Metalliferous minerals

Certain minerals may be mined and processed for more than one purpose. For instance, bauxite, on the one hand, can be utilized for making bricks or abrasives and, on the other, is used for the production of aluminum. It is often found that many nonmetallic minerals are associated with metalliferous minerals. As an example mention may be made of galena, the main mineral source of lead, which is found very frequently to be associated with fluorite (CaF2) and barytes (BaS04), both of which are important industrial minerals. 

Thus, most of the color in glass is produced by metallic ions derived from minerals, usually in relatively small amounts within the glass structure. Already in antiquity there was awareness of the effects of some other metals on the color of glass. It was known then, for example, that even relatively small amounts of specific metals, included as minerals in the components of a glass melt, could produce colored glass particular metalliferous minerals were therefore added to glass melts so as to produce special and... 

ORES. Mineral aggregates in which the valuable metalliferous minerals are sufficiently abundant to make the aggregates worth mining. Types and origins of ore deposits arc illustrated in Fig. 1. See also Copper and Iron. 

Ores are metalliferous minerals which can be extracted from their host rocks to yield their metals economically, ie, the costs of mining and extraction must be compared with the revenue from selling the ore concentrates. Ores are therefore localised concentration of metal compounds. These minerals are not usually the parent materials for... 

Nuclear techniques such as nuclear bore-hole logging and radiometric in-situ analysis play an increasingly important role in the exploration for oil, gas, and metalliferous minerals. 

Many metalliferous mineral deposits formed at depth are in the reduced state. Where they interface with the near-surface oxidising environment, there is considerable chemical reactivity. This typically takes the form of sulphide oxidation, which includes the generation of several meta-stable sulphur gases that have been shown to be useful in mineral exploration (Chapter 8). Incompletely oxidised sulphide anions and compounds are transported away from mineral deposits at depth by the groundwater, and can be mapped at surface as dispersion patterns of HjS (Chapter 9). 

John R. Wilmshurst, Dip RMIT, BSc, PhD, University of Melbourne, commenced work on exploration methods for base and precious metals within the CSIRO Division of Mineral Chemistry at North Ryde in 1972. His particular interest was the weathering of metalliferous minerals and he was involved with developing and applying an in-house mercury detector for base-metal and precious-metal exploration. He is presently working in the CSIRO Division of Petroleum Resources, developing tools for source-rock maturity estimation. 

Gangue the non-metalliferous or non-valuable metalliferous minerals associated with ore. 

Two key industries in non-metalliferous mineral ore processing are production of phosphate fertilisers and China Clay. China Clay production is used to illustrate the complexity of characterising NORM deposits in the case study below. 

The ocean is host to a variety and quantity of inorganic raw materials equal to or surpassiag the resources of these materials available on land. Inorganic raw materials are defined here as any mineral deposit found ia the marine environment. The mineral resources are classified generally as iadustrial minerals, mineral sands, phosphorites, metalliferous oxides, metalliferous sulfides, and dissolved minerals and iaclude geothermal resources, precious corals, and some algae. The resources are mosdy unconsoHdated, consoHdated, or fluid materials which are chemically enriched ia certain elements and are found ia or upon the seabeds of the continental shelves and ocean basias. These may be classified according to the environment and form ia which they occur (Table 1) and with few exceptions are similar to traditional mineral deposits on land. 

Ocean Basins. Ocean basins are primarily formed from oceanic basalts and maybe interspersed with continental remnants, ridges, seamounts, or volcanic islands rising from the depths. Average water depth is around 4000 m but the most significant mineralization is generally found at 5000 m for manganese nodules, 4000 m for biogenic oozes, and 3000 m for hydrothermal metalliferous sulfides. The area is poorly explored, however. 

Ocean Basins. Known consohdated mineral deposits in the deep ocean basins are limited to high cobalt metalliferous oxide cmsts precipitated from seawater and hydrothermal deposits of sulfide minerals which are being formed in the vicinity of ocean plate boundaries. Technology for drilling at depth in the seabeds is not advanced, and most deposits identified have been sampled only within a few centimeters of the surface. 

Deposits which are forming are frequentiy characterized by venting streams of hot (300°C) mineralized fluid known as smokers. These result in the local formation of metalliferous mud, rock chimneys, or mounds rich in sulfides. In the upper fractured zone or deep in the rock mass beneath the vents, vein or massive sulfide deposits may be formed by the ckculating fluids and preserved as the cmstal plates move across the oceans. These off-axis deposits are potentially the most significant resources of hydrothermal deposits, even though none has yet been located. 

Isotopic ages of metalliferous veins, altered country rocks and the igneous rocks which have genetical relations to the mineralization (Otsuki, 1989)... 

Sudo, T. (1954) Types of clay minerals closely a.s.sociated with metalliferous ores of the epithermal type. Sci. Repts. Tokyo Kyoiku Daigaku, Sen C, 3, 173-197. 

When nonrenewable mineral resources are processed for metal extraction and the metals extracted are utilized in various ways and in diverse forms, they become potentially available for reclamation and recycling. Recycled metals produced by the extraction and refining of metallic wastes are known as secondary metals, whereas metals produced from primary ores are termed primary metals. A classification of recyclable metalliferous resources such... 

Because little mass can precipitate from it, the brine, if related to deposition of the metalliferous muds, is likely to be a residuum of the original ore fluid. As it discharged into the deep, the ore fluid was richer in metals than in reduced sulfur. Mineral precipitation depleted the fluid of nearly all of its reduced sulfur without exhausting the metals, leaving the metal-rich brine observed in the deep. 

The chemical reactions that occur in hydrothermal systems are largely the result of interactions between seawater and relatively yoimg ocean crust. During these reactions, some elements are solubilized and released to seawater as ions or gases. Others are precipitated, forming minerals that end up as a component of new oceanic crust or the metalliferous sediments. For some elements, the resulting elemental fluxes rival those associated with river input, making hydrothermal activity a very important process in the crustal-ocean-atmosphere factory. 

Many metalliferous ore deposits and most coalfields are characterized by the presence of sulphide minerals, such as pyrite (FeS2), galena (PbS), or sphalerite (ZnS). When exposed to water and oxygen, these sulphides have a tendency to oxidize, releasing dissolved metals, sulphate and, in the case of pyrite, acid (equations I and 2). 

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