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زمین شناسی اقتصادی - سال یازدهم شماره 1 (بهار 1398)
  • سال یازدهم شماره 1 (بهار 1398)
  • تاریخ انتشار: 1398/03/04
  • تعداد عناوین: 9
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  • علیرضا زراسوندی *، محسن رضایی، مجید طاشی، زهرا فریدونی، مدینه ساعد صفحات 1-32

    توده های گرانیتوئیدی از جمله سنگ های نفوذی مهم مرتبط با کانه زایی های مس پورفیری در ایران هستند که اغلب در دو زون ساختاری ارومیه - دختر و سنندج - سیرجان، هم به صورت کانه دار و هم به صورت عقیم دیده می شوند. توده های گرانیتوئیدی در این دو زون ساختاری به ترتیب در دوره های مزوزوئیک و سنوزوئیک بر اثر فرورانش لیتوسفر اقیانوسی نئوتتیس و ماگماتیسم حاصل از برخورد و ذوب بخشی پوسته پایینی تشکیل شده اند. از جمله زون های ساختاری مهم همراه با کانه زایی مس پورفیری، زون ساختاری ارومیه – دختر است که شامل توده های گرانیتوئید بارور همچون توده نفوذی های سرچشمه، سونگون، میدوک، دره زرشک علی آباد، پرکام و دالی است. به موازات این زون آتشفشانی- نفوذی، زون ساختاری سنندج- سیرجان است که توده های گرانیتوئیدی غیر بارور نظیر توده های نفوذی الوند، حسن رباط، سیاه کوه، بروجرد، آستانه و الیگودرز را شامل می شود. بر اساس بررسی های انجام شده، از جمله ویژگی های زمین شیمیایی توده های گرانیتوئیدی بارور در زون ارومیه – دختر، می توان به آنومالی مثبت Eu، غنی شدگی LREE به HREE و نسبت های بالای Lan/Ybn ،Sr/Y، Dyn/Ybn، Lan/Smn اشاره کرد. اما در مقابل ویژگی های زمین شیمیایی بارز توده های گرانیتوئیدی نابارور در زون ساختاری سنندج - سیرجان نیز می توان آنومالی منفی Eu، شیب ملایم از LREE به HREEو نسبت های پایین Lan/Ybn، Sr/Y، Dyn/Ybn، Lan/Smn را بیان کرد. تمامی ویژگی های یاد شده، نشان دهنده این است که در قیاس با توده های بارور زون ارومیه - دختر، توده های گرانیتوئیدی جای گیر شده در زون سنندج – سیرجان به علت عدم ضخیم شدگی پوسته در زمان فرورانش لیتوسفر اقیانوسی، کنترل تفریق ماگمایی توسط تبلور بخشی پلاژیوکلاز و محتوای آب ماگمایی پایین، دارای توان کانه زایی پورفیری نیست. در صورتی که جای گیری توده های گرانیتوئیدها در بازه زمانی الیگومیوسن، ضخیم شدگی حاصل از برخورد، تفریق ماگمایی بیشتر توسط تبلور بخشی هورنبلند کنترل و موجب پدید آمدن احتمالی سنگ های شبه آداکیتی بارور و کانه زایی های مس پورفیری در زون ارومیه - دختر شده است.

    کلیدواژگان: زمین شیمی REE، گرانیتوئید، مس پورفیری، زون ساختاری سنندج- سیرجان، زون ساختاری ارومیه- دختر
  • سید جواد مقدسی *، محمد ابراهیمی، فرشته محمدی صفحات 33-55

    کانسار آهن گوزل دره در 44 کیلومتری جنوب شرق زنجان، در پهنه البرز غربی- آذربایجان قرار دارد. نفوذ توده گرانیتوئید گوزل دره به درون سنگ های کربناتی منطقه مورد بررسی، موجب دگرگونی مجاورتی، تشکیل اسکارن و کانی سازی آهن همراه آن شده است. گرانیتوئید گوزل دره شامل گرانیت، گرانودیوریت و کوارتز مونزونیت و از نوع I است. این گرانیتوئید در محیط زمین ساختی کمان آتشفشانی و حاشیه فعال قاره ای تشکیل شده است و در محدوده سنگ های کالک آلکالن پتاسیم بالا و دسته شوشونیتی قرار می گیرد. کانی سازی آهن اغلب به شکل توده های نامنظم، عدسی و رگه ای با خلوص زیاد یافت می شود. مگنتیت فراوان ترین کانه سازنده کانسار است و هماتیت، پیریت و کالکوپیریت کانی های فرعی هستند. با توجه به ویژگی های سنگ شناختی، کانی شناختی و زمین شیمیایی، کانسار اسکارن آهن گوزل دره در سه مرحله تشکیل شده است: 1- جای گیری توده گرانیتوئید گوزل دره و دگرگونی همبری سنگ های میزبان کربناتی و تشکیل مرمر با بافت گرانوبلاستیک و کانی های سیلیکات کلسیم (-منیزیم) بدون آب، 2- متاسوماتیسم و جانشینی که در ادامه مرحله قبلی رخ داده و با کانی سازی جزئی مگنتیت در زون پیش رونده اسکارن همراه است و 3- سرد شدن توده گرانیتوئید گوزل دره و سامانه گرمابی- ماگمایی وابسته به آن که با تشکیل کانی های اپیدوت، ترمولیت (-اکتینولیت)، سرپانتین، تالک، کلریت، کلسیت و کوارتز در زون پس رونده اسکارنی همراه بوده و مسئول کانی سازی اصلی آهن است. عملکرد فرایندهای سوپرژن و هوازدگی بر روی سامانه بالا موجب تشکیل کانی های هماتیت، گوتیت، لیمونیت، مالاکیت و آزوریت شده و کانی ها و بافت های اولیه از پیش موجود را متلاشی کرده است.

    کلیدواژگان: اسکارن آهن، کانی شناسی، زمین شیمی، گوزل دره، زنجان
  • محمد بومری *، حبیب بیابانگرد، زهرا زین الدینی صفحات 57-80

    کانسار مس پورفیری چاه فیروزه در 35 کیلومتری شمال غرب شهربابک در نوار دهج- ساردوئیه از کمربند ماگمایی ارومیه– دختر واقع شده و شامل دو بخش شمالی و جنوبی است. در این پژوهش، سنگ شناسی، کانی شناسی ، دگرسانی، سبک و نوع کانی زایی و مقدار و پراکندگی مس و مولیبدن در بخش شمالی بررسی می شود. زمین شناسی کانسار اغلب شامل آندزیت های ائوسن است که توسط سنگ های نفوذی و نیمه نفوذی میوسن قطع شده اند. این واحدهای سنگی توسط داسیت، کنگلومرا وآبرفت های جوان تر پوشیده شده اند. سنگ های نفوذی دارای ترکیب دیوریت، کوارتزدیوریت و گرانودیوریت و بافت پورفیری هستند. کانی زایی مس در بخش شمالی، اغلب از نوع هیپوژن است که به صورت رگچه های سیلیسی و پراکنده در سنگ های نفوذی الیگو- میوسن و آندزیت های ائوسن رخ داده است. سولفیدهای هیپوژن اغلب شامل پیریت، کالکوپیریت، بورنیت و مولیبدنیت است. کانی زایی سوپرژن در بخش شمالی گسترش چندانی ندارد و فقط بخش اکسیدان آن به صورت رخنمون های کوچکی از هیدرواکسیدهای آهن و کربنات مس دیده می شود. دگرسانی های عمده در بخش شمالی کانسار مس پورفیری چاه فیروزه، دگرسانی های پتاسیک و فیلیک است. دگرسانی پتاسیک اغلب شامل کوارتز، بیوتیت، سریسیت، کلریت و سولفیدهای مس با یا بدون ارتوکلاز و مگنتیت و دگرسانی فیلیک اغلب شامل کوارتز، سریسیت، کلریت و پیریت و کالکوپیریت می شوند. دگرسانی پروپیلیتیک با رنگ سبز و داشتن کانی های سبز کلریت و اپیدوت و دگرسانی آرژیلیک در حاشیه ها و مناطق سطحی مشاهده می شوند. با افزایش عمق در این کانسار، مقدار مس تقریبا ثابت است؛ ولی مقدار مولیبدن افزایش می یابد. بیشترین میزان مس مربوط به گمانه شماره 44 در عمق 210 تا 212 متری با مقدار 5/4 درصد مس درکوارتزدیوریت است و بیشترین مقدار مولیبدن 17/0 درصد در گمانه 80 ، عمق 608 متری در گرانودیوریت وجود دارد. میانگین مقدار مس و مولیبدن در بخش شمالی به ترتیب 21/0 درصد و ppm24 است. اندازه، عیار ، نوع دگرسانی، سبک کانی زایی و سنگ های همراه در بخش شمالی، مشابه با کانسارهای نوع مس پورفیری است که در آن کانی زایی مس بر اثر جدایش محلول های گرمابی وابسته به توده های نیمه نفوذی در زون پتاسیک و فیلیک تشکیل شده است.

    کلیدواژگان: محلول های گرمابی، کانی زایی مس - مولیبدن پورفیری، دهج- ساردوئیه، کمربند ماگمایی ارومیه- دختر
  • محمودرضا رحمتیان *، محمد لطفی، مجید قادری صفحات 81-103

    کانسار منگنز جون آباد در 16 کیلومتری جنوب شرق روستای جون آباد در شمال خاش و از لحاظ پهنه بندی رسوبی- ساختاری در بخش میانی زون فلیشی شرق ایران واقع شده است. سنگ میزبان لایه های منگنز در این کانسار، شیل های قرمز رنگ است که در قسمت های بالایی و به صورت بین لایه ای یا به صورت آغشتگی، کانی سازی منگنز در آنها دیده می شود. هندسه ماده معدنی به صورت لایه ای شکل و اغلب هم شیب و همراه با واحدهای دربرگیرنده (شیل های قرمز رنگ) است. شیمی عناصر اصلی، نسبت های Mn:Fe، Si:Al و وجود ضرایب همبستگی مثبت بین Al2O3، TiO2 و Fe2O3 نشان دهنده تاثیر هم زمان فرایندهای گرمابی در محیطی کم عمق همراه با ورود مواد آواری خاکی از جنس مافیک به درون حوضه رسوبی در محل شکل گیری کانسار است. نمودارهای عناصر فرعی، همگی بر محتوای پایین کانسنگ از عناصری همچون Ni، Cu و Co دلالت دارند که نمایانگر قرارگیری کانسار در محدوده کانسارهای با منشا گرمابی است. نسبت های Co:Ni، Co:Zn، LREE:HREE، غنی شدگی عناصر LREE نسبت به عناصر HREE و آنومالی های منفی Ce نیز بیانگر نقش سیال گرمابی کانه دار در این کانسار است. الگوی پراکندگی عناصر نادر خاکی برای این کانسار، همخوانی زیادی با الگوی توزیع عناصر نادر خاکی در کانسارهای با منشا گرمابی دارد.

    کلیدواژگان: منگنز، گرمابی، زمین شیمی، جون آباد، خاش
  • غلامرضا میرزابابائی *، مهرداد بهزادی، محمدرضا رضوانیان زاده، محمد یزدی، محمد قنادی مراغه صفحات 105-120

    منطقه بافق میزبان بزرگ ترین کانسارهای مگنتیت- آپاتیت در ایران است. ویژگی های کانی شناختی واحد برشی به عنوان یکی از مهم ترین رخدادهای زمین شناسی در منطقه بافق در ایران مرکزی و همچنین کانه زایی Th-REE در این واحد در کانسار سه چاهون مورد بررسی قرارگرفته است. سنگ های برشی اغلب در مجاورت و یا در داخل کانسار سه چاهون تشکیل شده و از نظر سنی، جوان تر است و متشکل از قطعاتی با لیتولوژی عمده سنگ های آتشفشانی و کانی های مگنتیت، تیتانومگنتیت، کلسیت، آمفیبول، اپیدوت، آپاتیت، اسفن و کانی های دیگر (کلریت، سرپانتین) است. سنگ های متعلق به این واحد اغلب دارای تمرکزهایی از کانی های Th-REE هستند که مربوط به کانه زایی عناصر کمیاب خاکی به صورت فسفات و توریم به صورت سیلیکات در این واحد سنگی است. بر اساس بررسی های کانی شناسی، سیلیکات های توریم در دو شکل بلورین، یکی منوکلینیک (هوتونیت) و دیگری تتراگونال (توریت)، در همراهی با فلدسپارها، اکتینولیت، مگنتیت و کربنات به صورت پاراژنز در واحد برشی تشکیل شده اند. بررسی های زمین شناسی انجام شده بیانگر نقش سیالات مشتق از ماگماهای کالک آلکالن تشکیل شده در موقعیت کمان ماگمایی (حاشیه قاره ای فعال) به عنوان عامل تامین عناصر کمیاب خاکی و توریم در واحد برشی است. بر اساس شواهد صحرایی، کانی شناسی و ژئوشیمیایی، انتقال بخش قابلتوجهی از توریم توسط کمپلکس های کربناتی در شرایط قلیایی و محیط احیایی صورت گرفته است.

    کلیدواژگان: کانه زایی Th-REE، واحد برشی، ماگمای کالک آلکالن، کانسار سه چاهون، منطقه بافق
  • رضا برآبادی، سید احمد مظاهری *، محمد حسن کریم پور صفحات 121-145

    منطقه اکتشافی سیمرغ در مرکز بلوک لوت و جنوب غربی نهبندان قرار دارد. در این منطقه طیف گسترده ای از توده های نیمه عمیق به شکل استوک و دایک در درون واحدهای آتشفشانی نفوذ کرده اند و دگرسانی های مهمی مانند سیلیسی، کوارتز+ سریسیت+ پیریت، کربنات+ کوارتز+ سریسیت+ پیریت، پروپیلیتیک و آرژیلیک را به وجود آورده اند. این توده ها متا آلومینوس با ماهیت کالک آلکالن تا کالک آلکالن پتاسیم بالا هستند. غنی شدگی عناصر LREE نسبت به HREE همراه با آنومالی منفی Eu نشان دهنده تشکیل ماگما در زون فرورانش است. سه نوع کانی سازی افشان، رگچه ای و برش های هیدروترمال در این منطقه دیده می شود. میزان عنصر مس از 2 تا 240 گرم در تن، مولیبدن 5/0 تا 49 گرم در تن، آرسنیک 2 تا 207 گرم در تن و طلا 1 تا 93 میلی گرم در تن متغیر است. سن سنجی U-Pb در دو دایک گرانیت پورفیری سن های 56/0±37/25 و 76/0±94/25 میلیون سال و توده پیروکسن دیوریت پورفیری سن 51/0±85/24 میلیون سال را نشان می دهد. مقادیر مثبت پایین ɛHf(t) منشا این توده ها را گوشته نشان می دهد که مقدار کمی با پوسته آغشتگی پیدا کرده است.

    کلیدواژگان: کانی سازی، توده های نیمه عمیق، کالک آلکالن، سن سنجی U-Pb، ایزوتوپ های Lu-Hf، سیمرغ، بلوک لوت
  • امین حسین مرشدی *، سید حسین مجتهدزاده، امیر حسین کوهساری صفحات 147-167

    امروزه، روش های گوناگونی برای اکتشاف کانسار ها و نهشته های معدنی مورد استفاده قرار می گیرد. یکی از روش های در حال گسترش برای اکتشاف کانسار ها، منابع زمین گرمایی و مخازن نفت و گاز، استفاده از میان بار های سیال است. بررسی های مختلفی از قبیل سنجش دما، فشار، شوری و ویژگی و فازهای سیال های مختلف در زمینه میان بار های سیال قابل انجام است. در این پژوهش، با استفاده از مدل سازی هندسی میان بار های سیال، ویژگی های ریزدماسنجی آنها بررسی شده و اطلاعات مربوط به میان بار سیال از طریق نمودار های فشار، دما و شوری استخراج شده است. یکی از مولفه هایی که در مطالعه میان بار های سیال مورد بررسی قرار می گیرد، شکل و هندسه میان بار سیال است که فعالیت انجام شده در این زمینه به تخمین درجه پرشدگی میان بارهای سیال در حالت سه بعدی منجر شده است و می توان به کمک آن، بدون فعالیت های زمان بر و هزینه بر گرمایش و سرمایش، اطلاعاتی مفید در زمینه دما، فشار، میزان شوری و عمق تشکیل به دست آورد. در این پژوهش، کانسار سرب و روی مهدی آباد به عنوان مطالعه موردی انتخاب شده است. پس از تهیه مقاطع دوبر صیقل مناسب برای بررسی میان بار های سیال و عکس برداری به صورت دو بعدی از مقاطع، با اندازه گیری مساحت کل، حباب و لکه میان بار سیال و با محاسبه بعد سوم میان بار سیال، درجه پرشدگی به صورت دو بعدی و سه بعدی محاسبه شد. سپس با انتخاب مدل مناسب سه بعدی میا ن بار سیال بسته به هندسه آن (که از نوع شش ضلعی هرمی و بیضی گون بود)، درجه پرشدگی حالت دو بعدی (سطحی) به حالت سه بعدی (حجمی) تبدیل شد که نتایج مدل محاسباتی با خروجی های مدل هندسی دارای همخوانی بالایی بوده و نسبت درجه پرشدگی دوبعدی به سه بعدی، در مدل محاسباتی و هندسی به ترتیب برابر 75/0 و 77/0 است. در کانسار سرب و روی مهدی آباد، مدل سازی سه بعدی هندسی نمونه هایی از میان بار های سیال مشخص کرد که میان بار های سیال با درجه پرشدگی فاز گازی تقریبی 25% و چگالی بین 65/0 تا 8/0 گرم بر سانتی متر مکعب، دارای دمای یکنواختی بین 100 تا 200 (دمای میانه 150) درجه سانتی گراد، فشار بین 400 تا 500 اتمسفر، دمای سازندی بین 250 تا 350 درجه سانتی گراد، شوری بین 10 تا 15 درصد معادل نمک طعام و عمق تشکیل بین 150 تا 200 متر است که سازگاری مناسبی با نوع کانسارهای مشابه سرب و روی مهدی آباد دارد.

    کلیدواژگان: میان بار سیال، مدل سازی سه بعدی هندسی، درجه پرشدگی، ویژگی های ریزدماسنجی، کانسار سرب و روی مهدی آباد
  • فرهنگ علی یاری * صفحات 169-189

    کانسار پلی متال آق زیارت در فاصله 75 کیلومتری شمال ارومیه، شمال غرب پهنه سنندج- سیرجان قرار دارد. واحدهای سنگی میزبان کانه زایی شامل توالی های آتشفشانی- رسوبی دگرگون شده با ترکیب گرانیت گنایس، آمفیبولیت، شیست و پیروکسنیت به سن نئوپروتروزوئیک تا پالئوزوئیک زیرین است. این واحدها به دلیل تزریق توده های نفوذی با ترکیب سینیت، گرانیت و دایک های آپلیتی متعلق به کرتاسه، تحت تاثیر دگرسانی گرمابی و کانی سازی طلا (مس±مولیبدن) قرار گرفته اند. دگرسانی های گرمابی غالب شامل دگرسانی های آرژیلیک، سیلیسی و سولفیدی است. کانسنگ ها دارای ژئومتری رگه ای و رگچه ای با بافت های جانشینی، دانه پراکنده و شکاف پرکن هستند. کانی شناسی کانسنگ شامل طلای آزاد، پیریت، کالکوپیریت، مولیبدنیت، مگنتیت، گالن، اسفالریت همراه با کانی های ثانویه و سوپرژن کالکوسیت، کوولیت، مالاکیت، آزوریت و گوتیت است. همچنین، نتایج بررسی های انجام شده به روش تجزیه ریزکاو الکترونی1 در 50 نقطه از کانی های پیریت، کالکوپیریت و مولیبدنیت نشان دهنده محتوای بالای گوگرد، مولیبدن، آهن و طلا (به ترتیب شامل میانگین 26/41، 33/52، 03/23 و 04/0 wt.%) و مقدار پایین عناصر سرب، تنگستن، مس، روی و آرسنیک (به ترتیب شامل میانگین 12/1، 46/0، 19/0، 08/0 و 03/0 wt.%) است. بررسی های لیتوژئوشیمیایی انجام شده، نشان دهنده همبستگی رتبه ای اسپیرمن مثبت و قوی بین عناصر Co، Ni، Cu، As، Pb و به ویژه Mo است. علاوه بر این، محاسبات ژئوشیمیایی انجام شده به روش تحلیل عاملی نشان می دهد که عناصر Au، As، Cu، Mo، Ni و Co در عامل اول، عنصر Cu در عامل دوم و عنصر Zn در عامل سوم قرار می گیرند. بررسی شبه مقاطع بارپذیری القائی و مقاومت ویژه ظاهری پروفیل های ژئوفیزیکی، بیانگر گسترش عمقی ناهنجاری ها به سمت جنوب محدوده با الگوی زون بندی قائم همانند بیشتر زون های دگرسانی است. تلفیق نتایج به دست آمده از بررسی های زمین شناسی که بیانگر عملکرد ماگماتیسم نسبتا گسترده مرتبط با ساختارهای گسلی کششی متعدد است، با اکتشافات ژئوشیمیایی و ژئوفیزیکی به شناسایی دو منطقه عمده پتانسیل دار در بخش های شمالی و جنوبی محدوده منجرشده است.

    کلیدواژگان: تجزیه ریزکاو الکترونی، ضرایب همبستگی، تحلیل عاملی، IP-RS، آق زیارت، پهنه سنندج- سیرجان، ایران
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  • Alireza Zarasvandi *, Mohsen Rezaei, Majid Tashi, Zahra Fereydouni, Madineh Saed Pages 1-32
    Introduction

    The formation of the Zagros orogenic belt is attributed to northeastward oblique subduction of the Neotethys beneath the western border of central Iran. This was followed by continental collision between the Afro-Arabian plate and the central Iran microcontinet (Zarasvandi et al., 2015). The Zagros orogen is characterized by three main parallel structural zones consisting of Zagros fold and thrust belt, the Sanandaj–Sirjan metamorphic zone, and the Urumieh–Dokhtar magmatic arc (Mohajjel et al., 2003). The Urumieh–Dokhtar magmatic arc is dominated by the widespread occurrence of Eocene to Quaternary intrusive and extrusive rocks. It is considered as being one of the main Cu bearing regions in the world, where world class giant porphyry deposits, as well as large and small sub-economic porphyry Cu ± Mo ± Au systems have been reported and investigated by many authors (Shafiei et al., 2009; Zarasvandi et al., 2005). In addition to UDMA, the Sanandaj-Sirjan zone (SSZ) hosts several Jurassic-Cretaceous intrusive complexes extending from the northwest to southeast SSZ. It should be noted that these granitoids are barren and porphyry mineralization has not been accompanied with these intrusions. This paper tried to compare the available geochemical data of productive granitoids in the Urumieh-Dokhtar (i.e., Dalli, Ali-Abad and Darreh-Zerreshk, Parkam, Sarcheshmeh, Meiduk and Sungun), and those of barren intrusions in the Sanandaj-Sirjan zone (i.e., Aligodarz, Bourujerd, Alvand, Astaneh, Hasan Robat, and Siah Koh).

    Materials and methods

    This investigation is based on the available geochemical data on the six barren intrusions in the SSZ (i.e., Aligodarz, Bourujerd, Alvand, Astaneh, Hasan Robat and Siah Kohe), and productive intrusive rocks (porphyry associated intrusions) in the UDMA (i.e., Dalli, Ali-Abad and Darreh-Zerreshk, Parkam, Sarcheshmeh, Meiduk and Sungun). Data for the UDMA porphyry intrusions (41 samples) were adopted from studies of Daneshjou (2014), Zarasvandi et al. (2005), Taghipour and Mohammadi Laghab (2014), Barzegar (2007), Taghipour (2007), and Hezarkhani (2006). Furthermore, the data of the SSZ barren intrusions (42 samples) comes from Esna Ashari et al. (2012), Khalaji et al. (2007), Aliani et al. (2012), Tahmasbi et al. (2010), Alirezaei and Hassanzadeh (2001), and Arvin et al. (2007). Two criteria were used for selection of 83 representative samples: (1) samples with a relatively similar mineralogical and compositional range (quartz diorite, quartz monzonite, granodiorite and granite), and (2) samples with the least amount of alteration (minimal amounts of Loss On Ignition; LOI wt.% = H2O + CO2).

    Results

    Productive intrusions in UDMA have positive Eu anomalies, LREE enrichment relative to HREE, and high Lan/Ybn ،Sr/Y، Dyn/Ybn، Lan/Smn ratios. In comparison, barren granitoids in the SSZ are characterized by steep downward LREE to HREE, negative Eu anomalies and low Lan/Ybn ، Sr/Y، Dyn/Ybn، Lan/Smn ratios.

    Discussion

    Based on the presented results, it is proved that due to the lack of considerable crustal thickness in SSZ (during the subduction of the Neotethyan oceanic lithosphere under the SSZ zone), and the presence of dry magma (low H2O contents), the SSZ granitoids exhibit barren characteristics. In contrast, during the ongoing processes of closure of Neo-Tethys and during compression and crustal shortening, magma mixing and evolution toward high magmatic water content lead to the increasing of metal endowment in the porphyry associated granitoids of (UDMA) It seems that magma generation from the melting of thickened lower crust (garnet amphibolite source) could be considered as one important key factors for the generation of metal-rich magmas with high oxidation state and high H2O contents has led to the development of porphyry Cu systems in the UDMA compared to those of SSZ granitoids.

    Keywords: REE geochemistry, Granitoid, Porphyry copper, Sanandaj-Sirjan zone, Urumieh–Dokhtar zone
  • Seyed Javad Moghaddasi *, Mohammad Ebrahimi, Fereshteh Mohammadi Pages 33-55
    Introduction

    The Zanjan area hosts several iron deposits with small reserves which are currently active. This extended abstract describes the geology, mineralogy and geochemistry of the Gozaldarreh iron deposit located 44 km south of Zanjan. To further clarify the origin of Gozaldarreh mineralization, the associated Gozaldarreh granitoid intrusion and skarn were also subjected to detail petrography and geochemical studies including the granitoid type and genesis.

    Materials and Methods

    During several field works, fifty-eight samples were collected from different rock types exposed in the area including granitoid intrusion, skarn unit and the iron ore body. Thirty-five thin, thin-polished and polished sections were prepared and studied in order to study the mineralogy, texture and paragenetic sequences. Based on the petrography and microscopy results, seen granitoid samples and eight ore samples were selected for chemical analysis. The major oxides were analysed by x-ray fluorescence (XRF) at the Geological Survey of Iran and the FeO was measured using wet chemical methods (titration). Trace elements and rare earth elements were measured by inductively coupled plasma mass spectrometry (ICP-MS) at the West Lab in Australia.

    Results

    The intrusion of the Gozaldarreh granitoid into the carbonaceous rocks of the Soltaniyeh and Barout Formations generated a contact methamorphism with a skarn developed and iron-oxide mineralization in the Gozaldarreh area. The Gozaldarreh granitoid is an I-type granite to grano-diorite and quartz-monzonite. The geochemistry of the Gozaldarreh granitoid suggests that this intrusion belongs to high-K calc-alkaline and shoshonite series of the volcanic arc of an active continental margin. The serisitic, argillic, silica-carbonate and chloritic alterations are the major alterations affected by the Gozaldarreh granitoid.
    The garnet, clinopyroxene and wollastonite are the major minerals generated in the prograde skarn phase in the iron oxide mineralization area. The major iron-oxide mineralization stage has happened during the retrograde skarn phase along with epidote, tremolite-actinolite, chlorite, serpentine, talc, calcite and quartz. The iron-oxide mineralization is generally in the form of high grade irregular lenses and veins of magnetite with minor hematite, pyrite and chalcopyrite. A small volume of magnetite has also been deposited during the prograde skarn phase.
    The evidences show that the Gozaldarreh ore mineralization took place in three stages: (1) intrusion of the Gozaldarreh granitoid and contact methamorphism of the carbonate host rocks and generating a marble with granoblastic texture and Ca-Mg silicates. The paragenetic sequence at this stage is garnet-wollastonite- calcite for carbonate rocks and garnet-clinopyroxene-calcite for dolomitic rocks, (2) metasomatism and replacement phase which created Ca-Mg silicates and minor magnetite as part of a prograde skarn phase, (3) the Gozaldarreh granitoid cooling stage and generation of the hydrothermal-magmatic system. This retrograde skarn phase has generated the main magnetite ore along with epidote, chlorite, tremolite-actinolite, serpentine, talc, calcite and quartz. The poor Ca-silicates, Fe-oxides, Fe-sulfides and carbonates were also generated as final stages of this retrograde phase. The later reactions and weathering affected these primary mineral assemblages and created the secondary minerals such as hematite, goethite, limonite, malachite and azurite.

    Discussion

    As a result of the intrusion of the Gozaldarreh granitoid into the carbonates of Soltanieh (PЄ-Єs) and Barout Formations (Єb), a skarn unit has developed at the contact metamorphic zone. The petrography of the Gozaldarreh granitoid shows a granular to micro-granular texture with alkali feldspar, plagioclase, quartz and biotite as major rock forming minerals and amphibole, zircon and sphene as accessory minerals. Epidot, calcite and chlorite are also present as secondary minerals. The sericitic, argilic, silica-carbonate and chlorite assembleges are presenting the major alterations of the Gozaldarreh granitoid. The analyses of the granitoid samples classify the intrusion as an I-type granite to grano-diorite and quartz-monzonite. The Y-Nb and (Nb+Y)-Rb plots (Pearce et al., 1984) suggest that the Gozaldarreh granitoid is part of the volcanic arc granitic intrusions. The Th-Co plot (Hastie et al., 2007) is placing Gozaldarreh granitoid in the high-K calc-alkaline and Shoshonite series.
    The comprehensive field work shows that the iron mineralization in the Gozaldarreh area is spatially associated with the granitoid skarn zone. The exoskarn is well developed in the region and is the major host for Fe-mineralization. The endoskarn which is mainly exposed at the vicinity of the granitoid, is less developed and consists of clinopyroxene, epidote, chlorite, calcite and garnet. The clinopyroxene and garnet are recognized as prograde and epidote, chlorite and calcite are retrograde minerals. The exoskarn mainly consists of retrograde minerals such as epidote, chlorite, tremolite-actinolite, serpentine, talc, calcite, chrysotile and quartz. These retrograde minerals are mainly replaced the residue of prograde minerals such as clinopyroxene, garnet and wollastonite. The other major skarn-related phenomena in the area are the carbonate rocks recrystalization and pyrite-chalcopyrite-iron-oxide mineralization.
    The Gozaldarreh iron ore exhibits different forms including massive, vein-type and disseminated iron-oxide mineralization. The ore bodies are mainly located in the exoskarn. Magnetite is the most abundant ore mineral followed by hematite, pyrite, chalcopyrite, limonite, malachite and azurite as minor minerals. The major gangue minerals are calcite, quartz, epidote, serpentine and chlorite.
    The magnetite chemistry plot in the Ni/(Cr+Mn) vs Ti+V and Ca+Al+Mn vs. Ti+V diagrams (Dupuis and Beaudoin, 2011) showing the skarn origin for the Gozalarreh deposit. The TiO2-V2O5 diagram plot (Hou et al., 2011) for these samples also points to the skarn and hydrothermal origin.

    Keywords: Iron skarn, mineralogy, geochemistry, Gozaldarreh, Zanjan
  • Mohammad Boomeri *, Habib Biabangard, Zahra Zeinadini Pages 57-80
    Introduction

    The Chahfiruzeh porphyry copper deposit is located at 35 Km northwest of Shar-e-Babak in Dehaj–Sarduieh part of the Urumieh- Dokhtar magmatic arc (UDMA). The world class porphyry Cu deposits, such as Sarcheshmeh, Meiduk, Sungun and several other Cu-porphyry in the UDMA have been numerously studied, for example: Boomeri, et al., (2009, 2010), and Asadi et al., (2014). The Chahfiruzeh Cu porphyry is divided into two parts of the southern and northern deposits. The southern deposit was studied by Hezarkhani (2006), and Sheikhzadeh et al., (2011). This paper studies the northern part to distinguish mineralized rock units, alteration types, mineralization style, ore mineralogy and geochemical characteristics.

    Geology

    Geology of the northern part of the Chahfiruzeh area consists of upper Cretaceous-Eocene andesitic lava, pyroclastic and volcanoclastic rocks that have been intruded by Oligo-Miocene intermediate stocks and dikes (Dimitrijevic, 1973). Neogene rocks in the area are mainly alkali basalt to dacitic domes and Quaternary alluvium deposits.

    Method and material

    During the field studies more than 100 samples were taken from the boreholes and outcrops. Among them 25 thin sections and 39 polished sections were studied by microscopic methods, 6 samples from the alteration zones, 8 samples from the less altered rocks and 25 samples from the mineralized rocks were examined and analyzed by XRD, XRF and ICP-OES, respectively. The analyses and XRD data are presented in Tables 1, 2 and 4.

    Result and discussion
    Petrography

    The igneous rocks in the northern part occur as extrusive and intrusive. The extrusive rocks are dacite and andesite and intrusive rocks are diorite, granodiorite and quartzdiorite. They are porphyry in texture and high-K calc-alkaline in magmatic series. The main mineral in all rocks is plagioclase that has variable size, shape and texture. K-feldespar, amphibole, biotite and quartz are other primary minerals in the study rocks. Biotite, quartz, and K-feldspar occur also as secondary minerals that are associated with chlorite, sericite, clays minerals and sulfide and oxide minerals.

    Mineralization

    Mineralization can be usually divided into the two hypogene and supergen types. The hypogene mineralization occurs mainly as silicic veinlets and disseminated in the intrusive porphyries and volcanic rocks. The silicic veins are in eleven types as follows: 1) quartz + chlorite + pyrite, 2) quartz + chlorite , 3) quartz + pyrite , 4) quartz , 5) chlorite , 6) pyrite + chalcopyrite + quartz , 7) quartz + magnetite , 8) pyrite , 9), chalcopyrite , 10) quartz + chalcopyrite + bornite, 11) molybdenite. The hypogene sulfides are pyrite, chalcopyrite, bornite and molybdenite that are associated with magnetite, hematite and ilmenite. The pyrites and chalcopyrites occur in all parts of the mineralized area from the surface to the depth while molybdenites and bornites occur only in the deep depths. The supergene mineralization occurs as small outcrops of iron oxide and hydroxide, copper carbonate and clay minerals.

    Alteration

    The alteration zones in the mineralized area are potassic, propylitic, phyllic and argillic. The main alteration is potassic that is characterized by biotite, sericite and chlorite and numerous sulfide-bearing silicic veinlets with or without orthoclase and magnetite. The orthoclase is probably present as anhedral in some parts and around the plagioclase. The hydrothermal biotites are fine and thin in shape and occur in groundmass. Magmatic biotites are also present as euhedral to subhedral grains. The propylitic alteration observes only in the surface as an outer zone and characterized mainly by chlorite and epidote. Calcite and clay minerals are other minerals of this zone while sulfides are rare. The phyllic alteration zone is characterized by a higher proportion of sericite, quartz veins and pyrite than the potassic alteration in the marginal parts of the mineralized area. The argillic alteration zone occurs locally in shallow depths. Based on XRD analyses, each one of the clay minerals such as kaolinite, montmorillonite, illite and dickite, are dominant in some samples.
    The alteration map of the northern part is presented in Fig.15 for two depths of 10 and 400 meters. The potassic alteration is the main alteration type in both levels. In level 10, the inner potassic alteration is surrounded by phyllic and outer propylitic alteration, while in level 400, the inner potassic alteration is only associated with the local phyllic alteration. Distribution of copper and molybdenum in different boreholes indicate that mineralization has occurred mainly in the potassic and phyllic alteration zones (Fig. 16). The copper shows similar contents from shallow to deeper depths while Mo contents are higher in the depths of more than 500 meters (Fig. 16).
    The following features show that the northern part of Chahfiruzeh ore deposit is a porphyry Cu-type ore deposit: style, grade, size and shape of the mineralization, alteration types, associated calc-alkaline intrusive porphyries and the tectonic setting.

    Keywords: Hydrothermal solutions, porphyry Cu-Mo mineralization, Dehaj–Sarduieh, Urumieh- Dokhtar magmatic belt
  • Mahmoudreza Rahmatian *, Mohammad Lotfi, Majid Ghaderi Pages 81-103
    Introduction

    Manganese deposits are classified as hydrogenous, diagenetic and hydrothermal deposits based on their mineralogy, chemical composition, and tectonic setting (Hein et al., 1997). Hydrogenous manganese deposits have slowly precipitated from seawater (2-10 mm/Myr) (Ingram et al., 1990). These deposits contain iron and are poor in manganese oxide. The Mn:Fe ratio is ~1 and Ni and Cu are represented by high concentrations (>3000 ppm) (Hein et al., 1997; Usui and Someya, 1997). Diagenetic manganese deposits occur as nodules and have precipitated from hydrothermal solutions or pore water within altered sediments (Klinkhammer et al., 1982). These deposits are usually related to organic matter oxidation and formation of Mn carbonate minerals (Polgari et al., 2012). Hydrothermal manganese deposits have directly precipitated from low-temperature hydrothermal solutions (Hein et al., 1997; Ingram et al., 1990). These deposits are generally laminated and stratabound or occur as irregular bodies and epithermal veins (Hein et al., 1997). Diagenetic and hydrothermal deposits are characterized by high Mn:Fe contents and low trace metal concentrations (Hein et al., 1994; Hein et al., 1996). Although there are similarities between these two deposit types, they are mostly distinguished by their morphologic, tectonic and growth rates (Kuhn et al., 1998). The Joun Abad manganese deposit is located 16 km southeast of the Joun Abad village, 72 km north of the city of Khash in the eastern longitude of 61° 06´ 0.7ʺ and the northern latitude of 28° 51´ 2.3ʺ. This zoning is structural-sedimentary that is located in the middle part of the flysch zone of Eastern Iran. In this paper, major, trace and rare earth element compositions of ores have been used as an approach to determine the conditions of ore formation.

    Materials and methods

    Twenty representative ore samples (~450 g) were selected from the Joun Abad manganese deposit. Geochemical analyses were made of samples taken from different surface mineral outcrops at various locations. Crushed and grounded ores (under 200 mesh) were analyzed at the Kansaran Binaloud Laboratories, Tehran, Iran. Major oxide and trace element contents were determined by X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), respectively, and the REEs were analyzed using the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) method.

    Discussion and results

    The Joun Abad manganese deposit is located 16 km southeast of the Joun Abad village, north of the city of Khash, and with respect to structural-sedimentary zoning in the middle part of the flysch zone of Eastern Iran. The host rocks of manganese layers are red shale, manganese mineralization is visible on the upper parts, as interlayers and/or contamination. The geometry of the ore mineral is in layered form and it is often conformable with units including red shales. The chemistry of the major elements, Mn:Fe and Si:Al ratios and the positive correlation coefficients between Al2O3, TiO2 and Fe2O3 indicate that they were affected by hydrothermal processes in a shallow environment together with entering mafic clastic materials in sedimentary basin where the ore formed. All trace element diagrams show low contents of elements such as Ni, Co and Cu in the manganese ores. The deposits of the study area in these diagrams plot in the field of hydrothermal deposits. Co:Ni, Co:Zn, LREE > HREE contents and total REE and negative Ce anomalies also indicate the role of ore-bearing hydrothermal fluid in the deposit. REE distribution patterns of the deposit are quite similar to those of hydrothermal deposits.

    Keywords: Manganase, Hydrothermal, Geochemistry, Joun Abad, Khash
  • Gholamreza Mirzababaei *, Mehrdad Behzadi, Mohammad Reza Rezvanianzadeh, Mohammad Yazdi, Mohammad Ghannadi Maragheh Pages 105-120
    Introduction

    The Bafq region hosts the most important magnetite-apatite deposits of Iran. The geology of this region has been studied by many researchers (e.g., Haghipour, 1977). The ore deposits are mainly hosted by a volcano-sedimentary unit. The presence of a brecciated unit at the margin of the magnetite -apatite ore deposits is discussed by several authors. This unit contains remarkable concentration of Th and REE minerals paragenetically associated with magnetite, actinolite, calcite and albite. Mineralogical properties of the brecciated unit as one of the most important geological events in the magnetite-apatite ore deposits of the Bafq region, and Th-REE mineralization hosted by this zone at the Se-Chahun ore deposit is discussed.

    Materials and methods

    The present study has been carried out in four stages including: field work, microscopic studies, ICP-MS and ICP-OEA analysis as well as EPMA analysis. The field work included observations, investigations, radiometry, spectrometry and sampling from different lithologies in both open pits and drilled cores. The microscopic studies were carried out in order to identify the minerals and examine the textural properties of these minerals found in the brecciated unit. The ICP-MS and ICP-OEA analysis were carried out on the samples taken from the ore bodies and the radioactive parts of the mine. The EPMA analysis was also carried out to achieve a more precise hint at the occurrences of the Th and REE minrals and also to investigate the paragenetic relationships between the minerals probed.

    Results

    The brecciated unit is generally formed at the margin of or within the ore deposits mentioned. The matrix of the brecciated unit at the Se-Chahun ore deposit is composed of different minerals including magnetite, titanomagnetite, actinolite, albite, apatite, titanite, calcite, epidote, chlorite and Th silicates. The coarse rock fragments are mainly of the rhyolitic rocks and metasomatic fragments. Based on the mineralogical studies, the brecciated unit is the host of Th-REE minerals. The Th-silicates are formed in two crystallized forms including monoclinic (huttonite) and tetragonal (thorite). Thorium occurrence is found in three types: granular, massive and veinlet. The geological investigations indicate the role of solutions derived from magmatic arc originated in calc-alkaline magmas as a source for Th(-REE) in the brecciated unit. Based on the field, mineralogical and geochemical evidence, a remarkable part of Th has been transported by carbonate complexes in basic and reduced solutions. Apatite and monazite show a notable concentration within the brecciated unit. Monazites are found mostly as single crystals not always hosted by apatite crystals. Two types of actinolite are recognized, 1. Older than Th mineralization within the magnetite ore and 2. A younger generation paragenetically associated with Th silicate. Two types of albites are recognized: an early (white) albite found within the magnetite ore; a late (red) albite also found within the brecciated zone in association with Th occurrences.
    Metals such as Th and REE, at the Se-Chahun magnetite-apatite ore deposit are thought to be predominantly derived from the associated magmas, via magmatic–hydrothermal fluids exsolved upon emplacement into the crust. Two main sources exist for the origin of the metals (Th and REE): 1: sediments on the downgoing slab subducted into the mantle wedge (located between the downgoing slab and the overriding plate); 2: assimilation of crustal rocks within the magma chamber and also during ascending of the magmas. Th-REE have been transported mainly by carbonate complexes in alkaline and reduced environments. The presence of a reduced environment during Th-REE mineralization is evidenced by paragenetic association of magnetite and pyrite (and minor chalcopyrite) supported by negative Eu anomaly. Presence of an alkaline environment is also supported by the presence of calcite crystals, veins and veinlets paragenetically associated with Th-REE minerals.

    Discussion

    A limited number of models have been suggested to explain the provenance of the brecciated unit. Mohseni and Aftabi (2012), among others, suggested that this zone is a proximal zone of magnetite-bearing keratophyres formed in submarine environments. By contrast, no clear source for thorium silicate is suggested. Recently, Khoshnoodi (2016) discussed the subject in one of the largest iron-apatite ore deposits in the region, the Choghart. According to his suggestions, the solutions derived from the calc-alkaline magmas are the source of thorium.
    According to our suggestions, the lower continental crust and also the continental derived sediments on the sea floor adjacent to the subduction zones can be proposed as one of the most important sources for limited amounts of thorium found within the magmatic arc magmas. It is proposed that these magmas and associated mineralization are not limited to the margin of the magnetite-apatite ore deposits. Until now, the importance of the Bafq mining district has been due to its discovered magnetite-apatite resources. Further exploration programs supported by mineralogical and geochemical studies may lead to opening new ways in exploration of uncovered ore deposits in the Bafq district containing more economical resources.

    Acknowledgements
    This research was supported by the Shahid Beheshti University of Tehran and the Atomic Energy Organization of Iran. The authors are truly grateful to the anonymous reviewers of the journal of economic geology for their constructive comments.
    Keywords: Th-REE mineralization, brecciated unit, calc-alkaline magma, Se-Chahun ore deposit, Bafq
  • Reza Borabadi, Seyed Ahmad Mazaheri *, Mohammad Hassan Karimpour Pages 121-145
    Introduction

    The Simorgh prospect area is located in 113 km southwest of the Nehbandan in South Khorasan province. This area is part of the Tertiary volcanic-plutonic rocks in the center of the Lut block. The Lut Block, which is located at the eastern part of the Central Iranian Microcontinent (CIM), is famous by its complex tectonic evolution and extensive magmatic activities with a range of interesting geochemistry. Extensive magmatic activities in Lut Block have produced several types of mineralization events (Karimpour et al., 2012). Around the Simorgh prospect area, various mineral deposits, including Cu-Mo porphyry Dehsalm in 90 km southwest of Nehbandan have been reported (Arjmandzadeh and Santos 2013) and Mahoor copper (Miri Beydokhti et al., 2015).
    Until now there has not been a detailed studies on the Simorgh prospect area especially on granitoids. In this study, we present field investigations, geology, alteration, mineralization, geochemical exploration, Petrogenesis, zircon U-Pb geochronology and Hf isotopes of sub-volcanic rocks in the Simorgh prospect area.

    Materials and methods

    1- Preparation of 336 thin sections for the study of petrography, alteration and mapping of geological and alteration maps.
    2- Preparation and study of twenty-five polished thin sections and thirty-two polished blocks for mineralization studies.
    3- Analysis of forty-five chip composite samples in the Zar Azma laboratory by using the fire assay method for Au element and ICP-OES for thirty-four elements. The solubilization method of 4- Acid (1EX) was used.
    4- Analysis of one hundred and sixty core samples in the Zar Azma laboratory by using the fire assay method for Au element and ICP-OES for 34 elements (method 1EX).
    5- Chemical analysis of seventeen samples of syn-mineralization sub-volvanic intrusive rocks with at least alteration, by ICP-MS for thirty-one trace and rare earth elements with LF100 method (alkali fusion) at the AcmeLabs Laboratory.
    6- Separation of three samples from syn-mineralization sub-volcanic intrusive rocks for U-Pb zircon geochronolg by Quadruple Laser-Ablation ICP-MS at the CODES, the Tasmania University of Australia.
    7- Analysis of three samples of syn-mineralization sub-volvanic intrusive rocks for Lu-Hf isotopes with multi-collector ICP-MS at the CCFS of Macquarie University of Sydney, Australia.

    Discussion and results

    Petrographic studies indicated that the composition of sub-volcanic rocks in the Simorgh area are diorite porphyry and pyroxene diorite porphyry stocks with granite porphyry and granodiorite porphyry dikes. Several alteration zones such as: propylitic, argillic, silicified quartz-sericite-pyrite (QSP) and carbonate-quartz-sericite-pyrite (CQSP) based on field and laboratory studies are identified Major oxides analysis shows that intrusive units are metaluminous to peraluminus, calc-alkaline to high-K calc-alkaline. More of these rocks belong to the I-type granitoid (Chappell and White, 2001), and they have been formed in a volcanic arc granitoids (VAG) tectonic setting (Pearce et al., 1984). Mantle-normalized, trace-element spider diagrams display enrichment in large ion lithophile elements, such as Rb, Sr, K, and Cs, and depletion in high field strength elements, e.g., Nb, Ti, P. Enrichment of LREE versus HREE and enrichment of LILE and depletion in HFSE indicate magma formation in the subduction zone. In the subduction zones, high oxygen fugacity leads to the depletion of Ti. All of the intrusive rocks have a negative Eu anomaly. The amount of Eu/Eu* in sub-volcanic units of the Simorgh area varies from 0.49 to 0.91. Therefore, negative Eu anomaly can be evidence of the partial presence of plagioclase in the origin (Tepper et al., 1993).
    Three types of mineralization occur in this area such as: veinlet, disseminated and hydrothermal breccia among which hydrothermal breccia is the most important. Pyrite is the most sulfide mineralization in the sub-volcanic and hydrothermal breccias.
    Compositional variations of elements within the Simorgh prospect are as follows: Cu = 2-240 ppm, Mo = 0.5-49 ppm, Zn = 9-935 ppm, Pb = 7-582 ppm, ppm, As = 2-207 ppm and Au = 1-93 ppb.
    In the Simorgh area, zircon U-Pb geochronology was carried out on syn-mineralization sub-volcanic intrusive rocks. The age of two granite porphyry dikes are 25.37±0.56 Ma and 25.94±0.76 Ma and the age of pyroxene porphyry diorite is 24.85±0.51 Ma (Chattian). Diorite porphyry is pre-mineralization because it is cut by granite porphyry dikes and pyroxene diorite porphyry, so diorite porphyry is the oldest sub-volcanic intrusive rock in this area. The low positive values of εHf(i) indicate that the origin of these sub-volcanic intrusive rocks is mantle, which has low contamination with the crust.
    According to the above evidence, the sub-volcanic units of this area are related to porphyry systems, and the hydrothermal breccias are the main host rock mineralization in this system. This system does not have any valuable mineralization expect pyrite, from the surface to 180 m depth.

    Keywords: Mineralization, sub-volcanic rocks, Calc-alkaline, U-Pb geochronology, Lu-Hf isotopes, Simorgh, Lut Block
  • Amin Hossein Morshedy *, Seyed Hossein Mojtahedzadeh, Amir Hossein Kouhsari Pages 147-167
    Introduction

    Fluid inclusions are small, usually microscopic, volumes of pore fluid, which are crystallographically trapped in rocks during diagenesis or fracture healing processes. Nowadays, various techniques are used for resource exploration. Application of a fluid inclusion is one of these methods that has been developed for mineral, geothermal, and petroleum reservoir exploration. The study of fluid inclusions represents our most reliable source of information on the temperature, pressure, and fluid composition data of the ore fluid, and it is one of the most important tools for research into the economic geology and genesis of ore deposits (Moon, 1991). To achieve these goals, transparent and polished slabs of rock material are prepared and optically studied with a petrographic microscope. Samples are viewed under transmitted plane-polarized white light as well as under reflected ultraviolet or blue-violet illumination. During the fluid inclusion petrography, the volume fractions of phases are routinely estimated at room temperature to deduce whether assemblages of cogenetic inclusions were originally trapped from a one-phase or a multi-phase pore fluid. In the present research study, the microthermometric properties of the fluid inclusion data through pressure, temperature, and salinity diagrams were computed by geometrical modeling of fluid inclusion (Bakker and Larryn, 2006). The proposed method provides a quick and low cost technique to preliminarily investigate the microthermometric parameters of the fluid inclusion.
    To evaluate the proposed geometrical model, the Mehdiabad Pb-Zn deposit is selected as the case study. The Mehdiabad Pb-Zn deposit is located at the Yazd-Anarak metallogenic belt, 110 km southeast of Yazd, in the Central Iran structural zone. The host rocks of the deposit consist of lower Cretaceous silty limestone and dolomite. The main occurrences are the Calamine mine (CM), the Black-Hill ore (BHO), the East Ridge (ER) and the Central Valley Orebody (CVOB). The ore body consists of a primary sulfide ore and a supergene non-sulfide ore, the latter one having been mined at CM (Ghasemi, 2007; Rajabi et al., 2012).

    Materials and methods

    The shape and geometry of fluid inclusion are one of the most important parameters, which were applied to estimate 3D degree of filling and find the useful information about temperature, pressure, salinity and depth of trapping without using time-consuming and costly heating-cooling operation. Inclusions in normal thick-sections are rotated stepwise and their projected areas and area-fractions are plotted against rotation angle. The outputs are systematically related to inclusion orientation, inclusion shape, and filling degree. The dependency on orientation is minimized when area fractions are measured at the position where the inclusions project their largest total areas. The shape factor is employed to present a new objective classification of inclusion projections, based on the extracted parameters from digital image processing (Bakker and Larryn, 2006).
    In this research, Mehdiabad Pb-Zn deposit has been chosen to evaluate the proposed method. Based on the fluid inclusion petrography, four fluid inclusion types are observed: 1) L+V; 2) L+L; 3) L; and 4) V; L+V phase is the most popular. After preparing 2D image of sections, 2D and 3D degree of fills were calculated by measuring the areas of total, bubble, and spot of fluid inclusion and computing the third dimension (Z) of fluid inclusion. Four geometrical models of volume fractions are defined, including cylinder, tetragonal prism, truncated cone, hexagon, and ellipsoid (Bakker and Larryn, 2006; Hossein Morshedy et al., 2008). In this case study, 3D proper models of the fluid inclusions are selected, depending on its geometry (hexagonal or ellipsoid). Then 2D degrees of filling (area fraction) is converted to 3D degrees of filling (volume fraction). The geometrical modeling results are well matched with computational outputs.

    Results and discussion

    In this research, the ratios of area to volume fractions in geometrical and computational modelling were calculated 0.75 and 0.77, respectively. In the Mehdiabad Pb-Zn deposit, the main geometrical shapes of fluid inclusions were followed up the hexagonal prism with hexagonal pyramids and ellipsoid models. 3D geometrical modeling of fluid inclusion showed vapor fraction, 25% and density, 0.7 g/cm3, which the microthermometric and other parameters were obtained homogenization temperature nearly 100-200 °C (average of 150 °C), pressure between 400-500 ATM, formation temperature about 250-350 °C, salinity within a range of 10 to 15 wt.% NaCl equiv. and depth of mineralization 150-200 m. This finally achieved results have a high similarity with the typical carbonate-hosted Pb-Zn deposit.

    Keywords: Fluid inclusion, 3D geometrical modeling, Degree of fill, Microthermometric parameters, Mehdiabad Pb-Zn deposit
  • Farhang Aliyari * Pages 169-189
    Introduction

    The Agh Ziarat (Au±Cu±Mo) Polymetallic deposit is located at 75 north of Urmia, northwestern part of the Sanandaj-Sirjan Zone. Several studies have been carried out on chemical composition, geochemistry, petrology, and petrogenesis of intrusive bodies of the Qushchi area, north of Urmia (Jahangiri, 1993; Behnia, 1996; Asadpour, 2001; Azimi, 2011; Shahabi, 2013; Sarjoughian and Kananian, 2015). However, the mineralization potential of the intrusion rocks and volcano-sedimentary sequences has not been investigated yet. The present investigation provides an overview of the geological framework, mineralogy of orebodies and gangue, geochemical, and geophysical characteristics of the Agh Ziarat deposit. Therefore, identification of mineralization style and potential in the study area can be used as an exploration guide in the regional scale in the Sanandaj-Sirjan zone and elsewhere.

    Materials and methods

    Petrography and ore mineralogy studies were carried out on 15 thin, 20 polished, 10 polished thin sections, and 11 XRD analyses to identify the alteration and ore mineral textures and mineral paragenesis at the Department of Mining Engineering, the Urmia University of Technology. X-Ray Fluorescence (XRF), SEM, ICP-MS analyses were performed on 6, 13, and 70 samples collected from different altered and mineralized host units including metamorphosed volcanic rocks, intrusive bodies, and aplitic dikes in the Kansaran Binaloud Laboratory, respectively. Mineralogical composition of ore minerals was examined by Electron Probe Micro Analysis (EPMA) on six selected samples in the Iran Mineral Processing Research Center. Structural controls, depth, and vertical distribution or mineralized zones investigated by Induced Polarization-Resistivity (IP/RS) geophysical exploration surveys on 10 east-west-trending profiles.

    Result

    The host rocks are Neoproterozoic to lower Plaeozoic volcano-sedimentary sequences consisting of gneissic granite, amphibolite, schist, and pyroxenite, which are metamorphosed to greenschist facies. The intrusion of Cretaceous syenite, granite, and aplitic dikes within host rocks caused are caused by hydrothermal alteration and gold (copper±molybdenum) mineralization. Hydrothermal alteration zones are predominantly including argillic, silicified and sulfide alterations, which have mainly occurred in granite gneiss, amphibolite, schist, and intrusive rocks, respectively. Gold (copper±molybenum) mineralization occurred as vein and veinlets consisting of replacement, disseminated, and open space filling textures. The mineralogy of orebodies comprises of native gold, pyrite, chalcopyrite, molybdenite, magnetite, galena, sphalerite, and Hg, Nd, Ag, Se, and Ba-bearing sulfosalt minerals together with supergene and oxidation mineral phases including chalcocite, covellite, malachite, azurite, hematite, and goethite. The EPMA micro analysis on pyrite, chalcopyrite, and molybdenite showed that these minerals are characterized by high abundance of S, Mo, Fe, and Au (41.26, 52.33, 23.03, 0.04 wt. %, respectively) and low contents of Pb, W, Cu, Zn, and As (1.12, 0.46, 0.19, 0.08, 0.03 wt. %, respectively). The multivariate measurement of geochemical data using the Spearman's Rank correlation method indicated by positive relationship of Cu, Co, Ni, As, Pb, and in particularly Mo. Copper displays a positive and strong correlation with Co, Ni, Au, As, Pb, Mo, and W in ore-bearing zones. Furthermore, the ore-related elements are distinguished by the presence of Au, As, Cu, Mo, Ni, and Co in factor I, Cu in factor II, and Zn in factor III using the factor analysis method. In addition, an important geochemical behavior was observed among altered Au, As, Mo, and Cu and mineralized zones. Therefore, ore elements and in particularly Au, Mo, and Cu elements are classified in the same cluster. The positive correlation of ore elements with most other elements is indicated by distribution of Au±Cu±Mo orebodies in the area. The positive and relatively strong correlation of Au and As can be inferred from the cogenetic nature of those elements. The IP/RS geophysical investigation is distinguished by low abundances of induced polarization (IP) and high resistivity (RS) values in most profiles. Consideration of IP and RS pseudo profiles indicate the distribution of anomalous zones toward southern part of the area together with vertical zoning pattern similar to other alteration zones. Integration of the obtained results from geology, which reflects relatively extensive magmatic activity related to active tectonism and extensional structures, together with exploration geochemistry and geophysics resulted in the identification of two main potential areas in both northern and southern parts of the study area.

    Discussion

    The main altered and mineralized zones in the study area are characterized by vein and veinlet textures of ore mineralization together with geochemical and geophysical anomalies. The supergene mineralization of some sulfide and oxide minerals (e.g., malachite, azurite, chalcocite, covellite, hematite, and goethite) resulted in the low abundances of chargeability (10-40 ml/v) in most IP-RS profiles in the area. The geological, geochemical, and geochpysical data are integrated to recognize the mineralized and promising zones.

    Acknowledgements

    The author gratefully acknowledges the management of the Kansar Bakhtar Azarbaijan Company for their logistic support to carry out filed works, access and sampling of drill cores. Journal of Economic Geology Reviewers and editor are also thanked for their constructive and valuable comments.

    Keywords: correlation coefficient, EPMA analysis, factor analysis, IP-RS, Agh Ziarat, Sanandaj-Sirjan Zone, Iran