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زمین شناسی اقتصادی - سال دهم شماره 2 (پیاپی 19، پاییز و زمستان 1397)
  • سال دهم شماره 2 (پیاپی 19، پاییز و زمستان 1397)
  • تاریخ انتشار: 1397/11/10
  • تعداد عناوین: 15
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  • علمی - پژوهشی
  • الهام هاشمیان، حمایت جمالی *، جمشید احمدیان صفحات 299-324
    کانسار تپه خرگوش در 15 کیلومتری جنوب غرب اردستان قرار دارد. رخنمون های سنگی منطقه شامل آندزیت پورفیری، داسیت و ریولیت با سن ائوسن است که در میان آنها توف و ایگنمبریت نیز دیده می شود. در شمال محدوده نیز سنگ های رسوبی الیگو- میوسن دارای رخنمون هستند. رگه های سیلیسی کانه دار در سنگ های ائوسن (آندزیت پورفیری، داسیت و توف های ریولیتی) تشکیل شده اند. دگرسانی ها از نوع سریسیتیک، آرژیلیک، پروپلیتیک و سیلیسی هستند. رگه های سیلیسی دارای ساخت و بافت های نواری، رگه- رگه چه ای، برشی و پر کننده فضاهای خالی بوده و حاوی کانه های اولیه پیریت، کالکوپیریت، بورنیت، کالکوسیت و طلا هستند. دمای همگن شدن میان بارهای سیال از 137 تا 194 درجه سانتی گراد و شوری از 4 تا 5/12 درصد معادل وزنی نمک طعام متغیر است. ترکیب سنگ میزبان، نوع کانه ها، ساخت و بافت، ژئومتری، دمای تشکیل، انواع دگرسانی ها و زمین شیمی کانسار، مشابه کانسارهای اپی ترمال سولفیداسیون پایین است.
    کلیدواژگان: کانه نگاری، دگرسانی، تپه خرگوش، میان بارهای سیال، ژئوشیمی، اپی ترمال سولفیداسیون پایین، اردستان
  • علیرضا غیاثوند، محمدحسن کریم پور *، آزاده ملکزاده شفارودی، محمدرضا حیدریان شهری صفحات 325-354
    معدن فیروزه در شمال غرب نیشابور و در شرق کمربند ماگمایی قوچان- سبزوار قرار دارد و از نظر ساختاری جزو بخش غربی زون بینالود است. زمین شناسی این منطقه متشکل از گدازه و پیروکلاستیک هایی با سن پالئوسن- ائوسن است که توده های نفوذی نیمه عمیق با سن ائوسن میانی در آنها نفوذ کرده اند. مهم ترین دگرسانی هایی که واحدهای آتشفشانی و نفوذی منطقه را تحت تاثیر قرار داده شامل سیلیسی، آرژیلیک و کربناتی است. کانی سازی در سطح و تونل ها در درز و شکستگی ها اغلب به شکل های افشان، استوک ورک، رگه- رگه چه و برش گرمابی دیده می شود. کانی های اولیه شامل اسپکیولاریت، مگنتیت، پیریت، کالکوپیریت و بورنیت و کانی های ثانویه شامل هماتیت، آلونیت، کوولیت، فیروزه و لیمونیت هستند. اکتشافات ژئوشیمیایی، ناهنجاری های عناصر مس (تا ppm 1074) ، طلا (تا ppb 699) ، آهن (تا 30 درصد) ، سریم (تا ppm 464) ، لانتانیم (تا ppm 227) ، اورانیوم (تا ppm 243) و کبالت (تا بیش از ppm 10000) را نشان می دهد. بر مبنای بررسی های سیالات درگیر، دمای تشکیل کانسار بین 147 تا 278 درجه سانتی گراد با میانگین 203 درجه سانتی گراد بوده و از محلولی شامل نمک های KCl، CaCl2، MgCl2 و NaCl با درجه شوری بین 56/5 تا 08/17 درصد وزنی معادل نمک طعام به وجود آمده است. فرایند اختلاط بین محلول ماگمایی گرم و شور با محلول سرد و کم شور جوی و نیز فرایند جوشش توانسته است باعث ته نشینی عناصر شود. این کانسار منشا ماگمایی- گرمابی دارد و مرتبط با فعالیت های ماگماتیکی ترشیری وابسته به زون فرورانش ورقه اقیانوسی نئوتتیس سبزوار به زیر صفحه توران است. بررسی های زمین شناسی، دگرسانی، کانی سازی، ژئوشیمی، ژئوفیزیکی و سیالات درگیر در معدن فیروزه نیشابور نشان دهنده حضور کانی سازی بزرگی از نوع اکسید آهن مس- طلا- اورانیوم- عناصر نادر خاکی سبک مشابه با بخش هماتیت - غالب کانسار IOCG المپیک دم است.
    کلیدواژگان: کانی سازی، اکتشافات زمین شیمیایی، سیالات درگیر، اکسید آهن مس- طلا، معدن فیروزه نیشابور
  • احمد جمشیدزایی، قدرت ترابی * صفحات 355-380
    توده نفوذی نیمه عمیق کوارتز مونزودیوریت پورفیری که توسط دایک های تراکی آندزیتی ائوسن قطع شده است، در جنوب غرب جندق (کوه گدارسیاه، شمال غرب خرد قاره شرق- ایران مرکزی) رخنمون دارد. بافت اصلی در کوارتز مونزودیوریت ها بافت پورفیریتیک بوده و کانی های آن شامل پلاژیوکلاز (آلبیت) ، سانیدین، کوارتز، بیوتیت، مسکویت، کلریت، مگنتیت، کلسیت و آپاتیت است. دایک های ائوسن بافت گرانولار، اینترگرانولار و پورفیریتیک دارند و کانی های آن پلاژیوکلاز (آندزین و لابرادوریت) ، کلینوپیروکسن (دیوپسید و اوژیت) ، سانیدین، فلوگوپیت، کوارتز، آمفیبول، مگنتیت، کلسیت و آپاتیت هستند. داده های ژئوشیمیایی سنگ کل از توده نفوذی و دایک های این منطقه ماهیت متاآلومین را برای این سنگ ها مشخص می کند. آنالیزهای سنگ کل ماهیت کالک آلکالن سنگ های توده نفوذی و ماهیت کالک آلکالن پتاسیم بالا تا شوشونیتی را برای دایک ها نشان می دهد. الگوهای بهنجار شده با کندریت و نمودار چند عنصری بهنجار شده با گوشته اولیه در کوارتز مونزودیوریت پورفیری و دایک های تراکی آندزیتی، غنی شدگی از LREE و LILE ها و تهی شدگی از HFSE ها مانند Ta، Nbو Ti نشان می دهند. در این سنگ ها آنومالی مثبت یا منفی مشخص عنصر Eu وجود ندارد. این سنگ ها احتمالا در محیط فرورانشی متعلق به کمان آتشفشانی تشکیل شده اند. کوارتز مونزودیوریت پورفیری دارای مقادیر بالای 89/41-95/17 =La/Yb، wt. %80/68- 60/64 =SiO2، ppm 434-1855=Sr و 63/168-58/53 =Sr/Y و مقادیر پایین wt. %10/1- 16/0 =MgO، ppm 11 > Yو ppm 95/0 >Yb هستند و ویژگی های آداکیت های غنی از سیلیس را نشان می دهند که از ذوب اسلب اقیانوسی فرورونده ایجاد شده اند. دایک های تراکی آندزیتی دارای مقادیر 76/59-45/33 =La/Yb، wt. %60/57- 40/53 =SiO2، ppm 859-2050 =Sr و 125-82/50 =Sr/Y و مقادیر wt. %53/4- 93/1 =MgO، ppm 8/13 > Yو ppm 14/1 >Yb هستند و ویژگی های مرتبط با آداکیت های فقیر از سیلیس را نشان داده که در نتیجه ذوب پریدوتیت گوشته ای متاسوماتیسم شده، حاصل شده اند. با در نظر گرفتن زمان و مکان تشکیل این سنگ ها می توان نتیجه گرفت که سنگ های مورد بررسی مرتبط با فرورانش پوسته اقیانوسی اطراف خرد قاره شرق- ایران مرکزی (مثلا پوسته های اقیانوسی عشین و نائین) هستند.
    کلیدواژگان: کوارتز مونزودیوریت، تراکی آندزیت، فرورانش، آداکیت، ائوسن، خرد قاره شرق- ایران مرکزی
  • محسن مباشری *، فردین موسیوند، مجتبی رستمی حصوری صفحات 381-402
    کانسار قلعه خم نخستین گزارش از وجود ذخایر بوکسیتی در توالی پالئوزوئیک آغازین پهنه سنندج- سیرجان است. این کانسار به صورت عدسی های نامنظم در درون مجموعه مرمرهای کلسیتی- دولومیتی متراکم و توده ای کامبرین پایانی جای گرفته است. کانسار قلعه خم از دو بخش غنی از هماتیت و کرندوم (افق بالا) و بخش حاوی آلومینوسیلیکات های ورق های (افق پایین) تشکیل شده است. بر اساس نتایج آنالیز XRD و بررسی های میکروسکوپی، حضور کانی هایی نظیر کرندوم، مگنتیت، دیاسپور و کلریتوئید در این کانسار به اثبات رسیده است. این هم یافت بیانگر تاثیر رخداد دگرگونی پس از فرایند بوکسیتی شدن در این کانسار است، به علت دگرگونی اعمال شده، کانسنگ بوکسیتی اولیه به نهشته های متابوکسیتی و یا ذخایر امری تبدیل شده است. نتایج حاصل از آنالیزهای XRF نیز بیانگر آن است که بوکسیت های قلعه خم حاوی مقادیر 25 تا 58 درصد Al2O3، 15 تا 34 درصد Fe2O3، 3 تا 15 درصد SiO2 و 2 تا 5 درصد TiO2 هستند. بررسی نمونه های بوکسیتی در نمودار تغییرات Al2O3 – Fe2O3 – SiO2 نشان دهنده آن است که اغلب این نمونه ها در گستره بوکسیت و بوکسیت های آهن دار قرار می گیرند. بر اساس نتایج پژوهش حاضر، در کامبرین پایانی و در شرایط اقلیمی مناسب، بوکسیت های جنوب خاور سیرجان تشکیل شده و سپس تحت تاثیر دگرگونی و دگرشکلی های ناشی از حرکات کوه زایی سیمیرین پیشین به متابوکسیت های غنی از کرندوم تبدیل شده اند.
    کلیدواژگان: متابوکسیت، کرندوم، پالئوزوئیک، قلعه خم، سنندج- سیرجان
  • طیبه رمضانی، محمد معانی جو *، سینا اسدی، دیوید لنتز، ناصر پیروزنیا صفحات 403-424
    منطقه فلززایی اهر- ارسباران یکی از مهم ترین زون های فلززایی ایران در ترشیاری به شمار می رود. کانه زایی در منطقه اغلب وابسته به سنگ های ماگمایی ترشیاری است. از این منطقه، دو سیستم مس پورفیری سونگون و کیقال برای بررسی مقایسه ای نحوه کانه زایی انتخاب شدند. بر روی این دو کانی سازی بررسی زمین شیمی، سیالات درگیر و کانی شناسی انجام شد. انواع سیالات درگیر دو معدن مشابه و شامل نوع دو فازی مایع- گاز (L-V) ، نوع دو فازی گاز- مایع (V-L) ، نوع سه فازی مایع- گاز- جامد (گاهی هماتیت) (L-V-S) ، نوع سه فازی مایع- گاز - نمک (L-V-H) و نوع چهار فازی مایع- گاز- نمک- جامد (L-V-H-S) است. نتایج نشان داد که با وجود شباهت سنگ درون گیر، سنگ مادر و انواع سیالات درگیر و حتی شوری و دمای همگن سازی تقریبا مشابه، در وسعت دگرسانی، ضخامت پوسته و میزان CO2 سیالات آنها تفاوت هایی وجود دارد. به بیان دیگر معدن سونگون به علت ضخامت بیشتر لیتوسفر شرایط بهتری در تامین فلزات و تشکیل کانی های سولفیدی داشته است. همچنین حضور CO2 و تشکیل فرایند نامیژاکی سیال در افزایش pH و ته نشینی کانسنگ سونگون موثر بوده است و این موجب بارور بودن معدن سونگون و نیمه بارور بودن اندیس کیقال شده است.
    کلیدواژگان: مس پورفیری، بارور، هاله زمین شیمی، سیالات درگیر، ضخامت لیتوسفر
  • رضا منظمی باقرزاده، محمدحسن کریم پور *، جی لنگ فارمر، چارلز استرن، ژوزه فرانسیسکو سانتوس، سارا ریبیرو، بهنام رحیمی، محمدرضا حیدریان شهری صفحات 425-498
    کمپلکس پلوتونیک برنورد واقع در زون ساختاری تکنار، در شمال خرد قاره ایران مرکزی و در20 کیلومتری شمال غرب شهرستان بردسکن قرار دارد. این مجموعه با سنی معادل اواخر پرکامبرین (نئوپروتروزوئیک) ، نتیجه فعالیت ماگمایی وسیع شمال خرد قاره ایران مرکزی در اثر پدیده کوه زایی کاتانگاهی است. مشابه این ماگماتیسم در شمال خرد قاره ایران مرکزی به صورت کمربند ولکانو- پلوتونیک خواف- کاشمر- بردسکن همچون گرانیتوئیدهای کاشمر وجود دارد. این کمپلکس بزرگ مقیاس در واقع مجموعه ای گرانیتوئیدی شامل سنگ های گرانیتی، گرانودیوریتی، تونالیتی و گرانوفیری است که بخش مرکزی آن از یک گروه واحدهای گابرویی، دیوریتی و کوارتزدیوریتی تشکیل شده است. بافت اصلی این سنگ های حدواسط و مافیک، گرانولار متوسط تا درشت بلور است و بافت های پورفیروئید به ویژه در سنگ های حدواسط و بافت های پوئی کلیتیک و ساب افیتیک در سنگ های گابرویی به صورت پراکنده به چشم می خورد. کانی اصلی فرومنیزین دار سنگ های مافیک و حدواسط، کانی هورنبلند است و در نمونه های کوارتزدیوریتی، بیوتیت نیز دیده می شود. سنگ های حدواسط و مافیک کمپلکس پلوتونیک برنورد از لحاظ ژنتیکی با سنگ های گرانیتوئیدی این مجموعه ارتباطی مستقیم دارند. از لحاظ ارتباط صحرایی و بررسی های سنی چنین مشخص می شود که این واحدهای مافیک و حدواسط نسبت به واحد گرانیتی و دیگر واحدهای نفوذی اسیدیی این کمپلکس قدیمی تر بوده و توسط این واحدها قطع شده اند. بر اساس سن سنجی دیوریت های منطقه برنورد با استفاده از کانی زیرکن به روش U-Pb، سن این توده های نفوذی 32/4± 96/551 میلیون سال قبل (اواخر پرکامبرین) به دست آمده است. بر پایه بررسی های ژئوشیمیایی، تحولات ماگمایی این سنگ ها از نوع تولئیتی و کالک آلکالن بوده و شاخص اشباع از آلومین این سنگ ها متاآلومین است. دیوریت ها و گابروهای برنورد از نوع پتاسیم متوسط بوده و از لحاظ ویژگی های ژئوشیمیایی نسبت به عناصر ناسازگار La, Rb, K, U, Pb به همراه Th غنی شدگی نشان می دهند؛ در حالی که عناصری مانند Nb, Ti, Ta, Sr, Ba تهی شدگی شاخصی را در مقایسه با کندریت ارائه می دهند. ویژگی ایزوتوپی i (143Nd/144Nd) دیوریت ها و گابروهای برنورد در گستره 51203/0 تا 51214/0 به دست آمده است. مقدار عددی نسبت i (87Sr/86Sr) این توده های نفوذی در گستره 7038/0 تا 7135/0 اندازه گیری شده است. مقدار عددی ƐNd (T=552) دیوریت ها و گابروهای برنورد از 0/2 تا 0/4 به دست آمده است. مقادیر پایین i (87Sr/86Sr) نمونه های دیوریت و گابروهای منطقه برنورد و مقادیر Ɛ0Nd (present) این توده های نفوذی که 2/0- تا 0/4 محاسبه شده است، نشان دهنده آن است که تولید چنین توده های نفوذی می تواند به منبعی از گوشته بالایی یا پوسته قاره ای زیرین تحت آلایش قرار گرفته شده، نسبت داده شود. محیط تشکیل این دسته از سنگ های کمپلکس پلوتونیک برنورد، حاشیه فعال قاره و محیط کمان آتشفشانی است که می تواند به فرورانش پوسته اقیانوسی موجود بین خرد قاره ایران مرکزی و بلوک افغان مرتبط باشد.
    کلیدواژگان: کمپلکس، سن سنجی زیرکن، خرد قاره، برنورد، تکنار
  • علمی- پژوهشی
  • معصومه سرگزی، قدرت ترابی * صفحات 449-470
    توده نفوذی گرانیتوئیدی تویره با سن ائوسن میانی در جنوب غرب جندق و در حاشیه غربی خرد قاره شرق– ایران مرکزی قرار گرفته است. این توده نفوذی در قسمت های جنوبی و شرقی، سنگ های آتشفشانی ائوسن را قطع کرده و خود نیز توسط بازالت های آلکالن الیگوسن زیرین قطع شده است. سنگ های سازنده این توده نفوذی گرانیت و گرانودیوریت است که گرانودیوریت ها از فراوانی بیشتری برخوردارند. کانی های اصلی و فرعی تشکیل دهنده واحد گرانودیوریتی شامل پلاژیوکلاز، کوارتز، ارتوکلاز، آمفیبول، بیوتیت، آپاتیت، زیرکن و اسفن است. آمفیبول های گرانودیوریت ها از نوع کلسیک، با Mg# (میانگین 61/0) و ترکیب مگنزیوهورنبلند تا اکتینولیت دارند. دامنه ترکیب پلاژیوکلاز های این توده نفوذی از آلبیت تا آندزین در نوسان است و مرکز برخی از بلور های پلاژیوکلاز ترکیب لابرادوریت دارند. بررسی شیمی کانی بیوتیت های این توده نفوذی نشان می دهد که بیوتیت های آن شبیه بیوتیت های متبلور شده از ماگما های کالک آلکالن هستند. با استفاده از دما – فشار سنجی زوج کانی هورنبلند- پلاژیوکلاز، دمای تبلور 700 – 800 درجه سانتی گراد و فشار 1- 15/1 کیلو بار (معادل عمق 5/3 – 6 کیلومتر) محاسبه شده است دماسنجی کلریت ها دمای دگرسانی حدود 245 - 262 درجه سانتی گراد را نشان می دهد. بررسی های پتروگرافی و شیمی کانی بیوتیت ها و آمفیبول های توده نفوذی نشان دهنده I-Type بودن این گرانیتوئید است که از ماگمایی با منابع مختلط پوسته - گوشته شکل گرفته است. فوگاسیته بالای اکسیژن (+1< ∆FQM < +2. 0) در مذاب سازنده آن شاهدی برای ارتباط آن با فرورانش است.
    کلیدواژگان: گرانیتوئید نوع I، گرانودیوریت، شیمی کانی، ترموبارومتری، ائوسن، تویره، جندق
  • صالح دیمر *، مهرداد بهزادی، محمد یزدی، محمدرضا رضوانیان زاده صفحات 471-496
    منطقه معدنی ساغند بخشی از پهنه زمین ساختی کاشمر- کرمان در خرده قاره ایران مرکزی است که در استان یزد واقع شده است. کانسار Ti-REE-U (Th) دگرنهادی ساغند، در مجاورت توده گرانیتوئیدی زریگان و در مجموعه ای از سنگ های نفوذی نیمه عمیق دیوریتی- کوارتزدیوریتی تشکیل شده است. تحول زمانی دگرنهادی از مبدا سنگ های میزبان، به سمت دگرنهادهای آلبیتی، آمفیبولی و در نهایت دگرنهاد فلوگوپیتی توسعه پیدا کرده است که با رگه- رگه چه های اپیدوت± کلریت± کوارتز± کلسیت قطع شده اند. کانه های اصلی کانسار ساغند، ایلمنیت، دیویدایت، برانریت، روتیل و اسفن هستند که در دگرنهادهای آمفیبولی- آلبیتی نهشته شده اند. سیال دگرنهاد کننده منشا تفریق ماگمایی دارد که در آغاز اکسیده و به شدت قلیایی بوده و برای نهشت آلبیت و حمل و مجموعه سازی U و REEها بسیار مناسب بوده است. تفسیر ویژگی های زمین شیمیایی عناصر U، Th و REE در سنگ های دگرنهادی کانه زایی شده، سنگ های مادر و گرانیت های مجاور کانسار و نیز نبود شواهدی از نفوذ ماگماهای کربناتیتی یا آلکالن در محدوده کانسار، بیانگر وجود ارتباط میان دگرنهادی و کانه زایی با ماگماتیسم گرانیتوئیدی کالک آلکالن در منطقه است.
    کلیدواژگان: دگرنهادی قلیایی، عناصر کمیاب خاکی، ساغند، ایران مرکزی
  • علمی - پژوهشی
  • سید نعمتاللهحقیقی بردینه، رضا زارعی سهامیه *، حسن زمانیان، احمد احمدی خلجی صفحات 497-535
    مجموعه ماگمایی و کانسار آهن تخت در شمال شرق شهر همدان و در شمال کمربند ماگمایی ارومیه- دختر قرار دارد. این مجموعه شامل سنگ های آتشفشانی- درونی است که سنگ های آتشفشانی از داسیت، ریوداسیت، تراکی آندزیت و سنگ های آذر آواری (توف و آگلومرا) تشکیل شده اند و سنگ های درونی به طور غالب عبارتند از: گرانودیوریت و دیوریت آنکلاو دار و به مقدار کمتر گابرو. نفوذ توده های درونی یادشده به درون آهک کرتاسه، کانی سازی آهن اسکارن کلسیک را سبب شده است. سنگ های آذرین درونی اغلب از نوع متاآلومین و گروه کالک آلکالن هستند. نسبت های Sr/Nd، Nb/La و Th/U نشان می دهد گرانودیوریت اغلب از ذوب پوسته قاره ای شکل گرفته است و آنکلاو ها بیشتر منشا ماگمای مافیک جبه ای را نشان می دهند. نمودارهای عنکبوتی عناصر کمیاب و REE در نمونه ها دارای آنومالی منفی Nb, Sr, Ti, P و Eu و آنومالی مثبت در Th, K, Yb و Rb بوده که بیانگر نقش مواد جبه ای و پوسته ای در منشاگیری ماگماست. ویژگی های هم زمان گرانیتوئیدهای I و A و نیز ویژگی ماگماتیسم درون و حاشیه قاره نشان می دهد، ماگمای تخت هیبریدی است و امکان حضور هم زمان مذاب های گوشته ای و پوسته ای وجود دارد (سطح بالایی از LILEs وHFSEs). سن سنجی U-Pb زیرکن برای توده گرانودیوریتی، سن 2/0 ± 8/16 میلیون سال (دوره میوسن) را نشان می دهد. در مجموعه ماگمایی تخت مقادیر ایزوتوپ اولیه 87Sr/86Sr بین 70678/0 تا 70778/0 در هزار است و مقدار εNd نیز مقادیر منفی داشته و بین 79398/0- تا 83370/5- هستند. ویژگی های ایزوتوپی Sr و Nd نشان از منشاگرفتن مجموعه ماگمایی تخت از پوسته اقیانوسی شکسته شده همراه با آلایش پوسته قاره ای در مرحله پس از برخورد است. نتایج این پژوهش نشان می دهد برخورد صفحه عربی و ایران قبل از میوسن رخ داده و ماگماتیسم در کمربند ماگمایی ارومیه- دختر بعد از بسته شدن نئوتتیس نیز ادامه داشته است؛ به طوری که بررسی های ایزوتوپی، سن سنجی و ژئوشیمیایی منطقه مورد بررسی که بخشی از کمربند ارومیه- دختر شمالی محسوب می شود، بیانگر این موضوع است.
    کلیدواژگان: گرانودیوریت، ژئوشیمی، سن سنجی، یزوتوپ Sr-Nd، پس از برخورد، اسکارن آهن تخت
  • مژده داودی فرد، گیتی فرقانی تهرانی*، هادی قربانی، حبیب الله قاسمی صفحات 537-560
    در این پژوهش، غلظت، تحرک و دسترس پذیری عناصر بالقوه سمی در باطله های فراوری و همچنین منشا آنها در خاک های اطراف معدن سرب - روی ایرانکوه ارزیابی شده است. نتایج حاصل از تحلیل واریانس نشان می دهد که تفاوت آماری شاخصی بین غلظت عناصر در خاک های معدنی و کشاورزی وجود دارد. آنالیز خوشه اینیز نشان دهنده تاثیر معدن کاری بر افزایش غلظت PTEs در خاک است. بر اساس نتایج تحلیل مولفه اصلی، عناصر دارای سه منشا است: 1- عناصر پایدار زمین زاد؛ 2- عناصر انسان زادی که نشان دهنده ژئوشیمیایی کانه زایی سرب و روی هستند و 3- محصولات هوازدگی واحدهای کربناتی. آنالیز عنصری باطله های فراوری، نشان دهنده غنی شدگی شدید باطله ها نسبت به آرسنیک، کادمیم، آنتیموان، روی و سرب است. نتایج آنالیز استخراج ترتیبی نشان می دهند که درصد نسبتا بالایی از مس، منگنز، کادمیم و آرسنیک (به ترتیب 9/24، 3/20، 6/18 و 2/15 درصد) به شکل تبادل پذیر حضور دارد. بنابراین، فرسایش باطله های فراوری می تواند زیست دسترس پذیری این عناصر را در خاک کشاورزی و آب های زیرزمینی اطراف محدوده معدنی افزایش دهد.
    کلیدواژگان: عناصر بالقوه سمی، خاک، آلودگی، معدن ایرانکوه، اصفهان
  • مجید حیدری، علیرضا زراسوندی*، محسن رضایی، یوهان رایت، عادل ساکی صفحات 561-587
    کانسار مس پورفیری چاه فیروزه از جمله کانسارهای مربوط به مراحل انتهایی فرورانش- برخورد در زون ماگمایی ارومیه- دختر و در ارتباط با واحدهای سنگی دیوریت/ گرانودیوریت تا کوارتزمونزونیت با سن میوسن پایانی در کمان ماگمایی سنوزوئیک کرمان است. هدف از این پژوهش بهره گیری از شیمی بیوتیت های ماگمایی برای بررسی شاخص های فیزیکوشیمیایی ماگمای کانسار چاه فیروزه و مقایسه با پورفیری های پیش از برخوردی (پورفیری ریگان) است. دماسنجی بیوتیت در پورفیری چاه فیروزه، کمینه و بیشینه 478 تا 632 درجه سانتی گراد و میانگین دمایی 3/565 درجه سانتی گراد را نشان می دهند. بر مبنای شیمی بیوتیت های ماگمایی، شرایط فوگاسیته اکسیژن در ماگمای مادر چاه فیروزه در محدوده نیکل- نیکل اکسید قرار دارد که مطابق با شرایط فوگاسیته اکسیژن در کانسار ریگان است. log fH2O/fHF و log fH2O/fHCl, برای کانسار چاه فیروزه به ترتیب 69/4-84/4 و 09/4-28/4 با میانگین 14/5 و 14/4 است که بیانگر آب بالاتر سیالات اولیه نسبت به محتوای هالوژنی است. افزایش نسبی F در پورفیری چاه فیروزه نسبت به ریگان را می توان ناشی از غنی شدگی این سامانه پورفیری از منیزیم دانست. نمودارهای XFe و XMg در مقابل XF/XOH و XCl/XOH در چاه فیروزه و ریگان نشان داد که با وجود افزایش اندک کلر در کانسار چاه فیروزه، هر دو پورفیری برخوردی و پیش از برخوردی، تحت شرایط فوگاسیته کلر تقریبا یکسان شکل گرفته اند. مقایسه نسبت fH2O/fHCl در مقابل fHF/fHCl و fH2O/fHF در چاه فیروزه و ریگان با سایر پورفیری های جهان، نزدیکی این کانسارها با کانسار سرچشمه و مس Santa Rita را نشان داد. همچنین fH2O/fHCl در مقابل IV (Cl) نشان دهنده شباهت فوگاسیته هالوژنی کانسار چاه فیروزه با مس پورفیری بینگهام است. مقادیر IV (F) و IV (Cl) و IV (F/Cl) تایید می کنند که پورفیری چاه فیروزه به همراه ریگان در زمره توده های مس پورفیری کانه زا قرار می گیرند. افزایش اندک کلر در نمونه های چاه فیروزه نسبت به ریگان را شاید بتوان مستندی در رابطه با عدم کانه زایی قابل توجه در پورفیری پیش از برخوردی ریگان دانست.
    کلیدواژگان: بیوتیت، شاخص های فیزیکوشیمیایی، کانسار مس پورفیری چاه فیروزه، کمان ماگمایی سنوزوئیک کرمان
  • مهین رستمی، ابراهیم طالع فاضل* صفحات 587-616
    کانسار آهن±آپاتیت لکه سیاه در ایالت فلززایی بافق- ساغند و پهنه ساختاری ایران مرکزی قرار دارد. کانسار لکه سیاه طی اواخر کامبرین پیشین در ارتباط با فعالیت های مجموعه کالدرایی لکه سیاه شکل گرفته است که مجموعه سنگ های پیروکلاستیک، آندزیت/ تراکی آندزیت و ریولیت سنگ میزبان ذخیره را تشکیل می دهند. بر اساس نسبت Th/Yb (بین 7/2 تا 17) و Ta/Yb (بین 33/0 تا 8/1) ، ریولیت های میزبان کانی سازی جزو دسته های ماگمایی کالک آلکالن غنی از پتاسیم تا شوشونیتی قرار می گیرند. طبق شواهد به نظر می رسد تبلور ماگمای ریولیتی پر آب موجب آزاد شدن حجم زیادی از عناصر فرار شده که به افزایش گران روی ماگمای باقی مانده منجر می شود. در این شرایط، سیال احیایی با شوری و دمای بالا که حاوی لیگاندهای کلریدی حامل آهن و فسفر بوده، به سمت بالا و مناطق کم فشار حرکت می کند. فوران های انفجاری تشکیل دهنده کالدرا، شکستگی و سیستم گسلی مناسبی برای ته نشست ماده معدنی و رخداد کانه زایی فراهم کرده است. شواهدی مثل: 1- وجود هاله های دگرسانی قلیایی غنی از کلر (مانند سدیک و سدیک- کلسیک و پتاسیک- کلسیک) در اطراف کانسنگ آهن، 2- وجود سنگ های ماگمایی پتاسیم بالا مرتبط با یک سیستم کالدرایی فعال و 3- تهی شدگی عناصری نظیر Ti، V، Al و Mn در ترکیب شیمیایی مگنتیت ها، گویای وجود منبع گوشته ای دگرنهادی در منطقه لکه سیاه بوده که اغلب طی تکوین و جای گیری با سنگ های پوسته ای اطراف نیز دچار آغشتگی شده اند.
    کلیدواژگان: دگرسانی قلیایی- اکسیدآهن، پتاسیم بالا تا شوشونیتی، مجموعه کالدرایی لکه سیاه، بافق
  • سید جواد مقدسی *، ابراهیم طالع فاضل، عالیه سادات بنی فاطمی صفحات 617-638
    کانسارهای فلوریت باقر آباد و دره بادام در جنوب شرق محلات (استان مرکزی) ، نمونه ای از ذخایر اپی ژنتیک در ایران محسوب می شوند. کانی سازی به صورت رگه هایی با شیب تقریبی قائم و در ارتباط با شکستگی های محلی با راستای شرقی- غربی در سنگ میزبان کربناتی- شیلی با گستره زمانی ژوراسیک زیرین تا میانی شکل گرفته است. ساخت و بافت های پرکننده فضای خالی، برشی و حفره ای همراه با دگرسانی های دما پایین سرسیتی، سیلیسی و آرژیلیک در این ذخایر دیده می شوند. طبق شواهد به دست آمده، میان بارهای سیال بر مبنای فازهای تشکیل دهنده، به ترتیب فراوانی شامل سه نوع: 1- میان بارهای دو فازی آبگین غنی از مایع (L+V) ، 2- میان بارهای تک فاز مایع (L) و گاز (V) و 3- میان بارهای آبگین- کربنیک حاوی فاز CO2 (L1+L2+V) ، در کانی های فلوریت، باریت و کلسیت هستند. با استفاده از تقاطع منحنی های هم چگال در میان بارهای آبگین و آبگین- کربنیک، کانی سازی فلوریت در کانسار باقر آباد در فشار تقریبی 1 تا 2 کیلوبار و دمای 180 تا 260 درجه سانتی گراد تشکیل شده است. در کانسارهای باقرآباد و دره بادام سیالات گرمابی H2O+CO2 بالا آمده از سنگ بستر دگرسان شده، شرایطی مناسب برای افزایش انحلال پذیری فلزات و تشکیل کمپلکس های هالیدی (Cl و F) فراهم کرده اند. شورابه های یادشده طی واکنش با سنگ دیواره و کاهش دمای تدریجی سیال ناشی از رقیق شدگی با آب های جوی، کانی سازی رگه ای فلوریت در فضای مناسب را ایجاد کرده اند.
    کلیدواژگان: کانسار فلوریت، میان بار سیال، کانی سازی، باقرآباد، دره بادام، محلات
  • مسلم فاتحی، هوشنگ اسدی هارونی * صفحات 639-676
    ژئوفیزیک اکتشافی روشی ارزان، سریع و کارآمد برای شناخت عوارض زیر سطحی است. اما ژئوفیزیک روشی غیرمستقیم است و بهره برداری از اطلاعات ژئوفیزیکی مستلزم تفسیر دقیق و هدفمند داده های برداشت شده است. برای تفسیر کارآمد داده های ژئوفیزیکی در اکتشاف کانسارها، ابتدا باید شناخت کاملی از مدل کانسار و ویژگی های زمین شناسی از قبیل سنگ های میزبان، آلتراسیون ها، کانی شناسی و جایگاه کانی سازی در آن نوع کانسار داشت. قبل از حفر گمانه های اکتشافی، با استفاده از مطالعات ژنتیکی و داده های اکتشافی اولیه و همچنین شواهد سطحی باید یک مدل مفهومی برای کانسار مورد بررسی ارائه کرد و با توجه به ویژگی های آن مدل مفهومی، روش های ژئوفیزیکی مناسب، انجام و داده های اکتسابی تعبیر و تفسیر می شوند. در این پژوهش با توجه به مدل مفهومی و کنترل کننده های کانی سازی عمومی کانسارهای مس- طلای پورفیری نظیر اهمیت زون پتاسیک با توجه به حضور کانی های همیافت مگنتیت، کالکوپیریت، بورنیت و پیریت در استوک های دیوریتی، داده های ژئوفیزیکی مغناطیس سنجی، مقاومت ویژه الکتریکی و پلاریزاسیون القایی کانسار مس- طلای پورفیری دالی در ایران مورد بررسی قرار گرفت. به دلیل غنی شدگی کانی مگنتیت در زون دگرسانی پتاسیک و تهی شدگی آن در زون دگرسانی فیلیک، روش مغناطیس سنجی روشی کارآمد برای زون بندی دگرسانی های مختلف در کانسارهای مس- طلای پورفیری است. همچنین با توجه به وجود کانی های سولفیدی به صورت افشان، روش پلاریزاسیون القایی، روشی مناسب برای تعیین گستره کانی های سولفیدی است. روش مقاومت ویژه الکتریکی نیز برای ردیابی لیتولوژی، دگرسانی و کانی های فلزی مفید است. این پژوهش نشان داد که در کانسار مس– طلای پورفیری دالی، زون های با آنومالی مثبت و قوی مغناطیسی معیار بسیار مناسبی برای ردیابی کانسار است. شارژپذیری به شدت متاثر از درصد پیریت است و زون های با رسانایی و شارژپذیری خیلی زیاد و آنومالی های منفی مغناطیسی، منطبق بر هاله های زون های دگرسانی فیلیک و آرژیلیک است و دارای کانی سازی ناچیز است. آنومالی مغناطیسی، رسانایی بالا (رسانایی کم نیز زون های سیلیسی را نشان می دهد که حاوی کانی سازی هستند) و شارژپذیری متوسط تا بالا منطبق بر زون دگرسانی پتاسیک که حاوی کانی سازی سولفیدی مس و طلاست، دارند. این ویژگی های ژئوفیزیکی مهم ترین ردیاب کانی سازی در این کانسار است.
    کلیدواژگان: ویژگی های ژئوفیزیکی، کانسارهای مس- طلای پورفیری، کانسار دالی، زون دگرسانی پتاسیک
  • محمدحسن کریم پور *، آزاده ملکزاده شفارودی، عباس اسماعیلی سویری، چارلز استرن صفحات 677-707
    کمربند ایرانکوه- آهنگران یکی از مهم ترین زو ن های کانی سازی سرب و روی ایران است که با روند شمال غربی- جنوب شرقی در مرکز زون ساختاری سنندج- سیرجان واقع شده است. سه منطقه ایرانکوه، آهنگران و حسین آباد به عنوان مثال موردی در این مقاله بررسی شده اند. بر پایه شواهد زمین شناسی، ساختاری، شکل و نوع کانی سازی، شیمی محلول هیدروترمالی، آلتراسیون و پاراژنز مینرالی و مقایسه با انواع ذخایر سرب و روی، کلیه کانسارهای سرب و روی کمربند ایرانکوه- آهنگران از نوع MVT هستند. این کانسارها با گسل های تراستی مرتبط بوده و در زون ساختاری جلوی کمانی مربوط به پوسته اقیانوسی فرورونده جوان و داغ تشکیل شده اند. در چنین پوسته هایی قبل از رسیدن به اعماق 40 کیلومتری، بیش از 90 درصد آب اقیانوسی آزاد و سیلیکات های غنی از منیزیوم شکسته می شوند. فلزات بخشی از پوسته اقیانوسی و بخشی از پوسته قاره ای تامین شده است. از آنجایی که گسل های تراستی سنگ های ژوراسیک تا کرتاسه بالایی را قطع کرده اند و با توجه به تعیین سن دقیق انجام شده در ایرانکوه، کانی سازی های این کمربند در دامنه سنی بین 66 تا 56 میلیون سال پیش اغلب در پالئوسن شکل گرفته اند. شیمی محلول کانه دار ذخایر MVT فقیر از Si و غنی از Mg و Fe است. چنین سیالی همراه با فلزات از طریق گسل های تراست بالا آمده است و در سنگ میزبان دولستون (ایرانکوه و آهنگران) یا شیل- سیلتستون (حسین آباد و بخشی از ایرانکوه و آهنگران) کانی سازی انجام شده است. تفاوت های فاحشی در نوع پاراژنزها، آلتراسیون، شکل، ابعاد، میزان ذخیره و عیار در کانسارهای این کمربند دیده می شود که توسط نوع سنگ میزبان کنترل شده است. با استناد به تمام شواهد سنگ شناسی، آلتراسیون، شکل و حالت کانی سازی، وجود گسل های تراست، پاراژنز مینرالی و موقعیت خاص زمین شناسی و جغرافیایی ارائه شده، می توان برای اکتشاف ذخایر MVT پنهان در این کمربند اقدام کرد.
    کلیدواژگان: کانسارهای نوع MVT، شیل، دولومیت، گسل تراست، فرورانش، کمربند ایرانکوه- آهنگران
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  • Elham Hashemian, Hemayat Jamali*, Jamshid Ahmadian Pages 299-324
    Introduction: The Tappeh-Khargoosh area is located at the 15 km SW of Ardestan, in the middle section of the Urumieh-Dokhtar magmatic arc (Aghanabati, 2004). Exploration in the study area began in 2006 by Kani Pajohan-e- Spadana Company and continued in detail by the Ardestan Copper-Gold Company. Their exploration activities consist of preparing the geological map (1:5000 in scale), drilling trenches and boreholes. Also minor extraction has been done. In this paper, our focus is on mineralogy, alteration, geochemistry and fluid inclusion of the Tappeh-Khargoosh deposit for determining the genesis of mineralization. The results of this study can be used for more exploration in the study and adjacent areas. Methodology: Samples collected along a traverses perpendicular to the mineralized veins and their alteration haloes. The geometry, morphology, mineralogy and texture of mineralization were examined. After careful microscopic studies, 7 samples were analyzed by the XRF method in the laboratory of the Tarbiat Modarres University and Iranian Mineral Processing Research Center (IMPRC) in Karaj. Six thin-polished sections and 8 polished sections were examined. Also, 32 samples of mineralized and altered zones were analyzed by Inductively Coupled Plasma with optical emission spectrometer (ICP-OES) in IMPRC. Six samples were analyzed for gold by Atomic Absorption Spectroscopy (A.A.S) method in the Kimia Pajoh Alborz laboratory. Three double polished sections prepared from mineralized quartz vein and micro thermometric studies had been analyzed by a model HF-S90 microscope in the University of Isfahan. For detail understanding of mineral composition and determination of some fine and rare minerals, the electron microprobe analyzing (EMPA) technique (model SX100) is used in IMPRC. Discussion and results: The Tappeh-Khargoosh deposit consist of quartz vein and veinlets which occur as open space filling in Eocene andesite and dacite. The mineralized veins mainly occur in the fault zones. The subparallel fault systems of dextral strike sleep Qom-Zefreh crustal scale fault (Tajmir Riahi et al., 2012) has had the main role in localization of mineralizing fluids. The alteration mainly consist of silicificaion, propylitization with minor sericitization and argillization represented as vein-veinlets, dissemination and pervasively in host volcanics. These alteration assemblages are indicative of near neutral to little alkaline hydrothermal fluids (Simmons et al., 2005). The silicic alteration has occurred in a wide range of pH and temperature, while the argillic alteration has occurred in low temperature and a wide range of pH. So where the silicic and argillic alterations have occurred together, the temperature of the causing fluid must be lower in the range of clay mineral stability field (Robb, 2005). The fluid inclusion in the quartz shows the low temperature (137-194˚C) and low to medium salinity (4-12.5 %) which coincide with low to medium sulfidation epithermal deposit conditions. According to fluid inclusion data, bisulfides were the main ligand for metals transportation. The absence of halite/sylvite daughter minerals in fluid inclusions and low salinity of fluid inclusions show that the chloride complexes not act as effective ligands. Opposed to high sulfidation epithermal deposits in which the magmatic waters are common, in the low sulfidation type, the meteoric waters are dominant (Foster, 1991; Vahabi Moghadam, 1993). Dilution by cold and low salinity meteoric water has the main role in mineral deposition. Pyrite, chalcopyrite, bornite, chalcocite and native gold are the primary minerals and hematite, goethite, covellite, chalcocite, cuprite, malachite, chrysocolla, azurite and atacamite are the secondary minerals, which have occurred as veinlets, open space filling, colloform, amygdal filling and dissemination in quartz vein and host rocks. Fine grain gold had be seen in the colloidal secondary Fe-oxides, which indicate that the gold probably occurred primarily in sulfide minerals and was released in the supergene process. According to microprobe analysis, Ag was measured as impurity in chalcocite. These features coincide with high correlation coefficient between precious metals and copper. So, the Cu can be used as a pathfinder element for gold exploration in this and adjacent areas. The abundance of Cu-bearing secondary minerals in the surface, indicate that the Cu has not leached effectively as a result of the little amount of pyrite and aridity of the area. In this condition, Cu which was created by oxidation of primary Cu minerals was fixed in the surface as silicate, carbonate and oxide minerals (Chavez, 2000). Geology, geometry, texture and structure, geochemistry, alteration schema, fluid inclusion and mineralogical data of the Tappeh-Khargoosh make it similar to low sulfidation (L.S) epithermal deposits.
    Keywords: Mineralography, Alteration, Fluid Inclusion, Geochemistry, low Sulfidation Epithermal, Tappeh-Khargoosh, Ardestan
  • Alireza Ghiasvand, Mohammad Hassan Karimpour*, Azadeh Malekzadeh Shafaroudi , Mohammad Reza Haidarian Shahri Pages 325-354
    Introduction
    The Firouzeh mine is located in the Northwest of Neyshabour in the Khorasan Razavi province, Northeast of Iran, and eastern side of the Quchan- Sabzevar Cenozoic magmatic arc. Widespread magmatic activity in the Quchan-Sabzevar arc, is spatially and temporally associated with several types of mineralizations such as IOCG, Cu-Au porphyry and Kiruna types (Ghiasvand et al., 2016; Karimpour et al., 2011; Fatehi, 2014; Zarei et al., 2016). The aim of this investigation is to provide an understanding of the geology, alteration, mineralization, geochemistry, fluids evolution and genesis of the Firouzeh mine.
    Materials and methods
    Two hundred and fifty thin and polished sections were prepared for microscopic study. Twenty-nine samples were analyzed by X-ray fluorescence (XRF) method at the laboratory of Zar Azma company, Tehran, Iran. Twenty-one samples were analyzed by the X-ray Diffraction (XRD) method at the laboratory of Kansaran Binalood company, Tehran, Iran. Sixty samples were selected for 55- elemental analysis by composition of ICP-AES (Inductively coupled plasma atomic emission spectroscopy) and ICP-MS (Inductively coupled plasma Mass Spectrometry). Moreover, Sixty samples were selected for Au analysis by Aqua Regia Digestion at the SGS Laboratories, Canada. Six doubly polished sections of quartz mineralization were prepared for microthermometric analysis. Homogenization and last ice-melting temperatures were measured using a Linkam THMSG 600 combined heating and freezing stage at the Ferdowsi University of Mashhad.
    Result
    The Firouzeh mine contains various Middle- Eocene subvolcanic rocks as dykes which have intruded into Paleocene-Eocene volcanic rocks. Important altrations consist of silicified, argillic and carbonate among which silicified is the most extensive. Primary minerals are magnetite, specularite, pyrite, chalcopyrite and bornite and secondary minerals are hematite, alunite, covellite, turquoise and limonite. Mineralization has occurred in the cracks and fractures at the surface and in tunnels, mainly as disseminated, stockwork, vein-veinlet and hydrothermal breccia. Geochemical explorations showed anomalies of copper (up to ppm 1074), gold (up to ppb 699), iron (up to over percent 30), cerium (up to ppm 464), lanthanum (up to ppm 227), uranium (up to ppm 243) and cobalt (up to over ppm 10000) that has many similarities with IOCG type deposits (Corriveau, 2007; Zamora and Castillo, 2001; Marschik et al., 2000). Fluid inclusions are relatively simple liduid+vapor types, with homogenization temperature from 147 to 278ºC and average temperature of 203ºC and Salinity containing 5.56 to 17.08 wt. percent NaCl equiv. which has resulted from fluids with KCl, CaCl2, MgCl2 and NaCl compositions. Mixing process between hot and saline fluid with cold and low saline fluid and also, boiling process can caused deposition of elements.
    Discussion
    Firouzeh mineral deposit has magmatichydrothermal source and is related to tertiary magmatic activities of subduction of Neothetys Sabzevar oceanic crust beneath the Turan crust. Fluid mixing has played an important role for precipitation during mineralization and includes the source of hot and saline magmatic fluids with high contents of metallogenic elements and the mixing with cold and low saline meteoric waters resulting in the formation of deposit (Bastrakov et al., 2007; Simard et al., 2006; Wilkinson, 2001; Beane, 1983). Based on geological characteristics, alteration, mineralization, geochemistry, geophysics and fluid inclusion studies, Firouzeh mine is a great mineralization of iron oxide copper-gold-U-LREE which has similarities to the hematite-dominant section of Olympic Dam IOCG deposit. Acknowledgments: The Research Foundation of the Ferdowsi University of Mashhad, Iran, supported this study (Project No. 3/18303). We would like to thank the Iranian mineral processing research center and laboratories of Zar Azma, Kansaran Binalood, ACME and SGS. We also thank rural cooperation of Firouzeh mine for its liaison in field survey.
    Keywords: Mineralization, Geochemical exploration, Fluid inclusions, IOCG, Neyshabour Firouzeh mine
  • Ahmad Jamshidzaei, Ghodrat Torabi* Pages 355-380
    Introduction
    The “adakite” term was used for the first time by Defant and Drummond (1990) to display Cenozoic arcs igneous rocks with intermediate composition (SiO2> 56 wt.%), which were produced by partial melting of subducted oceanic crust. The adakites are series of intermediate to acidic rocks, with composition range from hornblende-andesite to dacite and rhyolite; and basaltic composition are lacking. In adakitic magmas, phenocrysts are mainly plagioclase, hornblende and biotite; while orthopyroxene and clinopyroxene phenocrysts are known only in mafic andesites (Calmus et al., 2003). Geochemically, adakites are identified with SiO2> 56 wt.%, Al2O3> 15 wt.%, MgO< 3 wt.%, Sr> 400 ppm and enriched LILE and LREE and depleted Y and HREE (Y< 18 ppm, Yb< 1.9 ppm) and high ratios of Sr/Y> 40 and La/Yb> 20 (Castillo, 2006 and Castillo, 2012). By using geochemical data, adakites were classified into high silica adakites (HSA, SiO2> 60 wt.%) and low silica adakites (LSA, SiO2< 60 wt.%) main groups. The high silica adakites were produced by partial melting of subducted oceanic crust basalts and the resulting melts also interact with peridotite during their ascent through the mantle wedge. While, low silica adakites were produced by melting of mantle peridotite that were metasomatized by melts resulting from slab (Martin and Moyen, 2002). The intrusion bodies with porphyritic texture has been studied and reported in different areas (e.g. Lan et al., 2012; Zhang et al., 2015). This intrusion bodies are often in a stock shape and the texture is porphyritic due to fast crystallization. The study area (Kuh-e- Godar-e Siah) is located in southwest of Jandaq (northeast of Isfahan province) and northwest of Central-East Iranian Microcontinent. The quartz monzodiorite intrusion with stock shape cross cutting by Eocene dykes swarm with trachy andesitic composition. In this paper, the petrology and chemical characteristics of quartz monzodiorites and trachy andesitic dykes are discussed. Material and methods: The chemical compositions of minerals from quartz monzodiorites and dykes were conducted by a JEOL JXA-8600 (WDS) electron probe microanalyzer (EPMA) at the Kanazawa University, Japan. Analyses were performed by an accelerating voltage of 20 kV and a beam current of 20 nA. The Fe2+ and Fe3+ contents of minerals were calculated by assuming mineral stoichiometry. The Fe2+# and Mg# parameters of minerals are Fe2+/(Fe2++Mg) and Mg/(Mg+Fe2+) atomic ratios, respectively. Representative chemical analyses of the minerals are listed in Table 1 and 2. To obtain whole rock chemical data, eighteen samples of the studied rocks were analyzed at the ALS-Mineral Company of Canada, by a combination of inductively coupled plasma spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) methods. The whole rocks geochemical data are presented in Table 3 and 4. Also, X-ray diffraction analyses were carried out in order to typify the K-feldspar mineral using an XRD D8 ADVANCE, Bruker machine, at the Central Laboratory of the University of Isfahan. The FeO and Fe2O3 concentrations are recalculated from Fe2O3 *, using recommended ratios of Middlemost (1989). Mineral abbreviations are from Whitney and Evans (2010).
    Results and discussion
    The main texture in quartz monzodiorites is porphyritic; and Eocene dykes are granular, intergranular and porphyritic in texture. The quartz monzodiorites consist of plagioclase (albite), sanidine, quartz, biotite, muscovite, chlorite, magnetite, calcite and apatite. The minerals in trachy andesitic dykes are plagioclase (andesine and labradorite), clinopyroxene (diopside and augite), sanidine, phlogopite, quartz, amphibole, magnetite, calcite and apatite. The chondrite-normalized REE patterns and primitive mantle-normalized multi-elemental diagram of the quartz monzodiorites and trachy andesitic dykes show enrichment in LREE and LILEs and depletion in HFSEs such as Ta, Nb and Ti. There is no evident positive or negative anomaly of Eu. Petrographical and geochemical characteristics of quartz monzodiorites and trachy andesitic dykes show that these rocks have been derived from different sources. The quartz monzodiorites have high content of La/Yb= 17.49-41.89, SiO2= 64.60-68.80 wt.%, Sr= 434- 1855 ppm, Sr/Y= 53.58-168.63 and low content of MgO= 0.16-1.10 wt.%, Y< 11 ppm and Yb< 0.95 ppm that show characteristics of high silica adakites which have been produced by melting of subducted oceanic crust. The trachy andesitic dykes have La/Yb= 33.45-59.76, SiO2= 53.40- 57.60 wt.%, Sr= 859-2050 ppm, Sr/Y= 50.82-125, MgO= 1.93-4.53 wt.%, Y< 13.8 ppm and Yb< 1.14 ppm, which display characteristics related to low silica adakites, produced by melting of metasomatized mantle peridotite. Acknowledgments: The authors thank the University of Isfahan for financial supports.
    Keywords: Quartz monzodiorite, Trachy andesite, Subduction, Adakite, Eocene, Central-East IranianMicrocontinent
  • Mohsen Mobasheri*, Fardin Mousivand, Mojtaba Rostami Hussory Pages 381-402
    Introduction
    Bauxite deposits in Iran are dominantly hosted by Late Triassic-Early Jurassic sequences in the Alborz zone and Late Cretaceous in the Zagros zone (e.g., Zarasvandi et al., 2008). Metamorphosed bauxite deposits in Iran are very rare, such as Heidarabad corundum-rich deposit (Emamali-pour, and Mirmohammadi, 2011). The Qale-Kham ore deposit is the first report of bauxite mineralization in the Early Paleozoic sequences of Sanandaj- Sirjan zone. In southeastern Sirjan (Qale-Kham area), karstic pockets of Late-Cambrian metabauxites embedded in carbonate rocks. The corundum-rich metabauxites are very rare in the world. Bauxite deposits can be classified into three main groups: lateritic, sedimentary and karstic-types. The karstic bauxite deposits have formed on the paleokarstic surface of carbonates (Bárdossy, 1982; Bárdossy and Aleva, 1990; Bogatyrev et al., 2009). The aim of this paper is to discuss genesis of the Qale-Kham bauxite deposit based on geological, petrographic, mineralogical and geochemical evidences.
    Materials and Methods
    A number of 95 samples were collected from the bauxite lenses in the Qale-Kham ore deposit. Optical microscopic investigations were conducted on 40 thin sections, 35 thin-polished sections and 20 polished sections of the samples using a Zeiss optical microscope equipped at the Shahrood University of Technology. Mineralogical analyses were done by X-ray diffractometer equipped with a CuKα tube and monochrometer (XRD Philips PW 1800) at the Kansaran Binaloud Company. The concentration of the major elements in the samples was determined using a wavelength X-ray fluorescence spectrometer (XRF Philips PW 1480) at the Kansaran Binaloud Company.
    Discussion
    In the Qale-Kham area, the rock units consist of amphibolite, mica schist, chlorite schist, epidotic schist and marble. The ores are mainly massive; however, pisolitic texture was observed in the deposit. Detailed mineralogical analyses of the Qale-Kham metabauxite deposit have been performed by optical microscopy and X-ray diffraction (XRD) studies. XRD results show that ore at the metabauxite deposits is composed of corundum, diaspore, chloritoid, opaque minerals (magnetite, hematite, ilmenite, and rutile), white mica (margarite, muscovite), goethite and limonite. Mineralogy of ores (such as corundum) and textures are representative of the impact of a metamorphic event on bauxite ores. This metamorphism and deformation has created structures, textures and formation of new minerals such as corundum and magnetite in the Qale- Kham ore deposit. The ores are mainly composed of Al2O3 (25–58%), SiO2 (3–15%), Fe2O3 (15– 34%) and TiO2 (2–5%). Alkalis and alkali earth elements show low values, probably because these elements are highly mobile and have usually leached out during chemical weathering (Gu et al., 2013). The triangular variation diagrams of Al2O3–SiO2– Fe2O3 are commonly used to show the degree of lateritization, mineral control and bauxite classification. Based on the mineralogical classification of Aleva (1994), most of the bauxite samples in the studied areas fall within the bauxite and ferritic bauxite fields. The chemical composition of corundum-rich metabauxites in Qale-Kham is nearly similar to those of other karst bauxite and karstic metabauxite such as corundum-rich metabauxites of the Menderes Massif (e.g., Özlü, 1983). They show generally strong enrichment in Al2O3, Fe2O3 and strong depletion in K2O, Na2O contents. Overal, the studied corundum-rich metabauxites at Qale- Kham can be classified as karstbauxites based upon their geological, mineralogical and geochemical characteristics.
    Results
    Corundum-rich metabauxite of Qale-Kham in the best outcrop is located at the SE Sirjan town. The metabauxite formed in the Paleozoic metamporphosed carbonate sequences of the South Sanandaj-Sirjan zone as karst-type deposits. Based on petrological and X-ray studies, the Qale- Kham ores consist of corundum, diaspore, chloritoid, opaque minerals (magnetite, hematite, ilmenite and rutile), white mica (margarite and muscovite), goethite and limonite. These studies suggest that the Qale-Kham ore deposit has been formed under suitable climatic conditions in the late Cambrian. This deposit has been metamorphesd and deformed due to the effect of early Cimmerian orogenic movements.
    Keywords: Metabauxite, Corundum, Paleozoic, Qale-Kham, Sanandaj- Sirjan
  • Tayebeh Ramezani, Mohammad Maanijou*, Sina Asadi, David Lentz, Naser Pirouznia Pages 403-424
    Introduction
    Nowadays, more than half of the word’s copper production is obtained from porphyry copper deposits, large (greater than 100 Mt), low- to moderate-grade, disseminated, stockwork-veinlet, carrying at least trace elements, such as molybdenum, gold, and silver (Sillitoe, 1972). Porphyry Cu systems are related to granitoid porphyry intrusions and adjacent wall rocks and most of them form at convergent plate margins (John et al., 2010). The deposits are often localized within calc-alkaline porphyry magmatic systems in subduction zone settings. Some PCDs have been formed in post-subduction settings. Ahar-Arasbaran metallogenic zone is one of the most productive metallogenic zones in Iran. Mineralization in the area is mainly associated with Tertiary magmatic events. In order to perform a comparative study of mineralization, Sungun and Kighal porphyry copper deposits (PCDs) were selected. The Sungun copper deposit is located in the north Varzaqan and the Kighal copper deposit lies 10 km to the south of the Sungun PCD (Calagari, 2003; Calagari, 2004). As recent studies show there are some similarities between the Sungun and Kighal deposits in terms of the parent intrusions, the host rocks, age and geological setting. However, the grade of copper in the Sungun PCD is 0.62 % Cu and in the Kighal PCD is 0.2 % Cu. Therefore, what are the key factors that have made the Kighal PCD subeconomic? Material and methods: Geochemical, fluid inclusion, and mineralogical studies were done on collected samples of the two porphyry copper deposits. In order to mineralogically study the Sungun and Kighal PCDs, 100 thin and polished thin sections were prepared. Eleven doubly polished sections of different quartz veins of the two PCD borehole samples were prepared for fluid inclusion studies. The measurements of 205 fluid inclusions were conducted at the Iranian Mineral Processing Research Center (IMPRC) by ZEISS microscope and Linkam TMH600, at temperature limits of - 196 to +600 °C. The precision was ±0.6 °C at 414 °C (melting point of Cesium nitrate), and ±2°C at -94.3 (melting point of n-Hexane). SPSS 17 and Flincor computer programs (Brown, 1989) were used for data analysis. Discussion and Results: In addition to some similarities of parent intrusions and host rocks (Hassanpour, 2010), there are similar fluid inclusion types and even nearly identical salinity and homogenization temperatures in these deposits (Simmonds, 2013). However, some differences in geochemical and mineralogical features, such as different low zonality index, less sulfide minerals and CO2 contents of the Kighal PCD, are notable. Some researchers have pointed out erosion (Hassanpour, 2010) and uplifting (Simmonds, 2013) as the main reasons for the sub-economic nature of the Kighal (non-productivity), comparison of Moho depth in the two deposits shows a greater crustal thickness in the Sungun PCD area (Fig. 10). The thickness of the lower crust is thought to be critical for governing arc mineralization potential, because it leads to an increase of the amount of water, metal, sulfur in adakitic magma forming arc-related bodies that is known to affect the origin of more productive (economic) porphyry copper deposits. Also low-CO2 fluid inclusions of the Kighal can have originated from a CO2-rich fluid immiscibility at depth (Simmonds, 2013). Lack of CO2 can inhibit (delays) bulk volatile saturation and in turn boiling, which influences the efficiency of metal removal from melt as well (Candela, 1997). CO2 contents of mineralizing fluids is important in increasing of pH during boiling event and ore deposition. The nonproductivity of the Kighal PCD may have resulted from all these factors. Acknowledgement: This work was supported by Bu-Ali Sina University and Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO). The authors would like to thank of the Sungun and Ahar copper companies. Special thanks to all the staff for their kind help. Thanks to the reviewers for their suggestions.
    Keywords: Copper porphyry, productive, geochemical halo, Fluid inclusion, Lithospheric thickness
  • Reza Monazzami Bagherzadeh, Mohammad Hassan Karimpour *, G. Lang Farmer, Charles R.Stern, Jose Francisco Santos, Sara Ribeiro, Behnam Rahimi&, Mohammad Reza HaidarianShahri Pages 425-498
    Introduction
    The study area is located in the northeast of Iran (the Khorasan Razavi province) and 28 km northwest of Bardaskan city and in position of 57° 46΄ to 57° 52΄ latitude and 35° 21΄ to 35° 24΄ longitude. The study area is a part of Taknar zone. The Taknar geological-structural zone is situated in the north Central Iranian microcontinental and it is a part of Lut block (Fig.1). Taknar plutonic complex that is situated in the Taknar structural zone is located in the northern part of Iranian microcontinent.
    Materials and methods
    Chemical analysis of REE and minor elements of samples of the Bornaward diorites and gabbro’s took place in the ACME Lab. in Vancouver, Canada, by the ICP-MS method (Table. 1). For the Bornaward diorite dating by the U-Pb method, zircon grains of material remaining in the sieve, Bromoform were isolated from light minerals by cleaning and were isolated with a minimum size of 25 microns, and then studies took place in the Crohn's Laser Lab Arizona (Gehrels et al., 2008). Measurement of Rb, Sr, Sm and Nd isotopes and (143Nd/144Nd)i , (87Sr/86Sr)i ratios and ƐNd (T=552), ƐNd (T=0), ƐSr (T=552) and ƐSr (T=0) took place in radioisotope Laboratory, University of Aveiro in Portugal.
    Discussion
    Geology of study area The study area forms the central part of the Bornaward plutonic complex. This complex is a granitoid assemblage including granite, granodiorite, tonalite and granophyre.tscentral part has been formed by intermediate and basic intrusive rocks such as diorite, quartz diorite and gabbro units (Fig. 2). From the genetic point of view, the intermediate and mafic rocks of the Taknar plutonic complex does not have any relationship with granitoid rocks of this assemblage, and they are related to a similar magmatic phase but are separated from this granitoid assemblage. However, these mafic and intermediate units are older than granitic units at the rim of the complex that are called Bornaward granite. Petrography The main minerals in the diorite and quartz diorite rocks are plagioclase and hornblende and we can see biotite in the quartz dioritic rocks. Quartz exist as tiny grains and anhedral and in the matrix rock. The amount of Quartz in the quartz diorites is 5 to 20%. Plagioclases usually have normal zoning and are highly altered to sericite. Most of the plagioclases were saussuritized. Altered minerals resulted from plagioclase and hornblende are sericite, epidote, chlorite, zoisite and clinozoisite. The main minerals in the gabbro are pyroxene, hornblende, and fine grains plagioclase. Minor minerals in the rocks are apatite, magnetite and other opaque. The main texture of intermediate and mafic rocks in this assemblage is medium granular to coarse grain and especially in the intermediate rocks and gabbro rocks, we can see scattered poikilitic, intersertal, sub-ophitic and porphyroid texture. Geochemistry The area diorite and gabbro is located locate in Tholeiitic and Calc-alkaline series (Fig. 9). Shand index (Al2O3/(CaO+Na2O+K2O)) is obtained under 1.1, in Metaluminous field (Fig. 7) and Itype granite field (Chappell and White, 2001). Based on the TAS diagram (Middlemost, 1985), all the diorite and gabbro samples are located in diorite, gabbro-diorite and gabbro-norite groups (Fig. 6). The diorite and gabbro’s show enrichment LREE and low ascending pattern ((La/Yb)N =1.40-6.12 and LaN =12.26-75.81). U-Pb zircon geochronology Measurement of U-Th-Pb isotopes of the Bornaward diorite zircons of BKCh-03 sample (Table 2) show that its age is related to 551.96±4.32 Ma ago (Upper Precambrian (Neoproterozoic) (Ediacaran) (Fig. 14). Sr-Nd isotopes The ( 87Sr/86Sr)i and ( 143Nd/144Nd)i content of Bornaward diorite and gabbro rocks is located in the range of 0.7038 to 0.7135 and 0.51203 to 0.51214, respectively (Tables 3 and 4). It shows that the diorite and gabbro rocks can be affected by hydrothermal alteration because their (87Sr/86Sr)i is above (Fig. 16). The numeral amounts of ƐNd(T=552) of Bornaward diorite and gabbro are 2.0 to 4.0. Petrogenesis The Bornaward diorite and gabbro rocks show a widespread enriched pattern of Rb, U, K, Pb, La and Th elements than chondrite, while Ba, Ti, Ta, Sr and Nb elements show reduction as a result of fractional crystallization (Fig. 11). The rocks of this complex are formed at the continental margin and VAG environment (Fig. 18) which is related to the subduction of the oceanic crust that exists between the Iranian microcontinent and the Afghan Block.
    Results
    This assemblage with age of Late Neoproterozoic is the result of extensive magmatism in the northern part of the Iranian microcontinent due to Katangahi orogeny event. The similar magmatism in the northern part of the Iranian microcontinent is existing as Khaf-Kashmar-Bardeskan volcanoplutonic belt. Based on the geochemical investigations, the magmatism of these rocks has been tholeiitic and calk-alkaline and have formed the coexistent rocks with I-type granites. Alumina saturation index for intermediate and mafic rocks of Bornaward complex is metalumina. These are medium-K rocks and enriched in the LILE such as Rb, Pb, U and Th while depleted of the Nb, Ti, Ta, Sr and Ba. Therefore, it shows that these rocks have resulted from the mixing by the lower crust. The low (87Sr/86Sr)i Bornaward diorite and gabbro rocks and the numeral amounts of Ɛ0Nd(present) of these rocks from -0.2 to 4.0 show that production of such intrusive masses can be attributed to the source of upper mantle or contaminated lower continental crust. Environment of formation of the intermediate and basic rocks of the Bornaward plutonic complex is active continental margin and volcanic arc environment.
    Keywords: Complex, Zircon geochronology, microcontinent, Bornaward, Taknar
  • Masumeh Sargazi, Ghodrat Torabi* Pages 449-470
    Introduction
    Granitoids are the most common igneous rocks that are found in all parts of the continental crust and play an important role in the formation and evolution of the Earth’s continental crust (Clarke, 1992). Granitoid plutons contain useful information on factors and processes related to their generation and differentiation (Castro, 2013). The wide range of sources and processes that may be involved in the formation of granitoids is reflected in their compositional range. Although yet there is a long way to achieve a consensus about the origin of granite, different interpretations of the geochemical granitoid data represents geological understanding of the complexities of these rocks. Large parts of Iran and Central - East Iranian Microcontinent (CEIM) structural zone have suffered from the Eocene granitoid magmatism. Toveireh granitoid intrusive body cropped out in the southwest of the Jandaq city (NE of Isfahan Province) and is one of the Eocene granitoid bodies. It is hoped that this mineralogical and petrological research will be useful in understanding the nature of Eocene acidic magmatism of Central Iran. Material and methods: Chemical analyses of minerals in the Toveireh granodiorites were carried out by a JEOL JXA- 8800R (WDS) electron probe micro-analyzer (EPMA) at the Cooperative Center of Kanazawa University, Kanazawa, Japan. The analyses were performed under an accelerating voltage of 20 kV and a beam current of 20 nA with a counting time limit of 40 seconds. Natural minerals and synthetic materials were used as standards. The ZAF program was used for data correction. The amounts of Fe2+ and Fe3+ contents of minerals were estimated by assuming ideal mineral stoichiometry in structural formula. Mineral abbreviations in petrographic photomicrographs and tables are taken from Whitney and Evans (2010).
    Results and discussion
    Petrographic studies show that the Middle Eocene Toveireh granitoid intrusive consists of granodiorite and granite. Granodiorites are coarse grained, mesocratic and have microgranular mafic enclaves in hand specimen. They are composed of plagioclase, amphibole, quartz, orthoclase and biotite. Accessory minerals are zircon, apatite, sphene and magnetite. Chlorite, actinolite, epidote and sericite are present as the secondary minerals. In the study area, the most dominant texture of the granodiorites are granular but graphic, perthite, anti-perthite, anti-rapakivi textures are common. The plagioclase (An0.8-48) occurs mainly as medium to coarse grains, subhedral, with zoning and polysynthetic twinning that represent varying degrees of saussuritization. Quartz occurs commonly as medium to fine anhedral grains. Graphic texture intergrowths of quartz and feldspars are present. Graphic texture possibly indicate rapid and simultaneous crystallization of quartz and K–feldspar from an under-cooled liquid at shallow depths (Clarke, 1992; Barker, 1983). Hornblende is present as subhedral to anhedral grains and in some cases partly altered to chlorite and actinolite. Biotites are subhedral and sometimes altered to chlorite, titanite and epidote. Based on mineral chemistry data, amphiboles in the investigated plutons are calcic in composition and classify as magnesio-hornblende and actinolite. Amphiboles are characterized by Mg# 0.67 to 0.47 and present geochemical features of subduction zone-related amphiboles. Biotite is characterized by variable and high Fe contents, with Fe# [Fe2+/(Fe2+ + Mg)] ratios between 0.52 to 0.60. Using the nomenclature scheme of Foster (1960), they are Mg-biotite, and have composition range of the calc-alkaline granites among the different granitoid suites in discriminative trend defined by Abdel-Rahman (1994). Chlorites are brunsvigite in composition and have negligible K2O and TiO2 but show similar Fe/(Fe+Mg) ratios with amphibole and biotite. Therefore, it can be concluded that they are alteration products of mafic minerals. Chlorite alteration temperature is estimated to be 245 to 262°C from chlorite geothermometry. The chemistry of hornblende and biotite imply that Toveireh granodiorites have I-Type nature and are products of crust-mantle, mixed-source magma crystallization. Barometry calculations of amphiboles indicate that these rocks were emplaced at an average pressure of 1- 1.5 kbars corresponding to approximately 3.5-6 Km depth. Plagioclase-amphibole and biotite thermometry suggests an equilibrium temperature of 700 to 800°C. Estimation of Oxygen fugacity by Fe# of amphibole and biotite indicate high value of Oxygen fugacity (+1< ΔFQM < +2.0) and suggest that the Toveireh granitoids belong to the magnetite-series of granites. Petrography and mineral chemistry of the studied rocks indicated their subduction-related tectonic setting. Acknowledgments: The authors thank the University of Isfahan and Kanazawa University for financial supports and laboratory facilities.
    Keywords: I-Type granitoid, Granodiorite, Mineral chemistry, Thermobarometry, Eocene, Toveireh, Jandaq
  • Saleh Deymar*, Mehrdad Behzadi, Mohammad Yazdi, Mohammad Reza Rezvanianzadeh Pages 471-496
    Introduction
    The Saghand mining district is a part of Bafq- Saghand metallogenic zone in the Central Iranian geostructural zone which is located in northeast of city of Yazd. This area is known to be more susceptible to mineralization of U and Th radioactive elements, but in fact is that its main importance is for relatively large iron deposits. However, in this region similar to some of the ore deposits within the Bafq area, rare earth elements have a high anomaly. Alkali-metasomatism occurs in a large variety of environments and geological periods. It can be spatially associated with ore deposits, as for some IOCG deposits or exists in barren systems such as metasomatism within the ocean crust (Johnson and Harlow, 1999). Although average U and REEs contents of the ore bodies associated with alkalimetasomatism are not high, they represent a promising exploration target because the resources of such deposits are relatively large (Cuney et al., 2012). The alkali-metasomatism could take place in all kinds of rocks. In addition to wide distribution in granite and granodiorite, it could be also identified in all kinds of metamorphic rocks, pegmatites, subvolcanic and volcanic rocks, and they all have mineralization (Zhao, 2005).
    Materials and methods
    After field studies, host rocks and metasomatites were sampled from outcrops, trenches, and core drillings. Since the rare earth elements and radioactive elements are present within the same mineralogy (Samani, 1985), surface spectrometry measurements were used in the selection of appropriate samples. For microscopic studies, 210 samples were prepared and studied. Ore minerals were investigated in polished and polished thin sections using optical microscope and Scanning Electron Microscopy (SEM) analysis was done in the Iranian Mineral Processing Research Center. An LEO-1400 SEM with energy dispersive X-ray spectrometry and back-scatter electron (BSE) imaging capabilities was used (accelerating voltage, 17-19 kV, and beam current of 20 nA). The 16 samples were analyzed by the ICP-MS method at Zarazma Mineral Studies Company, Iran, for major and trace elements at the various radiations and lithological ranges. The detection limit and precision for determination of REE, U and Th concentration were 0.2 to 1 ppm and 1 to 0.1 ppm, respectively. Discussion and results: Based on field evidence and microscopic studies, four main stage of metasomatism with continuous evolution have been distinguished in the Saghand area, including: 1) Na-metasomatism, 2) Ca-Mg metasomatism, 3) K-metasomatism, and 4) Epidote±chlorite±calcite±quartz vein and veinlets. All metasomatic zones are generally enriched in U and REE and compared with the host rocks but economic grades are less widespread and limited to Ca-Mg metasomatite zones near pinkish to red color albitites. The major Ti-REE-U(Th) minerals are davidite and brannerite, which have mainly crystallized during the Ca-Mg metasomatic stage. Ti or Tibearing minerals as paragenesis with davidite and brannerite are also deposited in amphibole-albite metasomatic zones. All these minerals are usually fractured and along fractures and its margin is replaced by titanite, leucoxene and rutile. In this study, geochemical analysis results of igneous rocks in the Saghand ore deposit, confirm the active continental margin arc setting and the nature of calc-alkaline magmatism in the region. The good adaptation of the REEs patterns in granites with the quartzdiorite-diorite rocks, can be a strong reason for their common tectonomagmatic origin. This Geodynamic environment had been the appropriate background in terms of protolith, heat engine for metasomatism cycle and supply hydrothermal solution and controlling structural pathways. The proximity of mineralized metasomatic rocks with the granitic rocks and intrusion of the granite apophysises into the metasomatic rocks, mobility of REE elements in the metasomatic environments, adaptation of geochemical properties of REE, U and Th elements in the mineralized metasomatitic rocks with the granitic rocks and finally, there was no evidence of intrusion of unusual magmas such as the carbonatite or alkaline magmas at the current level of ore deposit outcrops. Thesesuggest a close relationship between mineralization and metasomatic events with the granite intrusion. Fluids differentiated from the Douzakh-Darreh granite have entered the fault and crushed zones in a tectonically active regime of marginal continental arc. Due to reaction of the high temperature fluid with the protolith rocks, the ratios of Na+/K+ and Na+/H+ in fluid in equilibrated to feldspars of protolith rock elevated (Cuney et al., 2012). A basically alkaline medium to low temperature hydrothermal fluid is a suitable environment for the activation and transfer of U and REE in the form of hydroxyl complex (Romberger, 1984). Conversely, Th remained essentially immobile during the metasomatic processes (Cuney et al., 2012) and therefore, cannot be in abundance carried by this fluid. Hematite pigmentation of albite and transfer of U shows that oxygen fugacity in the early hydrothermal fluid has been quite high. These geochemical conditions simply allow U, and REEs enter from wall rocks to fluids and form hydroxyl complex of these elements, which are sustainable and are portable. Titanium bearing minerals within the quartzdiorite-diorite rocks and Douzakh Dareh granite easily decompose under hydrothermal activity and form titanium hydroxides, which is a very strong absorbent for U. After mineralization of albite and hematite, oxidation degree of fluid quickly drops and as a result, conditions for instability of complexes containing Ti, REE and U are provided. Acknowledgements: This paper is based on a part of the first author's Ph.D thesis at Shahid Beheshti University. This research was also supported by Skam Company and Iranian Mines & Mining Industries Development & Renovation Organization.
    Keywords: Alkali-metasomatism, Rare Earth Element, Saghand, Central Iran
  • Seyed Nematollah Haghighi Bardineh, Reza Zarei Sahamieh*, Hassan Zamanian, Ahmad AhmadiKhalaji Pages 497-535
    Introduction
    The Urumieh-Dokhtar Magmatic Assemblage (UDMA) forms a distinct NW-SE linear intrusive– extrusive complex Magmatism of the UDMA that occurred from Eocene to Quaternary, although the maximum activity was in the middle Eocene (Berberian and King, 1981; Ghasemi and Talbot, 2006). Collision of Arabian and Iranian plates led to termination of Neo-Tethys crust subduction and magmatism activity was abated in the UDMA, although there is no common agreement on collision timing. The Takht magmatic complex is located in the north of the Hamedan province (west Iran), and it belongs to the UDMA. The assemblage of volcano-plutonic rocks is present in the study area. The volcanic rocks include dacite, rhyodacite and trachyandesite with some tuff and agglomerated and the plutonic rocks are mostly occupied by granodiorite and diorite (containing mafic micro-granular enclaves) with some gabbro. These bodies are mostly intruded in Jurassic schists and are in contact with Cretaceous limestone leading to the formation of a skarn iron-ore deposit. The detailed geochemical and isotopic data is lacking and the age of the Takht granodiorite has not been determined. In the present study, the authors mainly have focused on the geochemistry and Sr-Nd isotopic ratios of the Takht magmatic complex to clarify questions regarding pterogenesis and its geodynamic evolution. We also reported U–Pb zircon ages for Takht granodiorite to study the relationship between its genesis and geological evolution history of the UDMA.
    Materials and methods
    A total of about 80 samples from the Takht plutonic-volcanic rocks were collected. 16 plutonic-volcanic samples were selected for wholerock chemical analysis. Major element oxides were analyzed by the X-ray fluorescence spectrometry (XRF) method using an Optima 7300DV XRF instrument in the Lab West laboratory, Australia. Trace elements were also analyzed in this laboratory with the inductively-coupled plasma mass spectrometry (ICP-MS) method using a NeXION 300 ICPMS instrument. Three chip samples with equal weight (4.5 kg) were collected from the Takht granodiorite. Then upon mixing, average samples were obtained for U–Pb dating of zircon. Hand-picked zircon crystals were supplied to the ALC (Arizona Laser Chron Center) in Arizona University. The 14 selected samples for Nd-Sm and Rb-Sr isotope analysis were crushed to less than 60μm. All isotope analyses were performed on a Nu Instruments Nu Plasma HR in the MC-ICP-MS facility, in the University of Cape Town, Rondebosch, South Africa.
    Results
    The plutonic rocks have metaluminous nature and are of calc-alkaline affinity. The Sr/Nd, Nb/La and Th/U ratios of the granodiorite show that its magma was formed mainly by melting of continental crust, and that its enclaves were formed from a mantle derived mafic magma. The samples have negative anomalies in Nb, Sr, Ti, P and Eu and positive anomalies in Th, K, Zr, Yb and Rb thus indicating contribution of mantle and crustal materials in their generation. The Takht granodiorite has geochemical features of I and A-type granites and also shows properties of both volcanic arc and within plate magmatism association granitoids (high levels of LILEs and HFSEs). In order to obtain better results, all the data were plotted on a common 206Pb/238U versus 207Pb/235U diagram. The results show an age of 16.8 ± 0.24 Ma (Middle Miocene) for the Takht granodiorite. Based on the results, the Takht granodiorite was generated in Miocene. In the Takht magmatic complex initial 87Sr/86Sr range from 0.70678 to 0.70778 and εNd also changes from -0.79398 to -5.83370. Nd-Sm isotopic contents and trace element ratios indicate that the Takht magmatic complex has originated from oceanic slab break-off with continental crust mingling in the post-collision stage. The εNd (16.8 Ma) vs. initial 87Sr/86Sr ratios diagram reveals, the role of continental crust materials in the generation of the granodiorite samples, while where the enclaves lie are plotted in the mantle evolution array field.
    Discussion
    The Takht magmatic complex has geochemical properties of arc related igneous rocks such as Ba, Nb, Sr, P, Ti and Y negative anomalies and for Rb, Th, U, K, Nd and Zr positive anomalies. Most of the Takht area samples are plotted in the triple junction of volcanic arc granites (VAG), within plate granites (WPG) and syn-collision (syn- COLG) on Y versus Nb and the Y+Nb versus Rb diagrams (Pearce et al., 1984). These data suggest post-collisional tectonic setting for the Takht magmatic complex. Field, microscopic and geochemical evidences indicate that simple fractional crystallization of a mafic magma was not the only processes involved in the generation of the studied rocks. On this basis, continental crust material had extensive contribution in the generation of the granodiorites whereas the enclaves are from mantle derived magmas. Relatively high fractionated REE patterns of the granodiorite samples with high LREE/HREE indicate an amphibole-bearing, garnet-free source for the samples while small to moderate negative Eu anomalies require residual plagioclase in the source. The granodiorite samples basically have geochemical properties of I-type granites and it is confirmed by their Nd and Sr isotopic ratios. However, relatively high HFSE contents make them similar to A-type granites. Melting of a former continental arc crust and contamination with mantle derived magmas led to both volcanic arc and within plate geochemical properties of the granodiorites that make them similar to I-type and A-type granitoids. The age of 16.8 ± 0.24 Ma (Middle Miocene) of the Takht granodiorite is consistent with the other post-collisional igneous rocks of the area and regarding its post-collisional geochemical properties the age of collision and related orogeny must be considered at least before Miocene.
    Keywords: Granodiorite, Geochemistry, Geochronology, Sr-Nd Isotope, Post- collisional, Takht Fe-skarn
  • Mozhdeh Davoodifard, Giti Forghani Tehrani*, Hadi Ghorbani, Habibollah Ghasemi Pages 537-560
    Introduction: Pollution of soils with potentially toxic elements (PTEs) is one of the most important hazards threatening the health of natural ecosystems. In recent decades, the anthropogenic activities have led to the disruption of the geochemical and biochemical circles of these elements. Mining activities are one of the most important anthropogenic sources for PTEs. The mine tailings are the most important pollution sources of surrounding soils and groundwater (Ferreira da Silva et al., 2004; Boularbah et al., 2006). Indeed, agricultural activities have a significant impact on the soil pollution with PTEs (Keskin, 2010). Soil plays a vital role in human life. Thus, the monitoring and assessment of soils pollution is of great importance. The Irankuh Pb-Zn mine, located in the SW of Esfahan, is one of the most important mines of Iran. Mining and subsequent processing of ores in this region generates high volumes of mine wastes which are deposited near the mine site. On the other hand, agricultural activities in the Irankuh area are extensive and the mine's tailing ponds usually neighbor the farms. The present study aims to investigate the concentration, mobility and availability of PTEs in the Irankuh mine tailings and to determine the source of these pollutants in the surrounding soils. Material and Methods: After the preliminary field studies, 28 soil samples including 8 mine- and 20 agricultural soils as well as two representative tailing samples were collected. One manure sample was also collected to identify the impact of agricultural activities on the concentration of PTEs in the soils, if any. First, the soil samples were air-dried at room temperature. Then, the large fragments and plant residuals were removed from the samples and the remaining portion was passed through a 2 mm stainless steel sieve. The sieved samples were ground to about 0.074 mm using an agate mortar and pestle and finally stored in polyethylene bags prior to laboratory analysis. The total concentrations of elements were measured by ICP-OES instrument after digesting by strong acids. The five-stage method of Tessier et al. (1979) was employed for sequential extraction analysis. In order to assess the pollution of the soils and tailings, the enrichment factor was calculated. Having obtained the results of the analysis, descriptive and multivariate data analyses were conducted. Results and discussion: The average concentration of Ag, As, Ba, Cd, Co, Mn, Pb, Sb and Zn in the mine soils are higher than the agricultural soils. The application of manure to the agriclutural soils led to increase in Cu and Cr concentration of the soils; the high concentration of these two elements in the manure sample is indicative. The concentration of Ag, As, Cd, Ba, Pb, Ni, Zn and Sb in both agricultural and mine soils are higher than the average world soil composition (Kabata-Pendias, 2011), pointing to the impact of anthropogenic activities on the PTEs concentrations in the soils. The tailing samples are highly encirched with respect to As, Cd, Cu, Sb, Mn, Pb and Zn. Enrichment factor values confirms pollution of soils with respect to Ag, As, Cd, Pb, Sb and Zn. Tailing samples are also extremly contaminated by these elements. On the basis of the analysis of variance, there is a significant statistical difference between the element concentrations in mine and in agricultural soils. The cluster analysis indicates the impacts of mining activity on the PTEs concentrations in soils. On the basis of principal component analysis, the elements originate from three sources: 1- geogenic stable elements 2- anthropogenic elements and 3- the weathering products of carbonate units. Total concentrations of PTEs provide no information on their likely environmental impacts. The speciation studies through sequential extraction analysis could be used to determine the mobility and availability of PTEs. By employing sequential extraction procedure, it is possible to predict occurrence manner, mobility, solubility, bioavailability, toxicity and transport as well as the origin of PTEs (Favas et al., 2011). The results show that, on the average, 24.9, 20.3, 18.6, and 15.2 % of Cu, Mn, Cd and As, respectively, are present as exchangeable fraction. Therefore, the weathering of mine tailings may increase the bioavailability of these elements in agricultural soils and groundwater around the mining area. The mobility of arsenic and iron is lower than other studied elements. Chromium and nickel are not mobile. Acknowledgement: This research has been funded by the Research Office of the Shahrood University of Technology.
    Keywords: Potentially Toxic Elements, Soil, Pollution, Irankuh Mine, Esfahan
  • Majid Heidari, Alireza Zarasvandi*, Mohsen Rezaei, Johann Raith, Adel Saki Pages 561-587
    Introduction
    Almost all of the well-known porphyry copper deposits in Iran occur within the Kerman Cenozoic magmatic arc (KCMA) (Fig 1) in the southeastern part of Cenozoic Urumieh–Dokhtar magmatic belt (Hassanpour et al., 2015). The Miocene Chahfiruzeh porphyry copper deposit as an example of collisional porphyry intrusion is located in the Kerman Cenozoic magmatic arc (Fig 2) (Einali et al., 2014). In this research, we attempt to characterize the physicochemical attributes of parental magma in the Chahfiruzeh porphyry deposit, using chemistry of magmatic biotite.
    Materials and methods
    Samples from various rocks were collected from drill cores belonging to 123.1-667.1m depths. The chemical compositions of magmatic biotites were obtained by analyzing the carbon coated polished thin sections using electron probe microanalyzer (EPMA). All samples were prepared and analyzed in the Montanuniversität Leoben, Austria using a superprobe Jeol JXA 8200 instrument. The analyses were conducted with 15 kV accelerating voltage and 10 nA beam and beam size of about 1 μm. The counting times (upper and lower) were 100 and 20 s, respectively.
    Results
    Chahfirouzeh porphyry deposit containing 100 Mt ore reserves (Mohammaddoost et al., 2017), and 0.4-0.8% Cu is located at the 95 km NW of Sarcheshmeh deposit and 35 km NE of Shahr-e- Babak in the Kerman province. (Einali et al., 2014). The compositions of analysed magmatic biotites from the Chahfiruzeh porphyry copper deposit are summarized in Table 1. According to (Mg–Li) vs. (Fetot + Mg + Ti–AlVI) and Mg–(Fe2+ + Mn)–(AlVI + Fe3+ + Ti) diagrams, the biotite from Chahfiruzeh deposit are Mg-rich (Fig. 5- A,B). Chemical compositions of biotites on the ternary diagram of Beane (1974) shows a magmatic origin for the analysed samples (Fig 7). Magmatic biotites are characterized by high SiO2 values ranging from 37.44-44.71 (Wt. %). Also, MgO and FeO vary between 12.54-14.36 (Wt. %) and 14.94-16.3 (Wt.%), respectively. Moreover, TiO2, K2O, and Na2O range from 4.53-5.97, 8.3- 9.38, 0.15-0.29 (Wt.%), respectively (Fig 6-A-D). Fluorine and Cl contents in biotite range from 0.3 to 1.52 wt.% and 0.03 to 0.04 wt.%, respectively.
    Discussion
    Chemical compositions of selected biotites on the classification diagrams of Abdel-Rahman (1994) indicate that magmatic biotites from the Chahfiruzeh porphyry copper deposit belong to calc-alkaline (C) series (Fig. 8). Also, according to ternary Xpdo-Xan-Xph diagram (Wones and Egster , 1965), Oxygen fugacities of Chhfiruzeh and other pre-collisional porphyry deposits (e.g., Reagan) occur in NNO distinct (Fig 9). It is evident that granitic rocks of both studied deposits are formed in relatively similar oxidiant conditions. Moreover, the preformed geothermometry on the magmatic biotites in the Chahfiruzeh porphyry the copper deposit shows a range of temperatures between 478-632 °C (average 565.3 °C). Moreover, XMg/XFe values confirm that Mg is enriched in Chahfiruzeh (collisional porphyry) compared to that of Reagan (pre-collisional porphyry; Fig 10-A). Also, fluorine has the highest concentration in collisional porphyry copper deposits. The plot of the Chahfiruzeh biotites on the log (XMg/ XFe) versus log (XF/XOH) discrimination diagram of Brimhall and Crerar (1987) represent that the intrusion crystallized from a weakly to strongly crustal-contaminated, I-type granitic magma (Fig 11). The log fH2O/fHF and fH2O/fHCl ranges between 4.69-4.84 and 4.09-4.28 having an average value of 5.14 and 4.14, respectively (Table 1). According to XFe vs. XF/XOH and XCl/XOH, Cl fugacities in Chahfiruzeh are analogous to that of Reagan porphyry (Fig 12). The calculated halogen fugacity ratios (log fH2O/fHCl vs. log fH2O/fHF and fHF/fHCl) and log fH2O/fHCl vs. IV(Cl) of magma in equilibrium with biotite for Chahfiruzeh porphyry and comparison with Reagan and other known porphyry of the world show that Chafiruzeh and Ragan deposits are analogous to those of Sarcheshmeh and Bingham porphyry deposits (Fig 13 and 14). Finally, Chahfiruzeh deposit as collisional porphyry has higher IV(F) than Reagan deposit (pre-collisional). In comparison with collisional porphyry copper systems (Chahfiruzeh), poor mineralization in the Reagan pre-collisional deposit may be due to lower Cl content of the magma in Reagan deposit. Acknowledgements: This research was made possible by the help of the office of vice-chancellor for Research and Technology, Shahid Chamran University of Ahvaz. We acknowledge their support. Authors highly appreciate the efforts of Prof. Johann. Raith and Dr. Federica Zaccarini for EMPA analysis. We also gratefully acknowledge the staff of the National Iranian Copper Industries Company (NICICO), for helping us in sampling.
    Keywords: Biotite, Physicochemical Attributes, Chahfiruzeh porphyry copper deposit, Kerman CenozoicMagmatic Arc
  • Mahin Rostami, Ebrahim Tale Fazel* Pages 587-616
    Introduction
    Ore deposits of the Bafq-Saghand metallogenic province (IRAN) with Proterozoic age represent that they belong to classic genetic model for hydrothermal iron oxide (Cu, Au, U, REE) deposits, which is widely referred to as iron oxide coppergold (IOCG) and iron oxide-apatite (IOA) deposits (Samani, 1988; Daliran et al., 2007; 2010; Jami et al., 2007; Nabatian et al., 2015; Rajabi et al., 2015). According to the structural zone of Iran, the Bafq mining district is part of Central Iran and therein Kashmar-Kerman tectonic zone (Zarigan-Chahmir basin), and Lake Siah deposit occurs in Early Cambrian Volcano-Sedimentary Sequence (ECVSS). According to Förster et al. (1988) and Torab (2008), the Bafq mining district is composed of a huge volcanic suite in which sedimentary structures, fossils, and even glassy volcanics a surprisingly are well preserved. Calderas are important features in all volcanic environments and are commonly the sites of geothermal activity and mineralization (Cole et al., 2005). The Lake Siah iron±apatite deposit is located between Kusk and Esfordi deposits and 40 km northeastern Bafq (31°46´47 N and 55°42´56 E).
    Materials and methods
    A total of 50 samples were collected from the Lake Siah mine district. Ten samples of least-altered igneous rocks were analyzed for major, trace and rare earth elements by inductively coupled plasma spectrometry (ICP-MS), and X-ray fluorescence (XRF) at the Acme laboratory (Canada). The detection limit for major oxide analysis is 0.01%. Electron microprobe analyses (EMPA) and backscattered electron (BSE) images of minerals were obtained using a Cameca SX100 electron microprobe at the Iran Mineral Process and Research Center (IMPRC). An accelerating voltage of 15 to 25 kV and beam current of 20 mA was used for all analyses.
    Results and discussion
    The Lake Siah deposit with a covering area of about 5 km2 is located in the Central Iran Block and therein Kashmar-Kerman tectonic zone (Zarigan-Chahmir basin). The Nb/Y versus Zr/TiO2 diagram shows a typical trend from rhyolite and evolving to andesite/trachyandesite compositions, with few data plotting in the dacite/rhyodacitic rocks. Most of the igneous rocks plot within the high-potassic calcalkaline to shoshonitic fields in the Th/Yb versus Ta/Yb diagram (Pearce, 1983). All studied rocks show similar incompatible trace element patterns with an enrichment of large ion lithophile elements (LILE: K, Rb, Ba, Th) and depletion of high field strength elements (HFSE: Nb and Ti), which are typical features of magmas from convergent margin tectonic settings. The Lake Siah deposit is composed of the hematite and magnetite as major minerals and apatite, goethite, pyrite and chalcopyrite as minor minerals. The deposit is controlled by NE-SW normal faults and occurs within early Cambrian trachyte, trachyandesite and rhyolite of the Lake Siah caldera. Intermediate argillic, sodic (albitic), silisic, potassiccalcic, hydrolytic (acidic), and sodic-calcic (Fe) alterations occur near the ore deposit. Lipman (1992) identifies a number of stages in the development of a caldera which includes: 1) pre-collapse volcanism, 2) caldera subsidence, 3) post-collapse magmatism and resurgence, and 4) hydrothermal activity and mineralization. Flow of dacite and andesite into the shallow magmatic system is facilitated by regional fault systems which provide pathways for magma ascent. Dacite and remobilized rhyolite rise buoyantly to form domes by collapse of the chamber roof and producing surface resurgent uplift. The resurgent deformation caused by magma ascent fractures the chamber roof, increasing its structural permeability and allowing rhyolite magmas to intrude and/or cause eruption. Explosive eruption of high viscosity magma is the cause of creating fractures and breccia in the host rocks and facilitated percolation Fe-P bearing magmatic fluids.
    Keywords: alkali-Fe oxide alteration, high-potassic to shoshonitic, Lake Siah caldera complex, Bafq, Central Iran
  • Seyed Javad Moghaddasi*, Ebrahim Tale Fazel, Aliyeh Sadat Banifatemi Pages 617-638
    Introduction
    Fluorite ore deposits are classified into three main groups: (1) magmatic deposits, (2) structures related deposits, and (3) sedimentary deposits (Dill, 2010). More than 30 fluorite occurrences with approximately 1.35 million tons of reserves have been recognized in Iran (Miller, 2014). Bagher Abad and Darreh Badam fluorite ore deposits, located in the southeast of Delijan (Markazi province) occur between the central Iran structural zone from the north and the Sanandaj- Sirjan structural zone from the south. The geology of the area is dominated by folded and faulted structures of Jurassic carbonates and shales (Thiele et al., 1968). The main host rocks for fluorite mineralization in the studied area are the Lower-Upper Jurassic carbonates and shales of Shemshak and Badamu Formations.
    Materials and Methods
    In this study, 70 samples from the various rock types including fluorite veins, host rocks and related alterations were collected. 25 thin- and polished thin-sections were prepared and studied to explain the mineralogy and paragenetic sequence of the ore body. Eight double-polished sections were also prepared for microthermometric analysis. The micro-thermometric analyses were conducted on primary fluid inclusions using Linkam THM600 heatingfreezing stage connected to a TMS94 temperature controller and a liquid nitrogen pump (LNP) cooling system.
    Results
    The main host rocks for fluorite mineralization in the studied area are composed of the lower Jurassic slate and phyllite (Shemshak Formation) and the Middle to Upper Jurassic dolomitic limestone and calcareous sandstone (Badamu Formation). The main alterations associated with fluorite mineralization are sericitization, silicification and argillization. According to the fluid inclusions data, fluorite mineralization in Bagher Abad and Darreh Badam deposits were precipitated because of pressure reduction of ore bearing fluids and mixing of a primary moderate-salinity brine with less saline meteoric water. Estimation of trapping pressuretemperature of the mineralizing fluid in Bagher Abad fluorite deposit using the intersecting CO2 and H2O isochors for aqueous, aqueous-carbonic and carbonic fluid inclusions indicated that fluorite mineralization occurred at 180-260°C and 1-2 kbar pressure. According to the present study, circulation and upward flow of hydrothermal fluids (containing H2O and CO2) that originated from underlying altered bedrock provided appropriate conditions for increasing the solubility of metals and formation of halide (Cl¯ and F¯) metal complexes. Reaction with wallrock and gradual decrease in temperature due to mixing and dilution of the above-mentioned fluids with lowsalinity meteoric water resulted in fluorite mineralization in favorable structures such as veins.
    Discussion
    Bagher Abad and Darreh Badam fluorite ore deposits are examples of epigenetic mineralizations which are not related to igneous activities in Iran. The mineralization is formed in nearly vertical veins, which are relevant to local fractures hosted in the Lower-Upper Jurassic carbonates and shales with east-west trend. The main ore textures are open-space fillings, breccias, veins and cavities associated with sericitic, silicic and argillic alterations. Micro-thermometric measurements were carried out on primary fluid inclusions in fluorite, calcite and barite minerals from both Bagher Abad and Darreh Badam deposits. Three types of fluid inclusions were distinguished: (1) two phase aqueous fluid inclusions (LV), (2) liquid (L) or vapor (V) mono phase inclusions, and (3) aqueous-carbonic (L1+L2+V) fluid inclusions. The first ice melting temperatures (Te) of two phase aqueous inclusions (LV) in fluorite, calcite and barite from Bagher Abad and Darreh Badam deposits vary between -32 to -15°C and -35 to - 24°C, respectively, which represents a H2O+NaCl±KCl multiphase fluid (Van den Kerkhof and Hein, 2001). The last ice melting temperatures (Tmice) vary between -10.5 to -2.3°C and -12.0 to -5.6°C which are equal to salinities of 5.6-14.7 and 8.3-15.2 wt% NaCl equivalent for Bagher Abad and Darreh Badam deposits, respectively. The final homogenization temperatures (Thtotal) vary between 127 to 188 °C and 176 to 270°C for Bagher Abad and Darreh Badam deposits, respectively. The CO2 melting temperatures (TmCO2) of aqueous-carbonic inclusions in fluorite, calcite and barite show a range of -58.3 to -56.6°C which suggests CH4 and/or N2 impurities (Burruss, 1981). The clathrate melting temperatures (Tmclath) ranging from -6.0 to +1.0°C represent salinities between 5.5 to 18.2 wt% NaCl equivalent for both Bagher Abad and Darreh Badam fluorite deposits.
    Keywords: Fluorite ore deposit, fluid inclusion, mineralization, Bagher Abad, Darreh Badam, Mahallat
  • Moslem Fatehi, Hooshang Asadi Haroni* Pages 639-676
    Introduction
    Geophysical exploration is an inexpensive, fast and efficient tool to provide valuable information about the sub-surface geological complications (Dentith and Mudge, 2014). Modern geophysical methods are widely used to identify and characterize porphyry copper deposits on various scales (Holden et al., 2011; Hoschke, 2011; Clark, 2014). It is often an indirect exploration method; therefore, an accurate data interpretation is required to extract the proper information associated with mineralization (Clark, 2014). For efficient interpretation of geophysical data in mineral exploration, it is initially important to understand the geological properties of a deposit (i.e., host rock, hydrothermal alteration system, mineralogical characteristics, texture, structural controls, zones of outcropping mineralization, etc.). Then, according to these properties and other genetic information, a conceptual model is defined to choose the proper exploration criteria and geophysical exploration methods to identify real anomalies associated with mineralization. Finally, the geophysical data are interpreted by considering the physical properties of the conceptual model. The conceptual model and the interpretation of geophysical data could be updated by using the new information acquired from the exploratory boreholes. This paper discusses the effectiveness of several geophysical methods in exploration of gold-rich porphyry copper deposits, and presents the exploration models related to the geophysical features of such deposits. We mostly used the related papers published in the same field to prepare these models. Then, on the basis of the defined geophysical signatures of the porphyry deposits, the IP&RS and magnetic data of the Dalli Cu-Au porphyry deposit were interpreted.
    Materials and methods
    Porphyry deposits are the most important source of copper, molybdenum and rhenium (Sillitoe, 2010) and provide significant amount of gold, silver and some other metals (Cooke et al., 2014). These are intrusion- related deposits which are geometrically symmetrical and are affected by different hydrothermal potassic, phyllic, argillic and propylitic alterations that often show a spatial zonation. Copper-gold mineralization mostly occur in the potassic alteration zone within the contact of the intrusive body and its adjacent wall rock. The physical properties of minerals and hydrothermal alterations associated with porphyry deposits near the surface are very variable, and therefore allow the use of various geophysical methods for exploration of such deposits. In porphyry deposits, sulfide minerals are present in different alteration zones with varying abundance, which could provide the use of electrical resistivity (RS) and induction polarization (IP) surveys to detect them. In gold-rich porphyry copper deposits, phyllic alteration zone often contain sulfide mineralization, therefore, this zone could be identified by high chargeability anomalies and low resistivities in the induced polarization surveys. The potassic alteration zone also contains sulfide minerals and is characterized in IP data with moderate to high-chargeability values. The IP method is the most extensively used geophysical approach in exploration of porphyry deposits. Magnetic minerals are enriched and destroyed respectively in potassic and phyllic alteration zones. Therefore, a high circular or elliptical magnetic anomaly is detected at the potassic alteration zone and is surrounded by a low magnetic anomaly related to the phyllic alteration zone. Hence, the airborne and ground magnetic surveys are useful for targeting the copper-gold porphyry deposits. The potassic alteration zone consists of the radiometric K element facilitating the application of the radiometric survey for targeting this zone. Nevertheless, the investigation depth of the radiometric approach is less than a few centimeters, and therefore, it is suitable only for mapping the deeply eroded deposits in which the mineralization occurred in the potassic alteration zone.
    Result
    The ground magnetic and IP-RS geophysical data of the Dalli Cu-Au porphyry deposit were interpreted based on the proposed conceptual model of the geophysical signature of Cu-Au porphyry systems. Integrating and evaluating the geophysical processes with the result of preliminary drillings indicated that in the Dalli Cu-Au porphyry deposit, the zones with positive and strong magnetic anomalies, high to moderate chargeability and high conductivity, are associated with copper and gold mineralization. Therefore, these criteria should be considered in designing the additional/infill boreholes in further exploration plans for this deposit.
    Discussion
    The magnetic, IP and RS surveys are the most important and common geophysical methods for targeting the porphyry copper and gold deposits. In particular, implementation and integration of these three methods can be more effective. Other geophysical approaches such as gravity, electromagnetic and seismic methods are also applicable for this purpose, but they are more expensive and complicated than the aforementioned approaches. For proper analysis of the geophysical data, first, it is necessary to recognize the geological model, hydrothermal alteration and mineralization systems of the studied deposits and the geophysical signatures of each alteration zone. Then, an appropriate interpretation of geophysical data is provided through combining the geological information of the deposit with the geophysical data.
    Keywords: geophysical signature, porphyry copper-gold, Dalli deposit, potassic alteration
  • Mohammad Hassan Karimpour*, Azadeh Malekzadeh Shafaroudi, Zahra Alaminia, AbbasEsmaeili Sevieri, Charles R. Stern Pages 677-707
    Introduction
    Mississippi Valley-Type (MVT) deposits are epigenetic zinc and lead deposits with minor copper hosted by dolostone, limestone, and locally sandstone in platform carbonate sequences inboard of major orogenic belts (Leach and Sangster, 1993; Leach et al., 2010). The Irankuh-Ahangaran Belt, which is the most important Pb-Zn mineralized zone of Iran, is situated within the Sanandaj-Sirjan tectonic zone. This belt is 400 km in length and 100 km in width. Three deposits including Irankuh mininig district, Ahangaran and Hosseinabad deposits were studied in this article (Fig. 1). The aim of this research is study of thermal gradient of subducted slab and age of formation of Pb-Zn deposits at Irankuh-Ahangaran belt, which is contrary information has been published so far on the type and their formation. Also, chemistry of ore-fluid in MVT deposits and impact of dolomitic and shale host rock on paragenesis, alteration, style, reserves and grade of deposits were discussed.These parameters will certainly be useful for exploration of the hidden MVT type deposits in the Irankou-Ahangan belt. Result and Discussion: The Irankuh mineralization is hosted by Cretaceous dolostone and minor Jurassic shale rocks as epigenetic. The constructive thrust fault, which has been cut the Jurassic and Cretaceous host rocks, has played a major role in the rising of fluid and formation of mineralization. Mineralization is occurred as replacement and open space filling (fault breccia, veinlets and cavity of rock) in dolostone and breccia, veinlet and open space filling in shale host rock. The mineral assembelages are Fe-rich sphalerite, Feand Mn-rich dolomite, ankrite, galena, minor pyrite, bituminous, calcite ± quartz ± barite within carbonate host rocks, whereas quartz, pyrite, Ferich sphalerite, galena, minor chalcopyrite, low Fe-dolomite, bituminous, ± barite ± calcite are important primary minerals at clastic hos rocks (Karimpour et al., 2018). The Ahangaran deposit is very similar to Irankuh in host rock, alteration, paragenesis, and form of mineralization. Thrust fault has a constructive role for occurrence of mineralization and later destructive strike slip and normal faults have caused the displacement and destruction of mineralization. The Hosseinabad deposit is hosted by Jurassic shale, siltstone, and sandstone rocks as veinveinlets, breccia and open space filling with structural control. Alteratin consists of silicification, chlorite, bituminous, and minor siderite, dolomite and ankerite similar to mineralization hosted by shale in Irankuh district. The mineral assemblages are galena, Fe-rich sphalerite, pyrite, chalcopyrite and minor phyrotite. Due to the lack of a proper dolostone unit in the Husseinabad deposit, mineralization is concentrated in particular areas with low-grade and low-reserves. Based on lithology, alteration, mineralization style, structural control by thrust faults, mineral paragenesis, and comparison with differnet types of Pb-Zn deposits, all deposits of Irankuh- Ahangaran belt are MVT-type. Deep-seated thrust faults formed during the early stages of subduction (~ 70 to 75 Ma), and played an important role in the upward migration of hydrothermal fluids from the basement to shallow depths. The geochronology of pyrite in Irankuh district based on Re-Os method indicate age of Irankuh Pb-Zn mineralization is 66.5 ± 1.6 Ma (Liu et al., 2019). Since the thrust faults have been cut the Jurassic to Upper Cretaceous rocks, and according to the absoulte age determined in Irankuh, the mineralization of this belt have been formed in the age range of 66 to 56 million years ago, mainly in the Paleocene (Fig. 15). Karimpour and Sadeghi (2018) suggested the hydrothermal fluid originated from the dehydration of a hot and young oceanic subducted slab, which liberated Pb, Zn, and other metals, and may have removed metals from rocks and organic material of the continental crust. More than 90% of all the water within the oceanic slab was released in the depth zone of the forearc region (depth of 30 to 50 km) (Karimpour and Sadeghi, 2018). In the depth zone, Mg-rich silicate minerals (such as antigorite, hornblende, chlorite, talc) have broken and the produced fluid is rich in Mg and Fe (Fig. 17). The ore-fluid of MVT deposits is Si-poor and Feand Mg- rich. Such fluid is mineralized on the hosts of the dolstone (Irankuh and Ahangaran) or Shale-Siltstone (Hossein Abad, and part of Irankuh and Ahangaran). There are significant differences in the type of paragenesis, alteration, shape, dimensions, reserves and grade in the deposits of this belt, which is controlled by the host rock type. Based on all lithological evidence, alteration, shape of mineralization, existence of thrust faults, mineral paragenesis and specific geological and geographic location, it can be used to exploration of the hidden MVT deposits in this belt.
    Keywords: MVT-type deposits, Shale, Dolomite, Thrust fault, Subduction, Irankuh-Ahangaran belt