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The eastern part of the Cantabrian Zone (Iberian Massif, Spain) is well known by the variety of small and medium-sized mineral occurrences of Pb-Zn-Ba-Hg, F-Ba, Cu-Co-Ni, Hg-Ba, Sb-As, Fe-Mn, etc., which have been exploited since Neolithic time. There is also a conspicuous Carboniferous Mn-Fe sedimentary deposit consisting either of small nodules in a pelitic matrix or of massive Mn (Ricacabiello Formation of Bashkirian age). Twenty-four samples of nodules and matrix and 2 samples of hydrothermal Fe-Mn have been analyzed, and trace and REE elements have shown the existence of hydrothermal and hydrogenous nodules in the formation, which was deposited in a deep-marine environment related to Late Paleozoic tectonic episodes, and also the possibility of this being the source bed for most of the rest of the epithermal deposits in the Cantabrian Zone during an intensive epoch of hydrothermal circulation in Permian time.

The Saucelle-Barruecopardo mineralized (Au-W) area is located in the northwest of Salamanca province, Spain, within the Centroiberian zone (the most internal part of Hercynian CordilIera System). The quartz veins are spatially associated with the Barruecopardo granite, a syntectonic two-mica alkaline granite. The granite crosscuts regional metamorphic isograds and estimates of its emplacement age range from 311 to 326 M.a. Gold-tungsten-bearing veins crosscut the Barruecopardo granite and the surrounding country rocks. The vein mineralogy can be subdivided into five paragenetic stages. Gold deposition is associated with stage I (gold included in arsenopyrite) and stage II (gold in cracks in arsenopyrite). Stage I muscovites are dated (K-Ar method) at 277.9 ± 5.6 and 257.0 ± 5 M.a. Two main different compositional types of primary fluid inclusions were observed in quartz: type (l) C02-H20 inclusions, and type (2) C02-rich inclusions. Type 1 and type 2 inclusions are related to stage-I gold deposition and are thought to represent immiscible fluids because they are primary and the homogenization temperatures for both types (H20-rich and C02.rich) are in the same range, with a maximum homogenization temperature of 428QC. The calculated temperature of immiscibility ranges from 355 to 435QC and pressures from 1400 to 2100 bars. 8 34 S arsenopyrite values suggest a constant source of sulphur with values close to 0 per mil. Calculated 8Dfluid values are all quite D-enriched, but show significant variability (-32 to-2%0 SMOW), whereas 8 18 0tluid values show small variation (from + 7 to + 10.3 %0 SMOW). These values for the fluids are consistent with interaction between magmatic fluids and metamorphic rocks (from 0.1 to 0.01 fluid/rock ratios). The most likely mechanism for stage-I gold deposition is the loss of H2S during fluid immiscibility.

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