Rocks and Ore Deposits

All ore mineral deposits lie in or on solid rocks of which the Earth s crust is predominantly composed. The geological processes which are responsible for the formation of rocks also form the ore bodies associated with them. For the formation of an ore body, the metal or metals concerned must be enriched to a considerably higher level than their normal crustal abundance. The degree of such enrichment below which the extraction cost makes the processing of the ore uneconomical is termed the concentration factor. Typical values of the concentration factor for some of the common metals are given in Table 1.5. 

Metals Average crustal abundance (%) Average minimum exploitable grade Concentration factor 

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Geochemical Nature and Types of Deposits. The cmst of the earth contains approximately 2—3 ppm uranium. AlkaHc igneous rock tends to be more uraniferous than basic and ferromagnesian igneous rocks (10). Elemental uranium oxidizes readily. The solubiHty and distribution of uranium in rocks and ore deposits depend primarily on valence state. The hexavalent uranium ion is highly soluble, the tetravalent ion relatively insoluble. Uraninite, the most common mineral in uranium deposits, contains the tetravalent ion (II). 

Fluid Inclusion Oils in Igneous Rocks and Ore Deposits... 

Quartz Bresi by Didier Descouens. Quartz is the most abundant rock-forming mineral (Si02) as well as feldspar, occurring in wide varieties of rocks (igneous, sedimentary and metamorphic rocks) and ore deposits (see Chaps. 1 and 2)... 

Figure 1.12 shows the areal distribution of the B and C sub-type deposits in the Kosaka district. The Y sub-type deposits have not yet been found in the district. It appears that two zones characterized by the distribution of each sub-type deposit are distributed north-southernly in the Kosaka district as well as in the Hanaoka district (Fig. 1.13). Pyroclastic rocks in the Kosaka formation, in which all deposits occur, become thicker to the east, and probably moved from the eruptive centres to the east (Horikoshi, 1969). These types of evidence may indicate that the sea at that time became deeper to the east. Figure 1.12 shows also the top of the pre-Tertiary basements. Ore deposits, either B or C sub-type, occur above the crater-like depressions of basements. The Shinsawa deposit is the sole example of B sub-type in the midst of the Hanaoka-Kosaka district, so-called Hokuroku basin (Fig. 1.13). The Tsunokakezawa deposit in the Fukazawa mine and ore deposit in the Ezuri mine are also the B sub-type.

Reed, M. H., 1977, Calculations of hydrothermal metasomatism and ore deposition in submarine volcanic rocks with special reference to the West Shasta district, California. Ph.D. dissertation, University of California, Berkeley. 

Extensive research work has been carried out on ilmenite flotation from different ores [1-3], including hard rock and sand deposits. Because the chemical composition of ilmenite is unstable, flotation processing characteristics of ilmenite varies from one ore type to another. Figure 25.1 shows the flotation of ilmenite from different ore types at different pH levels using 200 g/t of oleic acid. 

Hollings, P., Cooke, D.R., Clark, A. 2005. Regionai geochemistry of Tertiary voicanic rocks in Centrai Chiie impiications for tectonic setting and ore deposit genesis. Economic Geology, 100, 887-904. 

Mitchell, R. H. 1996. Perovskites a revised classification scheme for an important rare earth element host in alkaline rocks. In Jones, A. P., Wall, F. Williams, C. T. (eds) Rare Earth Minerals, Chemistry, Origin and Ore Deposits. Chapman and Hall, London, 41-76. 

Oil fields and ore deposits in sedimentary rocks have several common features. Both are aggregates of widely dispersed matter accumulated... 

These associations are, at present, only tentative and assume a roughly single-stage lead isotope evolution, with negligible contamination of the copper ore deposits by lead derived from older country rocks. Nevertheless, this approach should be used as a basis for further field exploration of the areas in question. The mines and ore deposits in north and northwestern Turkey have recently been explored by a team from the Max Planck Institute for Nuclear Physics in Heidelberg (42, 59), and we hope that there will soon be more information available for the lead isotope fingerprints of Anatolian ore sources. Information available so far proves only that Troy did not get copper from its hinterland and does not identify its source. 

Mel nik, Yu.P. and Yaroshchuk, M.A., 1966. A thermodynamic analysis of the conditions of formation of the olivine-magnetite rocks and ores of the Volodarsk district of the Ukrainian shield. In Problemy teorii i eksperimenta v rudoobrazovanii (Problems of Theory and Experiment in Ore Deposition). Izd. Naukova Dumka, Kiev, pp. 98-113 (in Russian). Geochem. Int. 1966, 3 1218-1229 (in English). 

Mellott N. P., Brantley S. L., and Pantano C. G. (2002) Topography of polished plates of albite crystal and glass during dissolution. In Water-Rock Interactions, Ore Deposits, and Environmental Geochemistry, A Tribute to David A. Crerar, vol. Spec. Pub. No. 7 (eds. R. Hellmann and S. Wood). The Geochemical Society, St. Louis, MO, pp. 83-96. 

Our trace element data base now contains analyses of 586 samples of native copper from deposits throughout the world. However, the sample sources are skewed toward the northern United States, especially the Lake Superior region. Trace elements can be considered as those normally found in concentrations below 100 ppm (i.e., below the 0.01% normally used as the lower limit of standard rock and mineral analyses). Trace elements do not play a major part in the physicochemical reactions that take place in the formation of geologic deposits. They are either concentrated in or dispersed throughout rock, mineral, and ore deposits... 

An additional argument for considering the effect of pressure on ionization equilibria is presented in Figure 8. This figure plots calculated temperature and pressure conditions at which the modified seawater becomes saturated with calcite or anhydrite. At a constant pressure, the predicted temperature of mineral saturation is significantly different (higher for calcite and lower for anhydrite) when the effect of pressure on ionization equilibria are taken into account. This observation has important consequences for calculated geochemical models of water-rock interactions and ore deposition (23,24). 

Whether apatite represents the tail or the dog in halogen mass balance during metamorphism most likely depends on the environment. In high fluid/rock environments where fluid composition controls rock composition (e.g., veins, skams and ore deposits). 

No. 7. Water-Rock Interactions, Ore Deposits, and Environmental Geochemistry A Tribute to David A. Crerar. R. Heilman and S. A. Wood (Editors), 2002. 

Sodium is the most abundant of the alkali metals and is the sixth most abundant element in the Earth s crust, with an abundance of roughly 2.36 wt.%. Owing to its high chemical reactivity with water and, to a lesser extent, with air, sodium metal never occurs free in nature however, the element is ubiquitous and occurs naturally in a wide range of compounds. Sodium chloride is the most common compound of sodium and is dissolved either in seawater or in the crystalline form of halite or rock salt [NaCl, cubic]. However, it is widely present in numerous complex silicates such as feldspars and micas and other nonsilicate minerals such as cryolite [NajAlF, monoclinic], natronite or soda ash [Na COj, mono-clonic], borax [Na B O,. lOH O, monoclinic], sodium hydroxide or caustic soda [NaOH], Chilean saltpeter, and nitratite or soda niter [NaNOj, rhombohedral]. Obviously, the chief ore is the sodium chloride recovered from either brines or rock salt ore deposits. There are... 

Alaska, Washington, and Nevada. Ores of the Southeast Missouri lead belt and extensive deposits such as in Silesia and Morocco are of the replacement type. These deposits formed when an aqueous solution of the minerals, under the influence of changing temperature and pressure, deposited the sulfides in susceptible sedimentary rock, usually limestone and dolomites. These ore bodies usually contain galena, sphalerite, and pyrite minerals, but seldom contain gold, silver, copper, antimony, or bismuth. 

Mercury ore deposits occur in faulted and fractured rocks, such as limestone, calcareous shales, sandstones, serpentine, chert, andesite, basalt, and rhyolite. Deposits are mostiy epithermal in character, ie, minerals were deposited by rising warm solutions at comparatively shallow depths from 1—1000 m (6). 

Table 1. Metal Content of Igneous Rocks, Ore Deposits, and Concentrates, wt %...

Mining of the ore deposit constitutes a significant cost, especially in hard rock mining. Mining costs vary considerably from ore to ore and from a few cents to well over 100/t mined. Underground mining is the most expensive hydrauHc mining of sedimentary deposits is the least expensive. 

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