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| Titel |
Geological factors affecting the chemical characteristics of the thermal waters of the carbonate karstified aquifers of Northern Vietnam |
| VerfasserIn |
C. Drogue, N. N. Cat, J. Dazy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 4, no. 2 ; Nr. 4, no. 2, S.332-340 |
| Datensatznummer |
250001638
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| Publikation (Nr.) |
 copernicus.org/hess-4-332-2000.pdf |
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| Zusammenfassung |
| In northern Vietnam, exposed carbonate rock formations cover an area of more
than 50,000 km2 .Their accumulated thickness from the Cambrian to the Triassic
is in some places as much as 3000 m. Numerous thermal waters (springs and wells) occur in
these strongly karstified carbonate massifs. This is the result of significant ancient and
present orogenic activity, as the region demonstrates by its strong seismic activity. These
karstic formations are water-bearing and strongly recharged by rainfall of between 1600 mm
and 2000 mm per year in 90% of the area concerned. In view of the average annual air
temperatures (17°C-25°C according to the region), 23 sample springs or wells were
chosen with water temperatures of between 29°C and 68°C. Hydrochemical
characteristics of these thermal waters emerging in different carbonate-rock units were
examined by chemical analyses of major ions. In this large region, thermal waters are
divided into four hydrochemical types: the Na-Cl type resulting from the intrusion of
sea water for distances of up to several kilometres inland and depths of 1000 m, the
Ca-SO4 type, probably resulting from the leaching of deposits of metallic
sulphides that are widely distributed in these carbonate-rock units, and finally the
Ca-HCO3 and Mg-HCO3 types which are chemically similar to fresh
karstic waters in limestones and dolostones. The occurrence of these thermal groundwaters
as well as their chemical characteristics seem to indicate the existence of large-scale
deepseated groundwater flow systems in the karstic aquifers.
Keywords: Vietnam; thermal waters; karst; hydrochemistry |
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