Testing new models for sedimentary mineral behaviour

点击翻译按钮获取中文摘要

Minerals are the largest sources and sinks for metals, metalloids and volatile elements on Earth. Sedimentary minerals in particular have played an important role throughout Earth history in regulating element mobility and in preserving a record of biogeochemical change. Sedimentary rocks and metasediments also host important ores of uranium, lead, base metals (including iron, zinc and copper), phosphate, Rare Earth Elements, and precious metals (such as gold and silver). Although the structures, properties and environmental behaviours of sedimentary minerals have been well studied from a classical perspective, recent insights into the behaviour of minerals has thrown into question many of our fundamental assumptions about their stability as stores for contaminants and their role as long-term recorders of environmental change. While new models for sedimentary mineral behaviour continue to see development in the laboratory, their relative importance to geological processes has not been systematically tested in the field. A reassessment of the longevity and behaviour of sedimentary minerals is required in light of new insights that reveal the often transient nature of the isotopic and elemental information that they store. The core objectives of this proposal are to test the impacts of (1) gas-mineral reactions, (2) dynamic dissolution-precipitation (i.e., dynamic equilibrium), and (3) mineral replacement on preservation of the elemental, isotopic and biological information stored in carbonate, sulfate, sulfide, hydrotalcite, halide and hydroxide minerals. Experiments will be done to assess the importance of these behaviours within mineralogically similar lake sediments within the basaltic Cariboo Plateau and the Basque Lakes region in south-central British Columbia, Canada. The novelty of the proposed research lies in taking the study of non-classical mineral behaviour beyond the laboratory to quantify its impacts on real sediments in complex biogeochemical systems. All of the minerals that will be studied are ones that we rely upon for nutrient and contaminant management and that we use to reconstruct life's history on Earth. A greater understanding of how to tune the behaviour of mineral sources and sinks for the elements, and when sedimentary minerals can be relied upon as paleoenvironmental proxies, will result from this work.