The Montecchio cave (254 T/GR, close to Saturnia, Grosseto province) opens at 320 m asl, in a small outcrop of Calcare Massiccio, close to the Albegna river. Although known since a long time, there are no speleogenetical studies on this very special cave. This cave, with a development of over 1700 m, is characterised by the presence of the thermal aquifer at a depth of 100 m below the entrance. The water has a temperature of over 30°C and high sulphate content. The cave can thus be considered an active hypogenic system. The cave hosts large gypsum deposits, starting from 40 m below the entrance. This gypsum derives from the reaction between sulphuric acid and the carbonate hostrock. This process, that occurs in the vadose (oxygen rich) environment, has created a set of typical morphologies such as replacement pockets and bubble trails. The lower part of the cave hosts calcite cave raft deposits over 1 m thick, evidence of standing, probably thermal, water pools in strongly evaporative areas related to strong air currents. Eleven samples of weathering products have been sampled and analysed at the X-ray diffractometer and investigated under SEM/EDAX. These mineralogical analyses have identified residual minerals (quartz, feldspar), some oxides and hydroxides (hematite, goethite and boehmite), but especially weathering products such as chlorite and illite. The products of acid weathering are particularly interesting, like those derived from calcite (gypsum) and from clays (alunite, jarosite and caolinite). These minerals are strictly related to the speleogenesis of the cave, having formed by the interaction between the host rock and the sulphuric vapors rising from the thermal aquifer.
De Waele Jo, Galli Ermanno, Piccini Leonardo, Rossi Antonio (2013). Descrizione morfologica e mineralogica della grotta ipogenica sulfurea di Montecchio (Grosseto, Toscana).. Trieste : Edizioni Università di Trieste e Società Alpina delle Giulie.
Descrizione morfologica e mineralogica della grotta ipogenica sulfurea di Montecchio (Grosseto, Toscana).
DE WAELE, JO HILAIRE AGNES;
2013
Abstract
The Montecchio cave (254 T/GR, close to Saturnia, Grosseto province) opens at 320 m asl, in a small outcrop of Calcare Massiccio, close to the Albegna river. Although known since a long time, there are no speleogenetical studies on this very special cave. This cave, with a development of over 1700 m, is characterised by the presence of the thermal aquifer at a depth of 100 m below the entrance. The water has a temperature of over 30°C and high sulphate content. The cave can thus be considered an active hypogenic system. The cave hosts large gypsum deposits, starting from 40 m below the entrance. This gypsum derives from the reaction between sulphuric acid and the carbonate hostrock. This process, that occurs in the vadose (oxygen rich) environment, has created a set of typical morphologies such as replacement pockets and bubble trails. The lower part of the cave hosts calcite cave raft deposits over 1 m thick, evidence of standing, probably thermal, water pools in strongly evaporative areas related to strong air currents. Eleven samples of weathering products have been sampled and analysed at the X-ray diffractometer and investigated under SEM/EDAX. These mineralogical analyses have identified residual minerals (quartz, feldspar), some oxides and hydroxides (hematite, goethite and boehmite), but especially weathering products such as chlorite and illite. The products of acid weathering are particularly interesting, like those derived from calcite (gypsum) and from clays (alunite, jarosite and caolinite). These minerals are strictly related to the speleogenesis of the cave, having formed by the interaction between the host rock and the sulphuric vapors rising from the thermal aquifer.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
