In the past few years the systematic study of caves intercepted by mine workings in Southwest Sardinia has allowed to observe rare speleogenetic and minerogenetic processes, that have lead to the development of absolutely peculiar dissolution karst forms and/or secondary mineral associations. The most recent new corrosion forms have been discovered inside one of these mine caves, Santa Barbara 2 (Iglesias), characterised by a huge natural void which walls and roof are entirely covered with a thick layer of cave clouds. A large portion of these speleothems has been intensely corroded in both vadose and phreatic environments by acid waters derived from the oxidation of poly-sulphides abundantly present in the host rock. Many extremely well developed bubble trails have been observed in a lower and lateral part of the cave, also showing the presence of circular holes along their course and sometimes at the start of the trail. The morphological analysis has allowed to ascertain that these holes are perfectly rounded with mouth diameters of 10-15 cm and that they develop orthogonally respect to the cave cloud’s structure, slowly decreasing their diameter with depth. The inner walls of these conical holes present well marked grooves perpendicular to the direction of the tube elongation. These holes absolutely aren’t condensational convection cupolas but are curious vents from which the acid fluids, derived from the oxidation of the sulphides present at the centre of many of the cave clouds, were released in the cave environment. The conditions necessary for the formation of these particular corrosion forms, for the first time described herein, can be summarised as follows: 1-presence of metallic sulphides; 2- oxidation episodes; 3- the fluids derived from oxidation processes cannot degas in their place of formation; 4- few and narrow pathways across the thick phreatic speleothems reaching the cave void; 5- epiphreatic conditions of the cave with possibility for gas bubbles to develop.

A new hypogean karst form: the oxidation vent / De Waele J.; Forti P.. - STAMPA. - (2006), pp. 107-127.

A new hypogean karst form: the oxidation vent.

DE WAELE, JO HILAIRE AGNES;FORTI, PAOLO
2006

Abstract

In the past few years the systematic study of caves intercepted by mine workings in Southwest Sardinia has allowed to observe rare speleogenetic and minerogenetic processes, that have lead to the development of absolutely peculiar dissolution karst forms and/or secondary mineral associations. The most recent new corrosion forms have been discovered inside one of these mine caves, Santa Barbara 2 (Iglesias), characterised by a huge natural void which walls and roof are entirely covered with a thick layer of cave clouds. A large portion of these speleothems has been intensely corroded in both vadose and phreatic environments by acid waters derived from the oxidation of poly-sulphides abundantly present in the host rock. Many extremely well developed bubble trails have been observed in a lower and lateral part of the cave, also showing the presence of circular holes along their course and sometimes at the start of the trail. The morphological analysis has allowed to ascertain that these holes are perfectly rounded with mouth diameters of 10-15 cm and that they develop orthogonally respect to the cave cloud’s structure, slowly decreasing their diameter with depth. The inner walls of these conical holes present well marked grooves perpendicular to the direction of the tube elongation. These holes absolutely aren’t condensational convection cupolas but are curious vents from which the acid fluids, derived from the oxidation of the sulphides present at the centre of many of the cave clouds, were released in the cave environment. The conditions necessary for the formation of these particular corrosion forms, for the first time described herein, can be summarised as follows: 1-presence of metallic sulphides; 2- oxidation episodes; 3- the fluids derived from oxidation processes cannot degas in their place of formation; 4- few and narrow pathways across the thick phreatic speleothems reaching the cave void; 5- epiphreatic conditions of the cave with possibility for gas bubbles to develop.
2006
Zeitschrift für Geomorphologie, Supplementbände volume 147 Karst Sheets 18 - 21 International Atlas of Karst Phenomena Union Internationale de Spéléologie International Association of Geomorphologists 6th International Conference, Zaragoza 2005 - Karst papers
107
127
A new hypogean karst form: the oxidation vent / De Waele J.; Forti P.. - STAMPA. - (2006), pp. 107-127.
De Waele J.; Forti P.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/33841
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