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زمین شناسی اقتصادی - سال هفتم شماره 2 (پیاپی 13، پاییز و زمستان 1394)
  • سال هفتم شماره 2 (پیاپی 13، پاییز و زمستان 1394)
  • 154 صفحه،
  • تاریخ انتشار: 1394/12/05
  • تعداد عناوین: 11
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  • محمدعلی جزی، محمدحسن کریم پور، آزاده ملکزاده شفارودی صفحه 179
    کانسار Cu-Zn-As باقرق در شمال شرق شهر انارک و در استان اصفهان قرار دارد. کانی سازی به صورت دیرزاد، ماهیت چینه کران و بافت و ساخت پرکننده فضای خالی در سنگ میزبان کربناتی رخداده است. کانی شناسی بخش درون زاد شامل کالکوسیت، کالکوپیریت، پیریت، اسفالریت، گالن، انارژیت، باریت و کلسیت و کانی های بخش برون زاد شامل مالاکیت، آزوریت، کوولیت، کریزوکولا، کالکوسیت، سروزیت، اسمیت زونیت، مس طبیعی، هماتیت، گوتیت و لیمونیت می باشد. سنگ میزبان کربناتی در اطراف زون های کانه دار متحمل دگرسانی های دولومیتی شدن و کلسیتی شدن شده است. مس به عنوان عنصر اصلی ذخیره (با میانگین 28/20 درصد وزنی) و پس از آن عناصر روی (با میانگین تقریبی 1 درصد وزنی) و آرسنیک (با میانگین تقریبی 1 درصد وزنی) می باشند. مطالعات سیالات درگیر روی کانی باریت نشان می دهد سیال کانه دار سولفیدی دارای محدوده دمای همگن شدن بین 259 تا 354 درجه سانتی گراد و میزان شوری بین 8 تا 13 درصد وزنی معادل NaCl می باشد. سیال کانه دار در مراحل پایانی کانی سازی با آبهای جوی دچار اختلاط شده و فاز تاخیری غیر سولفیدی کلسیتی با محدوده دمای نسبتا پایین (78 تا 112 درجه سانتی گراد) و درجه شوری پایین (بین 3 تا 6 درصد وزنی معادل NaCl) را تشکیل داده است. محدوده مقادیر 34Sδ کانی باریت کانسار باقرق بین 13+ تا 14+ در هزار بوده در حالی که محاسبه مقدار 34Sδ مربوط به سیال کانه دار پس از تصحیح دمایی بین 7- تا 8- در هزار به دست آمد. منشا گوگرد باقرق با توجه به شباهت ایزوتوپ باریت با سولفات های دریایی کرتاسه، احتمالا از لایه های تبخیری این دوره زمانی تامین شده است. این سولفا ت ها توسط فرآیند های ترموشیمیایی به صورت بخشی به گوگرد احیایی با مقدار ایزوتوپی سبک تر (حدود 21 در هزار) تبدیل و جهت ته نشست سولفیدها مورد استفاده قرار گرفته است. کانسار باقرق با توجه به خصوصیاتی همچون سنگ میزبان کربناته، غیاب فعالیت آذرین، بافت پرکننده فضای خالی، دگرسانی دولومیتی،کانی شناسی، ژئوشیمی ماده معدنی (وجود As و Sb بالا و عدم حضور Bi)، داده های دماسنجی و مقادیر ایزوتوپ گوگرد، شباهت زیادی با کانسارهای مس با سنگ میزبان کربناته در افریقا و به ویژه نوع سومب (Tsumeb) در نامیبیا نشان می دهد. کانسار باقرق احتمالا مرتبط با سیالات دگرگونی آزاد شده در حین فازهای کوه زایی مرتبط با بسته شدن اقیانوس نئوتتیس می باشد.
    کلیدواژگان: مس، سنگ میزبان کربناته، سیال درگیر، ایزوتوپ پایدار گوگرد، باقرق
  • زهرا اعلمی نیا، محمدحسن کریم پور، سید مسعود همام صفحه 203
    ناحیه مطالعاتی در شمال استان خراسان رضوی و 45 کیلومتری جنوب نیشابور قرار دارد. رگه های طلادار درون سنگهای گرانیت، گرانودیوریت، گرانودیوریت پورفیری، آندزیت، برش و توف نفوذ کرده اند. رگه ها از جنس کوارتز و کلسیت هستند. مناطق اصلی دگرسانی شامل منطقه سرسیتیک، سیلیسی، پروپلیتیک و منطقه کربنات است. کانی زایی به طور نزدیکی با دگرسانی های سیلیسی و سرسیتیک به شکل رگه چه و با منطقه پروپلیتیک به شکل افشان همراه است. کانی شناسی کانی های باطله کوارتز، کلسدونی، سرسیت، آدولاریا، کلسیت، دولومیت، ایلیت، دیکیت، آلبیت، کائولینیت و کلریت است. کانی زایی رگه ای عمدتا با رگه چه ها، برش، افشان و استوک ورک همراه هستند. رگه چه ها از پیریت، مارکازیت، آرسنوپیریت و کمتر کالکوپیریت، اسفالریت، گالن، مگنتیت و هماتیت تشکیل شده اند. بیشترین عیار طلا در رگه های سیلیسی دیده می شود. پیریت کانی سولفیدی اصلی در کانی سازی اولیه است. سه نوع پیریت بر اساس ترکیب شیمیایی شناسایی شده است: پیریت خالص، پیریت غنی از آرسنیک و پیریت تیتانیوم- وانادیوم دار. تجزیه های ریزکاوشگر الکترونی بیشترین غلظت آرسنیک، تیتانیوم و وانادیوم را به ترتیب 62/3، 91/3 و 53/0 درصد وزنی در پیریتهای رگه های طلادار نشان می دهند. طلا معمولا همراه با پیریت آرسنیک دار و پیریت تیتانیوم- وانادیوم دار است. براساس مطالعه بافت و ترکیب پیریتها، رگه چه های پیریت آرسنیک دار همراه با کانی های سولفیدی آرسنوپیریت، کالکوپیریت، گالن، اسفالریت در دمای بالا و با کاهش دما و فشار، پیریتهای فرامبوئیدال با حاشیه حاوی آرسنیک و طلا شکل گرفته اند و در ادامه پیریتهای درشت تیتان دار به وجود آمده اند. پیریتهای خالص و تاخیری درشت بلور آخرین فاز کانی ساز در منطقه هستند.
    کلیدواژگان: عناصر کمیاب، پیریت، محدوده طلای چشمه زرد، شمال شرق ایران
  • فرشته بیات، قدرت ترابی صفحه 225
    سنگهای دگرگونی منطقه ترکمنی از شیست آبی و متاگری وک تشکیل یافتهاند و در امتداد گسل ترکمنی- اوردیب همراه با واحدهای سنگی پالئوزوئیک برونزد دارند. شیستهای آبی ترکمنی از مجموعه کانی های آلبیت، اکتینولیت، وینکایت و اپیدوت تشکیل شده اند. در اثر دگرگونی پس رونده شیست های آبی در شرایط دما- فشار رخساره شیست سبز، کانی های اکتینولیت و اپیدوت تشکیل شده اند. در متاگری وک ها مجموعه کانی های آلبیت، اپیدوت، کلریت، فنژیت ± گارنت یافت می شوند. در اثر رخداد دگرگونی پس رونده در شرایط رخساره شیست سبز کانی های اپیدوت و کلریت در متاگری وک ها تشکیل شده اند. ماهیت ماگمای سازنده پروتولیت شیست های آبی این منطقه برمبنای محتوای عناصر کمیاب و کم تحرک، یک بازالت تولئیتی بوده است. شیست های آبی از LREE بیشتری نسبت به HREE برخوردار هستند. عناصر LIL در این نمونه ها دارای مقادیر زیاد با نوسان قابل توجه هستند. آنومالی منفی عناصر HFS نظیر Nb، Hf، Zr و Ti در شیست های آبی ترکمنی مشاهده می شود. روندهای REE این سنگها شباهت نزدیکی به بازالت های حوضه های پشت کمان دارند. بر اساس نسبت Nb/La و مقادیر عناصر کمیاب، ماگمای سازنده پروتولیت شیست های آبی ترکمنی از یک اسپینل لرزولیت گوشته لیتوسفری با درجات ذوب بخشی پایین تا متوسط منشا گرفته است. فرآیندهای مرتبط با فرورانش پوسته اقیانوسی پالئوتتیس موجب غنی شدگی گوشته بالای اسلب فرورنده و متاسوماتیسم کربناته آن گردیده اند.
    کلیدواژگان: شیست آبی، گسل ترکمنی، اوردیب، فرورانش، پالئوتتیس، ایران مرکزی
  • احمد احمدی خلجی، زهرا طهماسبی صفحه 243
    محدوده همدان به طور عمده متشکل از سنگهای دگرگونی و پلوتونیک مزوزوئیک است. در این منطقه از غرب به شرق به ترتیب واحدهای متمایزی از توده های نفوذی، سنگهای دگرگونی مجاورتی و رگه های پگماتیتی و آپلیتی رخنمون دارند که در برخی مناطق این سنگها حاوی گارنت می باشند. بر اساس مطالعات انجام شده ترکیب اصلی گارنت در شیست های کمری و پگماتیت های ابرو از نوع آلماندین (گارنت غنی از آهن) و به مقدار کمتر اسپسارتین (گارنت غنی ازمنگنز) است که این دو نوع گارنت به گروه پیرالسپیت معروفند. الگوی منطقه بندی گارنت در سنگهای دگرگونی (شیست ها و هورنفلس ها) با سنگهای آذرین (پگماتیت) تغییرات متفاوتی از مرکز به حاشیه نشان می دهد. به طوری که ترکیب گارنت به ترتیب از مرکز به حاشیه در شیست ها از Alm0.63، Prp0.07، Sps0.24، Grs0.05 تا Alm0.71، Prp0.09، Sps0.13، Grs0.05در هورنفلس ها از Alm 0.79، Prp0.14، Sps 0.06، Grs0.07تا Alm0.8، Prp0.13، Sps 0.05، Grs0.01 و در پگماتیت ها، از Alm0.73، Prp0.015، Sps0.24، Grs0.07 تا Alm0.7، Prp0.011، Sps0.28، Grs0.00 تغییر می کند. شواهد پتروگرافی نظیر همراهی تورمالین با گارنت پگماتیت ها و آندالوزیت با گارنت سنگهای دگرگونی مجاورتی و شیمی کانی گارنت (افزایش Mn در هسته گارنت شیست ها و کاهش آن در هسته گارنت پگماتیت، کاهش عنصر Mg در مرکز گارنت پگماتیت و افزایش آن در هسته گارنت شیست ها، خطی بودن Ca، Al از حاشیه به مرکز در هورنفلس ها) و تقریبا 10 درصد گارنت پیروپ حاکی از منشا گرفتن گارنت موجود در شیست ها و هورنفلس ها از یک سیستم بسته (دگرگونی مجاورتی) و ماگمایی بودن آن در پگماتیت هاست.
    کلیدواژگان: همدان، دگرگونی، گارنت، منطقه بندی
  • محمدعلی رجب زاده، فاطمه آل سعدی صفحه 259
    مجموعه افیولیتی فاریاب در 140 کیلومتری شمال شرق بندرعباس در جنوب غرب زون مکران واقع شده است. این افیولیت از نظر ماهیت سنگ شناسی به دو بخش ماگمایی شمالی و دیرگداز جنوبی حاصل از سنگهای باقی مانده از ذوب بخشی گوشته فوقانی قابل تقسیم است. کانه زایی محدود سولفیدی در افقهای مختلف سنگ شناسی بخش شمالی صورت گرفته است. مطالعات پتروگرافی نشانگر ایجاد کانی های سولفیدی در دو نسل می باشد. در نسل اول، کانی های اولیه ماگمایی به صورت بی شکل با بافت افشان و به شکل بین دانه ای و در نسل دوم، کانی های ثانویه در اثر عملکرد سیال گرمابی به شکل رگه چه ای در امتداد شکستگی های سنگهای سیلیکاتی به وجود آمده اند. کانی های سولفیدی اولیه از نوع پیروتیت، پنتلاندیت و کانی های سولفیدی ثانویه اغلب شامل دیژنیت و پیریت می-باشند اسپینل های کروم دار همراه در سنگهای اولترامافیک به دو صورت انتشاری و توده ای دیده می شوند. میزان Cr#[100*Cr/(Cr+Al)] در نوع انتشاری از72 تا 74 و در نوع توده ای بین 82 تا 85 در تغییر است. همچنین میزان Mg#[100*Mg/(Mg+Fe+2)] به ترتیب برای نوع انتشاری بین 29 تا 33 و برای نوع توده ای بین 53 تا 58 است. این ترکیب شیمیایی متناسب با اسپینل های کروم داری هستند که از ماگمای بونینیتی در جایگاه زمین ساختی فوق فرورانش شکل می گیرند. کانی های سیلیکاتی سنگهای میزبان اغلب از نوع کلینوپیروکسن (دیوپسید و اوژیت) با Fs3-4،En45-48، Wo47-50 اولیوین با 95-Fo92 و ارتوپیروکسن (انستاتیت تا برونزیت) باEn85-87 می باشند. سنگهای میزبان سولفید از نوع ورلیت و کلینوپیروکسنیت هستند. مطالعات پتروگرافی نشانگر افزایش میزان و اندازه کانی های سولفیدی با ازدیاد میزان کانی کلینوپیروکسن در سنگ میزبان است.
    کلیدواژگان: سولفید، کانه زایی، سنگ اولترامافیک، افیولیت، فاریاب
  • علیرضا زراسوندی، فاطمه اسدی، هوشنگ پورکاسب، فرهاد احمدنژاد، حسن زمانیان صفحه 277
    کانسار مس- طلای پورفیری دالی در بخش مرکزی کمان ماگمایی ارومیه- دختر در شهرستان دلیجان، استان مرکزی واقع شده است. در این منطقه پورفیری های کانه دار میوسن با ترکیب غالب دیوریت و کوارتز دیوریت در امتداد شمال غرب-جنوب شرق درون سنگهای آندزیت تا آندزیت بازالت جای گیر شده اند. همچنین سیال گرمابی باعث غلبه بر فشار لیتوستاتیک در گسلها و شکستگی ها شده و این گسلها میزبان گسترده و متنوعی از رگه ها و رگه چه های کانه های کوارتزی با بافت استوک ورک گردیده اند. مشاهدات صحرایی و پتروگرافی صورت گرفته نشان می دهد که: پنج گروه اصلی رگه همراه با سه نسل کانه زایی در منطقه وجود دارد. همچنین پتروگرافی سیالات درگیر نشان می دهد که در کانسار دالی هفت گروه سیال درگیر شامل سیال درگیر تک فازی غنی از مایع (IA)، تک فازی غنی از بخار(IB)، دوفازی غنی از مایع (مایع + بخار) (IIA)، دوفازی غنی از بخار (بخار + مایع) (IIB)، سیال درگیر شور ساده (مایع + بخار + هالیت) (IIIA)، سیال درگیر شور حاوی کانی اپک (مایع + بخار + هالیت + پیریت + کالکوپیریت + هماتیت)(IIIB) و سیال درگیر چندفازی (مایع + بخار + هالیت + سیلویت + هماتیت + مگنتیت + پیریت + کالکوپیریت ± اریتروسیدریت)(IIIAB) قابل مشاهده می باشند. مطالعات دماسنجی نشان می دهد که محدوده دمای همگن شدگی نهایی و شوری برای سیال درگیر دوفازی غنی از مایع و غنی از بخار ̊C460 تا 140 و Wt.%NaCl 25 تا 0 و برای سیالات شور ساده، شور حاوی کانی اپک و سیالات درگیر چندفازی ̊C620 تا300 و Wt.%NaCl 75 تا 30 می باشد. همچنین فشار و عمق برای سیالات درگیر دوفازی غنی از مایع و غنی از بخار bar500 تا 100 و km 2 تا 4/0 و برای سیالات شور ساده، شور حاوی کانی اپک و سیالات درگیر چندفازی bar620 تا 200 و km3 تا 8/0 می باشد. سیالات درگیر چندفازی با بیشترین فراوانی دمای همگن شدگی در گستره ̊C620 تا 420 و بیشترین فراوانی شوری در گستره Wt.%NaCl 75 تا 70 نشان دهنده اولین سیالاتی هستند که سبب تشکیل کانسار دالی شده اند. سیالات ماگمایی دمای همگن شدگی و شوری بالایی دارند، اما شکستگی ها باعث اختلاط سیالات ماگمایی و جوی و تشکیل میان بارهای IIBبا دما و شوری پایین تر سیال ماگمایی می گردند. نتایج مطالعات نشان می دهد که در کانسار دالی فرآیندهای جوشش، سرد شدن، اختلاط و واکنش سیال- سنگ صورت گرفته است. مطالعه سیالات درگیر نمونه های کوارتزی حاصل از سیال کانه ساز در زون های دگرسانی پتاسیک و کوارتز- سرسیت- پیریت، کاهش درجه حرارت را از پهنه پتاسیک ̊C620 تا 300 به سمت کوارتز- سرسیت- پیریت ̊C480 تا 160 نشان می دهد که مطابق با سایر نهشته های پورفیری در جهان است.
    کلیدواژگان: سیال درگیر، دگرسانی، جوشش، مس، طلای پورفیری، کمان ماگمایی، دالی
  • آرش گورابجیری پور، محسن مباشری صفحه 307
    منطقه اکتشافی ماهور، یک سیستم پلی متال مس، روی و نقره است. کانی سازی در ماهور به دو صورت رگه ای و انتشاری نمود دارد. این منطقه در بلوک لوت و در غرب دهسلم واقع است. سنگ شناسی منطقه ماهور مشتمل بر بازالت، آندزیت، داسیت، ریولیت و آذرآوری هاست. این مجموعه در ائوسن پایانی – الیگوسن زیرین مورد هجمه توده هایی با ترکیب دیوریت تا کوارتز دیوریت قرار گرفته است. زون های دگرسانی در منطقه شامل آرژیلیک، سیلیسی، کوارتز- سریسیت- پیریت، کلریتی و پروپیلیتیک است. میزبان رگه های معدنی رخنمون یافته در کانسار ماهور سنگهای با ترکیب داسیتی است، که روندی شمالی – جنوبی دارند. رگه های کانی سازی با روند NNE-SSW و شیب 85 تا 90 درجه دیده می شوند. کانی های اولیه شامل پیریت، کالکوپیریت، اسفالریت، گالن، تتراهدریت، کوارتز و کانی های ثانویه مالاکیت، آتاکامیت، آزوریت و گوتیت است. ناهنجاری های بالایی از عناصر مس (تا ppm 60417)، روی (تا ppm 250438) و نقره (تا ppm 1988) در محدوده مورد مطالعه نمود دارد. برداشتهای IP/RS به منظور تعیین موقعیت و گسترش کانی سازی سولفیدی و اکسیدی در عمق انجام شد. خط مبنای مطالعات ژئوفیزیکی شمال شرق- جنوب غرب (N 7 E) هم روند با رگه معدنی و پروفیل ها عمود بر این روند طراحی شده اند. مقدار شارژابیلیته به msce40 می رسد که حاکی از وجود سولفید و کانی های فلزات پایه در منطقه است. در کانسار ماهور دو زون مقاومت ویژه بالا و کم قابل تشخیص است. زون مقاومت ویژه بالا تا ohm.m350 در شبه مقاطع، مرتبط با زونهای کمتر خردشده است. زون دارای مقاومت ویژه کمتر در ارتباط با زونهای به شدت خرد شده می باشد. به طور کلی برداشتهای شارژابیلیته در منطقه ماهور وجود دو زون نا هنجاری در شمال شرق و دیگری در جنوب غرب محدوده را به وضوح نشان می دهد. 6 گمانه حفر شده در محل نا هنجاری معرفی شده مطالعه و در فواصل 1 متری از مغزه ها نمونه ژئوشیمیایی اخذ گردید. بیشترین ناهنجاری ها همراه با آلتراسیون کوارتز- سرسیت- پیریت، سیلیسی، کلریت و مناطق با گسترش شدید اکسیدهای آهن ثانویه است.
    کلیدواژگان: شارژابیلیته، مقاومت ویژه، چاه نگاری، ماهور، بلوک لوت
  • سید جواد مقدسی، جواد یزدی صفحه 327
    پلاسرهای تیتانیوم دار منطقه فنوج در فاصله 35 کیلومتری شمال شهرستان فنوج در جنوب باختری استان سیستان و بلوچستان واقع است. منطقه مورد مطالعه بخش کوچکی از پیکره افیولیتی فنوج - مسکوتان (رمشک) با سن کرتاسه پسین را تشکیل می دهد. اکتشافات مقدماتی و نیمه تفصیلی در منطقه فنوج نشان داده است که ناحیه دره جوگز بالا پرعیارترین ناحیه تیتانیوم دار در منطقه فنوج است. واحدهای هورنبلند گابرو و الیوین گابرویی منطقه، سنگ مادر پلاسرهای تیتانیوم دار ناحیه دره جوگز بالا هستند و از نظر کانی شناختی شامل پلاژیوکلازهای دگرسان شده، کلینوپیروکسن، الیوین و آمفیبول می باشند. ایلمنیت مهمترین کانه تیتانیوم دار در واحدهای سنگی ذکر شده است. مطالعات کانی شناختی نشان می دهد که بخش سنگین رسوبات تیتانیوم دار ناحیه دره جوگز بالا عمدتا شامل ایلمنیت است و کانی های تیتانومگنتیت، روتیل و اسفن نیز به مقدار جزئی حضور دارند. بررسی میزان تمرکز کانی ایلمنیت در رسوبات رودخانه ای همچنین نشان می دهد که با افزایش فاصله از سنگ مادر، میزان تمرکز افزایش پیدا می کند و در پایین دست به حداکثر مقدار خود می رسد. شواهد زمین شناسی نشان می دهد که پلاسرهای تیتانیوم دار ناحیه دره جوگز بالا در اثر تخریب و هوازدگی سنگهای مادر گابرویی حاوی کانی های تیتانیوم دار، و تمرکز و نهشته شدن آنها در بستر رودخانه جوگز بالا تشکیل شده اند.
    کلیدواژگان: پلاسرهای تیتانیوم دار، ایلمنیت، دره جوگز بالا، فنوج
  • محمد معانی جو، معصومه وفایی زاد، فرهاد آلیانی صفحه 343
    کانسار سرب و نقره آهنگران در غرب ایران در استان همدان و در فاصله 25 کیلومتری جنوب شرقی شهر ملایر واقع شده است. سنگ میزبان کانسار آهنگران عمدتا سنگهای کربناتی کرتاسه زیرین است که به صورت دگرشیب بر روی سنگهای ژوراسیک قرار گرفته اند. کانه های اصلی شامل گالن، کالکوپیریت، پیریت، کانی های اکسیدآهن و پیروتیت و کانی های باطله شامل باریت، دولومیت، کلریت، کلسیت و کوارتز می شود. کانی سازی به صورت پرکننده فضای خالی، رگه ای، رگه چها ی، توده ای، پراکنده و جانشینی می باشد. دگرسانی شامل سیلیسی شدن، سریسیتی شدن و دولومیتی شدن است. بر اساس مطالعات سیالات درگیر بر روی کانی کوارتز و کلسیت، انواع سیالات درگیر اصلی عبارتند از: I: دو فازی مایع-گاز (L+V)،II: دو فازی گاز - مایع (V+L)، III: چهار فازی L+V+CO2 (L+V)،IV: دی اکسیدکربن CO2 (L+V) و V: سه فازی L+V+Sy. دمای همگن شدگی سیالات درگیر اولیه نشان می دهد که کانی سازی در محدوده دمای 130 تا 320 درجه سانتی گراد (میانگین C° 200) رخ داده است. در حالی که محدوده شوری آنها از 10 تا 15 درصد وزنی معادل نمک طعام است. نهایتا درجه حرارت و شوری سیالات درگیر کانسار آهنگران مشابه کانسارهای سرب و روی نوع ایرلندی است. مقادیر δ34S در پیریت و گالن به ترتیب در محدوده 5/25- تا 6/11 در هزار و 3/6- تا 5/8- در هزار و مقادیر δ34S باریت نیز در محدوده 26+ تا 2/27+ درهزار و مقادیر δ34SH2S سیال در حال تعادل با کانی های گالن در محدوده 9/2- تا 4/6- در هزار و پیریت 4/9 تا 9/27 در هزار می باشد. مقادیر δ34S باریت نزدیک مقادیر سولفات دریای کرتاسه است و سولفات آب دریا می تواند منشا باریت باشد. در حالی که مقادیر δ34SH2Sگالن در یک محدوده باریک قرار دارند که می تواند بیانگر آن باشد که منشا اصلی گوگرد احیای ترموشیمیایی سولفات است.
    کلیدواژگان: سرب و نقره، سیال درگیر، ایزوتوپ پایدار گوگرد، نوع ایرلندی، کانسار آهنگران، ملایر
  • غلامحسین شمعانیان، سیده فاطمه حسینی اشلقی صفحه 369
    زون ساختاری البرز در شمال ایران، میزبان تعداد مهمی از کانسارهای زغال سنگ است. معدن زغال سنگ قشلاق یکی از این کانسارهاست که در 35 کیلومتری آزادشهر قرار دارد. چینه های زغال دار در منطقه معدنی قشلاق در بخش میانی سازند شمشک تظاهر دارند که به طور عمده از شیل، سیلت سنگ و ماسه سنگ تشکیل شده است. زغال سنگهای قشلاق با مقادیر نسبتا کم گوگرد مشخص می شوند که نشان دهنده نهشت در محیطهای مردابی و دریاچه ای است. کوارتز، کائولینیت، مونتموریلونیت، آلبیت، مسکویت و ایلیت کانی های اصلی در این زغال سنگها هستند. پیریت به صورت بلورهای وجه دار تا بدون وجه و گاه تجمعات فرامبوییدی در زغال سنگ پراکنده است. تعیین میل ترکیبی عناصر به بخش آلی/ غیرآلی زغال سنگ با استفاده از ضریب همبستگی بین عناصر و خاکستر انجام شد. در کانی ها Si، Al، Ti، Fe، K، Na، Zn، Ga، Zr، Rb و Nb حضور دارند. Sr، Pb و Ni همراهی دوگانه ای با هر دو بخش دارند. غلظت اغلب عناصر جزئی در نمونه های زغال سنگ قشلاق در مقایسه با غلظتهای متداول جهانی بیشتر است که سرب و نیکل با بیشترین غنی شدگی مشخص می شوند.
    کلیدواژگان: زغال سنگ، کانی شناسی، ژئوشیمی، عناصر جزئی، البرز شرقی، قشلاق
  • علیرضا زراسوندی، بابک سامانی، هوشنگ پورکاسب، زهرا خورسندی، یعقوب جلیلی صفحه 385
    مناطق کانه دار خضرآباد و شهربابک به ترتیب واقع در استانهای یزد و کرمان، در کمربند آتشفشانی نفوذی ایران می باشند که دارای پتانسیل کانه زایی مس با عیار مطلوب هستند. توده های گرانیتوئیدی با نفوذ در واحدهای رسوبی کرتاسه و سکانس آتشفشانی رسوبی بعد از آن (ائوسن میوسن)، کانه زایی مس پورفیری و اسکارن سازی را در منطقه باعث شده اند. هدف از انجام این تحقیق بررسی نقش کنترل کننده های ساختاری به خصوص گسلهای امتدادلغز بزرگ و گسلهای ثانویه مرتبط با آنها در جای گیری کانسارهای مس پورفیری است. آنالیز Fry و Fractal به عنوان روش های مکمل جهت ایجاد این ارتباط در فهم چگونگی توزیع مکانی و ارزیابی ذخایر معدنی به کار رفته است. به طور کلی روند عمومی تجمع کانیایی در مناطق خضرآباد و شهربابک به صورت NW/SE، NE/SW می باشد و هم خوانی نسبتا خوبی را با روند شکستگی های غالب منطقه با ماهیت کششی نشان می دهد، نتایج آنالیز Fry و Fractal نشان دهنده همبستگی خوبی بین چگونگی توزیع مکانی اندیس های مس و روند عمومی شکستگی ها و گسلها می باشد. به طور کلی نتایج حاصله نشان می دهد که جای گیری این توده ها به همراه کانه زایی مس با زایش عمدتا پورفیری، در یک شکستگی و یا فضای کششی1 صورت گرفته که این زون های کششی مابین گسلهای راستالغز فرعی ناشی از یک مولفه دگرشکلی اصلی تشکیل شده است. لذا شناسایی این زون های کششی و توده های گرانیتوئیدی جای گیر شده در آنها می تواند به عنوان یک الگوی اکتشافی جهت کانسارسازی مس در مناطق خضرآباد و شهربابک مدنظر قرار گیرد.
    کلیدواژگان: کانه زایی مس، مس پورفیری، کنترل کننده های ساختاری، آنالیز Fry، Fractal
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  • Mohammad Ali Jazi, Mohammad Hassan Karimpour, Azadeh Malekzadeh Page 179
    Introduction
    The Baqoroq Cu-Zn-As deposit is located northeast of the town ofAnarak in Isfahan province, in theeast central areaof Iran. Copper mineralization occursin upper cretaceous carbonate rocks.Studyof thegeologyof the Nakhlak area, the location ofa carbonate-hosted base metaldeposit, indicatesthe importance of stratigraphic, lithological and structural controls in the placement of this ore deposit. (Jazi et al., 2015).Some of the most world’s most important epigenetic, stratabound and discordant copperdeposits are the carbonate hosted Tsumeb and Kipushi type deposits,located in Africa. The Baqoroq deposit is believed to be of this type.
    Materials And Methods
    In the current study, fifty rock samples were collected from old tunnels and surface mineralization. Twenty-two thin sections, ten polished sections and four thin-polished sections were prepared for microscopic study. Ten samples were selected for elemental analysis by ICP-OES (Inductively coupled plasma optical emission spectrometry) by the Zar Azma Company (Tehran) and AAS (Atomic absorption spectrometry) at the Ferdowsi University of Mashhad. Seven doubly polished sections of barite 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 Ferdowsi University of Mashhad. Sulfur isotopes of five barite samples were determined by the Iso-Analytical Ltd. Company of the UK. The isotopic ratios are presented in per mil (‰)notation relative to the Canyon Diablo Troilite.
    Results
    The upper Cretaceoushost rocks of the Baqoroq deposit include limestone, sandstone, and conglomerate units. Mineralization is controlled by two main factors: lithostratigraphy and structure. Epigenetic Cu-Zn mineralizationoccurs in ore zones as stratabound barite and barite-calcite veins and minor disseminated mineralization. Open space filling occurred as breccia matrix, crustification banding,andbotryoidaltexture. The host rock has undergone dolomitization alteration Hypogene minerals include chalcopyrite, pyrite, sphalerite, galena, enargite, barite, and calcite. Supergene minerals include malachite, azurite, covellite, chrysocolla, chalcocite, cerussite, smithsonite, native copper and iron oxide minerals. Sulfantimonides and sulfardenides are abundant in low- and moderate temperature stages of the deposit, while bismuth sulfides generally occur in higher temperature ores, according to Malakhov, 1968. Analysis of rich ore samples indicates copper is the most abundant heavy metal in the ore (average 20.28 wt%), followed by zinc (average ~ 1 wt%) and arsenic (average ~ 1 wt%), respectively. Thepresence of many trace elements in the ore, such as Sb, Pb, Ag and V, are very important. Element pairs such as Ag-Cu, Zn-Cd, Zn-Sb, Fe-V and Pb-Mo are correlated with each other. The Baqoroq ore minerals are rich in As, Sb and poor in Bi. Highamountsof antimony usually occur in a low temperature stage (Marshall and Joensuu, 1961). Malakhov (1968) suggested thata high Sb/Biratio in the ore indicates a low temperature of formation for the Baqoroq deposit. Sulfide mineralization fluids were found to have homogenization temperatures between 259 and 354°C and salinities between 8.37 and 13.18 wt% NaCl eq. Surface water apparently diluted theore-bearing fluids in the final stages and deposited sulfide-freecalcite veins at relatively low temperatures (78 to 112 °C) and low salinities (3.59 to 6.07 wt% NaCl eq.). The δ34S values of barite of the Baqoroq deposit range from +13.1 to +14.37‰from whichδ34S values of ore fluids were calculated to vary between -8.57‰ and -7.23‰. Sulfur within natural environments is derived ultimately from either igneous or seawater sources (Ohmoto and Rye, 1979). Barite δ34S values of Baqoroq deposit lie within the range of Cretaceous-age oceanic sulfate values. The reduction of sulfate to sulfide couldhave been caused either by bacterial sulfate reduction or by nonbacterial sulfate reduction through a reaction with organic materialin the sedimentary rocks (thermochemical sulfate reduction). However, the narrow range of δ34S and positive values indicates that they were not produced by bacterial sulfate reduction.Partial thermochemical reduction of sulfates has apparently produced light sulfurvalues (~ 21‰ lighter) and it has been effective inthe deposition of ore minerals. Organic matter occurs as graphite in the Baqoroq formation in proximity of Baqoroq deposit (Cherepovsky et al., 1982).
    Discussion
    Epigenetic, stratabound and discordant Cu-Zn-As mineralization in the Baqoroq deposit occurs as open space filling of upper Cretaceous rocks. Host rock is partially dolomitized by ascending warm, saline fluids. Seawater sulfates were the source of the sulfidesulfur and the sulfate in the barite. The reduced sulfur was generated by partial thermochemical reduction and it was effective inthe deposition ofthe ore minerals. Based onthe evidence of carbonate host rocks, the absence of igneous activity, the open space filling texture, mineralogy, dolomite alteration, ore geochemistry (As and Sb high content and absence of Bi), microthermometric data of ore bearing fluid and sulfur isotope values, the Baqoroq deposit is very similar to the carbonate hosted copper deposits in Africa and in particular the Tsumeb deposit in Namibia. The Baqoroqdepositmay have been produced bymetamorphicfluids during orogenyrelated to theclosureof the Neo-Tethys ocean.
    Keywords: Copper, Fluid inclusions, Sulfur isotopes Baqoroq, Anarak
  • Zahra Alaminia, Mohammad Hassan Karimpour, Seyed Massoud Homam Page 203
    Introduction
    Pyrite is the most abundant sulfide mineral in low sulfidation ore deposits. Experimental studies have shown that low-temperature (200°C) from hydrothermal or metamorphic fluids (Butler and Rickard, 2000). Framboidal pyrite mostly occurs in sedimentary environments, though it could also form during metamorphism and hydrothermal alteration (Scott et al., 2009). The pyrite formed tends to be enriched in various trace elements such as Au and As. For this study we have combined the geology, alteration, mineralization with recent studies of the description of the deposit from core logging and underground mapping and geochemistry in the CheshmehZard gold district and also investigated the compositional variation and textural differences between pyrite types. This study is based on the results of our alteration and mineralization mapping and detailed logging of 1937.8 m of drill core.
    Materials And Methods
    Geology, hydrothermal alteration and mineralization were examined in drill holes along several cross sections. Host-rock alteration minerals and veins were determined for 11 samples using standard X-ray diffraction (XRD) and X-ray fluorescence spectrometry (XRF) techniques. Polished sections were studied by reflected light microscopy and backscattered electron images (BSE). In this study, the trace-element composition of pyrite samples from the Au-III vein system was obtained using electron microprobe analyzer (EMPA) data. All analyseswere carried out at the department of Materials Engineering and Physics of the University of Salzburg in Austria. The EMPA measurements and BSE imaging were made using a JXA-8600 electron microprobe. Spot analyses of 30 pyrite grains from CheshmehZard are given in Table 1.
    Results
    The study area is located in the north of Khorasan Razavi Province 45 km to the south of Neyshabour. The area near CheshmehZard could become important as a site of economically significant gold mineralization. Six gold-bearing vein systems were recognized east of Arghash. The estimated resources are about 2 million metric tons of potential ore with an average of 1.9 g/t Au (Samadi, 2001;Ashrafpour et al., 2012). Multiple intrusive events are recognized in the region including Precambrian to post-Oligocene-Miocene igneous rocks (Alaminia et al., 2013a). This includes the Arghash diorite pluton, upper Cretaceous granitoids (minor diorite, mainly quartz monzodiorite and granodiorite), early Eocene granite and several lamprophyre and small intrusions of quartz monzodiorite porphyries. Volcanicsinclude andesite, dacite, pillow basalt and tuffs. Sedimentary rocks are conglomerate and minor limestone. Gold veins are hosted by intermediate to silicic volcanic rocks, tuffs, granite, granodiorite, and conglomerate. Veins consist of calcite and quartz. The main alteration zones mapped at the surface and underground are sericite-quartz-pyrite-calcite, withsilicified, propylitic, argillic, and carbonate zones. The mineralization associated with sericiticalteration and silicificationoccurs asveinlets and disseminated in the propylitic zone. Gangue minerals are quartz, chalcedony, calcite, adularia, illite, and kaolinite. Mineralization occurs as veinlets, breccia filling and disseminated. The veinlets are comprised of pyrite, arsenopyrite, minor chalcopyrite, sphalerite, galena, magnetite and hematite. Pyrite is the main sulfide mineral in the hypogene ore. Samples were collected with the objective of studying the pyrite in the Au (III) vein systems. All samples were therefore pyrite rich. The paragenesiswas determined to show four stages of mineralization based on the following microscopic observations: 1. an initial pyrite veinlet stage with associated quartz, chlorite, epidote. Pyrite is fine to medium grained, anhedral and gold-poor. 2. a second pyritic stage (polymetallic sulfide stage) contains pyrite, chalcopyrite, galena, sphalerite, quartz and chalcedony, minor adularia and arsenopyrite. 3. An As-bearing pyrite stage with sericite, chalcedony and quartz. The pyrite isframboidal.. 4. Finally, a carbonate-dominated stage. The pyrite is euhedral to anhedral and coarse grained. The Au concentration in Stages 2 and 3 pyrite is higher than that in Stage 4 pyrite.
    Conclusions
    The gangue mineral assemblages of carbonate, chlorite, quartz, and minor sericite and potassium feldspar in the ore-forming process of the CheshmehZard gold district suggest that the pH value of the hydrothermal fluids was near neutral to slightly acid (approximately 4.5 to 5.3 under 250 to 300 °C and 1 kbar conditions) and that gold would be transported mainly as Au(HS)2- (Stefansson and Seward, 2004). Three types of pyrite based on the chemical composition have been investigated: As- bearing pyrite, Ti-V - bearing pyrite and pure or barren pyrite. EMPA analyses of the pyrite in gold veins show maximum concentrations of As (3.62 wt.%), Ti (3.91 wt.%) and V (0.53 wt.%) respectively. The occurrence of the gold is usually associated with arsenian pyrite and Ti-V - bearing pyrite. Veinlets of the Py1 coexisting with arseno pyrite and gold Py2 implies the substitution of sulfur by arsenic. Gold precipitated under relatively reducing conditions in framboidal pyrite. Py3 formed prior to barren pyrite (IV).
    Keywords: Trace element, pyrite, CheshmehZard, gold district, NE Iran
  • Fereshteh Bayat, Ghodrat Torabi Page 225
    Introduction
    The occurrence of blueschist metamorphic facies is believed to mark the existence of former subduction zones. This facies is represented in the main constituents of subduction-accretion complexes, where it occurs in separate tectonic sheets, imbricated slices, lenses, or exotic blocks within a serpentinite mélange (Volkova et al., 2011). The evidence of the presence and maturity of Paleo- Tethys oceanic crust in the CEIM (define this) in Paleo-Tethys branches, subduction and collision has been studied by various authors (Bagheri, 2007; Zanchi et al., 2009; Bayat and Torabi, 2011; Torabi 2011). Late Paleozoic blueschists have recognized in the western part of the CEIM (e. g. Anarak, Chupanan and Turkmeni) in linear trends. Metamorphic rocks of the Turkmeni area (SE of Anarak) are composed of blueschist and meta-greywacke and are situated along the Turkmeni-Ordib fault associated with Paleozoic rock units and serpentinized peridotite bodies. Turkmeni blueschist and meta-greywackes have not been studied by previous workers. The Turkmeni blueschists consist of albite, winchite, actinolite and epidote. Granoblastic, nematoblastic and lepidoblastic are main textures in these rocks. Winchite is found in the matrix and around epidote grains. This sodic-calcic amphibole serves as an index mineral in blueschist facies. Actinolite and epidote formed during retrograde metamorphism of blueschists in the greenschist facies. The mineral assemblage of albite, epidote, chlorite and phengite ± garnet is present in meta-greywackes in the Turkmeni blueschists. Veins of garnet, muscovite, quartz and opaque minerals are extensive in these rocks. Epidote and chlorite formed in meta-greywackes by retrograde metamorphism in the greenschist facies. The aim of the present study is to determine the petrological and geochemical characteristics, P-T condition of blueschists and meta-greywackes, as well as the geotectonic setting of primary basaltic rocks of the Turkmeni blueschists.
    Material And Methods
    This study is based on field observations and petrographical and analytical studies. Satellite images and a geological map were prepared. About 20 thin sections were supplied for petrological studies. Mineral chemical analyses were carried out by a JEOL JXA-8800R electron probe micro-analyzer (EPMA) at the Cooperative Center of Kanazawa University, Japan. The analyses were performed under an accelerating voltage of 15 kV and a beam current of 15 nA with 3µm probe beam diameter. The Fe3+ contents of minerals were estimated by assuming ideal mineral stoichiometry. The representative mineral compositions are given in Tables 1-3. Major oxides, rare earth elements (REE) and trace elements of five blueschists samples were analyzed by the ICP-MS method (Kanpanzhouh Research Company, Tehran, Iran) of the SGS laboratory of Canada. Whole rock chemical data are presented in Table 4.
    Results And Discussion
    Petrographical and geochemical characteristics of Turkmeni blueschists reveal that they were derived from a similar mantle source and underwent analogous melt extraction and post magmatism occurrences. According to the trace and rare earth elements contents, the protolith of blueschists should be formed by crystallization of tholeiitic basalt and have sub-alkali basalt nature. Blueschists have LREE values more than HREE. High amounts and evident variations of LIL elements are obvious. Negative anomalies of HFSE such as Nb, Hf, Zr and Ti are evident in Turkmeni blueschist. REE trends of these rocks resemble as the back arc basin basalts. Based on the Nb/La ratio and REE contents, the original magma has been generated by low to medium degree of partial melting of a lithospheric mantle spinel lherzolite. Geochemical characteristics and normalized diagrams reveal that primary magma of protolith has been nature near to IAB and E-MORB. The related processes to subduction of Paleo-Tethys oceanic crust led to mantle enrichment and carbonate metasomatism. The Paleo-Tethys Ocean spreading in CEIM commenced in Late Ordovician and terminated in the Late Paleozoic-Triassic. Association of meta-greywackes with blueschist and LILE/HFSE contents shows that Paleo-Tethys oceanic crust subduction zone at Turkmeni region was been immature. Mineral chemistry and assemblages of the blueschists and meta-greywackes units reveal that they suffered different metamorphic evolution: (M1) greenschist metamorphism by existence of actinolite and albite in basaltic rocks, and then they passed a prograde metamorphism in the blueschist facies by existence of winchites (M2) which is followed by a retrograde metamorphism P-T condition in the greenschist facies (M3). Variscan tectono-metamorphism occurrence has been main metamorphic phase in Anarak region and it has led to metamorphism in blueschist facies of Turkmeni rocks. Acknowledgments: The authors wish to thank the University of Isfahan University for financial supports.
    Keywords: Blueschist, Turkmeni, Ordib fault, subduction, Paleo, Tethys, Central Iran
  • Ahmad Ahmadi Khalaji, Zahra Tahmasbi Page 243
    Introduction
    The area of this study is located near Hamadan within the Sanandaj - Sirjan tectonic zone. In the Hamadan area, consisting mainly of Mesozoic plutonic and metamorphic rocks, aplites and pegmatites locally contain garnets.(Baharifar et al., 2004, Amidi and Majidi, 1977; Torkian, 1995. Garnet-bearing schists and hornfelses in the area are products of regional metamorphism shown by slate and phyllite (Baharifar, 2004). In this investigation the distribution of elements in garnet in different rock type was studied to determine their mineral types and conditions of formation. Garnet samples from igneous and metamorphic rocks were analyzed by electron microprobe (EMPA), the results of which are presented in this article.
    Materials And Methods
    Thirty-five samples were selected for thin section preparation and twenty thin-polished sections were prepared for mineralogical and microprobe analysis. Thin sections of garnet-bearing igneous (pegmatite) and metamorphic rocks (schist and hornfels) were studied by polarizing microscope. Chemical analysis was performed on the garnets (38 points) using a Caimeca SX100 electron microprobe at an acceleration voltage of 15 kV and electric current of 15 nA in the Mineral Processing Research Center, Iran. Separation of iron (II) and Fe (III) was calculated by Droop’s method (1987) and the structural formulas of the garnets were calculated using 24 oxygens to determine the relative proportions of the end-members using the mineral spreadsheet software of Preston and Still (2001).
    Results
    Based on the analyses, almandine (Fe - Al garnet) and spessartine (Mn - Al garnet) are the principal types of the (Kamari) metamorphic and (Abaro) pegmatitic garnets, that belong to the well-known pyralspite garnet group. Chemical zoning patterns of the garnets in the metamorphic rocks (schists) differ from those in the igneous rocks (pegmatite), showing different compositions from core to rim. Petrographic evidence such as: co-existing tourmaline with pegmatite garnets and andalusite with schist garnets; zoning in garnets (oscillatory zoning of Al in pegmatite garnet, Mn increasing in the cores of schist garnet contrasted with Mn decreasing in the cores of pegmatite garnets; the decrease of Mg in the cores of pegmatite garnets, contrasted with the increase of this element in the cores of schist garnets; and the linear trends of Al and Ca in hornfels garnets) Pyrope garnet composition in schist indicates a closed system for garnet formation condition in schist and a magmatic source for pegmatites. The compositions of garnets from schists change from Alm0.63, Prp0.07, Sps0.24, Grs0.05 in the cores, to Alm0.71, Prp0.09, Sps0.13, Grs0.05 in the rims. Garnets from pegmatites show a change from Alm0.73, Prp0.015, Sps0.24, Grs0.07 in the cores, to Alm0.71, Prp0.011, Sps0.28, Grs0.00 in the rims. Garnets from hornfelses showed changes from Alm 0.79, Prp0.14, Sps 0.06, Grs0.07 in the cores to Alm 0.8, Prp0.13, Sps 0.05, Grs0.01 in the rims.
    Discussion
    The percent of almandine and spessartine in the garnets of the schists and pegmatites are higher than that of garnets in the hornfelses. Almandine and spessartine in the pegmatite garnets from core to rim show a completely reversed trend. In the schist garnets from core to rim, the almandine trend is decreasing outward– increasing inward, while the spessartine trend is increasing – decreasing. In the hornfels garnets no specific trend could be determined, there is no zoning. This difference in trend between pegmatite garnets from that in schist garnets and hornfels garnets shows differences in their origin. Texture homogenization, rich in potassium, metaluminous to peraluminous magma of Hamedan granitoid intrusion (Aliani et al., 2012), Peraluminous biotite in this intrusion and lack of garnet zoning show that garnet pegmatites have been formed directly from granitic melt crystallization.
    Keywords: Hamedan, metamorphic, garnet, zoning
  • Mohammad Ali Rajabzadeh, Fatemeh Al Saadi Page 259
    Introduction
    Worldwide, Ni-Cu and PGE magmatic sulfide deposits are confined to the lower parts of stratiform mafic and ultramafic complexes. However, ophiolite mafic and ultramafic complexes have been rarely explored for sulfide deposits despite the fact that they have been extensively explored and exploited for chromite. Sulfide saturation during magmatic evolution is necessary for sulfide mineralization, in which sulfide melts scavenge chalcophile metals from the parent magma and concentrate them in specific lithological zones. The lack of exploration for sulfides in this environment suggests that sulfide saturation is rarely attained in ophiolite-related magmas. Some ophiolites, however, contain sulfide deposits, such as at Acoje in Philippines, and Cliffs in Shetland, U.K. (Evans, 2000; Naldrett, 2004). The Faryab ophiolite complex in southern Kerman Province, the most important mining area for chromite deposits in Iran, is located in the southwest part of the Makran Zone. Evidence of sulfide mineralization has been reported there by some authors (e.g. Rajabzadeh and Moosavinasab, 2013). This paper discusses the genesis of sulfides in the Faryab ophiolite using mineral chemistry of the major mineral phases in different rocks of the ophiolite column in order to determine the possible lithological location of sulfide deposits.
    Materials And Methods
    Seventy three rock samples from cumulate units were collected from surficial occurrences and drill core. The samples were studied using conventional microscopic methods and the mineralogy confirmed by x-ray diffraction. Electron microprobe analysis was carried out on different mineral phases in order to determine the chemistry of the minerals used in the interpretation of magma evolution in the Faryab ophiolite. Lithologically, the Faryab ophiolite complex is divided into two major parts: the northern part includes magmatic rocks and the southern part is comprised of rocks residual after partial melting of the upper mantle. Sulfide mineralization in the complex is confined to cumulate rocks in northern part of ophiolite column. The mineralization is olivine-rich clinopyroxene and wehrlite. Petrographic investigation of sulfides in host ultramafics indicated two sulfide generations. In the first generation, primary magmatic sulfides occurred as interstitial disseminations, generally as anhedral grains. In the second generation, sulfides formed as veinlets along host rock fractures. The primary sulfides include pyrrhotite, pentlandite, and secondary digenite and pyrite. The primary sulfide content increases with increasing size and amount of clinopyroxene in host rocks. Associated chromian spinels in host ultramafics display disseminated and massive textures.
    Discussion
    Generally, mineralization in ophiolites is controlled by two major steps: a) partial melting of upper mantle rocks and b) crystal fractionation in a magma chamber (Rajabzadeh and Moosavinasab, 2013). The chemical compositions of the analyzed minerals were then used in estimating the conditions in these two steps. The composition of chromian spinel corresponds to chromite of boninitic melts formed in supra-subduction zone environments. Boninitic melts are produced at high degrees of partial melting of mantle peridotites in the presence of water (Edwards et al., 2002). Silicates of the host rocks are mainly clinopyroxene (diopside and augite) of the composition Wo47.50 En45.48 Fs3.4, olivine Fo92 and orthopyroxene (enstatite - bronzite) of En85 to En88. The main host ultramafic rocks of sulfides are wehrlite and clinopyroxenite, indicating that the sulfide saturation occurred during magmatic evolution of these rocks. This suggests that sulfide mineralization will occur in the northern part the ophiolite. The sulfide grains are anhedral, amoeboidal in shape, and appeared as disseminated interstitial phases, indicating that they were trapped as liquid phases during increase in sulfur fugacity and decrease in FeO content and temperature of crystallization of clinopyroxene-rich rocks (Talkington et al., 1984; Von Gruenewaldt et al., 1990). Nickel-rich pentlandite is the main sulfide in the Faryab complex. The composition of this is mineral is consistent with the crystallization in an equilibrium condition (Song et al., 2008). The sulfide may have been introduced from external sources during upward movement and emplacement of parent magma. Acknowledgments: The authors are grateful to the Research Council of Shiraz University for financially supporting this study.
    Keywords: sulfide, mineralization, ultramafic rock, ophiolite, Faryab
  • Alireza Zarasvandi, Fateme Asadi, Houshang Pourkaseb, Farhad Ahmadnejad, Hasan Zamanian Page 277
    Introduction
    A wide variety of world-class porphyry Cu deposits occur in the Urumieh-Dohktar magmatic arc (UDMA) of Iran.The arc is composed of calc-alkaline granitoid rocks, and the ore-hosting porphyry intrusions are dominantly granodiorite to quartz-monzonite (Zarasvandi et al., 2015). It is believed that faults played an important role in the emplacement of intrusions and subsequentporphyry-copper type mineralization (Shahabpour, 1999). Three main centers host the porphyry copper mineralization in the UDMA: (1) Ardestan-SarCheshmeh-Kharestan zone, (2) Saveh-Ardestan district; in the central parts of the UDMA, hosting the Dalli porphyry Cu-Au deposit, and (3) Takab-Mianeh-Qharahdagh-Sabalan zone. Mineralized porphyry coppersystems in the UDMA are restricted to Oligocene to Mioceneintrusions and show potassic, sericitic, argillic, propylitic and locally skarn alteration (Zarasvandi et al., 2005; Zarasvandi et al., 2015). In the Dalli porphyry deposit, four hydrothermal alteration zones, includingpotassic, sericitic, propylitic, and argillic types have been described in the two discrete mineralized areas, namely, northern and southern stocks. Hypogenemineralization includes chalcopyrite, pyrite, and magnetite, with minor occurrences of bornite.Supergene activity has produced gossan, oxidized minerals and enrichment zones. The supergene enrichment zone contains chalcocite and covellite with a 10-20 m thickness. Mineralization in the northern stock is mainly composed of pyrite and chalcopyrite. The aim of this study is the investigation and classification of hydrothermal veins and the constraining of physicochemical compositions of ore-forming fluids using systematic investigation of fluid inclusions.
    Materials And Methods
    Twenty samples were collected from drill holes. Thin and polished sections were prepared from hydrothermal veins of thepotassic, sericitic and propylitic alteration zones. Samples used for fluid inclusion measurements were collected from drill cores DH01, DH02, DH06, and DH07, and outcrop samples. Microthermometric data were obtained by freezing and heating of fluid inclusions on a Linkam THMSG600 mounted on an Olympus microscope at Lorestan University.
    Results
    1) Five main veintypes were identified, belonging to three stages of mineralization:type (I): barren quartz, type (II): quartz + pyrite + chalcopyrite ± bornite ± chalcocite ± covelite, type (III): quartz + magnetite ± chalcopyrite, type (IV): K-feldspar± quartz ± chalcopyrite, type (V): chlorite + biotite. 2) Seven groups of fluid inclusionswere observed: (IA) liquid-rich mono-phase, (IB) vapor-rich mono-phase, (IIA) liquid-rich two-phase (liquid + vapor), (IIB) vapor-rich two-phase (vapor + liquid), (IIIA) high salinity simple fluids (liquid + vapor + halite), (IIIB) high salinity opaque mineral-bearing fluids (liquid + vapor + halite + pyrite + chalcopyrite + hematite), (IIIAB) multi-phase fluids (liquid + vapor + halite + sylvite + hematite + magnetite + pyrite + chalcopyrite ± erythrosiderite) 3) Multiphase fluid inclusions with predominant homogenization temperatures 420 to 620˚C and predominant salinities 70 to 75 wt.%NaCl, are thought to be the early fluids involved in mineralization. 4) The coexistence of high saline liquid and vapor rich fluid inclusions (IIIAB, IIIB, IIIA and IIA types) resulted either from fluid entrapment during the boiling process or the co-presence of two immiscible fluids generated from the magma. 5) Dalliporphyry Cu-Au deposit was formed in a magmatic-meteoric system.
    Discussion
    Two conventional thermometric procedures, freezing and heating, were employed for the measurement of temperature of homogenization and approximate salinity. Freezing was conducted mainly for halite-under saturated inclusions (types IIA and IIB), to measure the initial melting temperature (Te) and the last melting point (Tmice), whereas heating was carried out on the halite-bearing inclusions (types IIIA, IIIB and IIIAB). Based on the microthermometric results, the Dalli fluid inclusions can be divided into two distinct groups: (1) medium-high temperature, hypersaline (Types IIIA, IIIB and IIIAB) and (2) low-medium temperature, low salinity group (Types IIA and IIB). Type IIB inclusions, which homogenize to the vapor phase and have a relatively low cooling rate, provide a fairly good estimate of entrapment pressure (Roedder and Bodnar, 1980). Based on the pressure estimated for the Dalli deposit, mineralization likely occurred at depth of 0.6-1.1 km. The calculated depth is coincident with the estimated mineralization depths of the porphyry deposits in the world (Pirajno, 2009). Fluid inclusions with a wide range of vapor and liquid ratios are abundant in all of the Dalli samples. This represents heterogeneous trapping of liquid and vapor. The coexistence of inclusions with different volumes of vapor contents, which homogenize either to liquid (Th(L-V)) or vapor (Th(V-L)), are interpreted as an evidence for the prevailing wide range of physico-chemical conditions during the cooling history of ore-forming fluid at the Dalliporphyry Cu-Au deposit. The boiling process is documented by the abundance of heterogeneously trapped fluid inclusions with extremely variable liquid to vapor ratios (Ahmad and Rose, 1980). Acknowledgements: We thank of ShahidChamran University of Ahvaz for their support and moreover, Lorestan University for microthermometric studies.
    Keywords: magmatic arc, Dalli, hydrothermal, alteration, porphyry Cu, Au, fluid inclusion
  • Arash Gorabjeiri Puor, Mohsen Mobasheri Page 307
    Introduction
    The Mahour exploration area is a polymetallic system containing copper, zinc and silver. The mineralization can be seen in two forms of veins and disseminations. This area is structurally within the Lut block, west of Deh-salm Village. Recent exploration work and studies carried out by geologists on this volcanic-plutonic area of Lut demonstate its importance indicating new reserves of copper, gold, and lead and zinc. Several articles have been published on the Mahour deposit in recent years, including work on fluid inclusions (Mirzaei et al., 2012a; Mirzaei et al., 2012b). The present report aims at completion of previous studies on Mahour. During the course of this research, the IP/RS geophysical methods were used to locate the extent and depth of sulfide veins in order to locate drill sites. The IP/RS method has been used extensively worldwide in locating sulfide mineralization at deposits such as Olympic Dam in Australia (Esdale et al., 1987), Hishikari epithermal gold deposit in Kagoshima, Japan (Okada, 1995) and Cadia-Ridgeway copper and gold deposit in New South Wales, Australia (Rutley et al., 2001).
    Materials And Methods
    1. Determination of mineralogy of ore and alteration by examination of 70 thin sections and 45 polished sections. 2. Compilation of geological and mineralization maps of the studied area at a scale of 1:1000. 3. Geological, alteration, mineralization and trace element geochemical studies of 6 drill holes. 4. IP/RS measurements for 2585 points on a rectangular grid with profile intervals of 50 meters and electrode intervals of 20 meters. 5. Interpretation of IP/RS results.
    Discussion
    The Mahour area is covered by a volcanic sequence of basalt, andesite, dacite, rhyolite and pyro-clastics. During the Late Eocene through Early Oligocene this volcanic complex was intruded by several diorite and quartz-diorite bodies, which were responsible for mineralization of the area. Mineralized veins hosted by dacite show NNE trends with 85 t0 90° dips, and which are accompanied by argillic, silicic, quartz-sericite-pyrite and propylitic alteration zones. The primary minerals include pyrite, chalcopyrite, sphalerite, galena, tetrahedrite, and quartz along with supergene minerals such as malachite, atacamite, azurite and goethite. High anomalies of copper (up to 103062 ppm), zinc (up to 213520 ppm) and silver (up to 1988 ppm) are present in the studied area. The IP/RS surveys were carried out on profiles perpendicular to the veins. The chargeability levels reached 40 msce, indicating the presence of sulfide minerals in the area. Two especially anomalous resistivity zones, high and low, were detected within the deposit. The high resistivity zone, up to 350 ohm.m, occurs along geophysical profiles in association with less-crushed zones, whereas the low anomaly zone is related to highly crushed zones. The geophysical anomalies agree with drilling results indicating zones of highest mineralization.
    Results
    Generally, the chargeability surveys have clearly revealed two anomalous zones: one in the northeast and the other in the southwest of the studied area. Six holes have been drilled through these anomalous zones and geochemical samples taken at intervals of 1 meter in each hole. Most of the anomalies are associated with quartz-sericite-pyrite, silicification and chloritic alteration as well as the intense distribution of secondary iron oxides. Geochemical results from the drill holes show the highest anomalies as follows: GBH-1, 78-92 m, 246-281 m GBH-3 20-40 m and 133-152 m GBH-7 20-32 m and 57-65m PB-1 85-94 m. and 133-140 m PD-1. 50-55 m, 298-301 m and 360-365 m PA-1 48-57 m, 152-161 m and 212-218 m
    Keywords: chargeability, especial resistivity, well logging, Mahour, Lut block
  • Seyed Javad Moghaddasi, Javad Yazdi Page 327
    Introduction
    The Fanuj titaniferous placer deposits are located 35 km northwest of the Fanuj, Sistan and Baluchestan province (1). The studied area comprises a (2) small part of the late Cretaceous Fanuj-Maskutan (Rameshk) ophiolite complex (Arshadi and Mahdavi, 1987). Reconnaissance and comprehensive exploration programs in the Fanuj district (East of the 1:100000 Fanuj quadrangle map,Yazdi, 2010) revealed that the Upper Jogaz Valley area has the highest concentration of titaniferous placer deposits. In this study, geology and formation of the titaniferous placer deposits in Upper Jogaz Valley area are discussed.
    Materials And Methods
    (3) Forty samples were collected from surface and drainage sediments to evaluate the potential for titaniferous placers. Mineralogical studies indicated the high Ti (ilmenite bearing) areas, which led to detailed exploration by 29 shallow drill holes and 9 trenches. A total of 61 sub-surface samples were collected for heavy mineral studies and ore grade determination. The exploration studies suggest that the the Upper Jogaz Valley area in the Fanuj district has a high potential for titaniferous placer deposits. Extensive exposures of black sands in the sreambeds of this area suggested detailed sampling, so that 12 holes were drilled (2-3 m depth)from which 26 samples were collected, and five trenches were excavated to 2-4 m depth (4). The distribution of drill holes and trenches were plotted with “Logplot” software for further interpretation. Twenty-two samples from these drill holes were analyzed for TiO2.
    Results
    The reconnaissance and comprehensive exploration in Fanuj district shows that the Upper Jogaz Valley area has the highest concentration of titaniferous placer deposits. The general geology of the region and petrology and mineralogy of collected samples suggest that the source rock of the Upper Jogaz Valley titaniferous placers is the hornblende- and olivine-gabbro unit of the Fanuj-Ramesh ophiolites. The Ti-rich sediment distribution in drill holes and trenches indicates that the titaniferous placers are distributed in an area of about 0.8 km2 and follow the Upper Jogaz river system. The titaniferous placers are concentrated mainly in three beds with thicknesses of 30 to 100 cm. The study of heavy minerals shows that ilmenite is the main ore mineral and titanomagnetite, rutile and sphene are present as trace minerals. The ilmenite concentration varies in the Upper Jogaz Valley fluvial sediments, in which the concentration of ilmenite generally increases away from source rock to reach a maximum concentration downstream. The geological evidence indicates that the titaniferous placers were deposited as a fluvial placer and originated from weathering and erosion of ilmenite-rich gabbros. The presence of low-grade deposits and sparse heavy minerals in the Upper Jogaz river coarse sediments is probably related to hydraulic equilibrium (Robb, 2005). Entrainment sorting created thin layers of heavy minerals (i.e., ilmenite) on the Upper Jogaz streambed. The occurrence of Ti-rich layers in fine sand and silt beds is probably due to shear sorting. (5)The ophiolite sequence is well exposed in the study area. This sequence is composed of cumulative peridotites, layered and massive gabbros, diabasic sheeted dikes, basaltic pillow lavas and pelagic sediments. The layered gabbros were the main source of the ilmenite Ti mineralization. The highest concentration of Ti was observed in the eastern and northern parts of Upper Jogaz Valley area, which are mainly covered by olivine- and hornblende-gabbros (6). The western part of the area is covered by an unaltered diabase unit. The study of several polished sections from the Upper Jogaz Valley gabbros shows ilmenite as the main Ti-bearing mineral with anhedral to subhedral crystals 5 to 400 microns in size. The drill hole and trench data suggest that the deposits follow the morphology of the present-day Upper Jogaz river. The Ti placer beds accumulated over an area of 0.8 km2 with 2.3 % and 5.06% ilmenite in Upper Jogaz Valley upstream and downstream consequently. The study of heavy minerals shows that ilmenite is the main heavy mineral in the Upper Jogaz Valley sediments with 120µ to 3 mm, semi-angular to rounded grains with weak sorting. Titanomagnetite, rutile and sphene are present as accessory minerals. Pentlandite, magnetite, chalchopyrite and millerite are also observed as intergrowths or inclusions in ilmenite.
    Conclusions
    The investigation of ilmenite concentration in fluvial sediments of the Upper Jogaz deposit represents a gradual increase of ilmenite concentration away from the source rock. Titanomagnetite, sphene and rutile have similar enrichment patterns to ilmenite. This suggests that all Ti-bearing minerals had a similar behavior in the Upper Jogaz Valley fluvial system. The geological and petrographic evidence suggests that the origin of the Upper Jogaz Valley placer is the weatherlng of the Ti-rich gabbros. The higher concentration of ilmenite in the lower part of the valley is probably caused by the lower water energy and flow downstream. The mechanisms of hydraulic sorting (Slingerland and Smith, 1986), such as free settling of grains, entrainment of grains from a granular bed load by flowing water and shear sorting of grains in a moving fluidized bed were important in the enrichment of titaniferous placers in the downstream sediments.
    Keywords: Titaniferous placer, ilmenite, Upper Jogaz Valley, Fanuj
  • Mohammad Maanijou, Masoumeh Vafaei Zad, Farhad Aliani Page 343
    Introduction
    The Ahangaran Pb-Ag deposit is located in the Hamedan province, west Iran, 25 km southeast of the city of Malayer. . The deposit lies in the strongly folded Sanandaj-Sirjan tectonic zone, in which the ore bodies occur as thin lenses and layers. The host rocks of the deposit are Early Cretaceous carbonates and sandstones that are unconformably underlain by Jurassic rocks. Ore minerals include galena, pyrite, chalcopyrite, pyrrhotite and supergene iron oxide minerals. Gangue minerals consist of barite, dolomite, chlorite, calcite and quartz. The mineralization occurs as open-space fillings, veins, veinlets, disseminations, and massive replacements. Alteration consists of silicification, sericitization, and dolomitization. In this study, we carried out studies of mineralogy, microthermometry of fluid inclusions and sulfur isotopes to determine the source of sulfur and the physico-chemical conditions of formation.
    Materials And Methods
    Seventy samples of different host rocks, alteration, and mineralization were collected from surface outcrops and different tunnels. Twenty of the samples were prepared for mineralogical studies at Tarbiat Modarres University in Tehran and 25 for petrological studies at the University of Bu-Ali Sina. Fluid-inclusion studies were done on 5 samples of quartz and calcite at Pouya Zamin Azin Company in Tehran using a Linkam THM 600 model heating-freezing stage (with a range of -196 to 480ºC). The accuracy and precision of the homogenization measurements are about ±1°C. Salinity estimates were determined from the last melting temperatures of ice, utilizing the equations by Bodnar and Vityk (1994) and for CO2 fluids using equations by Chen (1972). Nine samples of sulfides and barite were crushed and separated by handpicking under binocular microscope and powdered with agate mortar and pestle. About one gram of each sample was sent to the Stable Isotope and ICP/MS Laboratory of Queen’s University, Canada for sulfur isotope analysis. The sulfur isotopes in sulfides and sulfates were run on a Thermo Finnigan Delta Plus XP IRMS mass spectrometer. The analytical uncertainty for δ34S is ±0.2‰.
    Results And Discussion
    The main types of fluid inclusions in quartz and calcite are as follows: I: dominant liquid + less vapor (L+V); II: dominant vapor + less liquid (V + L); III: liquid + vapor+ CO2 (L+V+CO2)(L+V)); IV: CO2 (L+V); V: liquid + vapor + sylvite (L+V+Sy). Homogenization temperatures of primary fluid inclusions indicate that mineralization occurred at temperatures ranging from 130 to 320 °C (ave., 200°C) and their salinites range from 10 to 15 wt % NaCl equiv. The temperatures and salinities of the mineralizing fluids of the Ahangaran deposit are similar to the Irish type Zn-Pb deposits, and suggest a similar origin. The δ34S values of pyrite and galena are within the range of -25.5 to +11.6 ‰ and -6.3 to -8.5 ‰, respectively and for barite are in the range of 26 to 27.2 ‰. These values indicate that the δ34SH2S values of fluids in that deposited the pyrite and galena are within the range of -6.4 to-2.9 ‰ and 9.4 to 27.9 ‰, respectively. The δ34S values of marine sulfate were 13 to 20 ‰ during the Cretaceous (Hoefs, 2009). The δ34S values of barite are near to that of marine sulfate in the Cretaceous which indicate that the sulfate of the barite may have a marine origin. On the other hand, the δ34SH2S values of galena lie within a narrow range, suggesting that the main source of sulfur may be from thermochemical sulfate reduction (TSR). Acknowledgments: In this research, we thank Sormak Mines Company for its support during field work. We also thank Sormak Mines Managers, especially Mr. Khakbaz for his cooperation and support of this research. Parts of this research were supported by the research department of Bu-Ali Sina University. We also wish to express our appreciation of the isotopic analyses by Queen's University, Canada.
    Keywords: Pb, Ag, Fluid inclusion, Sulfur stable isotopes, Irish type
  • Gholam Hossein Shamanian, Fatemeh Hosseini Ashlaghi Page 369
    Introduction
    The Alborz structural zone in northern Iran is the host of a number of important coal deposits. The Gheshlagh coal mine is one of them, which is located 35 km southeast of Azadshahr. Coal bearing strata in the Gheshlagh mining district occur in the middle part of the Lower Jurassic Shemshak Formation which consists mainly of shales, siltstones and sandstones. The Geshlagh coals have a low sulfur content and a low ash yield. The ash content of coal and its geochemical character depends on the environment of deposition and subsequent geological history (Yazdi and Esmaeilnia, 2004). The purpose of this study was to investigate the texural and mineralogical characteristcs of the Ghashlagh coals and to identify the geochemistry of the major and trace elements and their relationship to specific mineralogical components. These results are necessary to improve the understanding of coal characterization and to relate the mineralogy of different materials to their potential for producing acidic or alkaline mine waters associated with mining and preparation processes.
    Materials And Methods
    About 20 samples were collected from the main coal seams. These samples were taken from fresh faces of the mine to avoid weathered surfaces and get fresh samples. The petrography of the samples was carried out by the conventional microscopic methods at the Golestan University. Mineralogical analyses were done by a X-ray diffractometer equipped with a CuKα tube and monochrometer (XRD Philips PW 1800) at the Kansaran Binaloud Company. The coal samples were initially crushed to less than 200 µm and homogenized. Then, 50 g from each sample was heated to 525 oC according to the United States Geological Survey procedure (Bullock et al., 2002). The concentration of the major and trace elements in the resulting ash samples was determined using a wavelength X-ray fluorescence spectrometer (XRF Philips PW 1480) at the Kansaran Binaloud Company.
    Results
    The Coal-bearing formation in the Ghashlagh mine belongs to the clastic unit of the Shemshak Formation, consisting mainly of about 2400 m sandstone, siltstone, shale. The middle part of this formation includes the economic coal beds. Petrographic and mineralogical investigations indicate that the dominant mineral phases of the Gheshlagh coals are quartz, kaolinite, montmorillonite, albite, muscovite, illite and pyrite. Pyrite occurs as euhedral to anhedral crystals and locally as framboids which are disseminated in the coal. Oxidation products consist mainly of iron hydrosulfate resulting from the oxidation of pyrite. The organic/inorganic affinity of elements in coal was determined using the correlation coefficient between the elements and ash yeild. Si, Al, Ti, Fe, K, Na, Ga, Zr, Rb and Nb are mainly associated with minerals. Sr, Pb and Ni have a dual association. The concentrations of most trace elements in the Gheshlagh coal samples are high when compared with the usual reported range in the world. The contents of Pb and Ni show the highest concentrations.
    Discussion
    The Gheshlagh coals are characterized by relatively low amount of sulfur indicating deposition in lacustrine and swamp environments (Goodarzi et al., 2006). The concentration of Ni, V, Sr, Ba and Ce in the Gheshlagh coals are relatively higher than the Shahroud and Lushan coals (Yazdi and Esmaeilnia, 2004). The comparison of the concentration of trace elements in the Gheshlagh coals and worldwide concentrations (Swaine, 1990) indicates the enrichment of Ni and Pb in the Gheshlagh coals. Gluskoter et al. (1977) used a value of six times the Clarke value to determine if an element is enriched in the whole coal. By these criteria, the concentration of Ni and Pb are enriched in the Gheshlagh coals when compared with the Clarke values. Generally, the distribution and abundance of reacting mineral species in the coal mines can be used to predict the extent of acidification and neutralization in particular area. In the Gheshlagh coal mine, the frequency of pyrite is moderately low. In addition, the availability of carbonates in the host rocks provides buffering capacity for acid produced by oxidation in this area. This investigation has led to a better understanding of coals and their roof and floor lithologies in the Gheshlagh coal mine. Acknowledgment: The authors wish to thank the Iran Minerals Production and Supply Company (Project No. 30716) and the Department of Geology, Faculty of Sciences at the Golestan University for financial assistance and all necessary resources needed to carry out this research.
    Keywords: Coal, Mineralogy, Geochemistry, Trace elements, Eastern Alborz, Gheshlagh
  • Alireza Zarasvandi, Babak Samani, Houshang Pourkaseb, Zahra Khorsandi, Yaghoub Jalili Page 385
    Introduction
    Two main principal aspects for the genesis of porphyry copper deposits have been determined. The first genetic model concerns the petrologic and geochemical processes and the other relates the genesis to crustal deformation and geodynamic conditions (Kesler, 1997). Recent studies (e.g., Padilla Garza et al., 2001) show that the generation and emplacement of porphyry copper deposits may not only be dependent on magmatic and hydrothermal processes, but also that the regional and local tectonic setting plays an important role. Therefore in determining the suitable setting for emplacement of copper and other porphyry intrusions, determination of location of partial melting of the lower crust, generation of batholiths, and their volatile-rich derivative intrusions in the crust seems to be necessary (Carranza and Hale, 2002). Almost all porphyry copper deposits in Iran are located in the Urumieh-Dokhtar magmatic belt. These deposits show distinct spatial and temporal relationship with Miocene granodiorite plutonic rocks emplaced along strike slip faults (Mehrabi et al., 2005). Accordingly, the tectonic setting of ore deposits seem to be the most important factor for regional exploration of porphyry copper systems (Vearncombe and Vearncombe, 1999). There are several methods for analysis of distribution of ore deposits. In this research the role of structural control in the spatial distribution of porphyry deposits has been studied using Fry and Fractal methods. Here, the Fry method is used as a complementary method for Fractal analysis.
    Materials And Methods
    Fry analysis is a self-adaptive method that is used for point objects. Fry analysis offers a visual approach to quantify the spatial trends in groups of point objects. Fry analysis can also be used to search for anisotropies in the distribution of point objects. More specifically it can be used to investigate whether a distribution of point objects occurs along linear trends, and whether such linear trends occur at a characteristic spacing. There is 37 and 42 copper point's index in the Khezr-Abad and Shar-B-Babak areas. The Fry patterns of copper index for two areas were determined with application of Dot Proc software. Fractal analysis is another technique for determination of regional distribution of faults. In this research the fractal dimension of joints and faults was determined in different locations using box-counting fractal method and drawing the logarithmic graphs.
    Results
    - The major faults show NW/SE trends in the Khezr-Abad area. They have a similar trend with Dehshir-Baft fault. Other sets of faults show NE/SW trend. These faults are younger than the Dehshir-Baft and release sinistral sense of shear. - Intrusion of two intrusive bodies leads to the accumulation of strike-slip faults in the vicinity of intrusive rocks. In this region faults and joints mainly show NW/SE and NE/SW trends. - The results of Fry analysis show that the mineralization in the Khezr-Abad occurred in the Cretaceous (and younger) rocks with NE/SW and NW/SE orientations. In the other words, these areas of mineralization are mainly related to the secondary faults or (P faults) in the pull basins and cross cutting points of these faults which have similar strike with the Dehshir-Baft fault. NE/SW mineralization is probably related to the tensional stress direction or faults having the general trends of central Iran structures. - The calculations of fractal dimension show that the southeastern parts of the Khezr Abad have higher amounts of fractal dimension (Db= 1.7002). Also there is a relatively higher copper index in this part, indicating a logical relation between fault structures and mineralization. -The generated maps indicate that the mineralization in the Shahr-e-Babak area occurred at the intersection of faults and volcanic system and the Fry analysis shows a NE/SW and NW/SE trend of ore concentration. - Northwestern parts of the Share-e-Babak show higher fractal dimension (Db= 1.748) that occurs in the areas with more volcanic rocks and copper indexes. - Results show that the porphyry copper mineralization mainly occurs near the great faults and related to the fault structures and shear zones in the Urumieh-Dokhtar structural zone. In the other word fault lineaments are the main factors in the local concentration of the ore deposits.
    Discussion
    The Study of geometry and mechanism of faults related to porphyry copper deposits is very important for determining the suitable location of ore concentration (Zarasvandi, 2004). For example, shear zones, pull apart basins, and step over along the strike slip faults are proper locations for concentration of porphyry ore deposits (Carranza and Hale, 2002). In this research the Khezr-Abad and Shahr-e-Babak areas have been studied. Plotted rose diagrams show the main role of the Dehshir-Baft shear zone for generating the joints and faults in the KhezrAbad area. In this area faults with NNW/SSE and NW/SE trends are the main direction of ore concentration. They are mainly related to the Dehshir-Baft fault. NE/SW faults show sinistral sense of shear and generally are younger than before mentioned sets. Finally the latest fault sets show N/S trend. The Shahre-e-Babak area is mainly dominated with Eocene igneous rocks. Volumetrically, andesite units are more abundant. Rose diagrams represent the existence of two main conjugate fault sets with NW/SE and NE/SW trends. The main copper indexes are located in the intersection of volcanic rocks with these two fault sets. Also the results of Fractal analyses reveal the higher Fractal dimension in the Northwestern part of the Shahr-e-Babak area. In the other words the most density of joint and faults occurred in this region.
    Keywords: Copper Mineralization, Copper Porphyry, Structural controls, Fry, Fractal