Mineraological and geochemical properties of bauxite in "Mamutovac Ia" deposit

Provedbom istražno-geološkog bušenja na ležištu boksita „Mamutovac Ia“ dobivena je bušotinska jezgra boksita duljine 25 metara. S ciljem ispitivanja geokemijskog i mineraloškog sastava bušotinske jezgre te njegove promjene s dubinom, detaljnije su se analizirala 42 uzorka. Difrakcijom rendgenskih zraka na prahu (XRPD) utvrđeno je kako su glavne mineralne faze u boksitu böhmit, gibbsit, hematit i anatas te da se uz njih pojavljuju faze kaolinita, goethita i rutila. Kombinacijom emisijske i masene spektrometrije s induktivno spregnutom plazmom (ICP-ES/MS) izmjereno je da značajni udio kemijskog sastava čine Al2O3, Fe2O3, SiO2 i TiO2 te da uzorci sadrže koncentracije REE (351,84-812,85 ppm). Iako su koncentracije REE uglavnom povišene u dubljim dijelovima jezgre, primijećeno je kako duž jezgre dolazi do značajne frakcionacije REE. Rezultati mjerenja magnetskog susceptibiliteta (MS) ukazuju na prisutnost superparamagnetičnih minerala u gornjim intervalima jezgre. Dodatne interpretacije i klasifikacije pokazale su ujednačenost jezgre te okarakterizirale glavninu uzoraka kao boksite nastale jakom laterizacijom bazičnih, mafičnih stijena.In order to determine geochemical and mineralogical properties of bauxite deposit “Mamutovac Ia”, along with their distribution pattern, 25 meters-long core was obtained by geological exploration drilling. Subsequently, 42 samples were collected from different parts of the drilling core. The X-ray powder diffraction analysis (XRPD) pattern indicated presence of boehmite, gibbsite, hematite and anatase as main mineral phases and presence of kaolinite, goethite and rutile as additional mineral phases. Results of geochemical analysis obtained by inductively coupled plasma emission/mass spectrometry (ICP-ES/MS) indicated that majority of geochemical content are composed of Al2O3, Fe2O3, SiO2 and TiO2. Also, geochemical analysis indicated significant content of REE (351,84-812,85 ppm). In spite of general enrichment of REE in lower parts of core, significant fractionation of REE along the core was observed. Magnetic susceptibility measurements (MS) determined presence of superparamagnetic minerals in upper part of bauxite core. Common classifications showed consistence of the core and characterized majority of samples as bauxites originated from basic, mafic precursors which underwent strong laterization