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The Banska Stiavnica Au-Ag base metals epithermal deposit is hosted within a Neogene-age volcanic caldera in central Slovakia. The caldera comprises a central granodiorite stock that has been capped by comagmatic andesire and rhyolite extrusions. The intrusive telsic rocks possess a close spatial and temporal relationship with the mineralization and associated hydrothermal alteration. To investigate the possible genetic link between magmatic and hydrothermal activity, paragenetically constrained melt and fluid inclusions in magmatic quartz and vein minerals were studied, using microthermometric techniques. Primary melt inclusions in magmatic quartz froin the granodiorite vary in composition from essentially silicate H20-and Cl-rich melt with low-salinity fluid (8.3-9.6 wt % NaC1 equiv) to high-density hypersaline brines (-80 wt % NaC1 equiv). Salinities of secondary fluid inclusions in magmatic quartz systematically decrease along the NaC1 saturation curve toward lower temperatures and salinities equivalent to those determined for primary fluid inclusions in sphalerite and vein minerals (quartz, barite, fluorite) within the deposit (<400øC, <12 wt % NaC1 equiv). This systematic evolution in measured and calculated characteristics (temperature, pressure, salinity, and density) of the studied fluid inclusions indicates that exsolved magmatic brines and aqueous chloride solutions were the primitive precursors to the hydrothermal ore-forming fluids that produced epithermal mineralization upon mixing with meteoric waters in the near-surface environment.

Rare Cu-Bi sulphosalt, hodrušite, occurs in the Rozália vein (levels X-XIV of the Rozália mine, Hodruša-Hámre ore deposit near Banská Štiavnica, central Slovakia) in two unusual morphological forms. The first type are brownish bronze thin acicular striated crystals, up to 3 mm long, in drusy cavities of quartz-hematite gangue, which are usually grouped into chaotic or irregular aggregates. The second hodrušite type comprises flattened columnar aggregates, up to 1.5 cm long, overgrown by hematite in quartz gangue. These aggregates are distinctly striated with brownish bronze colour and metallic lustre. Abundant W-and Al-rich hematite, chalcopyrite, kaolinite/dickite, siderite, baryte, rare bismuthinite and kupčíkite were found in the association. The earliest columnar aggregates of hodrušite are locally substantially replaced by bismuthinite; these hodrušite-bismuthinite aggregates are further intensively pushed back by hematite displaying W-and Al-rich zones. Acicular crystals of hodrušite in gangue cavities were later than bismuthinite and hematite and their formation was related to remobilisation of Cu and Bi from earlier altered gangue. Powder X-ray diffraction data and chemical composition of both hodrušite types are similar; their unit-cell parameters were refined (monoclinic space group C2/m) as: a 17.552(5), b 3.905(1), c 27.167(9) Å, β 92.44 (3) o , V 1860.5(9) Å 3 (acicular crystals) and a 17.567(2), b 3.9151 (7), c 27.155(5) Å, β 92.43 (1) o , V 1865.9(4) Å 3 (columnar aggregates). Cu-for-Bi substitution is characteristic of both hodrušite types; it influences calculated N chem values (0.98-1.33) to the point that it is impossible to distinguish hodrušite (ideal 1.5) from kupčíkite (ideal 1.0). The problem is resolved by Fe and Ag contents: kupčíkite has more than 2 at. % Fe, cuprobismutite contains more than 2 at. % of Ag; hodrušite usually has Ag and Fe contents below 2 at. %. Hematite is remarkable for its high WO 3 content reaching 4.96 wt. % (0.04 apfu), extremely unusual of a hematite from hydrothermal vein mineralization. Tungsten probably enters the hematite structure via the 2Fe 3+ ↔W 6+ +□ substitution.