# Spatial Variation of Water Chemistry in Aries River Catchment, Western Romania
## 2 Methodology  
### Geological Settings and Description of the Study Area  
The Aries River catchment is part of the Romanian Golden Quadrangle, recognized for the Au, Ag and porphyry copper deposits from Rosia Poieni [20; 21]. The Aries River catchment has more than 60% of its surface developed in the Apuseni Mountains and \(\sim\)40% on the Transylvanian Plateau and Feleacului Hills [22]. The Apuseni Mountains are particular mountains in western Romania, characterized by diverse and unique landforms belonging to the Western Carpathians. The Transylvanian Plateau is represented by three distinct units (Somes Plateau, Transylvanian Plain and Trin alveolar Plateau), defined mostly by depressions, low plateaus and hills (the transition areas near mountains) with different geological structu Ref. [23]. Feleacului Hills cover only a small area of the Aries River catchment (north-eastern part), where marly to sandy clay soils appear, intercalated with sands and sandstones. The Aries River springs from Bihor Mountains (near VirfulVirtopu, 1294 m) and flows into the MuRes. River (near GuraAriesului village, 317 m), with a total length of \(\sim\)166 km. The Aries River catchment covers several landscapes and landforms of Apuseni Mountains and Transylvanian Plateau (Bihor Mountains in the west part of the country; Metaliferi Mountains in thesouth-central area, Gilau-Muntele Mare in thenorth-central area of the catchment, Trascau Mountains in the south-east area, Feleacului Hills in the north-east area and Transylvanian Plateau in the east part of the country) [22]. The geological framework is diverse and represented by a variety of formations (from north to south), with basement tectonic units (metamorphic rocks and granites), sedimentary and volcanic cover in the northern area, while Middle Jurassic ophiolites, Late Jurassic volcanic rocks and Late Cretaceous sedimentary deposits dominate the southern part of Apuseni Mountains. Moreover, the groundwater resources in the Aries River catchment are mostly related to karst aquifers developed in limestones or fissured rocks,being part of local or discontinuous aquifers (southern part of the basin), while the northern area of the basin is characterized by formations with deep aquifers or without aquifers (Figure 1). The most significant exploitations conducted in the catchment area are Rosia Montana, Rosia Poieni, Baia de Aries and Iara (Table 1) [21; 25; 26]. Tailings resulting from the oRes. extractions were stored in several tailing ponds, while all the wastewaters resulted from the mining activities and secondary processing of the oRes. are discharged into the tributaries of the Aries Rivers (Figure 2).Most of the mining and ore processing facilities were demolished or conserved;however, some of them were simply abandoned [27].At present, the open-cast mine Rosia Poieni is the only unity in operation, although reopening the exploitation of gold and silver oRes. at Rosia Montana has been largely debated during the last few years. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Deposit Type** & **Extraction Technique** & **Current Status** & **Tailing** & **Deposit Volume (mil m\({}^{3}\))** \\ \hline Rosia Montana & Au ores & & & Closed & Seliste & 6.60 \\  & Ag ores & & since 2006 & & Gura Rosie & 5.80 \\ \hline Rosia Poieni & Porphritic Cu & & & & & \\  & & & & & \\  & & & & & \\ \hline Baia de Aries & Lead-zinc ferrous & & & Closed & Cutii & 1.62 \\  & Gold-silver ferrous & & & & & \\  & & & & & \\  & & & & & \\ \hline Iara & Fe ores & & & Closed & Baisoara & 3.33 \\  & Mg ores & & & & \\  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of the main tailing impoundments located in the Aries Ríver catchment [27]. Figure 1: Geologic map of the Aries catchment (modified after [PERSON] et al., 2002 [24]). 1. Neogene; 2. Paleogene; 3. Cretaceous; 4. Cretaceous-Jurassic; 5. Jurassic; 6. Triassic-Cretaceous; 7. Triassic; 8. Paleozoic inclusive rocks; 9. Paleozoic metamorphic rocks; 10. Undivided Precambrian.