No description available.

No description available.

No description available.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 67-68).

Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography: leaves 136-158. Also available online.

The grade of a mineral deposit is determined by the effectiveness of a geological ore forming process, which is the result of the interaction between an ore forming mechanism and the environment in which it operates. Properties of a mineral deposit controlled by ore forming processes include the distribution, density and nature of ore minerals and gangue, and the metal content and impurities of the ore minerals. More efficient ore forming processes tend to develop in the larger mineralizing systems giving rise to richer deposits. As the geological environment within which a mineral deposit evolves becomes more complex a greater number of variables interact to determine the grade of the deposit. This is reflected in the greater variability of the grade distribution, resulting in greater difficulties in obtaining reliable estimates of the recoverable grade, and increased difficulties in the processing of ores. In response to economic fluctuations the working grade of heterogeneous orebodies, that form in geologically complex environments, can often be altered to ensure the continued viability of a mining venture. In contrast the evenly mineralized orebodies that tend to develop in geologically simple environments do not have this flexibility. All the important decisions in the mining industry, such as feasibility studies, choice of ~ining and processing methods, selection and planning, are made on the basis of, or are related to, grade estimates. If the geological controls of grade are fully understood, then it is possible to optimize the selection of the various mining alternatives, leading to the efficient exploitation of ore deposits.

From introduction: The mining of porphyry type deposits accounts for about 50% of the world's present copper (Figs.I,2) and molybdenum production and resources. Mining organizations therefore invest substantial amounts of time, money and skills in the location and delineation of these types of deposit. The optimization of this investment effort is based on complex inter-relationships between geological, economic and political factors. The object of this dissertation is to review the geological and some of the economic aspects involved in the exploration and evaluation of porphyry deposits . These may hopefully provide some practical guidelines for decision making during the exploration and evaluation of such deposits. For the purpose of this dissertation, the exploration-evaluation of porphyry deposits, has been divided into three main stages:- Stage 1 : Geological mapping, interpretation of exploration drilling results and other geological factors which may help in understanding the shape and nature of the deposit. A knowledge of existing geological models for porphyry deposits will be essential in understanding the geological factors affecting tonnage and grade of these deposits Stage 2 Stage 3 (see Part I). Determination of grade-tonnage relationships. This is important in order to establish the different tonnage-grade alternatives for the deposit. Based on this, reserve estimations are calculated for different possible scales of mining. Drilling and sampling techniques, as well as statistical and preliminary economic evaluation methods are applied during this stage (see Part 2). Mine development and feasibility studies involve factors that influence type and scale of mining, and factors affecting mineral processing and extraction in relation to tonnage- grade alternatives. These factors are reviewed in Part 3.

No description available.

From Chapter 1: It has been a long standing belief that many nickel sulphide ores are derivatives of magmatic processes in ultramafic and mafic rocks, and that they segregate from these magmas as immiscible sulphide droplets which are then concentrated into an orebody by gravitational settling either during intrusion or extrusion, or during the early stages of crystallization of the magma (Naldrett, 1981). Some geologists however, have suggested alternative mechanisms to explain the concentration of nickeliferous sulphides in the mafic and ultramafic hosts. These include hydrothermal replacement (Fleet, 1977), exhalative volcanic processes (Lusk, 1976), or major metamorphic upgrading of low grade, initially magmatic deposits (Barrett et al., 1977). It is not the purpose of this study to verify or disprove these hypotheses, but in so far as the initial concentration of sulphides in most deposits is concerned, these effects are relatively unimportant (Naldrett, 1981). The nickel sulphide ores associated with these mafic and ultramafic host rocks, invariably consist of nickeliferous pyrrhotite as the dominant phase, together with lesser, but variable, amounts of magnetite, pentlandite, chalcopyrite, cubanite, and platinum group elements (Reynolds, 1982).