Abstract A precise understanding of the spatial distribution of rock mass properties is essential for the safe and economical design of rock structures. This paper adapts geostatistical methodologies, traditionally employed for estimating block ore grades and tonnage, to forecast rock properties crucial for structural modeling. The Rock Mass Rating (RMR) classification system, extensively utilized for evaluating rock mass quality, serves as a framework to inform excavation techniques and ensure slope stability in open-pit mining and rock support systems for tunnel construction. The study introduces a geostatistical simulation method to create three-dimensional (3D) models of rock mass quality distribution based on RMR. Geotechnical data from 37 drillholes, encompassing a total of 11,278 meters, were collected from the Miduk open pit mine in Iran. Two block models for RMR were constructed using the turning bands simulation method (TBM) with 100 realizations. The research utilized both direct and indirect approaches. In the direct method, the RMR value was considered a singular variable for simulation, whereas the indirect method involved simulating individual RMR parameters and subsequently summing them to derive the final RMR for each block. Cross-validation indicated strong consistency between the two approaches, reinforced by the 3D model of the faults and the contribution of joints, which were derived from scan-line mapping data collected from 24,160 surface stations. Although both methods yielded similar results, the block model developed via the indirect approach proved to be more comprehensive regarding geomechanical parameters and has thus been established as the final model.
Mapping hydrothermal alteration minerals using multispectral remote sensing satellite imagery provides vital information for the exploration of porphyry and epithermal ore mineralizations. The Ahar-Arasbaran region, NW Iran, contains a variety of porphyry, skarn and epithermal ore deposits. Gold mineralization occurs in the form of epithermal veins and veinlets, which is associated with hydrothermal alteration zones. Thus, the identification of hydrothermal alteration zones is one of the key indicators for targeting new prospective zones of epithermal gold mineralization in the Ahar-Arasbaran region. In this study, Landsat Enhanced Thematic Mapper+ (Landsat-7 ETM+), Landsat-8 and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral remote sensing datasets were processed to detect hydrothermal alteration zones associated with epithermal gold mineralization in the Ahar-Arasbaran region. Band ratio techniques and principal component analysis (PCA) were applied on Landsat-7 ETM+ and Landsat-8 data to map hydrothermal alteration zones. Advanced argillic, argillic-phyllic, propylitic and hydrous silica alteration zones were detected and discriminated by implementing band ratio, relative absorption band depth (RBD) and selective PCA to ASTER data. Subsequently, the Bayesian network classifier was used to synthesize the thematic layers of hydrothermal alteration zones. A mineral potential map was generated by the Bayesian network classifier, which shows several new prospective zones of epithermal gold mineralization in the Ahar-Arasbaran region. Besides, comprehensive field surveying and laboratory analysis were conducted to verify the remote sensing results and mineral potential map produced by the Bayesian network classifier. A good rate of agreement with field and laboratory data is achieved for remote sensing results and consequential mineral potential map. It is recommended that the Bayesian network classifier can be broadly used as a valuable model for fusing multi-sensor remote sensing results to generate mineral potential map for reconnaissance stages of epithermal gold exploration in the Ahar-Arasbaran region and other analogous metallogenic provinces around the world.
The determination of the most unstable areas in oil fields is critical for addressing engineering problems of wellbore and sand production as well as geologic problems such as understanding dynamic constraints on hydrocarbon migration and fracture permeability. In this research work, coherency seismic attribute has been used for the determination of the most critical areas in terms of drilling stabilities in the DQ oil field, Iran. The results obtained have shown that the (1) predominant features are the SSE–NNW and N–S trends (2) the central part of the DQ structure shows the highest concentration of segment bundles, (3) the segment bundles seem to be aligned along some lineaments oriented SE–NW and SSE–NNW, and (4) on the eastern and western margins of the map there is an anomalous concentration of segments oriented E–W. It can be concluded that coherency attribute is a valuable tool for structural analysis highlighting those areas containing unstable features.
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