Digestion methods for trace element measurements in shales: Paleoredox proxies examined

摘要: Abstract Trace elements such as U, Mo, Re, V and Ni in marine shales are commonly used to probe paleoenvironmental conditions. may have either a detrital or seawater source, both. The contribution is often modelled from whole-rock sediment analyses. Using trace element ratios paleoredox proxies, however, presents limitations. In this study, we compare three different methods of digestion using Middle Triassic black Svalbard Svalis Dome, Late Permian the mid-Norwegian shelf East Greenland. Multi-acid total provides compositions, including both contributions. Aqua regia inverse aqua digestions dissolve organic matter, sulfides carbonates, leaving behind major silicate components. Thus, concentrations by provide direct, though still imperfect approximation component. For most elements, their derived agree within 10%, roughly uncertainty analytical procedures. However, not apatite completely, which leads slightly lower Ca, P, Sc, U Pb contents than digestion. partial yield comparable abundances S, Co, Ni, Cu, Zn, Mn, Mo Pb, dominantly origin our samples. V, Sc Cr up 80% those digestion, suggesting significant contributions sources. We conclude that: (1) metals released predominantly reflect components, thus value (2) if absolute metal infer conditions, amount carbon sulphur must be taken into account, (3) threshold values for based on compositions (e.g., Th/U, V/Sc, V/V + Ni) globally applicable redox these combination