Identifying low-temperature hydrothermal karst and palaeowaters using stable isotopes: a case study from an alpine cave,Entrische Kirche,Austria |
| |
| Authors: | Christoph Spötl Yuri Dublyansky Michael Meyer Augusto Mangini |
| |
| Institution: | 1.Institut für Geologie und Pal?ontologie,Universit?t Innsbruck,Innsbruck,Austria;2.Forschungsstelle Radiometrie,Heidelberger Akademie der Wissenschaften,Heidelberg,Germany |
| |
| Abstract: | The area south of the prominent east–west trending Salzach Valley at the northern rim of the Central Alps of Austria has long
been known to host anomalously warm springs emerging from a highly deformed calcite marble (Klammkalk). This unit also hosts
cavities whose shapes suggest a hydrothermal karst origin and which are lined by calcite spar. We report here petrographic
and isotopic evidence suggesting that dissolution by ascending low-temperature thermal waters also played an important role
in the origin of a large cave in this region, Entrische Kirche. A paleo cave wall, preserved behind a thick flowstone in the
interior of this cave, revealed a brownish bleaching zone which contrasts to the medium grey colour of the unaltered marble
beneath. Across this zone the C and O isotope values gradually decrease by 3 and 11‰, respectively. These compositions are
very different from those of the speleothem above but are similar to phreatic calcite spar from hydrothermal karst cavities
in other outcrops in the area, where the absence of two-phase fluid inclusions suggests a low-temperature (less than ca. 50°C)
hydrothermal origin. U/Th dating of the flowstone capping the alteration zone yielded a minimum age of the thermal water invasion
in Entrische Kirche of ca. 240 kyr. There is no evidence in Entrische Kirche that these palaeowaters reached the point of
calcite precipitation, but it is physically conceivable that higher and as yet unexplored parts of this deep (ca. 900 m) cave
contain cavities lined by phreatic cave spar. |
| |
| Keywords: | Hydrothermal karst Stable isotopes Cave Water/rock interaction Austria |
| 本文献已被 SpringerLink 等数据库收录！ |
|
