Tracking Subsurface Active Weathering Processes In Serpentinite

We conducted a novel study to capture the on-going advancement of mineral weathering within a serpentinite formation by using an integrated approach of multi-scale quantitative rock magnetic analyses and nano-resolution geochemical imaging analyses. We studied a suite of rock samples from the Coast Range Ophiolite Microbial Observatory (CROMO) in California to conduct rock magnetic analyses enabling us to determine character of Fe-bearing minerals and to predict locations of reaction boundaries among various stages of weathering. QEMSCAN (R) and other electron micro-imagery analyses highlighted microstructural changes in amorphous minerals, and possible changes in porosity and coincides with the iron-enrichment region. This iron enrichment indicates initiation of iron (-oxides) nucleation, resulting in extremely fine gain magnetite formation. This is a newly documented mode of magnetite production in serpentinites and enhances the application of magnetite abundance as a proxy for the degree and extent of water-rock interaction in mantle peridotite and serpentinite.