Helium in groundwater

Answer 14.3 The maximum helium concentration expectable in newly recharged water is read from the curve in Fig. 13.1 to be 5 x 10-8 cc STP/cc water. Excesses over this concentration are of radiogenic helium. In groundwaters that have an age of over 10,000 years, this excess is significant. 

Fig. 10-7. Distribution of dissolved helium in groundwaters, Edgemont uranium district, South Dakota (from Bowles ct al., 1980).

Fig. 10-9. Frequency distribution of helium in groundwater, Yccrlirric area. Western Australia (A) data from stock wells, bores and shallow drill holes (n=70) and (B) data from slotted, cased stratigraphic bore holes (n=50) (from Butt and Gole, 1986).

Bulashevich, Y.P., Bashorin, V.N., Druzhinin, V.S. and Rybalka, V.M., 1973. Helium in groundwater along the Sverdlovsk deep seismic sounding traverse. Dokl. Akad. Nauk SSSR, 208 15-18. 

Clarke, W.B. and Kugler, G., 1973. Dissolved helium in groundwater a possible method for uranium and thorium prospecting. Econ. Geol., 68 243-251. 

Datta, P.S., Gupta, S.K., Jayasurya, A., Nuampurkar, V.N., Sharma, P. and Plusnin, M.I., 1980. A survey of helium in groundwater in parts of the Sabarmarti basin in Gujarat State and in the Jaisalmer district, Rajasthan. Hydrol. Sci. Bull., 26 183-193. 

Holland, P.W. and Emerson, D.E., 1979. Helium in groundwater and soil gas in the vicinity of Bush Dome Reservoir, Cliffside Field, Potter County, Texas. US Bureau Mines Inf Circ. No. 8807, 22... 

Torgersen T, Drenkard S, Farley K, Schlosser P, Shapiro A (1994) Mantle helium in groundwater of the Mirror Lake Basin, New Hampshire, USA. In Noble gas geochemistry and cosmochemistiy. Matsuda J (ed) Terra, Tokyo, p 279-292... 

Torgersen, T., Clarke, W. B. (1985) Helium accumulation in groundwater, I An evaluation of sources and the continental flux of crustal 4He in the Great Altesian Basin, Australia. Geochim. Cosmochim. Acta, 49, 1211-18. 

These assumptions are discussed in the following sections. Examples of helium concentrations in groundwaters of the world are given in Table 14.1. 

Case Studies and Observed Trends in the Distribution of Helium Concentrations in Groundwater Systems... 

Helium-rich groundwaters are as a rule encountered only in confined systems situated deep below sea level, an observation that in itself indicates that one is dealing with stagnant systems (section 2.13). Examples, included in Table 14.1 (from Mazor and Bosch, 1992a), are... 

Helium can be reliably measured in waters with an age of 104 years, but the age of groundwaters varies widely and may reach 108 years. Thus the measurable helium concentrations in groundwater may vary over four orders of magnitude due to differing ages therefore, helium concentration data are the most variable parameter of the age equation. 

Water has a high helium dissolution capacity, and groundwaters in nature contain helium in a concentration range spanning over five orders of magnitude, as seen in Table 14.1. In all these cases the partial helium pressure in the aquifers was orders of magnitude below the hydrostatic pressure, not to mention the lithostatic pressure, ensuring no gas losses took place. 

The accumulation of radiogenic helium in confined groundwaters is mainly determined by the duration of water entrapment. Applying the data available on uranium and thorium concentrations in the host rocks and rock water ratios, reliable, though semiquantitative, dating is possible in the range of 104 10s years. 

Answer 14.4 There are two basic arguments (1) in most rocks the helium age is found to be significantly lower than the corresponding age defined by all other isotopic methods, indicating much of the radiogenic helium left the rock and (2) as the partial pressure of helium in the rock crystals increases with age, the amount expelled increases as well, until a steady state is reached at which the newly produced helium is fully balanced by the helium expelled into the associated groundwater. 

State M., Sonntag C., Deak J., and Schlosser P. (1992) Helium in deep circulating groundwater in the Great Hungarian Plain—flow dynamics and crustal and mantle hehum fluxes. Geochim. Cosmochim. Acta 56, 2051 —2067. 

Helium-4. This isotope is also commonly found in excess to ASW concentrations in groundwater excesses are typically higher in older than in younger groundwaters. Unlike He excesses, " He result directly from radioactive decay of... 

He/ He ratio. The measurement of the He/ He ratio (R) in groundwaters is particularly important, because it reflects the relative importance of crustal (radiogenic/nucleogenic) and mantle helium sources. Typical crustal rock He/ He production ratios have been estimated... 

Torgersen T. and Ivey G. N. (1985) Helium accumulation in groundwater II. A model for the accumulation of the crustal... 

Reimer, G.M., Bowles, C.G., Murray, D.G. and Been, J.M., 1979a. Helium in soil-gas and hclium/radon in groundwater in the vicinity of a south Texas uranium roll-type deposit. US Geol. Survey, Open File Report, 79-1625, 10pp. 

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