Stable isotope and fluid inclusion study of sediment-hosted stratiform copper deposits from the Neuquén Basin, Argentina

Metal Flux from Dissolution of Iron Oxide Grain Coatings in Sandstones

“…The grains exhibit negligible (less than 1 ppm) concentrations of V and Co, while the surrounding iron oxide shows V and Co at up to 120 ppm and 60 ppm, respectively. [14,17,18], distal reprecipitation of leached metals [6,7], or whole rock data [11]. Measurements of some trace elements in iron oxide grain coatings were made by [33], including U and V and rare earth elements but not Cu, Co, or Se.…”

“…The combination of trace metal uptake and dissolution is a potential pathway to produce a mineralizing fluid [8][9][10][11][12]. This possibility has been invoked to explain moderate-to large-scale ore deposits in sandstones, such as copper and silver in Kazakhstan [13,14], copper and silver in Iran [15], uranium in Australia [16], copper in Argentina [17,18], vanadium in Argentina [19], copper in Arctic Canada [20], copper in Newfoundland [21], lead-zinc in China [22], and uranium in China [23]. The occurrence of red sandstones does not, however, necessarily explain mineralization, as other sources such as underlying basement may contribute more metal in certain hydrological regimes [24].…”

Copper, Uranium and REE Mineralisation in an Exhumed Oil Reservoir, Southwest Orkney, Scotland

“…A similar replacement mechanism of pyrite by chalcopyrite and sphalerite has occurred in the hydrothermal barite + sulphide veins in the Yesnaby Sandstone Fm (Figure 3D). There are several examples at the White Pine mine, some Chilean Manto-type deposits, and in the Neuquen Basin of hydrocarbons which acted as the primary reductant to facilitate Cu-mineralisation from the hydrothermal brines [7,9,11,53,54], which is also likely to have occurred at Yesnaby.…”

“…It is, therefore, valuable to identify whether specific aspects of the oil residues particularly enhanced mineralisation and how these compare to those at Yesnaby. Relevant characteristics include the reducing nature of the oil residues [53], a role for organic fluids in the transport of metals [67], and changes in permeability concomitant with biodegradation during uplift [68]. These factors contribute to a range of relationships between copper mineralisation and sedimentary organic matter (Table 6).…”

“…Reducing template on oil residue Post-oil Any [53] Evaporite sequences source oil and sulphides Any Any [69] Rift basin mixed volcanic copper and lacustrine oil Any Terrestrial [57] Oil charge strips metallic grain coatings Post-oil Terrestrial [70] Metal transport in low-pH organic fluids Any Any [67] Permeability enhanced in uplifted reservoir Post-oil Any [68] Assimilation organics in magmas to precipitate sulphides Any Any [71] Both uranium and copper are mobile in oxidising conditions, so are available for interaction with oil residues in continental sandstones. However, at Yesnaby the interactions occurred at different stages, at least in part due to the nature of the interaction (irradiation, reduction), but possibly also due to the timing of metal availability.…”