Mineralni sastav zemljišta razvijenog na vulkanitima Fruške Gore (Srbija)

The purpoose of this work was to study mineral composition of soil developed on quartz-latite and its tuffs over the ridge of Fruška Gora, near Rakovac. The samples are collected from an area that marks eutric-cambisol-'gajnjača' in pedological map of Vojvodina in scale 1: 50 000. After collection the samples were air-dried and sieved to pass a 2 mm sieve and were used for further laboratory analyses. Soil reaction was determined in water, 1M NaF and M KC1 suspensions. Phosphate retention is analyzed as well as a selective dissolution of Al, Fe and Si after acid ammonium oxalate and Na-pirophosphate treatments. Mineral composition of total soil was determined by use of the X-ray diffraction (XRD) analysis of powder specimens, and volcanic glass content was determined by Zeiss polarised light microscope. Clay minerals in the fraction lt 0,002mm were determined by XRD methods by means of SIMENS 2 kW diffractometer. Fresh volcanic rock comprises of zonal plagioclase, quartz, hornblende and minor amounbts of monoclinic yroxene and biotite, which are present either as phenocrystals or as cryptoi-crystals in ground mass of dark volcanic glassa, and are associated with apatite and opaque (ore) minerals. All feromagnesian minerals are strongly altered to chlorite and calcite. Clay fraction of the soil comprizes of kaolinite/halloysite, illite and chlorite, and some amorphpus minerals and minor amounts of quartz and feldspars. The soil has shown the phosphate retention between 23.6 and 34.5%, and Si, Al and Fe extracted in ammonium-oxalate and oxalic acid, have shown moderate content of allophane of about 14% and very low ferrihydrite. The Alox + 1/2 Feox content varies between 0.90 do 1.08%, what for the soil developed on quarz latite classifies in to vitric-andisol.U radu su prikazani rezultati proučavanja mineralnog sastava zemljišta razvijenog na kvarc-latitu i njegovim tufovima na grebenu Fruške Gore, kod Rakovca. Uzorci su sakupljeni sa područja obeleženom kao gajnjača na pedološkoj karti Vojvodine u razmeri 1:50 000. Posle uzorkovanja uzorci su osušeni na vazduhu i propušteni kroz sito od 2mm. Reakcija zemljišta je određena u vodi, u 1M NaF i 1M KC1 suspenziji. Retencija fosfata i selektivno rastvaranje Al, Fe i Si iz amorfnih mineralnih materija izvršeno je pomoću kiselog amonijum oksalata i Na-pirofosfata. Mineralogija ukupnog uzorka određena je pomoću polarizacionog mikroskopa i rendgen-difrakcione analize (XRD). Minerali frakcije gline su određeni pomoću XRD koristeći SIMENS 2 kW difractometar. Sveža vulkanska stena sastoji se od zonarnog plagioklasa, kvarca, hornblende kao i manjih količina monokliničnog piroksena i biotita, koji se nalaze u obliku feno- i kripto-kristala u osnovnoj masi tamnog vulkanskog stakla, a u asocijaciji sa apatitom i opakim (rudnim) mineralima. Svi feromagnezijski minerali su jako alterisani u hlorit i kalcit. Fraciju gline zemljišta čine kaolinit/halojzit, ilit, i hlorit, zatim amorfni minerali i manje količine kvarca i feldspata. Zemljište je pokazalo varijaciju retencije fosfata između 23.6 i 34.5%, a ekstrahovani Si, Al i Fe u NH4-oksalatu-oksalnoj kiselini, pokazali su umerene sadržaje alofana oko 14% i niske sadržaje ferihidrita. Sadržaj Alox + 1/2 Feox varira od 0.90 do 1.08%, što zemljište razvijeno na kvarc-latitu svrstava u vitrični-andosol