Hydro-thermal alteration

Giggenbach, W. R. 1984. Mass transfer in hydro-thermal alteration systems. A conceptual approach. Geochimica et Cosmochimica Acta, 48,2693-2711. 

FOURNIER (R.O.), 1967. The porphyry copper deposit exposed in the liberty open-pit mine near Ely, Nevada. Part II. The formation of hydro-thermal alteration zones. Econ. Geol. 62, 207-27. 

The iron extraction rates for both fresh and altered granite decrease for the first 24 h and become the same constant rate for the remaining 24 to 120 h. Thus the iron associated with oxyhydroxides (formed during recent exposure to GGW or during hydro-thermal alteration) is removed during the first 24-h exposure to... 

Boudier F. and Nicolas A. (1991) High-temperature hydro-thermal alteration of peridotite, Zabargad Island (Red Sea). In Orogenic Iherzolites and Mantle Processes, Spec. Vol., J. Petrol, (eds. M. A. Menzies, C. Dupuy, and A. Nicolas). Oxford University Press, Oxford, pp. 243 -254. 

Both heat-flow methods deliver similar results, suggesting that convective heat loss, hence hydro-thermal alteration, may occur for time periods... 

Lovlie R (1988) Evidence for deuteric magnetization in hydro-thermally altered Mesozoic basaltic rocks from East Antttfctica. Phys Earth Planet Interiors 52(3/4) 352-364... 

The ages of the Cenozoic volcanic rocks of the McMurdo Volcanic Group were determined by Armstrong (1978), Fleck et al. (1972), Forbes et al. (1974), Wright-Grassham (1987), and others by the whole-rock K-Ar method. Under ideal circumstances, these dates indicate the crystallization ages of late Cenozoic volcanic rocks that cooled rapidly after they were erupted on land, provided they were not hydro-thermally altered and provided that all " Ar was out-gassed from the lava at the time eruption. 

Hydrothermal alteration is classified into several types depending on the alteration minerals (Hemley and Jones 1964 Rose and Burt 1979). Important hydro-thermal alterations include propylitic alteration, argiUic alteration, advanced argUlic alteration and sericitic alteration (Meyer and Hemley 1967). 

Chapter 1 provides an extensive discussion of chemical equilibria as they pertain to minerals. This covers in detail chemical equilibria of solids and aqueous solutions, the solubility of various types of minerals, the weathering of silicate and aluminosilicate minerals, the composition of geothermal and groimd water, hydro-thermal alteration, oxidation and reduction reactions, and the partitioning of elements between aqueous solutions and crystals. 

These reactions could occur at temperatures -150-200 °C, where olivine transforms into serpentine, magnetite and brucite with the release of H2. At these temperatures, combined with the pressures encountered at the hydrothermal sites, many compounds are in their supercritical state and peculiar chemistry can occur. In this IJMS issue on the Origin of Life, syntheses of amino acids in a mixture of supercritical C02-liquid water (10 1) starting with hydroxylamine hydrochloride and pyruvic or glyoxylic acid are reported [52]. A hypothesis for the origin of the living systems could consequently be found at the bottom of the oceans, in ul-tramafic hosted hydrothermal systems, where tectonic plates separate to leave the upper mantle rock reacts with seawater to form hydro thermally altered peridotites and lead to the necessary molecules for life to emerge. 

An example of a hydrothermal deposit is the New Rambler deposit, described by McCal-lum et al. [4] in the Medicine Bow Mountains in south-western Wyoming, USA, which contains a significant amount of PGM. The ore occurs in irregular pods that are hydro-thermally decomposed into metadiorite and metagabbro zones. Pyroxenite and peridotite are reported to be intersected at a depth beneath the ore zone. All have been affected by supergene alteration. The main sulphides in the ore include pyrite, chalcopyrite, pyrrhotite, covellite and marcasite with associations of electrum, pentlandite and PGM. 

Synthetic MIO is used in primers as well as in topcoat paints the natural MIO was too coarse for use in undercoats. Weathering tests with different paint binders indicated that the performance of the synthetic product was as good or better than, that of the natural product (Carter and Laundon, 1990). The aspect ratio of MIO produced by hydro-thermal synthesis can be altered by doping with Al, Mn or Si, thus enabling a more lustrous material with a reddish-brown colour to be produced this material is suitable for decorative as well as for purely protective purposes (Pfaflfand Reynders, 1999). 

Hydrothermal circulation is viewed as flow of seawater with its ambient concentration into the hydrothermal zone to replace water that is heated and rises to exit on the sea floor (Fig. 2.9). Consequently, the right-hand side of Eq. (2.5) expresses the difference in Mg + concentration between seawater, [Mg +]sw. and the hydro-thermal solution, [Mg +]iiydro- In the case of Mg + the cool limb takes seawater to the hot zone, and the altered seawater rises with no Mg + left in solution at all. Since the river inflow of Mg + is about 4.5 x 10 mol y (Table 2.3), the hydrothermal flow is simply ... 

The descriptions above pertain only to those portions of the oceanic crust that have not been tecto-nized or chemically altered. Because of the dynamic nature of oceanic ridges and the pervasive hydro-thermal circulation related to magmatism, it is common for the basaltic rocks comprising the crust... 

In confirmation of these findings it should be noted that Li, Sn and B are all closely associated with the subsequent hydro-thermal ore-forming events in the Cornubian batholith. Li in stream sediments shown on the Wolfson atlas s is in the range 200-400 ppm in the vicinity of hydrothermally altered and kaolinized granite. Sn has a widespread occurrence in vrin-type mineralization and boron is the matrix of diatremes such as the Wheal Remfry breccia in the St Austell granite. ... 

FCC catalysts are deactivated via several mechanisms," which all result in a loss in activity and a change in yield selectivity Catalyst will age, meaning change chemical and physical structure due to the (hydro) thermal conditions during the 10,000 to 50,000 reaction and regeneration cycles it will endure. The catalysts can also be poisoned, whereby the active sites are covered by coke and/or polars (nitrogen) that neutralize the catalytic activity or by metals (vanadium, nickel, sodium) which can destroy or alter the activity. 

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