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    STUDIA GEOLOGIA - Ediţia nr.3 din 2003  
         
  Articol:   THE GENESIS OF CALCITE RAFTS FROM CAVES – A POINT OF VIEW.

Autori:  IOSIF VIEHMANN, LUCREĆąIA GHERGARI.
 
       
         
  Rezumat:  The present work is a conclusion of our previous observations and experiments concerning the genesis of calcite rafts (Viehmann, 1992; Viehmann et al., 1997). The main raft deposit studied was discovered in 1987 in the Hoanca Apei Cave (Bihor Mountains, Romania). Our results were compared with the ones obtained by Black (1953) in Carlsbad Caverns (New Mexico, USA), Pomar et al. (1975) in Spain, and by Forti & Chiesi (1995) in Italy. The main resemblance consists in the growth manner of the rhombohedral calcite crystals: these are partially developed, growing only on the lower part of the raft, at the contact with water. This crystallogenetic mechanism conditions raft floating. The same conclusion was drawn by Pomar et al. in 1975. The second cause of calcite rafts floating on the surface of undisturbed cave waters is the per ascensum elevation of the water in the pool. The filling of the cave pool may be repeated several times, with the same calcite rafts floating at each filling. Another cause of raft floating is the network of skeletal crystals retaining small air bubbles. When calcite rafts become heavier, they sink in the pool and thicken the local sediment....  
         
     
         
         
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