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    STUDIA GEOLOGIA - Issue no. 1 / 2001  
         
  Article:   NEW DATA ON THE VOLCANIC TUFF FROM PETREŞTII DE JOS (CLUJ DISTRICT).

Authors:  HOREA BEDELEAN, IOAN IVAN, DANA POP, IOAN BEDELEAN, GHEORGHE PLEŞOIU.
 
       
         
  Abstract:  New Data on the Volcanic Tuff from Petreştii de Jos (Cluj District). The present study was carried out on the cineritic interlayers from Petreştii de Jos (closed quarry from Indolului Valley), in order to present their detailed mineralogical-petrographical features. Previous work already noticed the similarity of this tuff level with Dej Tuff Complex in other areas. The studied outcrop consists of a compact volcanic tuff interlayered with marls and tuffaceous clays. The analytical investigations: chemical analyses, X-ray diffraction, IR spectroscopy and electron microscopy reveal the nature of the diagenetic transformations dominated by zeolitization. Besides clinoptilolite, which is the typical zeolite for Dej Tuff from the Transylvanian Depression, our investigation evidenced also the presence of phillipsite. The process was stepwise: during the primary, syngenetic stage K-clinoptilolite formed, while during the late epigenetic stage Ca-phillipsite crystallized; on behalf of the latter one, Ca-clinoptilolite was also generated. It is worth to mention that the highest amounts of zeolites are to be found in the basal horizon, while this amount decreases in the interlayers associated with the marly-clayey levels. From genetic point of view, the lower horizon in the outcrop represents a primary fall-out tuff. The thin interlayers within the upper horizons are resedimented tuffs. The tuff from Petreştii de Jos represents a cheap raw material located in the neighborhood of the industrial area of Turda town. For using it, only a more detailed research and the removal of the vegetal and soil layer on the top would be necessary.  
         
     
         
         
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