Magmatic water

Telethermal Essentially meteoric and connate waters with little addition of magmatic water, very low temperatures (< 100 °C) and pressures, near the surface Lead, zinc, cadmium germanium... 

There is increasing evidence, however, that a magmatic water component cannot be excluded in some volcanic systems. As more and more data have become available from volcanoes around the world, especially from those at very high latitudes, Giggenbach (1992) demonstrated that horizontal shifts are actually the excep-... 

Ore fluids may be generated in a variety of ways. The principal types include (1) sea water, (2) meteoric waters and (3) juvenile water, all of which have a strictly defined isotopic composition. All other possible types of ore fluids such as formation, meta-morphic, and magmatic waters can be considered recycled derivatives or mixtures from one or more of the three reference waters (see Fig. 3.11). 

The concept of juvenile water has influenced early discussions about ore genesis tremendously. The terms juvenile water and magmatic water have been used synonymously sometimes, but they are not exactly the same. Juvenile water originates from degassing of the mantle and has never existed as surface water. Magmatic water is a non-genetic term and simply means a water that has equilibrated with a magma. 

This group of deposits is closely associated in space and time with magmatic intrusions that were emplaced at relatively shallow depths. They have been developed in hydrothermal systems driven by the cooling of magma (e.g., porphyry-type deposits and skams). From 8D- and 8 0-measurements, it has been concluded that porphyry copper deposits show the clearest affinity of a magmatic water imprint (Taylor 1974) with variable involvement of meteoric water generally at late stages of ore formation. 

White, D. E., Anderson, E. T. Grubbs, D. K. 1963. Geothermal brine well Mile deep drill hole may tap ore-bearing magmatic water and rocks undergoing metamorphism. Science, 139, 919-922. 

Ion microprobe analyses of hydrous minerals in Martian meteorites reveal two different sources of hydrogen. One is interpreted as magmatic water, with 5D = 900 permil, and thought to reflect the mantle composition the other is thought to reflect the atmospheric composition, with 5D =4000 permil (Leshin, 2000). The incorporation of atmospheric water into these meteorites suggests some kind of cycling of water between the atmosphere and lithosphere on Mars. 

McSween, H. Y., Grove, T. L., Lentz, R. C. F. et al. (2001) Geochemical evidence for magmatic water within Mars from pyroxenes in the Shergotty meteorite. Nature, 409, 487-490. 

Magmatic water Water in or originating from a magma. 

Madison River 96 magmatic water 83 magnetic separation 397-8 Mainamoti 145 manganese arsenates 110 manganese (oxy)(hydr)oxides 93, 95, 107-8, 162, 172, 306... 

The presence of volatile-bearing phases such as phlogopite, apatite, and carbonates in kimberhtes testify to the volatile-rich nature of the parental magma (e.g., Mitchell, 1986). The ubiquitous serpentization present in kimberlites cannot be used as evidence of magmatic water, with the exception of groundmass serpentine that is interpreted to be primary in nature. As discussed by Mitchell (1986), there are hmited stable isotopic data consistent with a meteoric origin for some of the water in the serpentine. However, it is unclear if these results could be attributed to postemplacement exchange of deuteric serpentine with meteoric fluids. 

The D/H values of magmatic, hydrous minerals apatite, Ti-rich amphibole, and biotite have been analyzed in five martian meteorites by ion microprobe (Leshin 2000 Rubin et al. 2000 Watson et al. 1994). The elevated and variable D/H values of water discovered in the minerals (5D +800 to +4300) are interpreted qualitatively as representing a mixture of magmatic water in the minerals with a D-enriched component derived from the martian atmosphere (with a D/H value 5 times terrestrial), through isotopic exchange with D-enriched groundwaters introduced after the phases crystallized. 

Figure 13. D/H and water contents of apatite grains from martian meteorite QUE94201 after Leshin (2000). The data are interpreted to represent a mixture of two end members, and most plausibly represent addition (or exchange) of water with an atmospheric D/H signature (5D +4000 %o) to minerals which initially uniformly contained water with 5D of 90ftt250 %o, or approximately twice the D/H value cotmnonly assumed for magmatic water on Mars. The curve shows the mixing model from which the initial D/H of the minerals was calculated.

Figure 6. Oxygen and hydrogen isotope values of end-member vent flnids. The seawater-basalt reaction vector indicates calculated fluid evolution to decreasing water/rock mass ratios (Shanks et al. 1995). Most of these data follow the reaction vector within AD error of 1.5%o. Exceptions are the Mid-Atlantic Ridge samples, which have quite high AD values, and very low-chloride samples from fast spreading ridges, which are influenced by phase separation or magmatic water (see text).

Direct addition of magmatic water to the 9-10°N vent fluids seems unlikely because... 

Controversy arises over magmatic water, especially in MOR basaltic systems. Shanks et al. (1995) discovered vent fluids from the 1991 eruption area at 9°45-52 N on... 

Goff F, McMurtiy GM (2000) Tritium and stable isotopes of magmatic waters. J Volcanol Geotherm Res 97 347-396... 

Meteoric water Magmatic water Metamorphic water... 

Plot of 5D vs 5 0 diagram for difTerent water types, The fields of magmatic water and formation waters are taken from. Taylor (1974). The field for igneous hornblendes and biotites from Taylor (1974) and that of magmadc water from the granites of Cornwall firom Sheppard (1977). The meteoric water line is from Epstein et al, (1965) and Epstein (1970). The metamorphlc water field combines the values of Taylor (1974) and Sheppard (1981). 

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