A new 3D geological model and structural evolution of the Rio Tinto world-class VMS deposit is presented in this work. The Rio Tinto volcanogenic massive sulfide (VMS) deposit is located in the Spanish segment of the Iberian Pyrite Belt and is hosted by felsic porphyritic volcanic rocks and tuffs. Computer generated 3D modeling of the different orebodies and host rocks has been carried out using data from around 3,000 drill-core logs, allowing us to build 93 cross-sections and 6 plants (both 50 m spacing). This has enabled us to recognize of the geometry and relationships between the mineralization and the earliest Carboniferous transtensional tectonics through the development of an extensional pull-apart basin with two sub-basins separated by the NW-SE trending Eduardo Fault. The sub-basins, CerroColorado and San Dionisio, were limited by two E-W strike-slip faults, the Northern and Southern faults, and bounded in the east and west by the NW-SE-trending Nerva and Western faults, respectively. The generated pull-apart basin was first filled by a basaltic magmatism of mantle origin and later, following the deposition of the intermediate complex sedimentary unit, by rhyodacitic volcanic rocks of crustal origin. The evolution of the subsiding basins caused the development of an E-W oriented rollover anticline that affected these filling rocks.As a result of a counterclockwise rotation of the stress axes, the primitive pull-apart basin evolved into a basin affected by E-W transtensional sinistral shearing. Its northern and southern limits were favorable areas for increased hydrothermal fluid flow, which gave way A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 to the huge concentration of VMS mineralization located near the limits. The Northern and, to a lesser degree, the Southern extensional faults thus become channel areas for feeding and discharging of the VMS and stockwork ores. The main mineralizing period was related to this stage. Subsequently, during the Variscan transpressional phase, the E-W extensional faults were reactivated as inverse faults, affecting the volcanic sequence of mafic to felsic composition and the intermediate complex sedimentary unit. Fault propagation folds developed above these faults, affecting the massive sulfides, the transition series and the Culm flysch sediments, with buttressing playing a significant role in the geometry of tectonically inverted structures. The VMS mineralization and cupriferous stockworks were folded and dismembered from the original conduits in the volcanic series, and a dextral reactivation of the NW-SE trending faults also developed.Finally, it should be emphasized that this new 3D geological model is an approach to provide a better insight into the 3D structure of the world-class VMS Rio Tinto deposit and could be a key-point for further studies providing a new tool to increase knowledge of the VMS mineralizations and exploration guidelines elsewerein the IPB.

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Three-dimensional block models are the most frequently used tool for estimating mineral resources and reserves within a mineral deposit. In open pit mining, the basis of mine design and the long term mining schedule is calculation of the ultimate pit limit. The ultimate pit limit is the pit with the highest profit value. Over the years, different algorithms have been developed that enable us to calculate the final pit: floating or mobile cone, floating cone II and its corrected forms, floating cone III, the Korobov algorithm and its corrected form, the Lerchs–Grossmann 2D algorithm (dynamic programming), and the Lerchs–Grossmann 3D algorithm (graph theory). All these algorithms have advantages and disadvantages. The floating cone method stands out for its simplicity, speed, and easy implementation, even for calculating a pit with a variable slope angle. The main drawback of this method is that it is unable to examine all possible combinations. For this reason, the algorithm does not consistently give optimal results, which is why it has required improvements over time. However, the improved methods still have some problems. To overcome these problems, a new algorithm called the floating cone IV method will be demonstrated in this paper.

Abstract:In recent years, the introduction of specific software for the evaluation of geological resources and mineral reserves has increased significantly thanks to the use of block models capable of working with large databases and applicable to virtually all types of deposits. It is only in layered, tabular-shaped deposits where the use of block models poses certain drawbacks, not only in terms of visual representation but also during the process of interpolation. Other calculation methods for tabular bodies such as sections, polygons, and triangles work with 2D projections but not with 3D. The "Pentahedral" method described here is undoubtedly an innovative method that allows work to always be conducted in 3D, providing a fairly accurate representation of tabular bodies and making it possible to carry out calculations of resources and reserves using any interpolation method. It is demonstrated with figures and tables of the Carlés mineral deposit, a well-developed exoskarn gold deposit in northwestern Spain (Asturias) where the authors have worked extensively. The pentahedral method takes into account not only geological and stratigraphic data from the model interpolation, but also mining concepts such as "minimum thickness," related to the minimum seam size that can be economically and technically mined, and "overbreak," related to the dilution effect that appears during the mining process due to over-excavation.

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