## 4 Discussion
In the Fagaras Mts., part of the Southern Carpathians, the contents in Cr and Ni of the metamorphic rocks vary significantly in different areas of these mountains; for Cr, the range of the minimum values is 31-100 ppm, and the maximum is 1200-6500 ppm; for Ni, these ranges are 14-1000 ppm for the minimum and 300-16,000 ppm (1.6%) for the maximum. The Cr values are constantly lower than those for Ni in the transformed ultrabasic rocks [109]. In the southwestern part of the Banat Mts. (Western Romanian Carpathians) in the Almaj Mts., after analyzing 5258 samples of soil from basic and ultrabasic rocks parental material, it was established (using the parabola method [110]) that the geochemical background value was 400 ppm for Cr and 600 pm for Ni. In contrast, the threshold for geochemical anomalies was 1000 ppm (Cr) and 1500 ppm (Ni). In the same mountains, for the serpentinized basic and ultrabasic igneous rocks [111], the Ni content can reach a mean of over 2000 ppm up to 7300 ppm; the Cr content in the samples with massive chromite is 165,500-282,900 ppm (16.55-28.29%). The results of the geochemical explorations described above are in accordance with the outputs of geochemical analyses at the pan-European level carried out via FOREGS (Forum of European Geological Surveys) and GEMAS (Geochemical mapping of agricultural and grazing land soil) projects; although these did not include data and maps for Romania, the intense geochemical anomalies of Cr and Ni found in the area of the Balkans are in close relationship with the values found in Romania. The highest values of Cr and Ni in the Romanian geochemical explorations for areas in the Western Romanian Carpathians are related to the Vardar Ocean [70] and its chemically basic crust. Figure 8 shows the extension of the geological formations of the Carpathian chain in Romania to the south in the Balkan Peninsula. Chromium is predominantly found as chromite in magnesian igneous rocks, where it is commonly associated with minerals containing nickel, typically olivine [52]. The alteration of these rocks during the subduction of the Vardar oceanic plate [70], in conjunction with weathering and erosion [113], resulted in the enrichment of sediments and, subsequently, of soils' parent material regarding these elements. Pan-European geochemical studies carried out in the 1990s to establish the geochemical background values for soils and sediments in Europe, such as the FOREGS project (Forum of the European Geological Surveys)--initiated by the International Union of Geological Sciences and the International Association of Geochemistry and Cosmochemistry [76]--analyzed over 2000 samples in soils (top layer (or toposit), bottom layer, and humus), stream sediments, and floodplain sediments for a series of elements; this produced the Geochemical Atlas of Europe. Maps have been drawn up covering 26 European countries, but without Romania, Bulgaria, and some other countries from the Balkan peninsula (except for Greece and Albania). A geostatistical analysis carried out on FOREGS data [114] for the trace critical elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) highlighted a high correlation for Cr and Ni, related to ultramafic rocks and polymetallic sulfide minerals but also some sedimentary rocks and lateritic deposits, as well as soils enriched in these elements due to the weathering processes. The Geochemical Atlas of Europe shows an intense anomaly of Cr and Ni in Greece and Albania due to mineralized ophiolitic and sedimentary rocks derived from them. An important Cr-Ni mineral deposit is known at Vourinos, in northern Greece, and [115] mentions Greece, Albania, and Serbia amongst the Ni-producing countries in Europe. High values of Cr and Ni in soils and sediments are considered [116] to be of a geogenic nature, reflecting the composition of the substratum.