulted zones as well as karstic cavities in the host horizons. Coarse grain and euhedral fluorites with various colors, significant presence of barite as massive and vein, abundant galena and near contact between mineralization zones in carbonate host rocks (Elika Fm.) and pyrite-bearing coalified shales (base of Shemshak Fm.?) as faulted and/or interbedded are all distinctive geological features for the Kamarposht mine. Fluorite mainly occurs as interrupted, dense and voluminous massive bodies with/without galena which have occupied cavities and open spaces between brecciated fragments of dolomitic limestone relative to the form of disseminate grains, veinlets and geode. Massive and voluminous accumulations of barite in dissolution and karstic cavities and also as discordant veins relative to the bedding of the host rock which have been generated radial, breccias and zebra structures in barite ores. Galena occurs as veinlets and breccias with medium to coarse grain size with/without fluorite in dolomitic and silicified host rocks and also as vein-veinlets into and/or rime of massive barites.
    DiscussionBased on field evidences and mode occurrence of ore minerals and ore textures, mineralization in the Kamaposht mine has occurred as syn-diagenetic (primary) and post-diagenetic/epigenetic (main) fabrics. Ores with disseminate particles of ore minerals, stylolite, geode and tiny veinlets fabrics have been interpreted as primary textures that co-exist with diagenesis of host rocks. These fabrics have been formed under diagenetic processes such as nucleation, re-crystalization and disolution of host rocks by diagenetic phreatic reactions that have caused increasing temperature-pressure due to increasing depth of burial diagenesis (Force et al., 1991; Fontbote and Gorzawski 1990; Rastad and Shariatmadar, 2001; Haeri-Ardakani et al., 2013). The main textures of mineralization in the Kamarposht mine namely open-space filling fabrics including veins and breccias fabrics with replacement, network and zebra textures which are associated with dolomitized and silicified host rock have been caused by late and/or post-diagenetic processes (Fontbote and Gorzawski 1990; Sangster, 1996; Leach et al., 2005). Change and conversion of diagenetic mineralization fabrics to epigenetic ones which is associated with developing and increasing the intensity of fluorite-barite-galena mineralization, is attributed to the function of hydrothermal solutions/basianl brines generated due to the main Cimerian orogeny (Rajabi et al., 2013). The increasing dissolution of host rock along with its dolomitization and silicification were probably the main processes responsible for epigenetic mineralization in the Kamarposht mine. Finally, the present study shows that the Kamarposht mine is a fluorite-rich MVT deposit with poly-genetic origin.
    Keywords: The Kamarposht mine, Fluorite, Elika Formation, Mazandaran
  • Habibollah Bazdar, Hadi Fattahi, Feridon Ghadimi Pages 509-544
    IntroductionMineral exploration is a process by which it is decided whether or not continuing explorations at the end of each stage t will be cost-effective or not. This decision is dependent upon many factors including technical factors, economic, social and other related factors. All new methods used in mineral exploration are meant to make this decision making more simplified. In recent years, advanced computational intelligence methods for modeling along with many other disciplines of science, including the science of mineral exploration have been used. Although the results of the application of these methods show a good performance, it is essential to determine the mineral potential in terms of geology, mineralogy, petrology and other factors for a final decision. The purpose of this paper is to provide a comprehensive set of mineral exploration research and different applications of computational intelligence techniques in this respect during the last decades.
    Materials and methodsArtificial neural network and its application in mineral exploration Artificial neural network (ANN) is a series of communications between the units or nodes that try to function like neurons of the human brain (Jorjani et al., 2008). The network processing capability of communication between the units and the weights connection originates or comes from learning or are predetermined (Monjezi and Dehghani, 2008). The ANN method has been applied in different branches of mining exploration in the last decades (Brown et al., 2000; Leite and de Souza Filho, 2009; Porwal et al., 2003).
    Support vector machines (SVM) and its application in mineral exploration SVM uses a set of examples with known class of information to build a linear hyperplane separating samples of different classes. This initial dataset is known as a training set and every sample within it is characterized by features upon which the classification is based (Smirnoff et al., 2008). The SVM classifier is a new method that has been applied in mining exploration in recent years, for example for separating alterations in initial stages of mining exploration (Abbaszadeh et al., 2013).
    Neuro-fuzzy methods and its application in mineral exploration
    The base of fuzzy logic is to make flexible borders between different samples. By applying this method with other methods, we can improve their performance. The adaptive neuro-fuzzy inference system (ANFIS) is one of the useful approaches in this branch of intelligent methods in mining exploration. For example, we can note the use of this approach in mineral mapping (Porwal et al., 2004).
    Hybrid computational intelligence methods and its application in mineral exploration
    In order to improve the performance of intelligence methods, often a hybrid form of these methods and optimization algorithms is a fit option. For example, Genetic Algorithm (GA), Ant Colony Optimization and Particle Swarm Optimization (PSO) have been applied with ANN and SVM in research studies. For example, (Chatterjee et al., 2008) applied a genetic algorithm-based ANN for ore grade estimation.
    ConclusionsEarth sciences in general and more specifically mineral explorations have always been a part of science that encompasses all the factors involved due to their complexity and the factors that influence them thereby making the solution very difficult or almost impossible to solve. Because of the difficulty of accurate measurement parameters and boundaries, in recent years, researchers have been trying to use modeling in order to simplify natural disasters for better evaluation. One of the models that has received a lot of attention in recent years is modeling with of computational intelligent methods. The appropriate results show the usefulness of these methods.
    Keywords: Computational intelligence methods, exploration, minerals, modeling
  • Atefeh Ghaedi, Abbas Moradian, Hamid Ahmadipour Pages 545-559
    IntroductionBorate deposits are often important constituents of economic non - marine evaporates. They produce under arid climatic conditions in playa lakes (Floyd et al., 1998). In the south – western parts of the Kerman province, such as the Khatoonabad area (east of the city of Shahr –e –Babak) and Robat – Marvast basin (west of Shahr – e – Babak), there are several borate deposits. They can be seen mainly in Sanandaj – Sirjan depressions and they occur as borate bearing nodules beneath a thin layer of soil. In general, boron considerably reduces the thermal expansion of glass, provides good resistance to vibration, high temperatures and thermal shock, and improves its toughness, strength, chemical resistance and durability. It also greatly reduces the viscosity of the glass melt. These features, and others, allow it to form superior glass for many industrial and specialty applications (Garrett, 1998). In the past, the ancient residents used them as co-melting matters. Ulexite which is frequently found in the Khatoonabad playa (at 30 km South East of Shahr Babak) have Jewel properties (Ghaedi et al., 2014).
    Materials and methodsAfter reviewing and Library Studies, geological field studies on the borate deposits were carried out from Shahr – e – Babak Playa. In order to take better samples, several pits were excavated with a depth of 30 cm to 1 meter so that borate minerals became apparent. X-ray diffraction analysis (IMIDRO, Karaj), and ICP AES (ALS CHEMEX, Canada) methods were carried out on representative samples taken from the studied area.
    DiscussionField observations show that in the studied areas, borate bearing basins are fed by rivers which have originated from Sanandaj – Sirjan metamorphic rocks, Nain – Baft colored mélanges and igneous rocks of Urumieh – Dokhtar magmatic belt. Borate minerals also occur in fibrous aggregates and massive forms.
    MineralogyXRD results show that the studied borate minerals mainly belong to the hydrated borates and contain ulexite, borax, gowerite, sassolite and inyoite. Geochemichal data indicate that the boron is the dominant constituent in the studied playa. Borate minerals are divided into two groups of hydrated and non-hydrated borate category (Palache et al., 1952.; Garrett, 1998). Both hydrated and non-hydrated borate minerals have been formed in the Shahr-e-Babak playa.
    Hydrated borate in the study areas:Hydrated borates are those borates in which water molecules are involved (Garrett, 1998). In the studied area, the hydrated borate minerals include: Borax, Ulexite, Inyoite, Gowerite.
    Non-hydrated borate in the study areas:In the Shahr-e-Babak playa, Sassolite non-hydrated borate minerals are abundant.
    According to the XRD analyses performed on samples from the study areas, the hydrated borate minerals are more important minerals. The main economic valuable minerals include:1- Ulexite (NaCaB5O9.8H2O): Crystal Data: Triclinic. Point Group: 1 (Ghose et al., 1978). In the Shar – e - Babak playa, ulexite occurs as deposits with massive, cauliflower-like nodules and fibrous textures.
    2- Borax (Na2B4O5(OH)4 •8H2O): Crystal Data: Monoclinic. Point Group: 2/m. Crystals are commonly short to long prismatic [001] (Levy and Lisensky, 1978). In the studied borate samples, it can be found in association with the other borate minerals, and often occurs in the form of salt marsh.
    3- Gowerite (CaB6O8(OH)4 •3H2O): Crystal Data: Monoclinic. Point Group: 2/m (Erd et al., 1959). In the Khatoonabad samples, it was found as prismatic and spherical crystals along with ulexite.
    4- Inyoite (CaB3O3 (OH)5 •4H2O): Crystal Data: Monoclinic. Point Group: 2/m (Christ, 1953). This mineral has been detected in the studied area by XRD.
    Sassolite (H3BO3): Crystal Data: Triclinic. Point Group: 1 and as scaly pseudohexagonal crystals (Allen and Kramer, 1957). This mineral is found frequently in the Marvast Playa.
    GeochemistryGeochemical data indicate that in the studied playa, boron is very abundant. Good correlation between the elements, such as B and Ca confirms the formation of Calcium bearing borate mineral in the studied areas.
    OriginField observations show that in the studied areas, borate bearing basins are fed by rivers which have originated from the Sanandaj – Sirjan metamorphic rocks, Nain – Baft colored mélanges and igneous rocks of the Urumieh – Dokhtar magmatic belt.
    ResultThe XRD results show that the studied borate minerals mainly are hydrated ones and contain ulexite, borax, gowerite, sassolite and inyoite. Geochemichal data confirm the frequency of boron in the playa. Good correlation between the elements such as B and Ca verifies the formation of Calcium bearing borate mineral in the studied areas.
    AcknowledgementsThe authors wish to thank IMIDRO for performing XRD analyses.
    Keywords: The Sahr- e - Babak Playa, Borate, Ulexite, Sassolite
  • Susan Ebrahimi, Saeed Alirezaei, Yuanming Pan, Behzad Mohammadi Pages 561-586
    IntroductionThe Masjed- Daghi gold deposit lies in an area of widespread Cenozoic volcanic and plutonic rocks at the intersection of the Alborz- Azarbaijan and Urumieh- Dokhtar belts. The area was covered by a detailed exploration program, including geological maps at 1:1,000 scales (~8 km²), several hundred meters of trenches and systematic sampling for Au, Ag, Pb, Zn, Cu, As, Hg analysis, and 16 diamond drill holes at a total of 1200 meters (Mohammadi et al, 2005). The vein type gold deposit in Masjed- Daghi is closely associated with a porphyry type Cu-Au deposit.
    Our study focuses on the gold bearing veins system in an attempt to understand the characteristics of ore fluids and mechanisms of ore formation, and to develop exploration criteria for Masjed Daghi and similar occurrences in Alborz and other Cenozoic magmatic assemblages in Iran.
    Materials and methodsVarious rock types, alteration assemblages and mineral parageneses were characterized by transmitting and reflected light microscopy, X-ray diffraction (XRD) and electron microprobe analysis. Microprobe analyses were performed using a JEOL 8600 Superprobe electron microprobe at Saskatchewan University. Operating conditions were an accelerating voltage of 15 kV and a beam current of 50 nA.
    Representative samples from drill holes were selected for fluid inclusion studies. Fluid inclusion data were obtained using a fluid Inc. adapted USGS gas flow heating and freezing system at the Department of Geological Science at the University of Saskatchewan, Canada.
    To investigate the source of ore fluids, representative sulfidic samples from drill holes were selected for sulfur isotope studies. Isotopic analyses were performed using a Thermo Finnigan DeltaPlus at the G.G. Hatch Stable Isotope Laboratories, University of Ottawa. The standard error of analyses is less than ±0.1 per mil.
    ResultsAuriferous quartz veins in Masjed- Daghi are associated with porphyry style mineralization. Various alteration assemblages including argillic, silicic, potassic, phyllic, and propylitic occur in the district (Emamalipour et al., 2010). The auriferous quartz veins are hosted by silicified and kaolinitized volcanic rocks, dominated by trachyandesite. The mean grade of Cu is 0.15% the gold assay varies from
    Keywords: Masjed Daghi, Epithermal Gold, Porphyry, Arasbaran, Iran
  • Fayeq Hashemi, Fardin Mousivand, Mehdi Rezaei-Kahkhaei Pages 587-616
    IntroductionThe Varandan Ba-Pb-Cu deposits are located15 km southwest of the town of Qamsar and approximately 7 km south west of the Qazaan village, in the Urumieh- Dokhtar magmatic arc. The Kashan region that is situated in west-central Iran hosts several barite-base metal deposits and occurrences, the biggest ones are the Varandan Ba-Pb-Cu (case considered in this study) and the Tapeh-Sorkh (Khalajmaasomi et al., 2010) and Dorreh Ba (Nazari, 1994) deposits. Previous researchers (Izadi, 1996; Farokhpey et al., 2010) have proposed an epithermal model for formation of the Varandan deposit. However, based on some feature of the deposit, it seems that this genetic model may not be correct. Therefore, it is necessary to do more precise research studies on the deposit. The main purpose of this paper is to discuss the genesis of the Varandan deposit based on geological, ore facies, mineralogy, wall rock alterations, and geochemical studies.
    Materials and methodsA field study and sampling was performed during the summer of 2013. To assess the geochemical characteristics of the deposit, about 17 systematic samples from different ore facies of the first, second and third sub-horizon were collected for petrography and mineralogy, and for inductively coupled plasma-atomic emission spectroscopy(ICP-AES), X-ray diffraction (XRD) and X-ray fluorescence (XRF) geochemical analysis methods. The microscopic studies were done in the optics laboratory of the Shahrood University, and the geochemical analyzes were conducted in laboratories of the Center of Research and Mineral Processing Ore Minerals of Iran, Karaj, Iran.
    ResultsThe host sequence in the Varandan deposit involves three units, from bottom to top: Unit1: grey, green siliceous tuff, brecciated tuff, crystal tuff and andesite; Unit2: white grey nummulitic limestone, limy tuff and marl: and Unit3: tuff breccia and crystal lithic tuff. Mineralization in the Varandan deposit has occurred as four ore sub-horizons in Unit1, as lenticular to tabular ore bodies concordant to layering of the host rocks. Based on textural, structural and mineralogical studies, the Varandan deposit consists of five ore facieses including: 1) veins-veinlets (stringer zone) that involves cross-cuting barite, quartz and sulfide veins-veinlets, 2) brecciated barite and massive pyrite (vent complex zone) involving replacement texture, 3) massive barite and sulfide (massive zone), 4) alternations of barite- and galena- rich bands (Bedded-banded zone) and; 5) iron-manganese-bearing hydrothermal-exhalative sediments. Primary ore minerals are barite, galena, chalcopyrite, pyrite, sphalerite, tetrahedrite, magnetite, oligiste, braunite, pyrolusite and bornite, accompanied with secondary minerals such as native copper, cuprite, digenite, covellite, chalcosite, goethite, hematite and malachite. Gangue minerals consist of chlorite, sericite, quartz and calcite. Major wall rock alterations in the deposit are chloritic and quartz- sericitic. For determining the type of ore of the Varandan deposit, the Cu/Zn ratio for the barite and sulfide ore of the first, second and third sub-horizon are 1.08, 0.12 and 11.08, respectively. This lies in the yellow ore for the first and third sub-horizon, and it falls in the black ore for the second sub-.
    DiscussionAccording to the basic characteristics of mineralization such as geometry of ore bodies, textures and structures, ore facies, wall rock alterations, mineralogy, fluid inclusions data, metal zonation and geochemical features, the Varandan deposit could be classified as a bimodal-felsic or Kuroko-type voclanogenic massive sulfide (VMS) deposit, similar to those of the Hokuroko basin in Japan (Ohmoto and Skinner, 1983; Hoy, 1995, Huston et al., 2011). The Varandan deposit has been formed in an intra-arc setting due to subduction of the Neo-Tethyan oceanic crust beneath the Iranian plate during the Middle Eocene.
    AcknowledgementsThe authors are grateful to the Grant Commission for research funding of Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and the University of Shahrood.
    Keywords: Barite-Lead-Copper deposit, volconogenic massive sulphide (VMS), Kourko, Varandan, geochemical, Mineralization, Geology, Qamsar