@article { author = {Hossein Morshedy, Amin and Mojtahedzadeh, Seyed Hossein and Kouhsari, Amir Hossein}, title = {Geometrical modeling of fluid inclusion to predict the microthermometric properties: a case study at the Mehdiabad Pb-Zn deposit}, journal = {Journal of Economic Geology}, volume = {11}, number = {1}, pages = {147-167}, year = {2019}, publisher = {Ferdowsi University of Mashhad}, issn = {2008-7306}, eissn = {2423-5865}, doi = {10.22067/econg.v11i1.66558}, abstract = {Introduction Fluid inclusions are small, usually microscopic, volumes of pore fluid, which are crystallographically trapped in rocks during diagenesis or fracture healing processes. Nowadays, various techniques are used for resource exploration. Application of a fluid inclusion is one of these methods that has been developed for mineral, geothermal, and petroleum reservoir exploration. The study of fluid inclusions represents our most reliable source of information on the temperature, pressure, and fluid composition data of the ore fluid, and it is one of the most important tools for research into the economic geology and genesis of ore deposits (Moon, 1991). To achieve these goals, transparent and polished slabs of rock material are prepared and optically studied with a petrographic microscope. Samples are viewed under transmitted plane-polarized white light as well as under reflected ultraviolet or blue-violet illumination. During the fluid inclusion petrography, the volume fractions of phases are routinely estimated at room temperature to deduce whether assemblages of cogenetic inclusions were originally trapped from a one-phase or a multi-phase pore fluid. In the present research study, the microthermometric properties of the fluid inclusion data through pressure, temperature, and salinity diagrams were computed by geometrical modeling of fluid inclusion (Bakker and Larryn, 2006). The proposed method provides a quick and low cost technique to preliminarily investigate the microthermometric parameters of the fluid inclusion. To evaluate the proposed geometrical model, the Mehdiabad Pb-Zn deposit is selected as the case study. The Mehdiabad Pb-Zn deposit is located at the Yazd-Anarak metallogenic belt, 110 km southeast of Yazd, in the Central Iran structural zone. The host rocks of the deposit consist of lower Cretaceous silty limestone and dolomite. The main occurrences are the Calamine mine (CM), the Black-Hill ore (BHO), the East Ridge (ER) and the Central Valley Orebody (CVOB). The ore body consists of a primary sulfide ore and a supergene non-sulfide ore, the latter one having been mined at CM (Ghasemi, 2007; Rajabi et al., 2012).   Materials and methods The shape and geometry of fluid inclusion are one of the most important parameters, which were applied to estimate 3D degree of filling and find the useful information about temperature, pressure, salinity and depth of trapping without using time-consuming and costly heating-cooling operation. Inclusions in normal thick-sections are rotated stepwise and their projected areas and area-fractions are plotted against rotation angle. The outputs are systematically related to inclusion orientation, inclusion shape, and filling degree. The dependency on orientation is minimized when area fractions are measured at the position where the inclusions project their largest total areas. The shape factor is employed to present a new objective classification of inclusion projections, based on the extracted parameters from digital image processing (Bakker and Larryn, 2006). In this research, Mehdiabad Pb-Zn deposit has been chosen to evaluate the proposed method. Based on the fluid inclusion petrography, four fluid inclusion types are observed: 1) L+V; 2) L+L; 3) L; and 4) V; L+V phase is the most popular. After preparing 2D image of sections, 2D and 3D degree of fills were calculated by measuring the areas of total, bubble, and spot of fluid inclusion and computing the third dimension (Z) of fluid inclusion. Four geometrical models of volume fractions are defined, including cylinder, tetragonal prism, truncated cone, hexagon, and ellipsoid (Bakker and Larryn, 2006; Hossein Morshedy et al., 2008). In this case study, 3D proper models of the fluid inclusions are selected, depending on its geometry (hexagonal or ellipsoid). Then 2D degrees of filling (area fraction) is converted to 3D degrees of filling (volume fraction). The geometrical modeling results are well matched with computational outputs.   Results and discussion In this research, the ratios of area to volume fractions in geometrical and computational modelling were calculated 0.75 and 0.77, respectively. In the Mehdiabad Pb-Zn deposit, the main geometrical shapes of fluid inclusions were followed up the hexagonal prism with hexagonal pyramids and ellipsoid models. 3D geometrical modeling of fluid inclusion showed vapor fraction, 25% and density, 0.7 g/cm3, which the microthermometric and other parameters were obtained homogenization temperature nearly 100-200 °C (average of 150 °C), pressure between 400-500 ATM, formation temperature about 250-350 °C, salinity within a range of 10 to 15 wt.% NaCl equiv. and depth of mineralization 150-200 m. This finally achieved results have a high similarity with the typical carbonate-hosted Pb-Zn deposit.   References Bakker, R.J. and Larryn, W.D., 2006. Estimation of volume fractions of liquid and vapor phases in fluid inclusions, and definition of inclusion shapes. American Mineralogist, 91(1): 635–657. Ghasemi, M., 2007. Genesis of Mehdiabad Pb–Zn deposit and comparing with other Pb–Zn deposits. M.Sc. Thesis, Research Institute for Earth Science, Geological Survey of Iran, Tehran, Iran, 238 pp. (in Persian with English abstract) Hossein Morshedy, A., Mojtahedzadeh, H. and Kohsary, A.H., 2008. Measuring microthermic parameters of fluid inclusion with studying their geometries and models, case study: Mehdiabad Pb–Zn deposit. 15th Symposium of Crystallography and Mineralogy of Iran, Ferdowsi University of Mashhad, Mashhad, Iran. (in Persian with English abstract) Moon, K.J., 1991. Application of fluid inclusions in mineral exploration. Journal of Geochemical Exploration, 42(1): 205–221. Rajabi, A., Rastad, E. and Canet, C., 2012. Metallogeny of Cretaceous carbonate-hosted Zn–Pb deposits of Iran: geotectonic setting and data integration for future mineral exploration. International Geology Review, 54(14): 1649–1672.}, keywords = {fluid inclusion,3D geometrical modeling,Degree of fill,Microthermometric parameters,Mehdiabad Zn-Pb deposit}, title_fa = {مدل سازی هندسی میان بار‌های سیال به منظور پیش بینی ویژگی‌های ریزدماسنجی (مطالعه موردی: کانسار سرب و روی مهدی آباد)}, abstract_fa = {امروزه، روش‌های گوناگونی برای اکتشاف کانسار‌ها و نهشته‌های معدنی مورد استفاده قرار می‌گیرد. یکی از روش‌های در حال گسترش برای اکتشاف کانسار‌ها، منابع زمین­‌گرمایی و مخازن نفت و گاز، استفاده از میان­‌بار­های سیال است. بررسی‌های مختلفی از قبیل سنجش دما، فشار، شوری و ویژگی و فازهای سیال‌­های مختلف در زمینه میان­‌بار‌های سیال قابل انجام است. در این پژوهش، با استفاده از مدل­‌سازی هندسی میان­‌بار‌های سیال، ویژگی‌های ریزدماسنجی آنها بررسی‌شده و اطلاعات مربوط به‌ میان­‌بار‌ سیال از طریق نمودار‌های فشار، دما و شوری استخراج‌شده است. یکی از مؤلفه‌هایی که در مطالعه میان­‌بار‌های سیال مورد بررسی قرار می‌گیرد، شکل و هندسه میان­‌بار‌ سیال است که فعالیت انجام ­شده در این زمینه به‌ تخمین درجه پُرشدگی میان‌بارهای سیال در حالت سه‌­بعدی منجر‌شده است و می­‌توان به کمک آن، بدون فعالیت‌های زمان‌­بر و هزینه‌­بر گرمایش و سرمایش، اطلاعاتی مفید در زمینه دما، فشار، میزان شوری و عمق تشکیل به­‌دست آورد. در این پژوهش، کانسار سرب و روی مهدی‌آباد به‌عنوان مطالعه موردی انتخاب‌شده است. پس از تهیه مقاطع دوبر صیقل مناسب برای بررسی میان­‌بار‌های سیال و عکس‌­برداری به­‌صورت دو­بعدی از مقاطع، با اندازه­‌گیری مساحت کل، حباب و لکه میان­‌بار‌ سیال و با محاسبه بعد سوم میان­‌بار‌ سیال، درجه پرشدگی به‌صورت دو­بعدی و سه­‌بعدی محاسبه‌شد. سپس با انتخاب مدل مناسب سه­‌بعدی میا‌ن­‌بار سیال بسته به ­هندسه آن (که از نوع شش­‌ ضلعی هرمی و بیضی­‌گون بود)، درجه پرشدگی حالت دو­بعدی (سطحی) به‌حالت سه­‌بعدی (حجمی) تبدیل‌شد که نتایج مدل محاسباتی با خروجی­‌های مدل هندسی دارای همخوانی بالایی بوده و نسبت درجه پرشدگی دوبعدی به سه‌­بعدی، در مدل محاسباتی و هندسی به‌­ترتیب برابر 75/0 و 77/0 است. در کانسار سرب و روی مهدی­‌آباد، مدل­‌سازی سه­‌بعدی هندسی نمونه­‌هایی از میان‌­بار‌های سیال مشخص‌کرد که میان‌­بار‌های سیال با درجه پرشدگی فاز گازی تقریبی 25% و چگالی بین 65/0 تا 8/0 گرم بر سانتی‌­متر مکعب، دارای دمای یکنواختی بین 100 تا 200 (دمای میانه 150) درجه سانتی‌گراد، فشار بین 400 تا 500 اتمسفر، دمای سازندی بین 250 تا 350 درجه سانتی‌گراد، شوری بین 10 تا 15 درصد معادل نمک طعام و عمق تشکیل بین 150 تا 200 متر است که سازگاری مناسبی با نوع کانسارهای مشابه سرب و روی مهدی­‌آباد دارد.}, keywords_fa = {میانبار‌ سیال}, url = {https://econg.um.ac.ir/article_33751.html}, eprint = {https://econg.um.ac.ir/article_33751_e3420954b98c3ddd82ba19cba4f1af49.pdf} }