Ana Radosavljević-Mihajlović

Preparation of Porous Silica Ceramics Using the Wood Template

Porous silica (SiO2) ceramic with a wood-like structure was prepared by wet impregnation tetraethyl orthosilicate (TEOS) into biological template that was derived from linden wood (tilia amurensis). After repeated pressure impregnation the subsequent annealing in air atmosphere at 800°C resulted in burn out of the template and consolidation of the oxide layers. The products exhibit structures corresponding to negative replication of biological templates. X-ray diffraction (XRD), scanning electron microscopy (SEM), infra red (IR), and Brunauer Emmett Teller (BET) measurements were employed to characterize the phases and crystal structure of biomorphic ceramics. It was found that the bio-organic structure was converted into oxide ceramics (SiO2). At low temperature (800°C), pore radius varied between 2 and 10 nm indicating that the samples were mostly mesoporous. Samples treated at higher temperature (1300°C) lost the mesoporous character; however, they were still porous having the microstructural features of the biological perform.

Polymetallic mineralization of the Boranja orefield, Podrinje Metallogenic District, Serbia: zonality, mineral associations and genetic features

In the Serbo-Macedonian Metallogenetic Province, which is a part of the Alpine metallogenic unit, the ore deposits lie in number geotectonic units; they embrace part of the Vardar Zone, Serbo-Macedonian massif, and a small part of the Dinarides. This metallogenic province has been delineated mostly by reference to the Neogene metallogeny, related predominantly to granodiorite magma. These deposits include the most significant Pb-Zn and Sb deposits in Serbia, as well as smaller Bi, Mo, Cu, Fe, Sn, Au and minor U, W and Hg deposits. The Podrinje Metallogenic District belongs to the Serbo-Macedonian Metallogenetic Province. Smaller metallogenic provinces are isolated within the scope of the following orefields: Cer (Northwest Serbia), Boranja (West Serbia), and Srebrenica (East Bosnia & Herzegovina). Polymetallic deposits in the Boranja orefield are genetically related to the emplacement of a Tertiary granodiorite complex. It consists primarily of a large number of sulfide deposits with Pb-Zn, and Sb; with subordinate Cu, As, Bi and Ag. Among them, the presence of small magnetite deposits, connected to the pyrometasomatic (skarn) stage is significant. Skarns are of calcic type, and were formed along contacts of Triassic limestones and quartz diorites. Ore minerals are similar among the various types of orebodies in the Boranja orefield and consist of sulfides (pyrrhotite, pyrite, marcasite, chalcopyrrhotite, chalcopyrite, cubanite, mackinawite, valleriite, covelline, chalcocite, bismuthinite, molybdenite, sphalerite, mercurian sphalerite, greenockite, galena, arsenopyrite, stibnite, duranusite, realgar, orpiment, cinnabar, metacinnabar); sulfosalts (bursaite, cannizzarite, cosalite, aikinite, ustarasite, tetradymite, ferrian tetrahedrite, argentian tetrahedrite, pyrargyrite, diaphorite, freieslebenite, schirmerite, fizelyite, stannite, jamesonite, boulangerite, bournonite, As-bournonite, falkmanite, zinkenite, fuloppite, robinsonite, plagionite, twinnite, geocronite, gratonite); telluride (calaverite); native metals and alloys (gold, silver, electrum, bismuth, arsenic); oxides and complex-oxides (magnetite, hematite, rutile, anatase, scheelite, powellite, valentinite, senarmontite, kermesite, adamite, arsenolite); and gangue minerals (silicates, carbonates, fluorite, calcite, siderite, Mn-Zn siderite, fluorite, apatite, barite, dolomite, anglesite, cerussite, smithsonite, otavite, malachite, azurite, scorodite, quartz, limonite, organic matter). Minerals of the titled orefield were formed in several successive stages, which together correspond to a unique cycle of mineralization that is genetically related to the subvulcanic-plutonic intrusion of the Neogene-aged magmatic Boranja complex. Mineral associations, which have spatial-zonal arrangement, are rhythmically developed from the Tertiary granodiorite of Boranja to outside surroundings: A) Fe-Cu(Bi) belt → B) Pb(Ag)-Zn belt → C) Sb(As) belt → D) CaF 2 (Pb-Zn) belt.

Mineralogy and genetic characteristics of the Rudnik Pb-Zn/Cu,Ag,Bi,W polymetallic deposit (Central Serbia) - New occurrence of Pb(Ag)Bi sulfosalts

The mineral aschamalmite, of heyrovskyite-like composition, but different in structure, from the Rudnik Pb–Zn/Cu,Ag,Bi,W polymetallic deposit in the central part of Serbia has been investigated. This polymetallic deposit includes over 90 hydrothermal and skarn-replacement orebody types, primarily hosted by Cretaceous sediments and occassionally by Oligocene dykes and sills of dacitic composition, and contact-metamorphic-metasomatic rocks. These rocks are host to an assemblage of pyrrhotite, colloform pyrite, chalcopyrite, galena, arsenopyrite, native bismuth and scheelite as well as minor pyrite, sphalerite, bismuthinite, argentopentlandite, and native silver. The chemical composition of the ore is very complex, where weight contents of valuable metals range as follows (%): Zn 0.49–4.49; Pb 0.90–5.66; Cu 0.08–2.18; WO 3 0.05–1.18; Ag 0.005–0.030; Bi 0.005–0.081; and Cd 0.002–0.016. In reflected light, aschamalmite is optically anisotropic, with moderately high bireflectance ranging from slightly greenish to slightly gray. Electron-microprobe analysis gave an average crystallochemical formulae of (Pb 5.82 Ag 0.20 ) Σ6.02 Bi 2.03 (S 8.93 Te 0.02 Se 0.01 ) Σ8.96 . The strongest diffraction maximums of the X-ray powder pattern [ d (in A)(I)] are 3.419(100), 3.382(92), and 3.334(66). Monoclinic unit cell parameters are a =13.727(7); b =4.122(3); c =31.32(2) A; β =90.72(5) o ; and V =1771.8(1) A 3 . Mineral assemblages and genesis of the Rudnik polymetallic deposit are discussed in detail and the sulfobismuthite mineralization has been compared with similar well-known global deposits.

Mineraloška i kristalohemijska svojstva minerala HEU-tipa iz ležišta zeolitskih tufova Srbije

The results of perennial research of several Serbian zeolitic tuffs enriched with HEU-type minerals are presented in this paper. There are several recognized zeolitic tuff deposits containing HEU-type minerals: Zlatokop, Igros, Beocin, Toponica, Slanci, but their comparative mineralogical and crystallochemical features have not been studied in detail so far. These zeolitic tuff deposits are spatially and genetically connected to volcanic and pyroclastic rocks of marine and lake environments of Senonian and Eocene, and Neogene age, respectively. As a result of devitrification and diagenesis process of volcanic glass within zeolitic tuffs hypocrystalline porphiry and vitroclastic textures occur. The studied zeolitic tuffs are mainly composed of heulandite occuring in a form of needle- to plate-like crystals of 0,1 do 100 μm in length, associated with other silicates. Depending on the type and content of exchangeable cations as well as the thermal stability of these raw materials, 24 clinoptilolite-Ca and heulandite-Ca can be distinguished. The values of cation exchange capacity and surface area capacity range from 96 to 166 meq/100 g, and from 8,0 to 10,5 meq/100 g, respectively. HEU-type minerals can be distinguished either by a Si/Al ratio or arrangement of extra framework cations within the crystal structure of these minerals. [Projekat Ministarstva nauke Republike Srbije, br. TR 34013: Osvajanje tehnoloskih postupaka dobijanja ekoloskih materijala na bazi nemetalicnih mineralnih sirovina i br. 45012: Sinteza, procesiranje i karakterizacija nano strukturnih materijala za primenu u oblasti energije, mehanickog inţenjerstva, zastite životne sredine i biomedicine]

SREBRENICA OREFIELD, PODRINJE METALLOGENIC DISTRICT, REPUBLIC OF SRPSKA, B&H: HYDRATED Fe(Al)-PHOSPHATES AND THEIR PARAGENESES WITHIN THE Pb-Zn MINERALIZATION

The Srebrenica orefield is mostly composed of Tertiary dacite-andesites, and quartz latites, pyroclastites, Paleozoic schists, and Quaternary sediments, but in a in a lesser extent. The latest research showed that in the Srebrenica orefield occur complex mineral parageneses and associations deposited in pneumatolytic-hydrothermal and hydrothermal (from high- to low-temperature) stage, accompanied with very rare minerals. Beside ore mineral parageneses and associations, specials emphasis was on rare hydrated phosphates: vivianite, ludlamite, and vauxite. It is important to say that vauxite from the Srebrenica orefield is fourth discovery in the world. The minerals above were studied using DTA-TGA, IR-spectroscopy, and XRPD.