Hydrogeothermal Conditions in Ãire - Geological Survey of Ireland

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- 16 -III ORIGIN AND FUNCTIONINGAs yet, the data presented and analysed in the foregoing itemof this paper is too slight to allow of any firm hypothesis to beadvanced as to the origin and functioning of the warm springs of Ireland.However, some ideas have been formulated and are put forward fordiscussion here.III-I.Palaeozoic Thermal Springs and MineralizationOver the past two decades, the ability of thermal springs, oftenof brines, to leach and deposit metalliferous elements and form oredeposits has received renewed attention and confirmation, as in the Red Seainvestigations. Such an origin has been postulated for the Irish basemetal deposits found and exploited in the Lower Carboniferous of Ireland,as Williams & McArdle (1978) and Russell (J978).The latter postulated infiltration of sea water of thetransgressive Tournaisian seas into the great thickness of underlying LowerPalaeozoic sediments. In these the waters circulated under thermal forces,leaching out lead, zinc, copper and sulphur, and deposited them in thelimestone sediments forming on the bed of the sea. Russell's diagramrepresenting these events is reproduced here as Fig. 6.Since then, much heat has flowed out of the crust, and there canbe no possibility of such past thermal circulation of groundwaterinfluencing the supply of warm water to certain springs in Ireland. Butit seemed desirable to include this hypothesis of past circulation of warm/hot brines through the rocks which underlie the Dinantian limestones ofIreland, and from which the present day warm springs issue.III~2.Present-Day Circulation of Warm GroundwaterIt is thought that the present day groundwater circulation feedingwarm water to certain springs is due to the effects of a heat source orsources which has modified the normal groundwater circulation of the regionon the main warm springs of Leinster, and possibly those of Cos. Limerickand Clare. Mallow would be an exception, as usual.Fig. 7 sets out the manner in which hydrotherrr01 cells areconsidered to function. The idea is often applied to low-temperaturecirculation of groundwater, as in Facca's (1973) diagram of the basic modelof a low temperature hot water field. The cells are some 8 kilometres indiameter. Main infiltration occurs in lows (from streams ?) whiledischarge is on highs. These are based on location features. The springsform part of the hydrological cycle, with winter infiltration resulting inincreased yields (or higher groundwater levels) in spring. Some of thesprings dry-up in summer/autumn. This concept should become more definiteas actual discharges are gauged and related to the precipitation andinfiltration./ ...
FIGURE 7 - POSSIBLE PRESENT~DAY GROUNDWATE8 CIRCULATION FEEDING THE LEINSTER GROUP OF WARM SPRINGS~ HALF - CELLII.,.......II8 KILOMETER DIAMETER CELL ~ HALF-CELL>,Warm Spring I IMain Infilt-! Warm Spring I Warm Spring I.t , ration Zone ~ I'~ I _"~I~. '. I~~ ~f I ~-f\;----""'""I:, .........t ~ J' t. .AI fA' l'" ~~, oJ. ,tV" -/~-~ "')\ 11'~+-. V' \J-i'JIJ"' It »-ooV .::Jr 1~ It " .1- ~ ~ ~.. l' \ ¥t '" t~ It M ~ '-'_1, I ;f/\ ~ 'b -¥ ~ 4:'" ~ '\ 1.~ ~~ "v ~ I ~ ,.,\ . 1 ~. . i- --.L • ~ 1-1 ~. if . .-)I tv ., ~r ,'-11\ ~.)"::J ~~'_'*- 1- ';-:a .It: ~/. ~ -:} 6f ·1-.... ~ .,., . ~ ~ -'71,.. Jt -(, l' A\'\ V,'. . ... 11\ ~\~ ~ .\ .1- . .. IJ,I Downward Flow ofl ~ A+ 1PorOU5 Formation5 ~ ~permitting free ~ ~~ "' ~~ ~;t1Cold Water 'f ~~ c ~ ~Groundwater CircUlati~ ~ ."Upward F1 ow~ - _ ....... Ifof Warm Water )1-, Form of Geother-/f.. ........ mal Gradient.;:;,;:r.
Page 1 and 2: IIII1HXDROGEOTHERMAL CONDXTXONSIN E
Page 3 and 4: convection uprising of warm water i
Page 5 and 6: BallinalackNo .1011Hurler's .Cro~5N
Page 7 and 8: - 2 -Normal groundwater in Ireland
Page 9 and 10: - 3 -Ref. No.Name or NamesCounty100
Page 11 and 12: - 5 -II-l. LocationThe general loca
Page 13 and 14: - 7 -Thickness(m)Lithology+ 335 m+
Page 15 and 16: - 9 -Boreholes drilled for water, p
Page 17 and 18: IIII.JJJ.S 0 .No-- --~--f-22C:1. -
Page 19 and 20: - 12 -iSpring No. 2001 2001 2002 20
Page 21 and 22: - FIGURE 5 - TRACE ELEMENTS SILICON
Page 23 and 24: - 14 -Spring No. 2001 2001 2002 200
Page 25: M'ddl~Slo9~CrySlol\'n~ bos.m.ntor d
Page 29 and 30: - 18 -The effects of the varying th
Page 31 and 32: - 20 -CLAYTON, G. and HIGGS, K. (19

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Hydrogeothermal Conditions in Ãire - Geological Survey of Ireland