وارون‌‌سازی داده‎های مغناطیسی و IP/Res برای بررسی ارتباط فضایی بین مدل‎های ژئوفیزیکی و کانی‎سازی در کانسار مس-طلا پورفیری دالی جنوبی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی کارشناسی ارشد، دانشکده مهندسی معدن، دانشگاه صنعتی اصفهان، اصفهان، ایران

2 استادیار، دانشکده مهندسی معدن، دانشگاه صنعتی اصفهان، اصفهان، ایران

چکیده

با توجه به نیاز اکتشاف منابع کم‌عیار نظیر پورفیری‎ها به‌دلیل کاهش ذخایر کانه‎های معدنی پرعیار سطحی، امروزه پی‎جویی‎های ژئوفیزیکی مورد توجه بیشتری قرار گرفته‎اند. وجودکانی‎هایی با خودپذیری مغناطیسی و رسانایی الکتریکی بالا در محدوده زون پتاسیک کانسارهای مزبور، استفاده از روش‎های مغناطیس‌سنجی، مقاومت‌ویژه و پلاریزاسیون القایی را به‌منظور تخمین عمق و شکل کانسارهای مزبور امکان‌‌پذیر می‎سازد. در تحقیق حاضر داده‎های یادشده در محدوده کانسار پورفیری مس و طلای دالی جنوبی مورد مطالعه مجدد قرار گرفته‎اند تا با انجام پردازش‎ها و مدل‎سازی‎های جدید، نتایج مطالعات قبلی را بهبود بخشیده و ارتباط کانی‎زایی با مدل‎های ژئوفیزیکی جدید مشخص شود. در این بررسی برای اولین‌بار با انجام مدل­سازی وارون سه‌‌بعدی داده­های پردازش‎شده مغناطیس­سنجی در این منطقه و تحلیل خطای آن، مقاطعی از خودپذیری مغناطیسی در جهت آزیموت گمانه­های موجود در منطقه به‌همراه نتایج عیار طلا و مس به‌دست‌‌آمده از آنالیز ژئوشیمیایی گمانه‎ها ارائه شد. همچنین نتایج مدل­سازی وارون دو‌‌بعدی داده­های مقاومت‌ویژه و پلاریزاسیون القایی در راستای سه پروفیل با خطای مناسب نیز ضمن سازگاری با نتایج مطالعات قبلی، با خودپذیری مغناطیسی تخمین‌زده‌شده در راستای یک پروفیل IP/Res مقایسه شد. مقایسه مقاطع و صحت‌‌سنجی آنها با عیار مس و طلای موجود در طول گمانه­ها نشان می‎دهد که مناطق مشکوک به کانی­سازی، در ارتباط با خودپذیری مغناطیسی و شارژ‌‌پذیری بالا و مقاومت‌ویژه کم بوده و با توجه به مدل­مغناطیسی، حداکثر کانی­سازی در حاشیه توده با خودپذیری مغناطیسی بالا مشاهده می­شوند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Magnetic and IP/Res data inversion for investigation of the spatial relation between the geophysical models and mineralization in the southern Dalli Cu-Au porphyry deposit

نویسندگان [English]

  • Mohammad Hajheidari 1
  • Sayyed Mohammad Abtahi Forooshani 2
  • Hooshang Asadi Haroni 2
  • Keytash Moshtaghian 1
  • Ghazal Janghorban 1
1 M.Sc. Student, Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran
2 Assistant Professor, Department of Mining Engineering, Isfahan University of Technology, Isfahan, Iran
چکیده [English]

Because of declining high-grade ore deposits and increasing demands for metal resources, exploration of low-grade metal deposits, such as porphyries, have become feasible. Besides, humankind has spent most of the shallow metal ore deposits, and new prospecting projects focus on deeper deposits. Therefore, geophysical methods have gained more attention due to their ability to determine buried ore bodies' physical properties. Hence, most countries, including Iran, make significant investments in the geophysical exploration of deep porphyry deposits. According to widely accepted Lowell and Guilbert's model for porphyry copper deposits, the ore-bearing zones mainly concentrate at the edge of the potassic alteration zone. Pyrite, a highly conductive and chargeable metallic mineral, is a significant attribute in the potassic alteration. The model also states that the high susceptible magnetite-bearing rocks mainly occur at the bottom of the pyrite shell and the ore body. Due to the occurrence and presence of susceptible and conductive metallic minerals such as magnetite and pyrite in the potassic zone near to the ore body in the copper and gold porphyry deposits, the use of magnetometry, resistivity, and inducing polarization methods give reliable information about the location, depth, and shape of the deposits. For instance, in this research, we focus on the magnetic and IP/Res data in the southern Dalli porphyry deposit, with promising Cu-Au indices, which is located at Euromieh-Dokhtar ore-bearing zone Markazi Province. First, we applied standard processing techniques to remove the aliasing and regional effect in the magnetic data. Then, using the analytic signal technique, we showed the concentration of the magnetic sources over the study area. We also applied the power spectrum and Euler deconvolution techniques to the magnetic data and estimated the magnetic sources' depths. The estimated depth from the power spectrum is between the estimated depth from Euler deconvolution for possible sources with step and pillar shapes. Next, we used the average estimated depth from each of the depth estimation techniques in a three-dimensional magnetic data inversion as the depth of the sources in depth weighting. Also, we studied the inversion results via combining the cross-section of the magnetic susceptibility model along the boreholes and the lithology and geochemical information from core samples analysis. The results indicate that the higher grades for gold and copper occur at the edge of the magnetic sources and possible magnetite mineralization zones. The inversion results using the depth weighting with the depth extracted from the power spectrum show the best correlation and spatial relation with the geochemical data. Besides the magnetic data inversion, applying Oldenburg and Li algorithms for two-dimensional inverse modeling, we extracted the underground bodies' resistivity and chargeability model along with a IP/Res profile in the study area. The resulting chargeability models show a significant relationship with the presence of gold and copper mineralization. We also compared the resulting two-dimensional resistivity and changeability models with their corresponding magnetic susceptibility at the cross-sections along with the IP/Res. The comparison shows that the possible mineralization zones coincide with larger magnetic susceptibility values, high chargeability and low resistivity. The results show good accordance with Lowell and Guilbert's model. Also, highly susceptible rock in the shallower depth indicates that the erosion process has destroyed most possible orebody.

کلیدواژه‌ها [English]

  • Magnetic susceptibility
  • Resistivity
  • Chargeability
  • Inverse modeling
  • Porphyry copper deposits
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