Abstract
Purpose. Chromite samples from Aetoraches mine area in the southern part of the Vourinos complex in Western Macedonia, Greece were examined from mineralogical-geochemical perspective. Methods. Χ-ray Diffraction (XRD) mineral phase analysis, elemental Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) analysis and Thermogravimetry/Differential Thermogravimetry (TG/DTG) were carried out. Findings. The XRD results showed that all the samples contain mainly magnesium- and aluminum-chromite (“aluminum-picrochromite”) phases, along with forsterite (magnesian olivine), serpentine and chlorite occurrences. Based on the SEM-EDS results, the computed average chemical formula indicative of this specific chromite type is: (Fe0.4 Mg0.6) (Cr1.6 Al0.4/)O4. The TG-DTG weight losses found to be in the range of 4.4-14.36%, at temperatures between 600 and 750°C, indicated the presence of the hydroxyl-rich silicate minerals, serpentinite and chlorite, in agreement to the Loss of Ignition (LOI) results. The mineral phases detected in the present analyses appear in the dunite/diorite/harzburgite/peridotite main rocks of the ophiolitic complex that hosts the chromite ore. Originality.In the current research, an original characterization, via thorough elemental, phase and thermal analysis, is carried out aiming to enlighten the geochemistry aspects of the Vourinos chromite complex, Region of Western Macedonia, Greece, particularly of easily accessible and exploitable chromite deposits of the Aetoraches mine area. Practical implications. The chromite mineral, and especially the metallurgical type, is of substantial importance in metal industry. In that sense, the findings of the present investigation of chromite purity and mineral structure is a prerequisite for future exploitation of the Aetoraches chromite deposits in particular and broadly for the ongoing exploitation of chromite ore in the Vourinos complex, situated in Region of Western Macedonia, Greece, an area with high unemployment and rather slow economic growth. Keywords: chromite ore, Vourinos massif, Aetoraches mine area, mineralogical characterization, geochemistry, XRD, SEM-EDS, TG/DTG
Highlights
Chemical composition of the chromite is cha-Chromite is a mineral that belongs to the spinel group and is found in nature in ultrabasic rocks
The technological classification of chromite ores into categories depends on the Cr/Fe ratio and the aluminum content as follows: metallurgical chromite type Cr/Fe > 2.8:1; refractory chromite type Cr/Fe < 2.5:1
X-Ray Diffraction (XRD) was carried out in order to identify the mineralogical phases which are present in the chromite samples
Summary
Chemical composition of the chromite is cha-Chromite is a mineral that belongs to the spinel group and is found in nature in ultrabasic rocks (dunite, harzsbourgite). The technological classification of chromite ores into categories depends on the Cr/Fe ratio and the aluminum content as follows: metallurgical chromite type Cr/Fe > 2.8:1; refractory chromite type Cr/Fe < 2.5:1 This mineral, a ferrous and chromium variant of spinel (MgAl2O4) with the general chemical formula (Mg, Fe+2) (Cr, Al, Fe+3)2O4 constitutes an insignificant phase of basic and ultrabasic rocks and is of petrogenetic significance [1], while the combination with the content of various trace elements in chromatic ores appears to have particular importance for chromitogenesis. Racterized by large variation, mainly in trivalent elements, from Cr- rich (metallurgical type) to Al- rich (refractory type) Various trace elements, such as elements of the platinum group (Os, lr, Ru, Rh, Pt and Pd), or PGE, Ni, Cu, Co, V, Zn and Ti could likely appear as self-existing minerals (PGM, oxides of Ti) or replace major elements on the chromite lattice. V and Ti replace Cr and Al into octahedral positions, while Mn, Zn and Co substitute Mg and Fe+2 into tetrahedral positions of chromite [2], [3].
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