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| Titel |
Tamarugite from Diana Cave (SW Romania) -first true karst occurrence |
| VerfasserIn |
C. M. Pușcaș, B. P. Onac, H. S. Effenberger, I. Povara |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063206
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| Zusammenfassung |
| Diana Cave is located within the town limits of BÄăile Herculane (SW Romania) and develops
as a 14 m long, westward oriented, unique passage guided by the Diana fault [1]. At the far
end of the cave, the thermo-mineral Diana Spring wells forth. In the early 1970s a mine
gallery that intersected the cave was created to drain the water into a pumping station and the
original cave passage was somewhat altered and reinforced with concrete. Today the concrete
and the silty limestone cave walls are heavily corroded by H2SO4 outgassing from the hot
water (ca. 50ºC) and display abundant gypsum crusts, soggy aggregates of native S, and a
variety of more exotic sulfates. Among them, a mineral that has been previously
identified in caves only in connection to volcanic activity, either as thermal springs or
fumaroles [2]: tamarugite [NaAl(SO4)26H2O]. It was [3] that first mentioned the
occurrence of this Na and Al sulfate in Diana Cave, our research aiming to give a
detailed description of this mineral, its paragenesis, and mechanisms of precipitation.
Recently, tamarugite has also been identified in a sulfuric acid cave from Greece
[4].
Along with powder X-ray diffractions coupled with Rietveld refinement, scanning
electron microscope, and electron probe micro-analysis, δ18O and δ34S compositions of the
sulfate mineral as well as precipitates from the water were analyzed to identify and
better constrain the genesis of this rare sulfate. Regrettably, the crystal size of our
specimens is inappropriate for identification by means of single crystal X-ray diffraction.
Physical and chemical parameters of Diana Spring were as well measured on several
occasions.
Geochemical analysis suggests that the minute, white tamarugite flakes precipitated in
Diana Cave as a result of the interactions between the thermo-mineral water or
water vapor and the original limestone bedrock and concrete that blankets the mine
gallery.
[1] PovarÄă, I., Diaconu, G., Goran, C. (1972). Observations préliminaires sur les grottes
influencées par les eaux thermo-minérales de la zone BÄăile-Herculane. Trav. Inst. Speol.
“Emile Racovitza”, XI, 355-365.
[2] Rodgers, K.A., Hamlin, K.A., Browne, P.R.L., Campbell, K.A., Martin, R.
(2000). The steam condensate alteration mineralogy of Ruatapu cave, Orakei Korako
geothermal field, Taupo Volcanic Zone, New Zealand. Mineralogical magazine, 64(1),
125-142.
[3] Onac, B.P., Sumrall, J., TÄăma?¸ T., PovarÄă, I., Kerns, J., D-rmiceanu, V.,
Vere?¸ D., Lascu, C. (2009). The relationship between cave minerals and H2S-rich
thermal waters along the Cerna Valley (SW Romania). Acta Carsologica, 38(1),
27–39.
[4] Lazaridis G, Melfos, V, Papadopoulou L (2011). The first cave occurrence of orpiment
(As2S3) from the sulfuric acid caves of Aghia Paraskevi (Kassandra Peninsula, N. Greece).
International Journal of Speleology, 40(2): 133-139. |
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