The objective of this study is to describe the mineralogical composition and chemical properties of the Oraşu Nou bentonite, from northwestern Romania. For mineralogical determinations, the following were used: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FR-IR), thermogravimetric analysis, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The chemical compositions and physical properties of the bentonites and bentonitized rocks were also determined. Calcium type montmorillonite is the predominant mineral in this deposit. Its average mass fraction is between 35% and 75%, reaching up to 95%. A small amount of halloysite and very fine cristobalite were also identified in the fine fraction. Quartz, feldspar, and kaolinite were identified as impurities. The average pH of natural bentonite is 6.2. Its cation exchange capacity (CEC) is in the lower-middle range for smectites at 45.89 cmol/kg, absorption capacity 43.58 mL/g, swelling degree 9.41%. Because of the high amounts and purity of montmorillonite, the valuable component mineral, the way is open to an easy refinement of this important resource. This way very high-quality colloidal suspensions can be obtained which can be used in the most modern applications of micro- and nanostructured materials.

In the current study, different heavy minerals typical of gold placer deposits were identified by means of micro-Raman spectroscopy, and their chemical composition analyzed and discussed (garnet, kyanite, staurolite, zircon, allanite, monazite, xenotime, rutile, anatase, cassiterite, titanite, barite). Even complex solid solution series, such as those of garnets, can be deciphered with the aid of systematic trends observed in Raman line frequencies. The ν₁ mode in garnets will shift from high to low frequencies as a function of the ionic radius of the X²⁺ cation, from Mg²⁺, to Fe²⁺ and Mn²⁺, while the presence of Ca²⁺ will make the band to be shifted strongly to even lower wavenumbers. This approach has successfully been taken to differentiate between polymorph triplets such as kyanite-sillimanite-andalusite and rutile-anatase-brookite. Minerals under consideration with high contents of REE, U and Th are affected by intensive metamictization, particularly zircon and titanite. Raman peak features, such as shape, symmetry and intensity, respond to this radiation damage of the lattice and enable fine-tuning of these heavy minerals, such as in the case of fluorite (fetid fluorite).

Sphalerite is an abundant mineral in the hydrothermal deposits from the Baia Mare and Oaș areas (northwestern Romania). Sphalerite samples were analyzed with an electron probe microanalyzer and Raman spectroscopy. The obtained results indicated different amounts of Fe in the various deposits from the Baia Mare and Oaș areas. The sphalerites from Baia Sprie, Cavnic, Iba, Turț Penigher, and Breiner have a low Fe wt.% content. High Fe wt.% contents are at Herja and partly at Ghezuri and Nistru (copper stage) where sphalerite is associated with pyrrhotite. The correlation between iron and zinc from sphalerites is strongly negative. The negative correlation shows that iron is the main element that replaces zinc in the sphalerite structure. The manganese content of sphalerites in the Baia Mare and Oaș area is up to 0.84 wt.%. The cadmium content is quite uniform in the Baia Mare and Oaș area with contents ranging from 0.01 to 0.72 wt.%. The Fe content of sphalerites is an important indicator of the physico-chemical conditions of deposit formation because it is a function of temperature, pressure, and sulfur fugacity.

Sediment samples from the Săsar River and its main tributaries were analyzed for their potentially toxic elements at the site of the Romplumb metallurgical company and near the well-known Pb-Zn-Cu epithermal deposit of Baia Sprie located in the Neogene volcanic chain of the Eastern Carpathians, Romania. The average metal concentrations arranged in order of decreasing abundance are as follows (mg·kg⁻¹): Mn (4098) > Zn (2093) > Pb (918) > Cu (489) > As (160) > Cr (37.51) > Ni (30.25) > Co (28.13) > Cd (9.72) > Hg (1.81). Several pollution indices were successfully used to assess the degree of contamination and ecological risk. The majority of sampling sites indicate high degrees of pollution, with two major hotspots identified. There are further sources, such as the Șuior (Pb-Zn-Au) and Săsar (Au-Ag) epithermal deposits, Cuprom company, and Bozânta tailing ponds, identified as contaminants. The Baia Mare mining district is causing a serious threat to the aquatic systems in the region, and it can be taken as a reference area for the human impact derived from the mining of mineral deposits of Au-Ag-Cu-Pb-Zn. It is imperative to reduce ecological risks and thereby protect the population living within this abandoned mining area.

Gheorghe DAMIAN, Zsolt SZAKACS Gheorghe IEPURE & Floarea DAMIAN - DISTRIBUTION OF HEAVY METALS IN GRANULOMETRIC FRACTIONS AND ON SOIL PROFILES, Carpathian Journal of Earth and Environmental Sciences, August 2019, VOL. 14, NO. 2, P. 343 - 351; DOI:10.26471/cjees/2019/014/085