The effective management of geological risk in long-term production scheduling of open pit mines

Investment in mining projects, like most business investment, is susceptible to risk and uncertainty. The ability to effectively identify, assess and manage risk may enable strategic investments to be sheltered and operations to perform closer to their potential. In mining, geological uncertainty is seen as the major contributor to not meeting project expectations. The need to assess and manage geological risk for project valuation and decision-making translates to the need to assess and manage risk in any pertinent parameter of open pit design and production scheduling. This is achieved by taking geological uncertainty into account in the mine optimisation process. This thesis develops methods that enable geological uncertainty to be effectively modelled and the resulting risk in long-term production scheduling to be quantified and managed. One of the main accomplishments of this thesis is the development of a new, risk-based method for the optimisation of long-term production scheduling. In addition to maximising economic returns, the new method minimises the risk of deviating from production forecasts, given the understanding of the orebody. This ability represents a major advance in the risk management of open pit mining.

Diccionario de Terminos Geologicos Ingles/Espanol - Espanol/Ingles; English/Spanish - Spanish/English Dictionary of Geological Terms (Dialogue #85)

This dictionary provides a portable, easy to use, and inexpensive bilingual list of geological terms for those in the earth sciences and engineering who have to work in both English and Spanish. The dictionary includes two major sections. The first comprises English terms, arranged alphabetically, alongside their Spanish equivalents; the second section comprises Spanish terms arranged alphabetically, alongside their English equivalents.

The Evolution of the Los Negritos Porphyry Copper Deposit, Coquimbo, Chile: Geological, Geochronological, Mineralogical and Geochemical Evidence

The Los Negritos porphyry copper deposit is located ~ 4 km to the northeast of Carmen de Andacollo Mine in the Chilean Cretaceous metallogenic belt. The mineralization is hosted in andesite of the Quebrada Marquesa Formation and a series of at least four early to intramineral porphyry intrusive rock types: plagioclase quartz biotite porphyry (P1b and P1a dated at 109.60± 0.75 Ma and 107.22± 0.40 Ma); plagioclase biotite porphyry (P2: 106.30 ± 0.47 Ma); and quartz plagioclase biotite porphyry (P3: 106.19 ± 0.42 Ma). These units are cut by late‐ to post‐mineral plagioclase‐hornblende porphyritic rocks (P4b: 106.20 ± 0.69 Ma and P4a: 106.50 ± 0.68 Ma). The earliest intrusive units (P1) were affected by an initial stage of K‐feldspar‐biotite alteration, with chalcopyrite, molybdenite (date at 108.5 ± 0.5 Ma) and gold (up to 0.11 ppm), and the surrounding volcanic host rock was overprinted by chlorite‐epidote dominated (propylitic) alteration. Subsequent to the P2 and P3 intrusion, these rocks were affected by albite and then a second stage of potassic alteration. The Ti and Ba contents in hydrothermal biotite are notably lower (typically Ti = 0.100‐0.144 a.p.f.u. and Ba = 0.001‐0.005 a.p.f.u) than in magmatic ones (generally Ti = 0.186‐0.222 a.p.f.u. and Ba = 0.014‐0.023 a.p.f.u.), and constitute an excellent discriminant of the nature of biotite. These early stages of alteration were overprinted by copper‐molybdenum bearing chlorite‐sericite alteration at 106.60 ± 0.5 Ma (Re‐Os age in molybdenite) and by quartz‐sericite‐pyrite veins (phyllic), respectively in the southwest and northeast areas. The average temperature associated with these two alteration facies is estimated around 305 °C. Weak albite‐calcite alteration, spatially associated with sulfosalts and distributed along the margins of P3, overprinted the phyllic facies. The intrusive rock units at the Los Negritos and Carmen de Andacollo deposits are geochemically classified as diorite to granodiorite with a calc‐alkaline magmatic affinity, and formed in a volcanic arc setting from partial melting of a metasomatized mantle wedge. They are interpreted to be cogenetic, and related to a common long‐lived magma chamber that emplaced during a period of tectonic inversion known as the Subhercynian, Peruvian or Pacific event.

CHARACTERIZATION AND THERMAL-HYDRAULIC MODELING OF ENGINEERED BARRIERS FOR A CANADIAN DEEP GEOLOGICAL REPOSITORY FOR USED NUCLEAR FUEL

Within Canada there are more than 2.5 million bundles of spent nuclear fuel with another approximately 2 million bundles to be generated in the future. Canada, and every country around the world that has taken a decision on management of spent nuclear fuel, has decided on long-term containment and isolation of the fuel within a deep geological repository. At depth, a deep geological repository consists of a network of placement rooms where the bundles will be located within a multi-layered system that incorporates engineered and natural barriers. The barriers will be placed in a complex thermal-hydraulic-mechanical-chemical-biological (THMCB) environment. A large database of material properties for all components in the repository are required to construct representative models. Within the repository, the sealing materials will experience elevated temperatures due to the thermal gradient produced by radioactive decay heat from the waste inside the container. Furthermore, high porewater pressure due to the depth of repository along with possibility of elevated salinity of groundwater would cause the bentonite-based materials to be under transient hydraulic conditions. Therefore it is crucial to characterize the sealing materials over a wide range of thermal-hydraulic conditions. A comprehensive experimental program has been conducted to measure properties (mainly focused on thermal properties) of all sealing materials involved in Mark II concept at plausible thermal-hydraulic conditions. The thermal response of Canada’s concept for a deep geological repository has been modelled using experimentally measured thermal properties. Plausible scenarios are defined and the effects of these scenarios are examined on the container surface temperature as well as the surrounding geosphere to assess whether they meet design criteria for the cases studied. The thermal response shows that if all the materials even being at dried condition, repository still performs acceptably as long as sealing materials remain in contact.

Multi-Scale Visualization and Interpretation of Geological Relationships

Visualization and interpretation of geological observations into a cohesive geological model are essential to Earth sciences and related fields. Various emerging technologies offer approaches to multi-scale visualization of heterogeneous data, providing new opportunities that facilitate model development and interpretation processes. These include increased accessibility to 3D scanning technology, global connectivity, and Web-based interactive platforms. The geological sciences and geological engineering disciplines are adopting these technologies as volumes of data and physical samples greatly increase. However, a standardized and universally agreed upon workflow and approach have yet to properly be developed. In this thesis, the 3D scanning workflow is presented as a foundation for a virtual geological database. This database provides augmented levels of tangibility to students and researchers who have little to no access to locations that are remote or inaccessible. A Web-GIS platform was utilized jointly with customized widgets developed throughout the course of this research to aid in visualizing hand-sized/meso-scale geological samples within a geologic and geospatial context. This context is provided as a macro-scale GIS interface, where geophysical and geodetic images and data are visualized. Specifically, an interactive interface is developed that allows for simultaneous visualization to improve the understanding of geological trends and relationships. These developed tools will allow for rapid data access and global sharing, and will facilitate comprehension of geological models using multi-scale heterogeneous observations.