Molybdenum (Mo) is a widely used trace metal for investigating redox conditions. However, unanswered questions remain that concentration and bulk isotopic analysis cannot specifically answer. Improvements can be made by combining new geochemical techniques with traditional methods of Mo analysis. In this Element, we propose a refinement of Mo geochemistry within aquatic systems, ancient rocks, and modern sediments through molecular geochemistry (systematically combining concentration, isotope ratio, elemental mapping, and speciation analyses). Specifically, to intermediate sulfide concentrations governing Mo behaviour below the 'switch-point' and dominant sequestration pathways in low oxygen conditions. The aim of Molybdenum as a Paleoredox Proxy is to 1) aid and improve the breadth of Mo palaeoproxy interpretations by considering Mo speciation and 2) address outstanding research gaps concerning Mo systematics (cycling, partitioning, sequestration, etc.). The Mo palaeoproxy has the potential to solve ever-complex research questions. By using molecular geochemical recommendations, improved Mo palaeoproxy interpretations and reconstruction can be achieved.
1. Introduction
2. Refining redox conditions
3. Molybdenum speciation
4. Molybdenum isotopes
5. Research gaps
6. Future research directions
7. Recommended reading