Diatomaceous rocks of the Jawornik deposit (the Polish Outer Carpathians) - petrophysical and petrographical evaluatio

Abstract

Diatomites belonging to a list of raw materials used in the EU criticality assessment are essential to many industrial applications due to a unique combination of their physical properties, i.e. porous and permeable structure, high specific surface area and adsorption capacity, low density and thermal conductivity, and chemical inertness. The present study was undertaken to analyse the relationships between the pore network characteristics, petrophysical parameters, and mineralogical variability of the Lower Miocene diatomites from the Jawornik deposit (Skole Unit, the Polish Outer Carpathians, SE Poland). Five varieties of the diatomites, distinguished on the basis of the macroscopic features, i.e., colour and fracturing effects, have been investigated by SEM, chemical and XRD analysis, mercury intrusion porosimetry, helium pycnometry, and the Vickers hardness tests. Significantly differing are two varieties. The light-coloured, massive and block-forming diatomites (variety BL) consist mainly of poorly cemented siliceous skeletal remains of diatoms, and represent the rocks with high total porosity (38-43%), low bulk density (1.28-1.38 g/cm 3) and low microhardness (10.7 HV 0.3). The dark-gray silicified diatomites with a platy or prismatic splitting (variety PD) reveal obscured microfossils of diatoms and are the most compact and hard rocks (80.8 HV 0.3), with poor total porosity (17-24%) and higher bulk density (1.70-1.78 g/cm 3). The spatial distribution of the field identifiable rock varieties allows selective exploitation of the diatomites with the predictable petrophysical characteristics that define their future use.

The impact of calcination on changes in the physical and mechanical properties of the diatomites of the Leszczawka Member (the Outer Carpathians, Poland)

“…This rather obvious identifying feature, already mentioned by Kotlarczyk (1966), and rock colour have been accepted as the classification basis of the Leszczawka diatomites and permitted five lithological varieties to be distinguished (Figarska-Warchoł et al 2015): 1) light creamy diatomites with blocky disintegration (variety BL); 2) dark creamy, grey or dark grey diatomites with blocky disintegration (variety BD); 3) light creamy, dark creamy or light grey diatomites with platy or prismatic disintegration (variety PL); Kotlarczyk (1966Kotlarczyk ( , 1988b Figarska-Warchoł B., Rembiś M., Stańczak G. 4) dark grey diatomites with platy or prismatic disintegration (variety PD); 5) yellowish orange diatomites with nodular disintegration (variety N). The detailed lithological characteristics of these rock types were given by Figarska-Warchoł et al (2015). The major detrital component is represented by fragmented, less often complete frustules (Tab.…”

“…1). It is composed of silica of different ordering (opal-A and opal-CT) and clay minerals (illite, kaolinite and smectite) (Figarska-Warchoł et al 2015). The PD variety is characterized by the highest amorphous silica content of the groundmass (up to 35%) at a considerably lower content of clay minerals (ca.…”

“…Simultaneously, this variety contains only 9% of silica. The list of the groundmass components is completed with fragments of organic substances: 1-2% in the BL, PL and PD varieties and 4-5% in the BD and N ones (Figarska-Warchoł et al 2015).…”

“…1% (PD) to above 2% Na 2 O + K 2 O (PL), 1-5% Fe 2 O 3 (attributed to iron oxide/hydroxides) (with the variety N being an exception as it contains above 17% Fe 2 O 3 ) and ca. 7-10% LOI (attributed to the presence of an organic substance and to the water expelled from the hydrated forms of silica) (Figarska-Warchoł et al 2015).…”

“…The results showed that the diatomites from the eastern part of the Outer Polish Carpathians, despite being such unique rocks, have technological properties slightly inferior to those of their counterparts in other parts of the world (Fuya et al 1995, Aruntaş et al 1998, Hassan et al 1999, Abrantes et al 2007, Mohamedbakr & Burkitbaev 2009. More recent investigations of these rocks (Figarska-Warchoł et al 2015 focused on the relation between their petrographical development and physical and mechanical properties. The results of previous works have pointed out that the thermal treatment of diatomites from the Polish Carpathians is a promising method to improve some of their properties, which should pave the way for wider technological applications of these domestic raw materials.…”